use std::{
    collections::HashSet,
    env,
    ffi::{OsStr, OsString},
    io::{self, IsTerminal, Write},
    path::{Path, PathBuf},
    sync::Arc,
};

use {
    clap,
    grep::{
        cli,
        matcher::LineTerminator,
        printer::{
            default_color_specs, ColorSpecs, HyperlinkConfig,
            HyperlinkEnvironment, HyperlinkFormat, JSONBuilder, PathPrinter,
            PathPrinterBuilder, Standard, StandardBuilder, Stats, Summary,
            SummaryBuilder, SummaryKind, JSON,
        },
        regex::{
            RegexMatcher as RustRegexMatcher,
            RegexMatcherBuilder as RustRegexMatcherBuilder,
        },
        searcher::{
            BinaryDetection, Encoding, MmapChoice, Searcher, SearcherBuilder,
        },
    },
    ignore::{
        overrides::{Override, OverrideBuilder},
        types::{FileTypeDef, Types, TypesBuilder},
        {Walk, WalkBuilder, WalkParallel},
    },
    termcolor::{BufferWriter, ColorChoice, WriteColor},
};

#[cfg(feature = "pcre2")]
use grep::pcre2::{
    RegexMatcher as PCRE2RegexMatcher,
    RegexMatcherBuilder as PCRE2RegexMatcherBuilder,
};

use crate::{
    app, config,
    logger::Logger,
    messages::{set_ignore_messages, set_messages},
    search::{PatternMatcher, Printer, SearchWorker, SearchWorkerBuilder},
    subject::{Subject, SubjectBuilder},
    Result,
};

/// The command that ripgrep should execute based on the command line
/// configuration.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Command {
    /// Search using exactly one thread.
    Search,
    /// Search using possibly many threads.
    SearchParallel,
    /// The command line parameters suggest that a search should occur, but
    /// ripgrep knows that a match can never be found (e.g., no given patterns
    /// or --max-count=0).
    SearchNever,
    /// Show the files that would be searched, but don't actually search them,
    /// and use exactly one thread.
    Files,
    /// Show the files that would be searched, but don't actually search them,
    /// and perform directory traversal using possibly many threads.
    FilesParallel,
    /// List all file type definitions configured, including the default file
    /// types and any additional file types added to the command line.
    Types,
    /// Print the version of PCRE2 in use.
    PCRE2Version,
}

impl Command {
    /// Returns true if and only if this command requires executing a search.
    fn is_search(&self) -> bool {
        use self::Command::*;

        match *self {
            Search | SearchParallel => true,
            SearchNever | Files | FilesParallel | Types | PCRE2Version => {
                false
            }
        }
    }
}

/// The primary configuration object used throughout ripgrep. It provides a
/// high-level convenient interface to the provided command line arguments.
///
/// An `Args` object is cheap to clone and can be used from multiple threads
/// simultaneously.
#[derive(Clone, Debug)]
pub struct Args(Arc<ArgsImp>);

#[derive(Clone, Debug)]
struct ArgsImp {
    /// Mid-to-low level routines for extracting CLI arguments.
    matches: ArgMatches,
    /// The command we want to execute.
    command: Command,
    /// The number of threads to use. This is based in part on available
    /// threads, in part on the number of threads requested and in part on the
    /// command we're running.
    threads: usize,
    /// A matcher built from the patterns.
    ///
    /// It's important that this is only built once, since building this goes
    /// through regex compilation and various types of analyses. That is, if
    /// you need many of these (one per thread, for example), it is better to
    /// build it once and then clone it.
    matcher: PatternMatcher,
    /// The paths provided at the command line. This is guaranteed to be
    /// non-empty. (If no paths are provided, then a default path is created.)
    paths: Vec<PathBuf>,
    /// Returns true if and only if `paths` had to be populated with a single
    /// default path.
    using_default_path: bool,
}

impl Args {
    /// Parse the command line arguments for this process.
    ///
    /// If a CLI usage error occurred, then exit the process and print a usage
    /// or error message. Similarly, if the user requested the version of
    /// ripgrep, then print the version and exit.
    ///
    /// Also, initialize a global logger.
    pub fn parse() -> Result<Args> {
        // We parse the args given on CLI. This does not include args from
        // the config. We use the CLI args as an initial configuration while
        // trying to parse config files. If a config file exists and has
        // arguments, then we re-parse argv, otherwise we just use the matches
        // we have here.
        let early_matches = ArgMatches::new(clap_matches(env::args_os())?);
        set_messages(!early_matches.is_present("no-messages"));
        set_ignore_messages(!early_matches.is_present("no-ignore-messages"));

        if let Err(err) = Logger::init() {
            return Err(format!("failed to initialize logger: {}", err).into());
        }
        if early_matches.is_present("trace") {
            log::set_max_level(log::LevelFilter::Trace);
        } else if early_matches.is_present("debug") {
            log::set_max_level(log::LevelFilter::Debug);
        } else {
            log::set_max_level(log::LevelFilter::Warn);
        }

        let matches = early_matches.reconfigure()?;
        // The logging level may have changed if we brought in additional
        // arguments from a configuration file, so recheck it and set the log
        // level as appropriate.
        if matches.is_present("trace") {
            log::set_max_level(log::LevelFilter::Trace);
        } else if matches.is_present("debug") {
            log::set_max_level(log::LevelFilter::Debug);
        } else {
            log::set_max_level(log::LevelFilter::Warn);
        }
        set_messages(!matches.is_present("no-messages"));
        set_ignore_messages(!matches.is_present("no-ignore-messages"));
        matches.to_args()
    }

    /// Return direct access to command line arguments.
    fn matches(&self) -> &ArgMatches {
        &self.0.matches
    }

    /// Return the matcher builder from the patterns.
    fn matcher(&self) -> &PatternMatcher {
        &self.0.matcher
    }

    /// Return the paths found in the command line arguments. This is
    /// guaranteed to be non-empty. In the case where no explicit arguments are
    /// provided, a single default path is provided automatically.
    fn paths(&self) -> &[PathBuf] {
        &self.0.paths
    }

    /// Returns true if and only if `paths` had to be populated with a default
    /// path, which occurs only when no paths were given as command line
    /// arguments.
    pub fn using_default_path(&self) -> bool {
        self.0.using_default_path
    }

    /// Return the printer that should be used for formatting the output of
    /// search results.
    ///
    /// The returned printer will write results to the given writer.
    fn printer<W: WriteColor>(&self, wtr: W) -> Result<Printer<W>> {
        match self.matches().output_kind() {
            OutputKind::Standard => {
                let separator_search = self.command() == Command::Search;
                self.matches()
                    .printer_standard(self.paths(), wtr, separator_search)
                    .map(Printer::Standard)
            }
            OutputKind::Summary => self
                .matches()
                .printer_summary(self.paths(), wtr)
                .map(Printer::Summary),
            OutputKind::JSON => {
                self.matches().printer_json(wtr).map(Printer::JSON)
            }
        }
    }
}

/// High level public routines for building data structures used by ripgrep
/// from command line arguments.
impl Args {
    /// Create a new buffer writer for multi-threaded printing with color
    /// support.
    pub fn buffer_writer(&self) -> Result<BufferWriter> {
        let mut wtr = BufferWriter::stdout(self.matches().color_choice());
        wtr.separator(self.matches().file_separator()?);
        Ok(wtr)
    }

    /// Return the high-level command that ripgrep should run.
    pub fn command(&self) -> Command {
        self.0.command
    }

    /// Builder a path printer that can be used for printing just file paths,
    /// with optional color support.
    ///
    /// The printer will print paths to the given writer.
    pub fn path_printer<W: WriteColor>(
        &self,
        wtr: W,
    ) -> Result<PathPrinter<W>> {
        let mut builder = PathPrinterBuilder::new();
        builder
            .color_specs(self.matches().color_specs()?)
            .hyperlink(self.matches().hyperlink_config()?)
            .separator(self.matches().path_separator()?)
            .terminator(self.matches().path_terminator().unwrap_or(b'\n'));
        Ok(builder.build(wtr))
    }

    /// Returns true if and only if ripgrep should be "quiet."
    pub fn quiet(&self) -> bool {
        self.matches().is_present("quiet")
    }

