//! The type system. We currently use this to infer types for completion, hover
//! information and various assists.

#[allow(unused)]
macro_rules! eprintln {
    ($($tt:tt)*) => { stdx::eprintln!($($tt)*) };
}

mod autoderef;
mod builder;
mod chalk_db;
mod chalk_ext;
pub mod consteval;
mod infer;
mod interner;
mod lower;
mod mapping;
mod tls;
mod utils;
mod walk;
pub mod db;
pub mod diagnostics;
pub mod display;
pub mod method_resolution;
pub mod primitive;
pub mod traits;

#[cfg(test)]
mod tests;
#[cfg(test)]
mod test_db;

use std::sync::Arc;

use chalk_ir::{
    fold::{Shift, TypeFoldable},
    interner::HasInterner,
    NoSolution,
};
use hir_def::{expr::ExprId, type_ref::Rawness, TypeOrConstParamId};
use itertools::Either;
use utils::Generics;

use crate::{consteval::unknown_const, db::HirDatabase, utils::generics};

pub use autoderef::autoderef;
pub use builder::{ParamKind, TyBuilder};
pub use chalk_ext::*;
pub use infer::{
    could_coerce, could_unify, Adjust, Adjustment, AutoBorrow, BindingMode, InferenceDiagnostic,
    InferenceResult,
};
pub use interner::Interner;
pub use lower::{
    associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
    TyDefId, TyLoweringContext, ValueTyDefId,
};
pub use mapping::{
    from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id, from_placeholder_idx,
    lt_from_placeholder_idx, to_assoc_type_id, to_chalk_trait_id, to_foreign_def_id,
    to_placeholder_idx,
};
pub use traits::TraitEnvironment;
pub use utils::{all_super_traits, is_fn_unsafe_to_call};
pub use walk::TypeWalk;

pub use chalk_ir::{
    cast::Cast, AdtId, BoundVar, DebruijnIndex, Mutability, Safety, Scalar, TyVariableKind,
};

pub type ForeignDefId = chalk_ir::ForeignDefId<Interner>;
pub type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
pub type FnDefId = chalk_ir::FnDefId<Interner>;
pub type ClosureId = chalk_ir::ClosureId<Interner>;
pub type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
pub type PlaceholderIndex = chalk_ir::PlaceholderIndex;

pub type VariableKind = chalk_ir::VariableKind<Interner>;
pub type VariableKinds = chalk_ir::VariableKinds<Interner>;
pub type CanonicalVarKinds = chalk_ir::CanonicalVarKinds<Interner>;
pub type Binders<T> = chalk_ir::Binders<T>;
pub type Substitution = chalk_ir::Substitution<Interner>;
pub type GenericArg = chalk_ir::GenericArg<Interner>;
pub type GenericArgData = chalk_ir::GenericArgData<Interner>;

pub type Ty = chalk_ir::Ty<Interner>;
pub type TyKind = chalk_ir::TyKind<Interner>;
pub type DynTy = chalk_ir::DynTy<Interner>;
pub type FnPointer = chalk_ir::FnPointer<Interner>;
// pub type FnSubst = chalk_ir::FnSubst<Interner>;
pub use chalk_ir::FnSubst;
pub type ProjectionTy = chalk_ir::ProjectionTy<Interner>;
pub type AliasTy = chalk_ir::AliasTy<Interner>;
pub type OpaqueTy = chalk_ir::OpaqueTy<Interner>;
pub type InferenceVar = chalk_ir::InferenceVar;

pub type Lifetime = chalk_ir::Lifetime<Interner>;
pub type LifetimeData = chalk_ir::LifetimeData<Interner>;
pub type LifetimeOutlives = chalk_ir::LifetimeOutlives<Interner>;

pub type Const = chalk_ir::Const<Interner>;
pub type ConstData = chalk_ir::ConstData<Interner>;
pub type ConstValue = chalk_ir::ConstValue<Interner>;
pub type ConcreteConst = chalk_ir::ConcreteConst<Interner>;

pub type ChalkTraitId = chalk_ir::TraitId<Interner>;
pub type TraitRef = chalk_ir::TraitRef<Interner>;
pub type QuantifiedWhereClause = Binders<WhereClause>;
pub type QuantifiedWhereClauses = chalk_ir::QuantifiedWhereClauses<Interner>;
pub type Canonical<T> = chalk_ir::Canonical<T>;

pub type FnSig = chalk_ir::FnSig<Interner>;

pub type InEnvironment<T> = chalk_ir::InEnvironment<T>;
pub type Environment = chalk_ir::Environment<Interner>;
pub type DomainGoal = chalk_ir::DomainGoal<Interner>;
pub type Goal = chalk_ir::Goal<Interner>;
pub type AliasEq = chalk_ir::AliasEq<Interner>;
pub type Solution = chalk_solve::Solution<Interner>;
pub type ConstrainedSubst = chalk_ir::ConstrainedSubst<Interner>;
pub type Guidance = chalk_solve::Guidance<Interner>;
pub type WhereClause = chalk_ir::WhereClause<Interner>;

