use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::sync::Lrc;
use rustc_data_structures::unord::UnordSet;
use rustc_errors::emitter::{DynEmitter, EmitterWriter};
use rustc_errors::json::JsonEmitter;
use rustc_errors::TerminalUrl;
use rustc_feature::UnstableFeatures;
use rustc_hir::def::Res;
use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LocalDefId};
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{HirId, Path};
use rustc_interface::interface;
use rustc_lint::{late_lint_mod, MissingDoc};
use rustc_middle::hir::nested_filter;
use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
use rustc_session::config::{self, CrateType, ErrorOutputType, ResolveDocLinks};
use rustc_session::Session;
use rustc_session::{lint, EarlyErrorHandler};
use rustc_span::symbol::sym;
use rustc_span::{source_map, Span};

use std::cell::RefCell;
use std::mem;
use std::rc::Rc;
use std::sync::LazyLock;

use crate::clean::inline::build_external_trait;
use crate::clean::{self, ItemId};
use crate::config::{Options as RustdocOptions, OutputFormat, RenderOptions};
use crate::formats::cache::Cache;
use crate::passes::{self, Condition::*};

pub(crate) use rustc_session::config::{Input, Options, UnstableOptions};

pub(crate) struct DocContext<'tcx> {
    pub(crate) tcx: TyCtxt<'tcx>,
    /// Used for normalization.
    ///
    /// Most of this logic is copied from rustc_lint::late.
    pub(crate) param_env: ParamEnv<'tcx>,
    /// Later on moved through `clean::Crate` into `cache`
    pub(crate) external_traits: Rc<RefCell<FxHashMap<DefId, clean::Trait>>>,
    /// Used while populating `external_traits` to ensure we don't process the same trait twice at
    /// the same time.
    pub(crate) active_extern_traits: DefIdSet,
    // The current set of parameter substitutions,
    // for expanding type aliases at the HIR level:
    /// Table `DefId` of type, lifetime, or const parameter -> substituted type, lifetime, or const
    pub(crate) args: DefIdMap<clean::SubstParam>,
    pub(crate) current_type_aliases: DefIdMap<usize>,
    /// Table synthetic type parameter for `impl Trait` in argument position -> bounds
    pub(crate) impl_trait_bounds: FxHashMap<ImplTraitParam, Vec<clean::GenericBound>>,
    /// Auto-trait or blanket impls processed so far, as `(self_ty, trait_def_id)`.
    // FIXME(eddyb) make this a `ty::TraitRef<'tcx>` set.
    pub(crate) generated_synthetics: FxHashSet<(Ty<'tcx>, DefId)>,
    pub(crate) auto_traits: Vec<DefId>,
    /// The options given to rustdoc that could be relevant to a pass.
    pub(crate) render_options: RenderOptions,
    /// This same cache is used throughout rustdoc, including in [`crate::html::render`].
    pub(crate) cache: Cache,
    /// Used by [`clean::inline`] to tell if an item has already been inlined.
    pub(crate) inlined: FxHashSet<ItemId>,
    /// Used by `calculate_doc_coverage`.
    pub(crate) output_format: OutputFormat,
    /// Used by `strip_private`.
    pub(crate) show_coverage: bool,
}

impl<'tcx> DocContext<'tcx> {
    pub(crate) fn sess(&self) -> &'tcx Session {
        self.tcx.sess
    }

    pub(crate) fn with_param_env<T, F: FnOnce(&mut Self) -> T>(
        &mut self,
        def_id: DefId,
        f: F,
    ) -> T {
        let old_param_env = mem::replace(&mut self.param_env, self.tcx.param_env(def_id));
        let ret = f(self);
        self.param_env = old_param_env;
        ret
    }