    /// Returns true if and only if the search should quit after finding the
    /// first match.
    pub fn quit_after_match(&self) -> Result<bool> {
        Ok(self.matches().is_present("quiet") && self.stats()?.is_none())
    }

    /// Build a worker for executing searches.
    ///
    /// Search results are written to the given writer.
    pub fn search_worker<W: WriteColor>(
        &self,
        wtr: W,
    ) -> Result<SearchWorker<W>> {
        let matches = self.matches();
        let matcher = self.matcher().clone();
        let printer = self.printer(wtr)?;
        let searcher = matches.searcher(self.paths())?;
        let mut builder = SearchWorkerBuilder::new();
        builder
            .json_stats(matches.is_present("json"))
            .preprocessor(matches.preprocessor())?
            .preprocessor_globs(matches.preprocessor_globs()?)
            .search_zip(matches.is_present("search-zip"))
            .binary_detection_implicit(matches.binary_detection_implicit())
            .binary_detection_explicit(matches.binary_detection_explicit());
        Ok(builder.build(matcher, searcher, printer))
    }

    /// Returns a zero value for tracking statistics if and only if it has been
    /// requested.
    ///
    /// When this returns a `Stats` value, then it is guaranteed that the
    /// search worker will be configured to track statistics as well.
    pub fn stats(&self) -> Result<Option<Stats>> {
        Ok(if self.command().is_search() && self.matches().stats() {
            Some(Stats::new())
        } else {
            None
        })
    }

    /// Return a builder for constructing subjects. A subject represents a
    /// single unit of something to search. Typically, this corresponds to a
    /// file or a stream such as stdin.
    pub fn subject_builder(&self) -> SubjectBuilder {
        let mut builder = SubjectBuilder::new();
        builder.strip_dot_prefix(self.using_default_path());
        builder
    }

    /// Execute the given function with a writer to stdout that enables color
    /// support based on the command line configuration.
    pub fn stdout(&self) -> cli::StandardStream {
        let color = self.matches().color_choice();
        if self.matches().is_present("line-buffered") {
            cli::stdout_buffered_line(color)
        } else if self.matches().is_present("block-buffered") {
            cli::stdout_buffered_block(color)
        } else {
            cli::stdout(color)
        }
    }

    /// Return the type definitions compiled into ripgrep.
    ///
    /// If there was a problem reading and parsing the type definitions, then
    /// this returns an error.
    pub fn type_defs(&self) -> Result<Vec<FileTypeDef>> {
        Ok(self.matches().types()?.definitions().to_vec())
    }

    /// Return a walker that never uses additional threads.
    pub fn walker(&self) -> Result<Walk> {
        Ok(self
            .matches()
            .walker_builder(self.paths(), self.0.threads)?
            .build())
    }

    /// Returns true if and only if `stat`-related sorting is required
    pub fn needs_stat_sort(&self) -> bool {
        return self.matches().sort_by().map_or(
            false,
            |sort_by| match sort_by.kind {
                SortByKind::LastModified
                | SortByKind::Created
                | SortByKind::LastAccessed => sort_by.check().is_ok(),
                _ => false,
            },
        );
    }

    /// Sort subjects if a sorter is specified, but only if the sort requires
    /// stat calls. Non-stat related sorts are handled during file traversal
    ///
    /// This function assumes that it is known that a stat-related sort is
    /// required, and does not check for it again.
    ///
    /// It is important that that precondition is fulfilled, since this function
    /// consumes the subjects iterator, and is therefore a blocking function.
    pub fn sort_by_stat<I>(&self, subjects: I) -> Vec<Subject>
    where
        I: Iterator<Item = Subject>,
    {
        let sorter = match self.matches().sort_by() {
            Ok(v) => v,
            Err(_) => return subjects.collect(),
        };
        use SortByKind::*;
        let mut keyed = match sorter.kind {
            LastModified => load_timestamps(subjects, |m| m.modified()),
            LastAccessed => load_timestamps(subjects, |m| m.accessed()),
            Created => load_timestamps(subjects, |m| m.created()),
            _ => return subjects.collect(),
        };
        keyed.sort_by(|a, b| sort_by_option(&a.0, &b.0, sorter.reverse));
        keyed.into_iter().map(|v| v.1).collect()
    }

    /// Return a parallel walker that may use additional threads.
    pub fn walker_parallel(&self) -> Result<WalkParallel> {
        Ok(self
            .matches()
            .walker_builder(self.paths(), self.0.threads)?
            .build_parallel())
    }
}

/// `ArgMatches` wraps `clap::ArgMatches` and provides semantic meaning to
/// the parsed arguments.
#[derive(Clone, Debug)]
struct ArgMatches(clap::ArgMatches<'static>);

/// The output format. Generally, this corresponds to the printer that ripgrep
/// uses to show search results.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum OutputKind {
    /// Classic grep-like or ack-like format.
    Standard,
    /// Show matching files and possibly the number of matches in each file.
    Summary,
    /// Emit match information in the JSON Lines format.
    JSON,
}

/// The sort criteria, if present.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct SortBy {
    /// Whether to reverse the sort criteria (i.e., descending order).
    reverse: bool,
    /// The actual sorting criteria.
    kind: SortByKind,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum SortByKind {
    /// No sorting at all.
    None,
    /// Sort by path.
    Path,
    /// Sort by last modified time.
    LastModified,
    /// Sort by last accessed time.
    LastAccessed,
    /// Sort by creation time.
    Created,
}

impl SortBy {
    fn asc(kind: SortByKind) -> SortBy {
        SortBy { reverse: false, kind }
    }

    fn desc(kind: SortByKind) -> SortBy {
        SortBy { reverse: true, kind }
    }

    fn none() -> SortBy {
        SortBy::asc(SortByKind::None)
    }

    /// Try to check that the sorting criteria selected is actually supported.
    /// If it isn't, then an error is returned.
    fn check(&self) -> Result<()> {
        match self.kind {
            SortByKind::None | SortByKind::Path => {}
            SortByKind::LastModified => {
                env::current_exe()?.metadata()?.modified()?;
            }
            SortByKind::LastAccessed => {
                env::current_exe()?.metadata()?.accessed()?;
            }
            SortByKind::Created => {
                env::current_exe()?.metadata()?.created()?;
            }
        }
        Ok(())
    }

    /// Load sorters only if they are applicable at the walk stage.
    ///
    /// In particular, sorts that involve `stat` calls are not loaded because
    /// the walk inherently assumes that parent directories are aware of all its
    /// decendent properties, but `stat` does not work that way.
    fn configure_builder_sort(self, builder: &mut WalkBuilder) {
        use SortByKind::*;
        match self.kind {
            Path if self.reverse => {
                builder.sort_by_file_name(|a, b| a.cmp(b).reverse());
            }
            Path => {
                builder.sort_by_file_name(|a, b| a.cmp(b));
            }
            // these use `stat` calls and will be sorted in Args::sort_by_stat()
            LastModified | LastAccessed | Created | None => {}
        };
    }
}

impl SortByKind {
    fn new(kind: &str) -> SortByKind {
        match kind {
            "none" => SortByKind::None,
            "path" => SortByKind::Path,
            "modified" => SortByKind::LastModified,
            "accessed" => SortByKind::LastAccessed,
            "created" => SortByKind::Created,
            _ => SortByKind::None,
        }
    }
}

/// Encoding mode the searcher will use.
#[derive(Clone, Debug)]
enum EncodingMode {
    /// Use an explicit encoding forcefully, but let BOM sniffing override it.
    Some(Encoding),
    /// Use only BOM sniffing to auto-detect an encoding.
    Auto,
    /// Use no explicit encoding and disable all BOM sniffing. This will
    /// always result in searching the raw bytes, regardless of their
    /// true encoding.
    Disabled,
}

impl ArgMatches {
    /// Create an ArgMatches from clap's parse result.
    fn new(clap_matches: clap::ArgMatches<'static>) -> ArgMatches {
        ArgMatches(clap_matches)
    }