// FIXME: get rid of this
pub fn subst_prefix(s: &Substitution, n: usize) -> Substitution {
    Substitution::from_iter(
        Interner,
        s.as_slice(Interner)[..std::cmp::min(s.len(Interner), n)].iter().cloned(),
    )
}

/// Return an index of a parameter in the generic type parameter list by it's id.
pub fn param_idx(db: &dyn HirDatabase, id: TypeOrConstParamId) -> Option<usize> {
    generics(db.upcast(), id.parent).param_idx(id)
}

pub(crate) fn wrap_empty_binders<T>(value: T) -> Binders<T>
where
    T: TypeFoldable<Interner> + HasInterner<Interner = Interner>,
{
    Binders::empty(Interner, value.shifted_in_from(Interner, DebruijnIndex::ONE))
}

pub(crate) fn make_type_and_const_binders<T: HasInterner<Interner = Interner>>(
    which_is_const: impl Iterator<Item = Option<Ty>>,
    value: T,
) -> Binders<T> {
    Binders::new(
        VariableKinds::from_iter(
            Interner,
            which_is_const.map(|x| {
                if let Some(ty) = x {
                    chalk_ir::VariableKind::Const(ty)
                } else {
                    chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General)
                }
            }),
        ),
        value,
    )
}

pub(crate) fn make_single_type_binders<T: HasInterner<Interner = Interner>>(
    value: T,
) -> Binders<T> {
    Binders::new(
        VariableKinds::from_iter(
            Interner,
            std::iter::once(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General)),
        ),
        value,
    )
}

pub(crate) fn make_binders_with_count<T: HasInterner<Interner = Interner>>(
    db: &dyn HirDatabase,
    count: usize,
    generics: &Generics,
    value: T,
) -> Binders<T> {
    let it = generics.iter_id().take(count).map(|id| match id {
        Either::Left(_) => None,
        Either::Right(id) => Some(db.const_param_ty(id)),
    });
    crate::make_type_and_const_binders(it, value)
}

pub(crate) fn make_binders<T: HasInterner<Interner = Interner>>(
    db: &dyn HirDatabase,
    generics: &Generics,
    value: T,
) -> Binders<T> {
    make_binders_with_count(db, usize::MAX, generics, value)
}

// FIXME: get rid of this
pub fn make_canonical<T: HasInterner<Interner = Interner>>(
    value: T,
    kinds: impl IntoIterator<Item = TyVariableKind>,
) -> Canonical<T> {
    let kinds = kinds.into_iter().map(|tk| {
        chalk_ir::CanonicalVarKind::new(
            chalk_ir::VariableKind::Ty(tk),
            chalk_ir::UniverseIndex::ROOT,
        )
    });
    Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(Interner, kinds) }
}

// FIXME: get rid of this, just replace it by FnPointer
/// A function signature as seen by type inference: Several parameter types and
/// one return type.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct CallableSig {
    params_and_return: Arc<[Ty]>,
    is_varargs: bool,
}

has_interner!(CallableSig);

/// A polymorphic function signature.
pub type PolyFnSig = Binders<CallableSig>;

impl CallableSig {
    pub fn from_params_and_return(mut params: Vec<Ty>, ret: Ty, is_varargs: bool) -> CallableSig {
        params.push(ret);
        CallableSig { params_and_return: params.into(), is_varargs }
    }

    pub fn from_fn_ptr(fn_ptr: &FnPointer) -> CallableSig {
        CallableSig {
            // FIXME: what to do about lifetime params? -> return PolyFnSig
            params_and_return: fn_ptr
                .substitution
                .clone()
                .shifted_out_to(Interner, DebruijnIndex::ONE)
                .expect("unexpected lifetime vars in fn ptr")
                .0
                .as_slice(Interner)
                .iter()
                .map(|arg| arg.assert_ty_ref(Interner).clone())
                .collect(),
            is_varargs: fn_ptr.sig.variadic,
        }
    }

