use crate::ty::print::{with_forced_trimmed_paths, FmtPrinter, PrettyPrinter};
use crate::ty::{self, BoundRegionKind, Region, Ty, TyCtxt};
use rustc_errors::pluralize;
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind};
use rustc_hir::def_id::DefId;
use rustc_span::symbol::Symbol;
use rustc_target::spec::abi;
use std::borrow::Cow;
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
use std::path::PathBuf;

#[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
pub struct ExpectedFound<T> {
    pub expected: T,
    pub found: T,
}

impl<T> ExpectedFound<T> {
    pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
        if a_is_expected {
            ExpectedFound { expected: a, found: b }
        } else {
            ExpectedFound { expected: b, found: a }
        }
    }
}

// Data structures used in type unification
#[derive(Copy, Clone, Debug, TypeVisitable, PartialEq, Eq)]
#[rustc_pass_by_value]
pub enum TypeError<'tcx> {
    Mismatch,
    ConstnessMismatch(ExpectedFound<ty::BoundConstness>),
    PolarityMismatch(ExpectedFound<ty::ImplPolarity>),
    UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
    AbiMismatch(ExpectedFound<abi::Abi>),
    Mutability,
    ArgumentMutability(usize),
    TupleSize(ExpectedFound<usize>),
    FixedArraySize(ExpectedFound<u64>),
    ArgCount,
    FieldMisMatch(Symbol, Symbol),

    RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
    RegionsInsufficientlyPolymorphic(BoundRegionKind, Region<'tcx>),
    RegionsPlaceholderMismatch,

    Sorts(ExpectedFound<Ty<'tcx>>),
    ArgumentSorts(ExpectedFound<Ty<'tcx>>, usize),
    IntMismatch(ExpectedFound<ty::IntVarValue>),
    FloatMismatch(ExpectedFound<ty::FloatTy>),
    Traits(ExpectedFound<DefId>),
    VariadicMismatch(ExpectedFound<bool>),

    /// Instantiating a type variable with the given type would have
    /// created a cycle (because it appears somewhere within that
    /// type).
    CyclicTy(Ty<'tcx>),
    CyclicConst(ty::Const<'tcx>),
    ProjectionMismatched(ExpectedFound<DefId>),
    ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>>),
    ConstMismatch(ExpectedFound<ty::Const<'tcx>>),

    IntrinsicCast,
    /// Safe `#[target_feature]` functions are not assignable to safe function pointers.
    TargetFeatureCast(DefId),
}

impl TypeError<'_> {
    pub fn involves_regions(self) -> bool {
        match self {
            TypeError::RegionsDoesNotOutlive(_, _)
            | TypeError::RegionsInsufficientlyPolymorphic(_, _)
            | TypeError::RegionsPlaceholderMismatch => true,
            _ => false,
        }
    }
}

/// Explains the source of a type err in a short, human readable way. This is meant to be placed
/// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
/// afterwards to present additional details, particularly when it comes to lifetime-related
/// errors.
impl<'tcx> TypeError<'tcx> {
    pub fn to_string(self, tcx: TyCtxt<'tcx>) -> Cow<'static, str> {
        use self::TypeError::*;
        fn report_maybe_different(expected: &str, found: &str) -> String {
            // A naive approach to making sure that we're not reporting silly errors such as:
            // (expected closure, found closure).
            if expected == found {
                format!("expected {expected}, found a different {found}")
            } else {
                format!("expected {expected}, found {found}")
            }
        }