    /// Run clap and return the matches using a config file if present. If clap
    /// determines a problem with the user provided arguments (or if --help or
    /// --version are given), then an error/usage/version will be printed and
    /// the process will exit.
    ///
    /// If there are no additional arguments from the environment (e.g., a
    /// config file), then the given matches are returned as is.
    fn reconfigure(self) -> Result<ArgMatches> {
        // If the end user says no config, then respect it.
        if self.is_present("no-config") {
            log::debug!(
                "not reading config files because --no-config is present"
            );
            return Ok(self);
        }
        // If the user wants ripgrep to use a config file, then parse args
        // from that first.
        let mut args = config::args();
        if args.is_empty() {
            return Ok(self);
        }
        let mut cliargs = env::args_os();
        if let Some(bin) = cliargs.next() {
            args.insert(0, bin);
        }
        args.extend(cliargs);
        log::debug!("final argv: {:?}", args);
        Ok(ArgMatches(clap_matches(args)?))
    }

    /// Convert the result of parsing CLI arguments into ripgrep's higher level
    /// configuration structure.
    fn to_args(self) -> Result<Args> {
        // We compute these once since they could be large.
        let patterns = self.patterns()?;
        let matcher = self.matcher(&patterns)?;
        let mut paths = self.paths();
        let using_default_path = if paths.is_empty() {
            paths.push(self.path_default());
            true
        } else {
            false
        };
        // Now figure out the number of threads we'll use and which
        // command will run.
        let is_one_search = self.is_one_search(&paths);
        let threads = if is_one_search { 1 } else { self.threads()? };
        if threads == 1 {
            log::debug!("running in single threaded mode");
        } else {
            log::debug!("running with {threads} threads for parallelism");
        }
        let command = if self.is_present("pcre2-version") {
            Command::PCRE2Version
        } else if self.is_present("type-list") {
            Command::Types
        } else if self.is_present("files") {
            if threads == 1 {
                Command::Files
            } else {
                Command::FilesParallel
            }
        } else if self.can_never_match(&patterns) {
            Command::SearchNever
        } else if threads == 1 {
            Command::Search
        } else {
            Command::SearchParallel
        };
        Ok(Args(Arc::new(ArgsImp {
            matches: self,
            command,
            threads,
            matcher,
            paths,
            using_default_path,
        })))
    }
}

/// High level routines for converting command line arguments into various
/// data structures used by ripgrep.
///
/// Methods are sorted alphabetically.
impl ArgMatches {
    /// Return the matcher that should be used for searching.
    ///
    /// If there was a problem building the matcher (e.g., a syntax error),
    /// then this returns an error.
    fn matcher(&self, patterns: &[String]) -> Result<PatternMatcher> {
        if self.is_present("pcre2") {
            self.matcher_engine("pcre2", patterns)
        } else if self.is_present("auto-hybrid-regex") {
            self.matcher_engine("auto", patterns)
        } else {
            let engine = self.value_of_lossy("engine").unwrap();
            self.matcher_engine(&engine, patterns)
        }
    }

    /// Return the matcher that should be used for searching using engine
    /// as the engine for the patterns.
    ///
    /// If there was a problem building the matcher (e.g., a syntax error),
    /// then this returns an error.
    fn matcher_engine(
        &self,
        engine: &str,
        patterns: &[String],
    ) -> Result<PatternMatcher> {
        match engine {
            "default" => {
                let matcher = match self.matcher_rust(patterns) {
                    Ok(matcher) => matcher,
                    Err(err) => {
                        return Err(From::from(suggest(err.to_string())));
                    }
                };
                Ok(PatternMatcher::RustRegex(matcher))
            }
            #[cfg(feature = "pcre2")]
            "pcre2" => {
                let matcher = self.matcher_pcre2(patterns)?;
                Ok(PatternMatcher::PCRE2(matcher))
            }
            #[cfg(not(feature = "pcre2"))]
            "pcre2" => Err(From::from(
                "PCRE2 is not available in this build of ripgrep",
            )),
            "auto" => {
                let rust_err = match self.matcher_rust(patterns) {
                    Ok(matcher) => {
                        return Ok(PatternMatcher::RustRegex(matcher));
                    }
                    Err(err) => err,
                };
                log::debug!(
                    "error building Rust regex in hybrid mode:\n{}",
                    rust_err,
                );

                let pcre_err = match self.matcher_engine("pcre2", patterns) {
                    Ok(matcher) => return Ok(matcher),
                    Err(err) => err,
                };
                Err(From::from(format!(
                    "regex could not be compiled with either the default \
                     regex engine or with PCRE2.\n\n\
                     default regex engine error:\n{}\n{}\n{}\n\n\
                     PCRE2 regex engine error:\n{}",
                    "~".repeat(79),
                    rust_err,
                    "~".repeat(79),
                    pcre_err,
                )))
            }
            _ => Err(From::from(format!(
                "unrecognized regex engine '{}'",
                engine
            ))),
        }
    }

    /// Build a matcher using Rust's regex engine.
    ///
    /// If there was a problem building the matcher (such as a regex syntax
    /// error), then an error is returned.
    fn matcher_rust(&self, patterns: &[String]) -> Result<RustRegexMatcher> {
        let mut builder = RustRegexMatcherBuilder::new();
        builder
            .case_smart(self.case_smart())
            .case_insensitive(self.case_insensitive())
            .multi_line(true)
            .unicode(self.unicode())
            .octal(false)
            .fixed_strings(self.is_present("fixed-strings"))
            .whole_line(self.is_present("line-regexp"))
            .word(self.is_present("word-regexp"));
        if self.is_present("multiline") {
            builder.dot_matches_new_line(self.is_present("multiline-dotall"));
            if self.is_present("crlf") {
                builder.crlf(true).line_terminator(None);
            }
        } else {
            builder.line_terminator(Some(b'\n')).dot_matches_new_line(false);
            if self.is_present("crlf") {
                builder.crlf(true);
            }
            // We don't need to set this in multiline mode since mulitline
            // matchers don't use optimizations related to line terminators.
            // Moreover, a mulitline regex used with --null-data should
            // be allowed to match NUL bytes explicitly, which this would
            // otherwise forbid.
            if self.is_present("null-data") {
                builder.line_terminator(Some(b'\x00'));
            }
        }
        if let Some(limit) = self.regex_size_limit()? {
            builder.size_limit(limit);
        }
        if let Some(limit) = self.dfa_size_limit()? {
            builder.dfa_size_limit(limit);
        }
        match builder.build_many(patterns) {
            Ok(m) => Ok(m),
            Err(err) => Err(From::from(suggest_multiline(err.to_string()))),
        }
    }

    /// Build a matcher using PCRE2.
    ///
    /// If there was a problem building the matcher (such as a regex syntax
    /// error), then an error is returned.
    #[cfg(feature = "pcre2")]
    fn matcher_pcre2(&self, patterns: &[String]) -> Result<PCRE2RegexMatcher> {
        let mut builder = PCRE2RegexMatcherBuilder::new();
        builder
            .case_smart(self.case_smart())
            .caseless(self.case_insensitive())
            .multi_line(true)
            .fixed_strings(self.is_present("fixed-strings"))
            .whole_line(self.is_present("line-regexp"))
            .word(self.is_present("word-regexp"));
        // For whatever reason, the JIT craps out during regex compilation with
        // a "no more memory" error on 32 bit systems. So don't use it there.
        if cfg!(target_pointer_width = "64") {
            builder
                .jit_if_available(true)
                // The PCRE2 docs say that 32KB is the default, and that 1MB
                // should be big enough for anything. But let's crank it to
                // 10MB.
                .max_jit_stack_size(Some(10 * (1 << 20)));
        }
        if self.unicode() {
            builder.utf(true).ucp(true);
        }
        if self.is_present("multiline") {
            builder.dotall(self.is_present("multiline-dotall"));
        }
        if self.is_present("crlf") {
            builder.crlf(true);
        }
        Ok(builder.build_many(patterns)?)
    }

    /// Build a JSON printer that writes results to the given writer.
    fn printer_json<W: io::Write>(&self, wtr: W) -> Result<JSON<W>> {
        let mut builder = JSONBuilder::new();
        builder
            .pretty(false)
            .max_matches(self.max_count()?)
            .always_begin_end(false);
        Ok(builder.build(wtr))
    }