    pub fn to_fn_ptr(&self) -> FnPointer {
        FnPointer {
            num_binders: 0,
            sig: FnSig { abi: (), safety: Safety::Safe, variadic: self.is_varargs },
            substitution: FnSubst(Substitution::from_iter(
                Interner,
                self.params_and_return.iter().cloned(),
            )),
        }
    }

    pub fn params(&self) -> &[Ty] {
        &self.params_and_return[0..self.params_and_return.len() - 1]
    }

    pub fn ret(&self) -> &Ty {
        &self.params_and_return[self.params_and_return.len() - 1]
    }
}

impl TypeFoldable<Interner> for CallableSig {
    fn fold_with<E>(
        self,
        folder: &mut dyn chalk_ir::fold::TypeFolder<Interner, Error = E>,
        outer_binder: DebruijnIndex,
    ) -> Result<Self, E> {
        let vec = self.params_and_return.to_vec();
        let folded = vec.fold_with(folder, outer_binder)?;
        Ok(CallableSig { params_and_return: folded.into(), is_varargs: self.is_varargs })
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
pub enum ImplTraitId {
    ReturnTypeImplTrait(hir_def::FunctionId, u16),
    AsyncBlockTypeImplTrait(hir_def::DefWithBodyId, ExprId),
}

#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub struct ReturnTypeImplTraits {
    pub(crate) impl_traits: Vec<ReturnTypeImplTrait>,
}

has_interner!(ReturnTypeImplTraits);

#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub(crate) struct ReturnTypeImplTrait {
    pub(crate) bounds: Binders<Vec<QuantifiedWhereClause>>,
}

pub fn static_lifetime() -> Lifetime {
    LifetimeData::Static.intern(Interner)
}

pub(crate) fn fold_free_vars<T: HasInterner<Interner = Interner> + TypeFoldable<Interner>>(
    t: T,
    for_ty: impl FnMut(BoundVar, DebruijnIndex) -> Ty,
    for_const: impl FnMut(Ty, BoundVar, DebruijnIndex) -> Const,
) -> T {
    use chalk_ir::{fold::TypeFolder, Fallible};
    struct FreeVarFolder<F1, F2>(F1, F2);
    impl<
            'i,
            F1: FnMut(BoundVar, DebruijnIndex) -> Ty + 'i,
            F2: FnMut(Ty, BoundVar, DebruijnIndex) -> Const + 'i,
        > TypeFolder<Interner> for FreeVarFolder<F1, F2>
    {
        type Error = NoSolution;

        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
            self
        }

        fn interner(&self) -> Interner {
            Interner
        }

        fn fold_free_var_ty(
            &mut self,
            bound_var: BoundVar,
            outer_binder: DebruijnIndex,
        ) -> Fallible<Ty> {
            Ok(self.0(bound_var, outer_binder))
        }

        fn fold_free_var_const(
            &mut self,
            ty: Ty,
            bound_var: BoundVar,
            outer_binder: DebruijnIndex,
        ) -> Fallible<Const> {
            Ok(self.1(ty, bound_var, outer_binder))
        }
    }
    t.fold_with(&mut FreeVarFolder(for_ty, for_const), DebruijnIndex::INNERMOST)
        .expect("fold failed unexpectedly")
}

pub(crate) fn fold_tys<T: HasInterner<Interner = Interner> + TypeFoldable<Interner>>(
    t: T,
    mut for_ty: impl FnMut(Ty, DebruijnIndex) -> Ty,
    binders: DebruijnIndex,
) -> T {
    fold_tys_and_consts(
        t,
        |x, d| match x {
            Either::Left(x) => Either::Left(for_ty(x, d)),
            Either::Right(x) => Either::Right(x),
        },
        binders,
    )
}

pub(crate) fn fold_tys_and_consts<T: HasInterner<Interner = Interner> + TypeFoldable<Interner>>(
    t: T,
    f: impl FnMut(Either<Ty, Const>, DebruijnIndex) -> Either<Ty, Const>,
    binders: DebruijnIndex,
) -> T {
    use chalk_ir::{
        fold::{TypeFolder, TypeSuperFoldable},
        Fallible,
    };
    struct TyFolder<F>(F);
    impl<'i, F: FnMut(Either<Ty, Const>, DebruijnIndex) -> Either<Ty, Const> + 'i>
        TypeFolder<Interner> for TyFolder<F>
    {
        type Error = NoSolution;