    /// Call the closure with the given parameters set as
    /// the substitutions for a type alias' RHS.
    pub(crate) fn enter_alias<F, R>(
        &mut self,
        args: DefIdMap<clean::SubstParam>,
        def_id: DefId,
        f: F,
    ) -> R
    where
        F: FnOnce(&mut Self) -> R,
    {
        let old_args = mem::replace(&mut self.args, args);
        *self.current_type_aliases.entry(def_id).or_insert(0) += 1;
        let r = f(self);
        self.args = old_args;
        if let Some(count) = self.current_type_aliases.get_mut(&def_id) {
            *count -= 1;
            if *count == 0 {
                self.current_type_aliases.remove(&def_id);
            }
        }
        r
    }

    /// Like `hir().local_def_id_to_hir_id()`, but skips calling it on fake DefIds.
    /// (This avoids a slice-index-out-of-bounds panic.)
    pub(crate) fn as_local_hir_id(tcx: TyCtxt<'_>, item_id: ItemId) -> Option<HirId> {
        match item_id {
            ItemId::DefId(real_id) => {
                real_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
            }
            // FIXME: Can this be `Some` for `Auto` or `Blanket`?
            _ => None,
        }
    }
}

/// Creates a new diagnostic `Handler` that can be used to emit warnings and errors.
///
/// If the given `error_format` is `ErrorOutputType::Json` and no `SourceMap` is given, a new one
/// will be created for the handler.
pub(crate) fn new_handler(
    error_format: ErrorOutputType,
    source_map: Option<Lrc<source_map::SourceMap>>,
    diagnostic_width: Option<usize>,
    unstable_opts: &UnstableOptions,
) -> rustc_errors::Handler {
    let fallback_bundle = rustc_errors::fallback_fluent_bundle(
        rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
        false,
    );
    let emitter: Box<DynEmitter> = match error_format {
        ErrorOutputType::HumanReadable(kind) => {
            let (short, color_config) = kind.unzip();
            Box::new(
                EmitterWriter::stderr(color_config, fallback_bundle)
                    .sm(source_map.map(|sm| sm as _))
                    .short_message(short)
                    .teach(unstable_opts.teach)
                    .diagnostic_width(diagnostic_width)
                    .track_diagnostics(unstable_opts.track_diagnostics)
                    .ui_testing(unstable_opts.ui_testing),
            )
        }
        ErrorOutputType::Json { pretty, json_rendered } => {
            let source_map = source_map.unwrap_or_else(|| {
                Lrc::new(source_map::SourceMap::new(source_map::FilePathMapping::empty()))
            });
            Box::new(
                JsonEmitter::stderr(
                    None,
                    source_map,
                    None,
                    fallback_bundle,
                    pretty,
                    json_rendered,
                    diagnostic_width,
                    false,
                    unstable_opts.track_diagnostics,
                    TerminalUrl::No,
                )
                .ui_testing(unstable_opts.ui_testing),
            )
        }
    };

    rustc_errors::Handler::with_emitter(emitter)
        .with_flags(unstable_opts.diagnostic_handler_flags(true))
}

/// Parse, resolve, and typecheck the given crate.
pub(crate) fn create_config(
    handler: &EarlyErrorHandler,
    RustdocOptions {
        input,
        crate_name,
        proc_macro_crate,
        error_format,
        diagnostic_width,
        libs,
        externs,
        mut cfgs,
        check_cfgs,
        codegen_options,
        unstable_opts,
        target,
        edition,
        maybe_sysroot,
        lint_opts,
        describe_lints,
        lint_cap,
        scrape_examples_options,
        expanded_args,
        ..
    }: RustdocOptions,
    RenderOptions { document_private, .. }: &RenderOptions,
) -> rustc_interface::Config {
    // Add the doc cfg into the doc build.
    cfgs.push("doc".to_string());

    let input = Input::File(input);