    /// Build a Standard printer that writes results to the given writer.
    ///
    /// The given paths are used to configure aspects of the printer.
    ///
    /// If `separator_search` is true, then the returned printer will assume
    /// the responsibility of printing a separator between each set of
    /// search results, when appropriate (e.g., when contexts are enabled).
    /// When it's set to false, the caller is responsible for handling
    /// separators.
    ///
    /// In practice, we want the printer to handle it in the single threaded
    /// case but not in the multi-threaded case.
    fn printer_standard<W: WriteColor>(
        &self,
        paths: &[PathBuf],
        wtr: W,
        separator_search: bool,
    ) -> Result<Standard<W>> {
        let mut builder = StandardBuilder::new();
        builder
            .color_specs(self.color_specs()?)
            .hyperlink(self.hyperlink_config()?)
            .stats(self.stats())
            .heading(self.heading())
            .path(self.with_filename(paths))
            .only_matching(self.is_present("only-matching"))
            .per_match(self.is_present("vimgrep"))
            .per_match_one_line(true)
            .replacement(self.replacement())
            .max_columns(self.max_columns()?)
            .max_columns_preview(self.max_columns_preview())
            .max_matches(self.max_count()?)
            .column(self.column())
            .byte_offset(self.is_present("byte-offset"))
            .trim_ascii(self.is_present("trim"))
            .separator_search(None)
            .separator_context(self.context_separator())
            .separator_field_match(self.field_match_separator())
            .separator_field_context(self.field_context_separator())
            .separator_path(self.path_separator()?)
            .path_terminator(self.path_terminator());
        if separator_search {
            builder.separator_search(self.file_separator()?);
        }
        Ok(builder.build(wtr))
    }

    /// Build a Summary printer that writes results to the given writer.
    ///
    /// The given paths are used to configure aspects of the printer.
    ///
    /// This panics if the output format is not `OutputKind::Summary`.
    fn printer_summary<W: WriteColor>(
        &self,
        paths: &[PathBuf],
        wtr: W,
    ) -> Result<Summary<W>> {
        let mut builder = SummaryBuilder::new();
        builder
            .kind(self.summary_kind().expect("summary format"))
            .color_specs(self.color_specs()?)
            .hyperlink(self.hyperlink_config()?)
            .stats(self.stats())
            .path(self.with_filename(paths))
            .max_matches(self.max_count()?)
            .exclude_zero(!self.is_present("include-zero"))
            .separator_field(b":".to_vec())
            .separator_path(self.path_separator()?)
            .path_terminator(self.path_terminator());
        Ok(builder.build(wtr))
    }

    /// Build a searcher from the command line parameters.
    fn searcher(&self, paths: &[PathBuf]) -> Result<Searcher> {
        let (ctx_before, ctx_after) = self.contexts()?;
        let line_term = if self.is_present("crlf") {
            LineTerminator::crlf()
        } else if self.is_present("null-data") {
            LineTerminator::byte(b'\x00')
        } else {
            LineTerminator::byte(b'\n')
        };
        let mut builder = SearcherBuilder::new();
        builder
            .line_terminator(line_term)
            .invert_match(self.is_present("invert-match"))
            .line_number(self.line_number(paths))
            .multi_line(self.is_present("multiline"))
            .before_context(ctx_before)
            .after_context(ctx_after)
            .passthru(self.is_present("passthru"))
            .memory_map(self.mmap_choice(paths))
            .stop_on_nonmatch(self.is_present("stop-on-nonmatch"));
        match self.encoding()? {
            EncodingMode::Some(enc) => {
                builder.encoding(Some(enc));
            }
            EncodingMode::Auto => {} // default for the searcher
            EncodingMode::Disabled => {
                builder.bom_sniffing(false);
            }
        }
        Ok(builder.build())
    }

    /// Return a builder for recursively traversing a directory while
    /// respecting ignore rules.
    ///
    /// If there was a problem parsing the CLI arguments necessary for
    /// constructing the builder, then this returns an error.
    fn walker_builder(
        &self,
        paths: &[PathBuf],
        threads: usize,
    ) -> Result<WalkBuilder> {
        let mut builder = WalkBuilder::new(&paths[0]);
        for path in &paths[1..] {
            builder.add(path);
        }
        if !self.no_ignore_files() {
            for path in self.ignore_paths() {
                if let Some(err) = builder.add_ignore(path) {
                    ignore_message!("{}", err);
                }
            }
        }
        builder
            .max_depth(self.usize_of("max-depth")?)
            .follow_links(self.is_present("follow"))
            .max_filesize(self.max_file_size()?)
            .threads(threads)
            .same_file_system(self.is_present("one-file-system"))
            .skip_stdout(!self.is_present("files"))
            .overrides(self.overrides()?)
            .types(self.types()?)
            .hidden(!self.hidden())
            .parents(!self.no_ignore_parent())
            .ignore(!self.no_ignore_dot())
            .git_global(!self.no_ignore_vcs() && !self.no_ignore_global())
            .git_ignore(!self.no_ignore_vcs())
            .git_exclude(!self.no_ignore_vcs() && !self.no_ignore_exclude())
            .require_git(!self.is_present("no-require-git"))
            .ignore_case_insensitive(self.ignore_file_case_insensitive());
        if !self.no_ignore() && !self.no_ignore_dot() {
            builder.add_custom_ignore_filename(".rgignore");
        }
        self.sort_by()?.configure_builder_sort(&mut builder);
        Ok(builder)
    }
}

/// Mid level routines for converting command line arguments into various types
/// of data structures.
///
/// Methods are sorted alphabetically.
impl ArgMatches {
    /// Returns the form of binary detection to perform on files that are
    /// implicitly searched via recursive directory traversal.
    fn binary_detection_implicit(&self) -> BinaryDetection {
        let none = self.is_present("text") || self.is_present("null-data");
        let convert =
            self.is_present("binary") || self.unrestricted_count() >= 3;
        if none {
            BinaryDetection::none()
        } else if convert {
            BinaryDetection::convert(b'\x00')
        } else {
            BinaryDetection::quit(b'\x00')
        }
    }

    /// Returns the form of binary detection to perform on files that are
    /// explicitly searched via the user invoking ripgrep on a particular
    /// file or files or stdin.
    ///
    /// In general, this should never be BinaryDetection::quit, since that acts
    /// as a filter (but quitting immediately once a NUL byte is seen), and we
    /// should never filter out files that the user wants to explicitly search.
    fn binary_detection_explicit(&self) -> BinaryDetection {
        let none = self.is_present("text") || self.is_present("null-data");
        if none {
            BinaryDetection::none()
        } else {
            BinaryDetection::convert(b'\x00')
        }
    }

    /// Returns true if the command line configuration implies that a match
    /// can never be shown.
    fn can_never_match(&self, patterns: &[String]) -> bool {
        patterns.is_empty() || self.max_count().ok() == Some(Some(0))
    }

    /// Returns true if and only if case should be ignore.
    ///
    /// If --case-sensitive is present, then case is never ignored, even if
    /// --ignore-case is present.
    fn case_insensitive(&self) -> bool {
        self.is_present("ignore-case") && !self.is_present("case-sensitive")
    }

    /// Returns true if and only if smart case has been enabled.
    ///
    /// If either --ignore-case of --case-sensitive are present, then smart
    /// case is disabled.
    fn case_smart(&self) -> bool {
        self.is_present("smart-case")
            && !self.is_present("ignore-case")
            && !self.is_present("case-sensitive")
    }

    /// Returns the user's color choice based on command line parameters and
    /// environment.
    fn color_choice(&self) -> ColorChoice {
        let preference = match self.value_of_lossy("color") {
            None => "auto".to_string(),
            Some(v) => v,
        };
        if preference == "always" {
            ColorChoice::Always
        } else if preference == "ansi" {
            ColorChoice::AlwaysAnsi
        } else if preference == "auto" {
            if std::io::stdout().is_terminal() || self.is_present("pretty") {
                ColorChoice::Auto
            } else {
                ColorChoice::Never
            }
        } else {
            ColorChoice::Never
        }
    }