        match self {
            CyclicTy(_) => "cyclic type of infinite size".into(),
            CyclicConst(_) => "encountered a self-referencing constant".into(),
            Mismatch => "types differ".into(),
            ConstnessMismatch(values) => {
                format!("expected {} bound, found {} bound", values.expected, values.found).into()
            }
            PolarityMismatch(values) => {
                format!("expected {} polarity, found {} polarity", values.expected, values.found)
                    .into()
            }
            UnsafetyMismatch(values) => {
                format!("expected {} fn, found {} fn", values.expected, values.found).into()
            }
            AbiMismatch(values) => {
                format!("expected {} fn, found {} fn", values.expected, values.found).into()
            }
            ArgumentMutability(_) | Mutability => "types differ in mutability".into(),
            TupleSize(values) => format!(
                "expected a tuple with {} element{}, found one with {} element{}",
                values.expected,
                pluralize!(values.expected),
                values.found,
                pluralize!(values.found)
            )
            .into(),
            FixedArraySize(values) => format!(
                "expected an array with a fixed size of {} element{}, found one with {} element{}",
                values.expected,
                pluralize!(values.expected),
                values.found,
                pluralize!(values.found)
            )
            .into(),
            ArgCount => "incorrect number of function parameters".into(),
            FieldMisMatch(adt, field) => format!("field type mismatch: {adt}.{field}").into(),
            RegionsDoesNotOutlive(..) => "lifetime mismatch".into(),
            // Actually naming the region here is a bit confusing because context is lacking
            RegionsInsufficientlyPolymorphic(..) => {
                "one type is more general than the other".into()
            }
            RegionsPlaceholderMismatch => "one type is more general than the other".into(),
            ArgumentSorts(values, _) | Sorts(values) => {
                let expected = values.expected.sort_string(tcx);
                let found = values.found.sort_string(tcx);
                report_maybe_different(&expected, &found).into()
            }
            Traits(values) => {
                let (mut expected, mut found) = with_forced_trimmed_paths!((
                    tcx.def_path_str(values.expected),
                    tcx.def_path_str(values.found),
                ));
                if expected == found {
                    expected = tcx.def_path_str(values.expected);
                    found = tcx.def_path_str(values.found);
                }
                report_maybe_different(&format!("trait `{expected}`"), &format!("trait `{found}`"))
                    .into()
            }
            IntMismatch(ref values) => {
                let expected = match values.expected {
                    ty::IntVarValue::IntType(ty) => ty.name_str(),
                    ty::IntVarValue::UintType(ty) => ty.name_str(),
                };
                let found = match values.found {
                    ty::IntVarValue::IntType(ty) => ty.name_str(),
                    ty::IntVarValue::UintType(ty) => ty.name_str(),
                };
                format!("expected `{expected}`, found `{found}`").into()
            }
            FloatMismatch(ref values) => format!(
                "expected `{}`, found `{}`",
                values.expected.name_str(),
                values.found.name_str()
            )
            .into(),
            VariadicMismatch(ref values) => format!(
                "expected {} fn, found {} function",
                if values.expected { "variadic" } else { "non-variadic" },
                if values.found { "variadic" } else { "non-variadic" }
            )
            .into(),
            ProjectionMismatched(ref values) => format!(
                "expected `{}`, found `{}`",
                tcx.def_path_str(values.expected),
                tcx.def_path_str(values.found)
            )
            .into(),
            ExistentialMismatch(ref values) => report_maybe_different(
                &format!("trait `{}`", values.expected),
                &format!("trait `{}`", values.found),
            )
            .into(),
            ConstMismatch(ref values) => {
                format!("expected `{}`, found `{}`", values.expected, values.found).into()
            }
            IntrinsicCast => "cannot coerce intrinsics to function pointers".into(),
            TargetFeatureCast(_) => {
                "cannot coerce functions with `#[target_feature]` to safe function pointers".into()
            }
        }
    }
}

impl<'tcx> TypeError<'tcx> {
    pub fn must_include_note(self) -> bool {
        use self::TypeError::*;
        match self {
            CyclicTy(_) | CyclicConst(_) | UnsafetyMismatch(_) | ConstnessMismatch(_)
            | PolarityMismatch(_) | Mismatch | AbiMismatch(_) | FixedArraySize(_)
            | ArgumentSorts(..) | Sorts(_) | IntMismatch(_) | FloatMismatch(_)
            | VariadicMismatch(_) | TargetFeatureCast(_) => false,

            Mutability
            | ArgumentMutability(_)
            | TupleSize(_)
            | ArgCount
            | FieldMisMatch(..)
            | RegionsDoesNotOutlive(..)
            | RegionsInsufficientlyPolymorphic(..)
            | RegionsPlaceholderMismatch
            | Traits(_)
            | ProjectionMismatched(_)
            | ExistentialMismatch(_)
            | ConstMismatch(_)
            | IntrinsicCast => true,
        }
    }
}