    // By default, rustdoc ignores all lints.
    // Specifically unblock lints relevant to documentation or the lint machinery itself.
    let mut lints_to_show = vec![
        // it's unclear whether these should be part of rustdoc directly (#77364)
        rustc_lint::builtin::MISSING_DOCS.name.to_string(),
        rustc_lint::builtin::INVALID_DOC_ATTRIBUTES.name.to_string(),
        // these are definitely not part of rustdoc, but we want to warn on them anyway.
        rustc_lint::builtin::RENAMED_AND_REMOVED_LINTS.name.to_string(),
        rustc_lint::builtin::UNKNOWN_LINTS.name.to_string(),
        rustc_lint::builtin::UNEXPECTED_CFGS.name.to_string(),
        // this lint is needed to support `#[expect]` attributes
        rustc_lint::builtin::UNFULFILLED_LINT_EXPECTATIONS.name.to_string(),
    ];
    lints_to_show.extend(crate::lint::RUSTDOC_LINTS.iter().map(|lint| lint.name.to_string()));

    let (lint_opts, lint_caps) = crate::lint::init_lints(lints_to_show, lint_opts, |lint| {
        Some((lint.name_lower(), lint::Allow))
    });

    let crate_types =
        if proc_macro_crate { vec![CrateType::ProcMacro] } else { vec![CrateType::Rlib] };
    let resolve_doc_links =
        if *document_private { ResolveDocLinks::All } else { ResolveDocLinks::Exported };
    let test = scrape_examples_options.map(|opts| opts.scrape_tests).unwrap_or(false);
    // plays with error output here!
    let sessopts = config::Options {
        maybe_sysroot,
        search_paths: libs,
        crate_types,
        lint_opts,
        lint_cap,
        cg: codegen_options,
        externs,
        target_triple: target,
        unstable_features: UnstableFeatures::from_environment(crate_name.as_deref()),
        actually_rustdoc: true,
        resolve_doc_links,
        unstable_opts,
        error_format,
        diagnostic_width,
        edition,
        describe_lints,
        crate_name,
        test,
        ..Options::default()
    };

    interface::Config {
        opts: sessopts,
        crate_cfg: interface::parse_cfgspecs(handler, cfgs),
        crate_check_cfg: interface::parse_check_cfg(handler, check_cfgs),
        input,
        output_file: None,
        output_dir: None,
        file_loader: None,
        locale_resources: rustc_driver::DEFAULT_LOCALE_RESOURCES,
        lint_caps,
        parse_sess_created: None,
        register_lints: Some(Box::new(crate::lint::register_lints)),
        override_queries: Some(|_sess, providers| {
            // We do not register late module lints, so this only runs `MissingDoc`.
            // Most lints will require typechecking, so just don't run them.
            providers.lint_mod = |tcx, module_def_id| late_lint_mod(tcx, module_def_id, MissingDoc);
            // hack so that `used_trait_imports` won't try to call typeck
            providers.used_trait_imports = |_, _| {
                static EMPTY_SET: LazyLock<UnordSet<LocalDefId>> = LazyLock::new(UnordSet::default);
                &EMPTY_SET
            };
            // In case typeck does end up being called, don't ICE in case there were name resolution errors
            providers.typeck = move |tcx, def_id| {
                // Closures' tables come from their outermost function,
                // as they are part of the same "inference environment".
                // This avoids emitting errors for the parent twice (see similar code in `typeck_with_fallback`)
                let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
                if typeck_root_def_id != def_id {
                    return tcx.typeck(typeck_root_def_id);
                }

                let hir = tcx.hir();
                let body = hir.body(hir.body_owned_by(def_id));
                debug!("visiting body for {def_id:?}");
                EmitIgnoredResolutionErrors::new(tcx).visit_body(body);
                (rustc_interface::DEFAULT_QUERY_PROVIDERS.typeck)(tcx, def_id)
            };
        }),
        make_codegen_backend: None,
        registry: rustc_driver::diagnostics_registry(),
        ice_file: None,
        expanded_args,
    }
}

pub(crate) fn run_global_ctxt(
    tcx: TyCtxt<'_>,
    show_coverage: bool,
    render_options: RenderOptions,
    output_format: OutputFormat,
) -> (clean::Crate, RenderOptions, Cache) {
    // Certain queries assume that some checks were run elsewhere
    // (see https://github.com/rust-lang/rust/pull/73566#issuecomment-656954425),
    // so type-check everything other than function bodies in this crate before running lints.