    /// Returns the color specifications given by the user on the CLI.
    ///
    /// If the was a problem parsing any of the provided specs, then an error
    /// is returned.
    fn color_specs(&self) -> Result<ColorSpecs> {
        // Start with a default set of color specs.
        let mut specs = default_color_specs();
        for spec_str in self.values_of_lossy_vec("colors") {
            specs.push(spec_str.parse()?);
        }
        Ok(ColorSpecs::new(&specs))
    }

    /// Returns true if and only if column numbers should be shown.
    fn column(&self) -> bool {
        if self.is_present("no-column") {
            return false;
        }
        self.is_present("column") || self.is_present("vimgrep")
    }

    /// Returns the before and after contexts from the command line.
    ///
    /// If a context setting was absent, then `0` is returned.
    ///
    /// If there was a problem parsing the values from the user as an integer,
    /// then an error is returned.
    fn contexts(&self) -> Result<(usize, usize)> {
        let both = self.usize_of("context")?.unwrap_or(0);
        let after = self.usize_of("after-context")?.unwrap_or(both);
        let before = self.usize_of("before-context")?.unwrap_or(both);
        Ok((before, after))
    }

    /// Returns the unescaped context separator in UTF-8 bytes.
    ///
    /// If one was not provided, the default `--` is returned.
    /// If --no-context-separator is passed, None is returned.
    fn context_separator(&self) -> Option<Vec<u8>> {
        let nosep = self.is_present("no-context-separator");
        let sep = self.value_of_os("context-separator");
        match (nosep, sep) {
            (true, _) => None,
            (false, None) => Some(b"--".to_vec()),
            (false, Some(sep)) => Some(cli::unescape_os(&sep)),
        }
    }

    /// Returns whether the -c/--count or the --count-matches flags were
    /// passed from the command line.
    ///
    /// If --count-matches and --invert-match were passed in, behave
    /// as if --count and --invert-match were passed in (i.e. rg will
    /// count inverted matches as per existing behavior).
    fn counts(&self) -> (bool, bool) {
        let count = self.is_present("count");
        let count_matches = self.is_present("count-matches");
        let invert_matches = self.is_present("invert-match");
        let only_matching = self.is_present("only-matching");
        if count_matches && invert_matches {
            // Treat `-v --count-matches` as `-v -c`.
            (true, false)
        } else if count && only_matching {
            // Treat `-c --only-matching` as `--count-matches`.
            (false, true)
        } else {
            (count, count_matches)
        }
    }

    /// Parse the dfa-size-limit argument option into a byte count.
    fn dfa_size_limit(&self) -> Result<Option<usize>> {
        let r = self.parse_human_readable_size("dfa-size-limit")?;
        u64_to_usize("dfa-size-limit", r)
    }

    /// Returns the encoding mode to use.
    ///
    /// This only returns an encoding if one is explicitly specified. Otherwise
    /// if set to automatic, the Searcher will do BOM sniffing for UTF-16
    /// and transcode seamlessly. If disabled, no BOM sniffing nor transcoding
    /// will occur.
    fn encoding(&self) -> Result<EncodingMode> {
        if self.is_present("no-encoding") {
            return Ok(EncodingMode::Auto);
        }

        let label = match self.value_of_lossy("encoding") {
            None => return Ok(EncodingMode::Auto),
            Some(label) => label,
        };

        if label == "auto" {
            return Ok(EncodingMode::Auto);
        } else if label == "none" {
            return Ok(EncodingMode::Disabled);
        }

        Ok(EncodingMode::Some(Encoding::new(&label)?))
    }

    /// Return the file separator to use based on the CLI configuration.
    fn file_separator(&self) -> Result<Option<Vec<u8>>> {
        // File separators are only used for the standard grep-line format.
        if self.output_kind() != OutputKind::Standard {
            return Ok(None);
        }

        let (ctx_before, ctx_after) = self.contexts()?;
        Ok(if self.heading() {
            Some(b"".to_vec())
        } else if ctx_before > 0 || ctx_after > 0 {
            self.context_separator()
        } else {
            None
        })
    }

    /// Returns true if and only if matches should be grouped with file name
    /// headings.
    fn heading(&self) -> bool {
        if self.is_present("no-heading") || self.is_present("vimgrep") {
            false
        } else {
            std::io::stdout().is_terminal()
                || self.is_present("heading")
                || self.is_present("pretty")
        }
    }

    /// Returns true if and only if hidden files/directories should be
    /// searched.
    fn hidden(&self) -> bool {
        self.is_present("hidden") || self.unrestricted_count() >= 2
    }

    /// Returns the hyperlink pattern to use. A default pattern suitable
    /// for the current system is used if the value is not set.
    ///
    /// If an invalid pattern is provided, then an error is returned.
    fn hyperlink_config(&self) -> Result<HyperlinkConfig> {
        let mut env = HyperlinkEnvironment::new();
        env.host(hostname(self.value_of_os("hostname-bin")))
            .wsl_prefix(wsl_prefix());
        let fmt: HyperlinkFormat =
            match self.value_of_lossy("hyperlink-format") {
                None => "default".parse().unwrap(),
                Some(format) => match format.parse() {
                    Ok(format) => format,
                    Err(err) => {
                        let msg = format!("invalid hyperlink format: {err}");
                        return Err(msg.into());
                    }
                },
            };
        log::debug!("hyperlink format: {:?}", fmt.to_string());
        Ok(HyperlinkConfig::new(env, fmt))
    }

    /// Returns true if ignore files should be processed case insensitively.
    fn ignore_file_case_insensitive(&self) -> bool {
        self.is_present("ignore-file-case-insensitive")
    }

    /// Return all of the ignore file paths given on the command line.
    fn ignore_paths(&self) -> Vec<PathBuf> {
        let paths = match self.values_of_os("ignore-file") {
            None => return vec![],
            Some(paths) => paths,
        };
        paths.map(|p| Path::new(p).to_path_buf()).collect()
    }

    /// Returns true if and only if ripgrep is invoked in a way where it knows
    /// it search exactly one thing.
    fn is_one_search(&self, paths: &[PathBuf]) -> bool {
        if paths.len() != 1 {
            return false;
        }
        self.is_only_stdin(paths) || paths[0].is_file()
    }

    /// Returns true if and only if we're only searching a single thing and
    /// that thing is stdin.
    fn is_only_stdin(&self, paths: &[PathBuf]) -> bool {
        paths == [Path::new("-")]
    }

    /// Returns true if and only if we should show line numbers.
    fn line_number(&self, paths: &[PathBuf]) -> bool {
        if self.output_kind() == OutputKind::Summary {
            return false;
        }
        if self.is_present("no-line-number") {
            return false;
        }
        if self.output_kind() == OutputKind::JSON {
            return true;
        }

        // A few things can imply counting line numbers. In particular, we
        // generally want to show line numbers by default when printing to a
        // tty for human consumption, except for one interesting case: when
        // we're only searching stdin. This makes pipelines work as expected.
        (std::io::stdout().is_terminal() && !self.is_only_stdin(paths))
            || self.is_present("line-number")
            || self.is_present("column")
            || self.is_present("pretty")
            || self.is_present("vimgrep")
    }

    /// The maximum number of columns allowed on each line.
    ///
    /// If `0` is provided, then this returns `None`.
    fn max_columns(&self) -> Result<Option<u64>> {
        Ok(self.usize_of_nonzero("max-columns")?.map(|n| n as u64))
    }

    /// Returns true if and only if a preview should be shown for lines that
    /// exceed the maximum column limit.
    fn max_columns_preview(&self) -> bool {
        self.is_present("max-columns-preview")
    }

    /// The maximum number of matches permitted.
    fn max_count(&self) -> Result<Option<u64>> {
        Ok(self.usize_of("max-count")?.map(|n| n as u64))
    }

    /// Parses the max-filesize argument option into a byte count.
    fn max_file_size(&self) -> Result<Option<u64>> {
        self.parse_human_readable_size("max-filesize")
    }