impl<'tcx> Ty<'tcx> {
    pub fn sort_string(self, tcx: TyCtxt<'tcx>) -> Cow<'static, str> {
        match *self.kind() {
            ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(),
            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
                _ => "fn item".into(),
            },
            ty::FnPtr(_) => "fn pointer".into(),
            ty::Dynamic(ref inner, ..) if let Some(principal) = inner.principal() => {
                format!("`dyn {}`", tcx.def_path_str(principal.def_id())).into()
            }
            ty::Dynamic(..) => "trait object".into(),
            ty::Closure(..) => "closure".into(),
            ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
            ty::GeneratorWitness(..) => "generator witness".into(),
            ty::Infer(ty::TyVar(_)) => "inferred type".into(),
            ty::Infer(ty::IntVar(_)) => "integer".into(),
            ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
            ty::Placeholder(..) => "placeholder type".into(),
            ty::Bound(..) => "bound type".into(),
            ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
            ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
            ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
            ty::Alias(ty::Projection | ty::Inherent, _) => "associated type".into(),
            ty::Param(p) => format!("type parameter `{p}`").into(),
            ty::Alias(ty::Opaque, ..) => if tcx.ty_is_opaque_future(self) { "future".into() } else { "opaque type".into() },
            ty::Error(_) => "type error".into(),
            _ => {
                let width = tcx.sess.diagnostic_width();
                let length_limit = std::cmp::max(width / 4, 15);
                format!("`{}`", tcx.ty_string_with_limit(self, length_limit)).into()
            }
        }
    }

    pub fn prefix_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
        match *self.kind() {
            ty::Infer(_)
            | ty::Error(_)
            | ty::Bool
            | ty::Char
            | ty::Int(_)
            | ty::Uint(_)
            | ty::Float(_)
            | ty::Str
            | ty::Never => "type".into(),
            ty::Tuple(ref tys) if tys.is_empty() => "unit type".into(),
            ty::Adt(def, _) => def.descr().into(),
            ty::Foreign(_) => "extern type".into(),
            ty::Array(..) => "array".into(),
            ty::Slice(_) => "slice".into(),
            ty::RawPtr(_) => "raw pointer".into(),
            ty::Ref(.., mutbl) => match mutbl {
                hir::Mutability::Mut => "mutable reference",
                _ => "reference",
            }
            .into(),
            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
                _ => "fn item".into(),
            },
            ty::FnPtr(_) => "fn pointer".into(),
            ty::Dynamic(..) => "trait object".into(),
            ty::Closure(..) => "closure".into(),
            ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
            ty::GeneratorWitness(..) => "generator witness".into(),
            ty::Tuple(..) => "tuple".into(),
            ty::Placeholder(..) => "higher-ranked type".into(),
            ty::Bound(..) => "bound type variable".into(),
            ty::Alias(ty::Projection | ty::Inherent, _) => "associated type".into(),
            ty::Alias(ty::Weak, _) => "type alias".into(),
            ty::Param(_) => "type parameter".into(),
            ty::Alias(ty::Opaque, ..) => "opaque type".into(),
        }
    }
}

impl<'tcx> TyCtxt<'tcx> {
    pub fn ty_string_with_limit(self, ty: Ty<'tcx>, length_limit: usize) -> String {
        let mut type_limit = 50;
        let regular = FmtPrinter::new(self, hir::def::Namespace::TypeNS)
            .pretty_print_type(ty)
            .expect("could not write to `String`")
            .into_buffer();
        if regular.len() <= length_limit {
            return regular;
        }
        let mut short;
        loop {
            // Look for the longest properly trimmed path that still fits in length_limit.
            short = with_forced_trimmed_paths!(
                FmtPrinter::new_with_limit(
                    self,
                    hir::def::Namespace::TypeNS,
                    rustc_session::Limit(type_limit),
                )
                .pretty_print_type(ty)
                .expect("could not write to `String`")
                .into_buffer()
            );
            if short.len() <= length_limit || type_limit == 0 {
                break;
            }
            type_limit -= 1;
        }
        short
    }

    pub fn short_ty_string(self, ty: Ty<'tcx>) -> (String, Option<PathBuf>) {
        let regular = FmtPrinter::new(self, hir::def::Namespace::TypeNS)
            .pretty_print_type(ty)
            .expect("could not write to `String`")
            .into_buffer();

        if !self.sess.opts.unstable_opts.write_long_types_to_disk {
            return (regular, None);
        }

        let width = self.sess.diagnostic_width();
        let length_limit = width.saturating_sub(30);
        if regular.len() <= width {
            return (regular, None);
        }
        let short = self.ty_string_with_limit(ty, length_limit);
        if regular == short {
            return (regular, None);
        }
        // Multiple types might be shortened in a single error, ensure we create a file for each.
        let mut s = DefaultHasher::new();
        ty.hash(&mut s);
        let hash = s.finish();
        let path = self.output_filenames(()).temp_path_ext(&format!("long-type-{hash}.txt"), None);
        match std::fs::write(&path, &regular) {
            Ok(_) => (short, Some(path)),
            Err(_) => (regular, None),
        }
    }
}