    // NOTE: this does not call `tcx.analysis()` so that we won't
    // typeck function bodies or run the default rustc lints.
    // (see `override_queries` in the `config`)

    // HACK(jynelson) this calls an _extremely_ limited subset of `typeck`
    // and might break if queries change their assumptions in the future.
    tcx.sess.time("type_collecting", || {
        tcx.hir().for_each_module(|module| tcx.ensure().collect_mod_item_types(module))
    });

    // NOTE: This is copy/pasted from typeck/lib.rs and should be kept in sync with those changes.
    tcx.sess.time("item_types_checking", || {
        tcx.hir().for_each_module(|module| tcx.ensure().check_mod_item_types(module))
    });
    tcx.sess.abort_if_errors();
    tcx.sess.time("missing_docs", || rustc_lint::check_crate(tcx));
    tcx.sess.time("check_mod_attrs", || {
        tcx.hir().for_each_module(|module| tcx.ensure().check_mod_attrs(module))
    });
    rustc_passes::stability::check_unused_or_stable_features(tcx);

    let auto_traits =
        tcx.all_traits().filter(|&trait_def_id| tcx.trait_is_auto(trait_def_id)).collect();

    let mut ctxt = DocContext {
        tcx,
        param_env: ParamEnv::empty(),
        external_traits: Default::default(),
        active_extern_traits: Default::default(),
        args: Default::default(),
        current_type_aliases: Default::default(),
        impl_trait_bounds: Default::default(),
        generated_synthetics: Default::default(),
        auto_traits,
        cache: Cache::new(render_options.document_private, render_options.document_hidden),
        inlined: FxHashSet::default(),
        output_format,
        render_options,
        show_coverage,
    };

    for cnum in tcx.crates(()) {
        crate::visit_lib::lib_embargo_visit_item(&mut ctxt, cnum.as_def_id());
    }

    // Small hack to force the Sized trait to be present.
    //
    // Note that in case of `#![no_core]`, the trait is not available.
    if let Some(sized_trait_did) = ctxt.tcx.lang_items().sized_trait() {
        let sized_trait = build_external_trait(&mut ctxt, sized_trait_did);
        ctxt.external_traits.borrow_mut().insert(sized_trait_did, sized_trait);
    }

    debug!("crate: {:?}", tcx.hir().krate());

    let mut krate = tcx.sess.time("clean_crate", || clean::krate(&mut ctxt));

    if krate.module.doc_value().is_empty() {
        let help = format!(
            "The following guide may be of use:\n\
            {}/rustdoc/how-to-write-documentation.html",
            crate::DOC_RUST_LANG_ORG_CHANNEL
        );
        tcx.struct_lint_node(
            crate::lint::MISSING_CRATE_LEVEL_DOCS,
            DocContext::as_local_hir_id(tcx, krate.module.item_id).unwrap(),
            "no documentation found for this crate's top-level module",
            |lint| lint.help(help),
        );
    }

    fn report_deprecated_attr(name: &str, diag: &rustc_errors::Handler, sp: Span) {
        let mut msg =
            diag.struct_span_warn(sp, format!("the `#![doc({name})]` attribute is deprecated"));
        msg.note(
            "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
            for more information",
        );

        if name == "no_default_passes" {
            msg.help("`#![doc(no_default_passes)]` no longer functions; you may want to use `#![doc(document_private_items)]`");
        } else if name.starts_with("passes") {
            msg.help("`#![doc(passes = \"...\")]` no longer functions; you may want to use `#![doc(document_private_items)]`");
        } else if name.starts_with("plugins") {
            msg.warn("`#![doc(plugins = \"...\")]` no longer functions; see CVE-2018-1000622 <https://nvd.nist.gov/vuln/detail/CVE-2018-1000622>");
        }

        msg.emit();
    }

    // Process all of the crate attributes, extracting plugin metadata along
    // with the passes which we are supposed to run.
    for attr in krate.module.attrs.lists(sym::doc) {
        let diag = ctxt.sess().diagnostic();