    /// Returns whether we should attempt to use memory maps or not.
    fn mmap_choice(&self, paths: &[PathBuf]) -> MmapChoice {
        // SAFETY: Memory maps are difficult to impossible to encapsulate
        // safely in a portable way that doesn't simultaneously negate some of
        // the benfits of using memory maps. For ripgrep's use, we never mutate
        // a memory map and generally never store the contents of memory map
        // in a data structure that depends on immutability. Generally
        // speaking, the worst thing that can happen is a SIGBUS (if the
        // underlying file is truncated while reading it), which will cause
        // ripgrep to abort. This reasoning should be treated as suspect.
        let maybe = unsafe { MmapChoice::auto() };
        let never = MmapChoice::never();
        if self.is_present("no-mmap") {
            never
        } else if self.is_present("mmap") {
            maybe
        } else if paths.len() <= 10 && paths.iter().all(|p| p.is_file()) {
            // If we're only searching a few paths and all of them are
            // files, then memory maps are probably faster.
            maybe
        } else {
            never
        }
    }

    /// Returns true if ignore files should be ignored.
    fn no_ignore(&self) -> bool {
        self.is_present("no-ignore") || self.unrestricted_count() >= 1
    }

    /// Returns true if .ignore files should be ignored.
    fn no_ignore_dot(&self) -> bool {
        self.is_present("no-ignore-dot") || self.no_ignore()
    }

    /// Returns true if local exclude (ignore) files should be ignored.
    fn no_ignore_exclude(&self) -> bool {
        self.is_present("no-ignore-exclude") || self.no_ignore()
    }

    /// Returns true if explicitly given ignore files should be ignored.
    fn no_ignore_files(&self) -> bool {
        // We don't look at no-ignore here because --no-ignore is explicitly
        // documented to not override --ignore-file. We could change this, but
        // it would be a fairly severe breaking change.
        self.is_present("no-ignore-files")
    }

    /// Returns true if global ignore files should be ignored.
    fn no_ignore_global(&self) -> bool {
        self.is_present("no-ignore-global") || self.no_ignore()
    }

    /// Returns true if parent ignore files should be ignored.
    fn no_ignore_parent(&self) -> bool {
        self.is_present("no-ignore-parent") || self.no_ignore()
    }

    /// Returns true if VCS ignore files should be ignored.
    fn no_ignore_vcs(&self) -> bool {
        self.is_present("no-ignore-vcs") || self.no_ignore()
    }

    /// Determine the type of output we should produce.
    fn output_kind(&self) -> OutputKind {
        if self.is_present("quiet") {
            // While we don't technically print results (or aggregate results)
            // in quiet mode, we still support the --stats flag, and those
            // stats are computed by the Summary printer for now.
            return OutputKind::Summary;
        } else if self.is_present("json") {
            return OutputKind::JSON;
        }

        let (count, count_matches) = self.counts();
        let summary = count
            || count_matches
            || self.is_present("files-with-matches")
            || self.is_present("files-without-match");
        if summary {
            OutputKind::Summary
        } else {
            OutputKind::Standard
        }
    }

    /// Builds the set of glob overrides from the command line flags.
    fn overrides(&self) -> Result<Override> {
        let globs = self.values_of_lossy_vec("glob");
        let iglobs = self.values_of_lossy_vec("iglob");
        if globs.is_empty() && iglobs.is_empty() {
            return Ok(Override::empty());
        }

        let mut builder = OverrideBuilder::new(current_dir()?);
        // Make all globs case insensitive with --glob-case-insensitive.
        if self.is_present("glob-case-insensitive") {
            builder.case_insensitive(true).unwrap();
        }
        for glob in globs {
            builder.add(&glob)?;
        }
        // This only enables case insensitivity for subsequent globs.
        builder.case_insensitive(true).unwrap();
        for glob in iglobs {
            builder.add(&glob)?;
        }
        Ok(builder.build()?)
    }

    /// Return all file paths that ripgrep should search.
    ///
    /// If no paths were given, then this returns an empty list.
    fn paths(&self) -> Vec<PathBuf> {
        let mut paths: Vec<PathBuf> = match self.values_of_os("path") {
            None => vec![],
            Some(paths) => paths.map(|p| Path::new(p).to_path_buf()).collect(),
        };
        // If --file, --files or --regexp is given, then the first path is
        // always in `pattern`.
        if self.is_present("file")
            || self.is_present("files")
            || self.is_present("regexp")
        {
            if let Some(path) = self.value_of_os("pattern") {
                paths.insert(0, Path::new(path).to_path_buf());
            }
        }
        paths
    }

    /// Return the default path that ripgrep should search. This should only
    /// be used when ripgrep is not otherwise given at least one file path
    /// as a positional argument.
    fn path_default(&self) -> PathBuf {
        let file_is_stdin = self
            .values_of_os("file")
            .map_or(false, |mut files| files.any(|f| f == "-"));
        let search_cwd = !cli::is_readable_stdin()
            || (self.is_present("file") && file_is_stdin)
            || self.is_present("files")
            || self.is_present("type-list")
            || self.is_present("pcre2-version");
        if search_cwd {
            Path::new("./").to_path_buf()
        } else {
            Path::new("-").to_path_buf()
        }
    }

    /// Returns the unescaped path separator as a single byte, if one exists.
    ///
    /// If the provided path separator is more than a single byte, then an
    /// error is returned.
    fn path_separator(&self) -> Result<Option<u8>> {
        let sep = match self.value_of_os("path-separator") {
            None => return Ok(None),
            Some(sep) => cli::unescape_os(&sep),
        };
        if sep.is_empty() {
            Ok(None)
        } else if sep.len() > 1 {
            Err(From::from(format!(
                "A path separator must be exactly one byte, but \
                 the given separator is {} bytes: {}\n\
                 In some shells on Windows '/' is automatically \
                 expanded. Use '//' instead.",
                sep.len(),
                cli::escape(&sep),
            )))
        } else {
            Ok(Some(sep[0]))
        }
    }

    /// Returns the byte that should be used to terminate paths.
    ///
    /// Typically, this is only set to `\x00` when the --null flag is provided,
    /// and `None` otherwise.
    fn path_terminator(&self) -> Option<u8> {
        if self.is_present("null") {
            Some(b'\x00')
        } else {
            None
        }
    }

    /// Returns the unescaped field context separator. If one wasn't specified,
    /// then '-' is used as the default.
    fn field_context_separator(&self) -> Vec<u8> {
        match self.value_of_os("field-context-separator") {
            None => b"-".to_vec(),
            Some(sep) => cli::unescape_os(&sep),
        }
    }

    /// Returns the unescaped field match separator. If one wasn't specified,
    /// then ':' is used as the default.
    fn field_match_separator(&self) -> Vec<u8> {
        match self.value_of_os("field-match-separator") {
            None => b":".to_vec(),
            Some(sep) => cli::unescape_os(&sep),
        }
    }

    /// Get a sequence of all available patterns from the command line.
    /// This includes reading the -e/--regexp and -f/--file flags.
    ///
    /// If any pattern is invalid UTF-8, then an error is returned.
    fn patterns(&self) -> Result<Vec<String>> {
        if self.is_present("files") || self.is_present("type-list") {
            return Ok(vec![]);
        }
        let mut seen = HashSet::new();
        let mut pats = vec![];
        let mut add = |pat: String| {
            if !seen.contains(&pat) {
                seen.insert(pat.clone());
                pats.push(pat);
            }
        };
        match self.values_of_os("regexp") {
            None => {
                if self.values_of_os("file").is_none() {
                    if let Some(os_pat) = self.value_of_os("pattern") {
                        add(self.pattern_from_os_str(os_pat)?);
                    }
                }
            }
            Some(os_pats) => {
                for os_pat in os_pats {
                    add(self.pattern_from_os_str(os_pat)?);
                }
            }
        }
        if let Some(paths) = self.values_of_os("file") {
            for path in paths {
                if path == "-" {
                    let it = cli::patterns_from_stdin()?
                        .into_iter()
                        .map(|p| self.pattern_from_string(p));
                    for pat in it {
                        add(pat);
                    }
                } else {
                    let it = cli::patterns_from_path(path)?
                        .into_iter()
                        .map(|p| self.pattern_from_string(p));
                    for pat in it {
                        add(pat);
                    }
                }
            }
        }
        Ok(pats)
    }