        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
            self
        }

        fn interner(&self) -> Interner {
            Interner
        }

        fn fold_ty(&mut self, ty: Ty, outer_binder: DebruijnIndex) -> Fallible<Ty> {
            let ty = ty.super_fold_with(self.as_dyn(), outer_binder)?;
            Ok(self.0(Either::Left(ty), outer_binder).left().unwrap())
        }

        fn fold_const(&mut self, c: Const, outer_binder: DebruijnIndex) -> Fallible<Const> {
            Ok(self.0(Either::Right(c), outer_binder).right().unwrap())
        }
    }
    t.fold_with(&mut TyFolder(f), binders).expect("fold failed unexpectedly")
}

/// 'Canonicalizes' the `t` by replacing any errors with new variables. Also
/// ensures there are no unbound variables or inference variables anywhere in
/// the `t`.
pub fn replace_errors_with_variables<T>(t: &T) -> Canonical<T>
where
    T: HasInterner<Interner = Interner> + TypeFoldable<Interner> + Clone,
    T: HasInterner<Interner = Interner>,
{
    use chalk_ir::{
        fold::{TypeFolder, TypeSuperFoldable},
        Fallible,
    };
    struct ErrorReplacer {
        vars: usize,
    }
    impl TypeFolder<Interner> for ErrorReplacer {
        type Error = NoSolution;

        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
            self
        }

        fn interner(&self) -> Interner {
            Interner
        }

        fn fold_ty(&mut self, ty: Ty, outer_binder: DebruijnIndex) -> Fallible<Ty> {
            if let TyKind::Error = ty.kind(Interner) {
                let index = self.vars;
                self.vars += 1;
                Ok(TyKind::BoundVar(BoundVar::new(outer_binder, index)).intern(Interner))
            } else {
                let ty = ty.super_fold_with(self.as_dyn(), outer_binder)?;
                Ok(ty)
            }
        }

        fn fold_inference_ty(
            &mut self,
            _var: InferenceVar,
            _kind: TyVariableKind,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Ty> {
            if cfg!(debug_assertions) {
                // we don't want to just panic here, because then the error message
                // won't contain the whole thing, which would not be very helpful
                Err(NoSolution)
            } else {
                Ok(TyKind::Error.intern(Interner))
            }
        }

        fn fold_free_var_ty(
            &mut self,
            _bound_var: BoundVar,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Ty> {
            if cfg!(debug_assertions) {
                // we don't want to just panic here, because then the error message
                // won't contain the whole thing, which would not be very helpful
                Err(NoSolution)
            } else {
                Ok(TyKind::Error.intern(Interner))
            }
        }

        fn fold_inference_const(
            &mut self,
            ty: Ty,
            _var: InferenceVar,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Const> {
            if cfg!(debug_assertions) {
                Err(NoSolution)
            } else {
                Ok(unknown_const(ty))
            }
        }

        fn fold_free_var_const(
            &mut self,
            ty: Ty,
            _bound_var: BoundVar,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Const> {
            if cfg!(debug_assertions) {
                Err(NoSolution)
            } else {
                Ok(unknown_const(ty))
            }
        }

        fn fold_inference_lifetime(
            &mut self,
            _var: InferenceVar,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Lifetime> {
            if cfg!(debug_assertions) {
                Err(NoSolution)
            } else {
                Ok(static_lifetime())
            }
        }

        fn fold_free_var_lifetime(
            &mut self,
            _bound_var: BoundVar,
            _outer_binder: DebruijnIndex,
        ) -> Fallible<Lifetime> {
            if cfg!(debug_assertions) {
                Err(NoSolution)
            } else {
                Ok(static_lifetime())
            }
        }
    }
    let mut error_replacer = ErrorReplacer { vars: 0 };
    let value = match t.clone().fold_with(&mut error_replacer, DebruijnIndex::INNERMOST) {
        Ok(t) => t,
        Err(_) => panic!("Encountered unbound or inference vars in {:?}", t),
    };
    let kinds = (0..error_replacer.vars).map(|_| {
        chalk_ir::CanonicalVarKind::new(
            chalk_ir::VariableKind::Ty(TyVariableKind::General),
            chalk_ir::UniverseIndex::ROOT,
        )
    });
    Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(Interner, kinds) }
}