        let name = attr.name_or_empty();
        // `plugins = "..."`, `no_default_passes`, and `passes = "..."` have no effect
        if attr.is_word() && name == sym::no_default_passes {
            report_deprecated_attr("no_default_passes", diag, attr.span());
        } else if attr.value_str().is_some() {
            match name {
                sym::passes => {
                    report_deprecated_attr("passes = \"...\"", diag, attr.span());
                }
                sym::plugins => {
                    report_deprecated_attr("plugins = \"...\"", diag, attr.span());
                }
                _ => (),
            }
        }

        if attr.is_word() && name == sym::document_private_items {
            ctxt.render_options.document_private = true;
        }
    }

    info!("Executing passes");

    for p in passes::defaults(show_coverage) {
        let run = match p.condition {
            Always => true,
            WhenDocumentPrivate => ctxt.render_options.document_private,
            WhenNotDocumentPrivate => !ctxt.render_options.document_private,
            WhenNotDocumentHidden => !ctxt.render_options.document_hidden,
        };
        if run {
            debug!("running pass {}", p.pass.name);
            krate = tcx.sess.time(p.pass.name, || (p.pass.run)(krate, &mut ctxt));
        }
    }

    tcx.sess.time("check_lint_expectations", || tcx.check_expectations(Some(sym::rustdoc)));

    if tcx.sess.diagnostic().has_errors_or_lint_errors().is_some() {
        rustc_errors::FatalError.raise();
    }

    krate = tcx.sess.time("create_format_cache", || Cache::populate(&mut ctxt, krate));

    (krate, ctxt.render_options, ctxt.cache)
}

/// Due to <https://github.com/rust-lang/rust/pull/73566>,
/// the name resolution pass may find errors that are never emitted.
/// If typeck is called after this happens, then we'll get an ICE:
/// 'Res::Error found but not reported'. To avoid this, emit the errors now.
struct EmitIgnoredResolutionErrors<'tcx> {
    tcx: TyCtxt<'tcx>,
}

impl<'tcx> EmitIgnoredResolutionErrors<'tcx> {
    fn new(tcx: TyCtxt<'tcx>) -> Self {
        Self { tcx }
    }
}

impl<'tcx> Visitor<'tcx> for EmitIgnoredResolutionErrors<'tcx> {
    type NestedFilter = nested_filter::OnlyBodies;

    fn nested_visit_map(&mut self) -> Self::Map {
        // We need to recurse into nested closures,
        // since those will fallback to the parent for type checking.
        self.tcx.hir()
    }

    fn visit_path(&mut self, path: &Path<'tcx>, _id: HirId) {
        debug!("visiting path {path:?}");
        if path.res == Res::Err {
            // We have less context here than in rustc_resolve,
            // so we can only emit the name and span.
            // However we can give a hint that rustc_resolve will have more info.
            let label = format!(
                "could not resolve path `{}`",
                path.segments
                    .iter()
                    .map(|segment| segment.ident.as_str())
                    .intersperse("::")
                    .collect::<String>()
            );
            let mut err = rustc_errors::struct_span_err!(
                self.tcx.sess,
                path.span,
                E0433,
                "failed to resolve: {label}",
            );
            err.span_label(path.span, label);
            err.note("this error was originally ignored because you are running `rustdoc`");
            err.note("try running again with `rustc` or `cargo check` and you may get a more detailed error");
            err.emit();
        }
        // We could have an outer resolution that succeeded,
        // but with generic parameters that failed.
        // Recurse into the segments so we catch those too.
        intravisit::walk_path(self, path);
    }
}

/// `DefId` or parameter index (`ty::ParamTy.index`) of a synthetic type parameter
/// for `impl Trait` in argument position.
#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub(crate) enum ImplTraitParam {
    DefId(DefId),
    ParamIndex(u32),
}

impl From<DefId> for ImplTraitParam {
    fn from(did: DefId) -> Self {
        ImplTraitParam::DefId(did)
    }
}

impl From<u32> for ImplTraitParam {
    fn from(idx: u32) -> Self {
        ImplTraitParam::ParamIndex(idx)
    }
}