    /// Converts an OsStr pattern to a String pattern. The pattern is escaped
    /// if -F/--fixed-strings is set.
    ///
    /// If the pattern is not valid UTF-8, then an error is returned.
    fn pattern_from_os_str(&self, pat: &OsStr) -> Result<String> {
        let s = cli::pattern_from_os(pat)?;
        Ok(self.pattern_from_str(s))
    }

    /// Converts a &str pattern to a String pattern. The pattern is escaped
    /// if -F/--fixed-strings is set.
    fn pattern_from_str(&self, pat: &str) -> String {
        self.pattern_from_string(pat.to_string())
    }

    /// Applies additional processing on the given pattern if necessary
    /// (such as escaping meta characters or turning it into a line regex).
    fn pattern_from_string(&self, pat: String) -> String {
        if pat.is_empty() {
            // This would normally just be an empty string, which works on its
            // own, but if the patterns are joined in a set of alternations,
            // then you wind up with `foo|`, which is currently invalid in
            // Rust's regex engine.
            "(?:)".to_string()
        } else {
            pat
        }
    }

    /// Returns the preprocessor command if one was specified.
    fn preprocessor(&self) -> Option<PathBuf> {
        let path = match self.value_of_os("pre") {
            None => return None,
            Some(path) => path,
        };
        if path.is_empty() {
            return None;
        }
        Some(Path::new(path).to_path_buf())
    }

    /// Builds the set of globs for filtering files to apply to the --pre
    /// flag. If no --pre-globs are available, then this always returns an
    /// empty set of globs.
    fn preprocessor_globs(&self) -> Result<Override> {
        let globs = self.values_of_lossy_vec("pre-glob");
        if globs.is_empty() {
            return Ok(Override::empty());
        }
        let mut builder = OverrideBuilder::new(current_dir()?);
        for glob in globs {
            builder.add(&glob)?;
        }
        Ok(builder.build()?)
    }

    /// Parse the regex-size-limit argument option into a byte count.
    fn regex_size_limit(&self) -> Result<Option<usize>> {
        let r = self.parse_human_readable_size("regex-size-limit")?;
        u64_to_usize("regex-size-limit", r)
    }

    /// Returns the replacement string as UTF-8 bytes if it exists.
    fn replacement(&self) -> Option<Vec<u8>> {
        self.value_of_lossy("replace").map(|s| s.into_bytes())
    }

    /// Returns the sorting criteria based on command line parameters.
    fn sort_by(&self) -> Result<SortBy> {
        // For backcompat, continue supporting deprecated --sort-files flag.
        if self.is_present("sort-files") {
            return Ok(SortBy::asc(SortByKind::Path));
        }
        let sortby = match self.value_of_lossy("sort") {
            None => match self.value_of_lossy("sortr") {
                None => return Ok(SortBy::none()),
                Some(choice) => SortBy::desc(SortByKind::new(&choice)),
            },
            Some(choice) => SortBy::asc(SortByKind::new(&choice)),
        };
        Ok(sortby)
    }

    /// Returns true if and only if aggregate statistics for a search should
    /// be tracked.
    ///
    /// Generally, this is only enabled when explicitly requested by in the
    /// command line arguments via the --stats flag, but this can also be
    /// enabled implicitly via the output format, e.g., for JSON Lines.
    fn stats(&self) -> bool {
        self.output_kind() == OutputKind::JSON || self.is_present("stats")
    }

    /// When the output format is `Summary`, this returns the type of summary
    /// output to show.
    ///
    /// This returns `None` if the output format is not `Summary`.
    fn summary_kind(&self) -> Option<SummaryKind> {
        let (count, count_matches) = self.counts();
        if self.is_present("quiet") {
            Some(SummaryKind::Quiet)
        } else if count_matches {
            Some(SummaryKind::CountMatches)
        } else if count {
            Some(SummaryKind::Count)
        } else if self.is_present("files-with-matches") {
            Some(SummaryKind::PathWithMatch)
        } else if self.is_present("files-without-match") {
            Some(SummaryKind::PathWithoutMatch)
        } else {
            None
        }
    }

    /// Return the number of threads that should be used for parallelism.
    fn threads(&self) -> Result<usize> {
        if self.sort_by()?.kind != SortByKind::None {
            return Ok(1);
        }
        let threads = self.usize_of("threads")?.unwrap_or(0);
        let available =
            std::thread::available_parallelism().map_or(1, |n| n.get());
        Ok(if threads == 0 { std::cmp::min(12, available) } else { threads })
    }

    /// Builds a file type matcher from the command line flags.
    fn types(&self) -> Result<Types> {
        let mut builder = TypesBuilder::new();
        builder.add_defaults();
        for ty in self.values_of_lossy_vec("type-clear") {
            builder.clear(&ty);
        }
        for def in self.values_of_lossy_vec("type-add") {
            builder.add_def(&def)?;
        }
        for ty in self.values_of_lossy_vec("type") {
            builder.select(&ty);
        }
        for ty in self.values_of_lossy_vec("type-not") {
            builder.negate(&ty);
        }
        builder.build().map_err(From::from)
    }

    /// Returns the number of times the `unrestricted` flag is provided.
    fn unrestricted_count(&self) -> u64 {
        self.occurrences_of("unrestricted")
    }

    /// Returns true if and only if Unicode mode should be enabled.
    fn unicode(&self) -> bool {
        // Unicode mode is enabled by default, so only disable it when
        // --no-unicode is given explicitly.
        !(self.is_present("no-unicode") || self.is_present("no-pcre2-unicode"))
    }

    /// Returns true if and only if file names containing each match should
    /// be emitted.
    fn with_filename(&self, paths: &[PathBuf]) -> bool {
        if self.is_present("no-filename") {
            false
        } else {
            let path_stdin = Path::new("-");
            self.is_present("with-filename")
                || self.is_present("vimgrep")
                || paths.len() > 1
                || paths
                    .get(0)
                    .map_or(false, |p| p != path_stdin && p.is_dir())
        }
    }
}

/// Lower level generic helper methods for teasing values out of clap.
impl ArgMatches {
    /// Like values_of_lossy, but returns an empty vec if the flag is not
    /// present.
    fn values_of_lossy_vec(&self, name: &str) -> Vec<String> {
        self.values_of_lossy(name).unwrap_or_else(Vec::new)
    }

    /// Safely reads an arg value with the given name, and if it's present,
    /// tries to parse it as a usize value.
    ///
    /// If the number is zero, then it is considered absent and `None` is
    /// returned.
    fn usize_of_nonzero(&self, name: &str) -> Result<Option<usize>> {
        let n = match self.usize_of(name)? {
            None => return Ok(None),
            Some(n) => n,
        };
        Ok(if n == 0 { None } else { Some(n) })
    }

    /// Safely reads an arg value with the given name, and if it's present,
    /// tries to parse it as a usize value.
    fn usize_of(&self, name: &str) -> Result<Option<usize>> {
        match self.value_of_lossy(name) {
            None => Ok(None),
            Some(v) => v.parse().map(Some).map_err(From::from),
        }
    }

    /// Parses an argument of the form `[0-9]+(KMG)?`.
    ///
    /// If the aforementioned format is not recognized, then this returns an
    /// error.
    fn parse_human_readable_size(
        &self,
        arg_name: &str,
    ) -> Result<Option<u64>> {
        let size = match self.value_of_lossy(arg_name) {
            None => return Ok(None),
            Some(size) => size,
        };
        Ok(Some(cli::parse_human_readable_size(&size)?))
    }
}

/// The following methods mostly dispatch to the underlying clap methods
/// directly. Methods that would otherwise get a single value will fetch all
/// values and return the last one. (Clap returns the first one.) We only
/// define the ones we need.
impl ArgMatches {
    fn is_present(&self, name: &str) -> bool {
        self.0.is_present(name)
    }

    fn occurrences_of(&self, name: &str) -> u64 {
        self.0.occurrences_of(name)
    }

    fn value_of_lossy(&self, name: &str) -> Option<String> {
        self.0.value_of_lossy(name).map(|s| s.into_owned())
    }

    fn values_of_lossy(&self, name: &str) -> Option<Vec<String>> {
        self.0.values_of_lossy(name)
    }

    fn value_of_os(&self, name: &str) -> Option<&OsStr> {
        self.0.value_of_os(name)
    }

    fn values_of_os(&self, name: &str) -> Option<clap::OsValues<'_>> {
        self.0.values_of_os(name)
    }
}

/// Inspect an error resulting from building a Rust regex matcher, and if it's
/// believed to correspond to a syntax error that another engine could handle,
/// then add a message to suggest the use of the engine flag.
fn suggest(msg: String) -> String {
    if let Some(pcre_msg) = suggest_pcre2(&msg) {
        return pcre_msg;
    }
    msg
}

/// Inspect an error resulting from building a Rust regex matcher, and if it's
/// believed to correspond to a syntax error that PCRE2 could handle, then
/// add a message to suggest the use of -P/--pcre2.
fn suggest_pcre2(msg: &str) -> Option<String> {
    #[cfg(feature = "pcre2")]
    fn suggest(msg: &str) -> Option<String> {
        if !msg.contains("backreferences") && !msg.contains("look-around") {
            None
        } else {
            Some(format!(
                "{}

Consider enabling PCRE2 with the --pcre2 flag, which can handle backreferences
and look-around.",
                msg
            ))
        }
    }

    #[cfg(not(feature = "pcre2"))]
    fn suggest(_: &str) -> Option<String> {
        None
    }

    suggest(msg)
}

fn suggest_multiline(msg: String) -> String {
    if msg.contains("the literal") && msg.contains("not allowed") {
        format!(
            "{}

Consider enabling multiline mode with the --multiline flag (or -U for short).
When multiline mode is enabled, new line characters can be matched.",
            msg
        )
    } else {
        msg
    }
}

/// Convert the result of parsing a human readable file size to a `usize`,
/// failing if the type does not fit.
fn u64_to_usize(arg_name: &str, value: Option<u64>) -> Result<Option<usize>> {
    use std::usize;

    let value = match value {
        None => return Ok(None),
        Some(value) => value,
    };
    if value <= usize::MAX as u64 {
        Ok(Some(value as usize))
    } else {
        Err(From::from(format!("number too large for {}", arg_name)))
    }
}

/// Sorts by an optional parameter.
//
/// If parameter is found to be `None`, both entries compare equal.
fn sort_by_option<T: Ord>(
    p1: &Option<T>,
    p2: &Option<T>,
    reverse: bool,
) -> std::cmp::Ordering {
    match (p1, p2, reverse) {
        (Some(p1), Some(p2), true) => p1.cmp(&p2).reverse(),
        (Some(p1), Some(p2), false) => p1.cmp(&p2),
        _ => std::cmp::Ordering::Equal,
    }
}

/// Returns a clap matches object if the given arguments parse successfully.
///
/// Otherwise, if an error occurred, then it is returned unless the error
/// corresponds to a `--help` or `--version` request. In which case, the
/// corresponding output is printed and the current process is exited
/// successfully.
fn clap_matches<I, T>(args: I) -> Result<clap::ArgMatches<'static>>
where
    I: IntoIterator<Item = T>,
    T: Into<OsString> + Clone,
{
    let err = match app::app().get_matches_from_safe(args) {
        Ok(matches) => return Ok(matches),
        Err(err) => err,
    };
    if err.use_stderr() {
        return Err(err.into());
    }
    // Explicitly ignore any error returned by write!. The most likely error
    // at this point is a broken pipe error, in which case, we want to ignore
    // it and exit quietly.
    //
    // (This is the point of this helper function. clap's functionality for
    // doing this will panic on a broken pipe error.)
    let _ = write!(io::stdout(), "{}", err);
    std::process::exit(0);
}

/// Attempts to discover the current working directory. This mostly just defers
/// to the standard library, however, such things will fail if ripgrep is in
/// a directory that no longer exists. We attempt some fallback mechanisms,
/// such as querying the PWD environment variable, but otherwise return an
/// error.
fn current_dir() -> Result<PathBuf> {
    let err = match env::current_dir() {
        Err(err) => err,
        Ok(cwd) => return Ok(cwd),
    };
    if let Some(cwd) = env::var_os("PWD") {
        if !cwd.is_empty() {
            return Ok(PathBuf::from(cwd));
        }
    }
    Err(format!(
        "failed to get current working directory: {} \
         --- did your CWD get deleted?",
        err,
    )
    .into())
}

/// Retrieves the hostname that ripgrep should use wherever a hostname is
/// required. Currently, that's just in the hyperlink format.
///
/// This works by first running the given binary program (if present and with
/// no arguments) to get the hostname after trimming leading and trailing
/// whitespace. If that fails for any reason, then it falls back to getting
/// the hostname via platform specific means (e.g., `gethostname` on Unix).
///
/// The purpose of `bin` is to make it possible for end users to override how
/// ripgrep determines the hostname.
fn hostname(bin: Option<&OsStr>) -> Option<String> {
    let Some(bin) = bin else { return platform_hostname() };
    let bin = match grep::cli::resolve_binary(bin) {
        Ok(bin) => bin,
        Err(err) => {
            log::debug!(
                "failed to run command '{bin:?}' to get hostname \
                 (falling back to platform hostname): {err}",
            );
            return platform_hostname();
        }
    };
    let mut cmd = std::process::Command::new(&bin);
    cmd.stdin(std::process::Stdio::null());
    let rdr = match grep::cli::CommandReader::new(&mut cmd) {
        Ok(rdr) => rdr,
        Err(err) => {
            log::debug!(
                "failed to spawn command '{bin:?}' to get \
                 hostname (falling back to platform hostname): {err}",
            );
            return platform_hostname();
        }
    };
    let out = match io::read_to_string(rdr) {
        Ok(out) => out,
        Err(err) => {
            log::debug!(
                "failed to read output from command '{bin:?}' to get \
                 hostname (falling back to platform hostname): {err}",
            );
            return platform_hostname();
        }
    };
    let hostname = out.trim();
    if hostname.is_empty() {
        log::debug!(
            "output from command '{bin:?}' is empty after trimming \
             leading and trailing whitespace (falling back to \
             platform hostname)",
        );
        return platform_hostname();
    }
    Some(hostname.to_string())
}

/// Attempts to get the hostname by using platform specific routines. For
/// example, this will do `gethostname` on Unix and `GetComputerNameExW` on
/// Windows.
fn platform_hostname() -> Option<String> {
    let hostname_os = match grep::cli::hostname() {
        Ok(x) => x,
        Err(err) => {
            log::debug!("could not get hostname: {}", err);
            return None;
        }
    };
    let Some(hostname) = hostname_os.to_str() else {
        log::debug!(
            "got hostname {:?}, but it's not valid UTF-8",
            hostname_os
        );
        return None;
    };
    Some(hostname.to_string())
}

/// Returns a value that is meant to fill in the `{wslprefix}` variable for
/// a user given hyperlink format. A WSL prefix is a share/network like thing
/// that is meant to permit Windows applications to open files stored within
/// a WSL drive.
///
/// If a WSL distro name is unavailable, not valid UTF-8 or this isn't running
/// in a Unix environment, then this returns None.
///
/// See: <https://learn.microsoft.com/en-us/windows/wsl/filesystems>
fn wsl_prefix() -> Option<String> {
    if !cfg!(unix) {
        return None;
    }
    let distro_os = env::var_os("WSL_DISTRO_NAME")?;
    let Some(distro) = distro_os.to_str() else {
        log::debug!(
            "found WSL_DISTRO_NAME={:?}, but value is not UTF-8",
            distro_os
        );
        return None;
    };
    Some(format!("wsl$/{distro}"))
}

/// Tries to assign a timestamp to every `Subject` in the vector to help with
/// sorting Subjects by time.
fn load_timestamps<G>(
    subjects: impl Iterator<Item = Subject>,
    get_time: G,
) -> Vec<(Option<std::time::SystemTime>, Subject)>
where
    G: Fn(&std::fs::Metadata) -> io::Result<std::time::SystemTime>,
{
    subjects
        .map(|s| (s.path().metadata().and_then(|m| get_time(&m)).ok(), s))
        .collect()
}