use std::{
    hash::{Hash, Hasher},
    sync::Arc,
};

use ra_db::{LocationInterner, FileId};
use ra_syntax::{TreeArc, SourceFile, AstNode, ast};
use ra_arena::{RawId, ArenaId, impl_arena_id};
use mbe::MacroRules;

use crate::{
    Module, DefDatabase, AstId, FileAstId,
};

#[derive(Debug, Default)]
pub struct HirInterner {
    macros: LocationInterner<MacroCallLoc, MacroCallId>,
    fns: LocationInterner<ItemLoc<ast::FnDef>, FunctionId>,
    structs: LocationInterner<ItemLoc<ast::StructDef>, StructId>,
    enums: LocationInterner<ItemLoc<ast::EnumDef>, EnumId>,
    consts: LocationInterner<ItemLoc<ast::ConstDef>, ConstId>,
    statics: LocationInterner<ItemLoc<ast::StaticDef>, StaticId>,
    traits: LocationInterner<ItemLoc<ast::TraitDef>, TraitId>,
    types: LocationInterner<ItemLoc<ast::TypeAliasDef>, TypeAliasId>,
}

impl HirInterner {
    pub fn len(&self) -> usize {
        self.macros.len()
            + self.fns.len()
            + self.structs.len()
            + self.enums.len()
            + self.consts.len()
            + self.statics.len()
            + self.traits.len()
            + self.types.len()
    }
}

/// hir makes heavy use of ids: integer (u32) handlers to various things. You
/// can think of id as a pointer (but without a lifetime) or a file descriptor
/// (but for hir objects).
///
/// This module defines a bunch of ids we are using. The most important ones are
/// probably `HirFileId` and `DefId`.

/// Input to the analyzer is a set of files, where each file is identified by
/// `FileId` and contains source code. However, another source of source code in
/// Rust are macros: each macro can be thought of as producing a "temporary
/// file". To assign an id to such a file, we use the id of the macro call that
/// produced the file. So, a `HirFileId` is either a `FileId` (source code
/// written by user), or a `MacroCallId` (source code produced by macro).
///
/// What is a `MacroCallId`? Simplifying, it's a `HirFileId` of a file
/// containing the call plus the offset of the macro call in the file. Note that
/// this is a recursive definition! However, the size_of of `HirFileId` is
/// finite (because everything bottoms out at the real `FileId`) and small
/// (`MacroCallId` uses the location interner).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct HirFileId(HirFileIdRepr);

impl HirFileId {
    /// For macro-expansion files, returns the file original source file the
    /// expansion originated from.
    pub fn original_file(self, db: &impl DefDatabase) -> FileId {
        match self.0 {
            HirFileIdRepr::File(file_id) => file_id,
            HirFileIdRepr::Macro(macro_call_id) => {
                let loc = macro_call_id.loc(db);
                loc.ast_id.file_id().original_file(db)
            }
        }
    }

    /// XXX: this is a temporary function, which should go away when we implement the
    /// nameresolution+macro expansion combo. Prefer using `original_file` if
    /// possible.
    pub fn as_original_file(self) -> FileId {
        match self.0 {
            HirFileIdRepr::File(file_id) => file_id,
            HirFileIdRepr::Macro(_r) => panic!("macro generated file: {:?}", self),
        }
    }

    pub(crate) fn hir_parse_query(
        db: &impl DefDatabase,
        file_id: HirFileId,
    ) -> TreeArc<SourceFile> {
        match file_id.0 {
            HirFileIdRepr::File(file_id) => db.parse(file_id),
            HirFileIdRepr::Macro(macro_call_id) => {
                // returning an empty string looks fishy...
                parse_macro(db, macro_call_id).unwrap_or_else(|| SourceFile::parse(""))
            }
        }
    }
}

fn parse_macro(db: &impl DefDatabase, macro_call_id: MacroCallId) -> Option<TreeArc<SourceFile>> {
    let loc = macro_call_id.loc(db);
    let macro_call = loc.ast_id.to_node(db);
    let (macro_arg, _) = macro_call.token_tree().and_then(mbe::ast_to_token_tree)?;

    let macro_rules = db.macro_def(loc.def)?;
    let tt = macro_rules.expand(&macro_arg).ok()?;
    Some(mbe::token_tree_to_ast_item_list(&tt))
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
enum HirFileIdRepr {
    File(FileId),
    Macro(MacroCallId),
}

impl From<FileId> for HirFileId {
    fn from(file_id: FileId) -> HirFileId {
        HirFileId(HirFileIdRepr::File(file_id))
    }
}

impl From<MacroCallId> for HirFileId {
    fn from(macro_call_id: MacroCallId) -> HirFileId {
        HirFileId(HirFileIdRepr::Macro(macro_call_id))
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct MacroDefId(pub(crate) AstId<ast::MacroCall>);

pub(crate) fn macro_def_query(db: &impl DefDatabase, id: MacroDefId) -> Option<Arc<MacroRules>> {
    let macro_call = id.0.to_node(db);
    let arg = macro_call.token_tree()?;
    let (tt, _) = mbe::ast_to_token_tree(arg)?;
    let rules = MacroRules::parse(&tt).ok()?;
    Some(Arc::new(rules))
}

/// `MacroCallId` identifies a particular macro invocation, like
/// `println!("Hello, {}", world)`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct MacroCallId(RawId);
impl_arena_id!(MacroCallId);

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct MacroCallLoc {
    pub(crate) def: MacroDefId,
    pub(crate) ast_id: AstId<ast::MacroCall>,
}

impl MacroCallId {
    pub(crate) fn loc(self, db: &impl AsRef<HirInterner>) -> MacroCallLoc {
        db.as_ref().macros.id2loc(self)
    }
}

impl MacroCallLoc {
    pub(crate) fn id(&self, db: &impl AsRef<HirInterner>) -> MacroCallId {
        db.as_ref().macros.loc2id(&self)
    }
}

#[derive(Debug)]
pub struct ItemLoc<N: AstNode> {
    pub(crate) module: Module,
    ast_id: AstId<N>,
}

impl<N: AstNode> PartialEq for ItemLoc<N> {
    fn eq(&self, other: &Self) -> bool {
        self.module == other.module && self.ast_id == other.ast_id
    }
}
impl<N: AstNode> Eq for ItemLoc<N> {}
impl<N: AstNode> Hash for ItemLoc<N> {
    fn hash<H: Hasher>(&self, hasher: &mut H) {
        self.module.hash(hasher);
        self.ast_id.hash(hasher);
    }
}

impl<N: AstNode> Clone for ItemLoc<N> {
    fn clone(&self) -> ItemLoc<N> {
        ItemLoc { module: self.module, ast_id: self.ast_id }
    }
}

#[derive(Clone, Copy)]
pub(crate) struct LocationCtx<DB> {
    db: DB,
    module: Module,
    file_id: HirFileId,
}

impl<'a, DB: DefDatabase> LocationCtx<&'a DB> {
    pub(crate) fn new(db: &'a DB, module: Module, file_id: HirFileId) -> LocationCtx<&'a DB> {
        LocationCtx { db, module, file_id }
    }
    pub(crate) fn to_def<N, DEF>(self, ast: &N) -> DEF
    where
        N: AstNode,
        DEF: AstItemDef<N>,
    {
        DEF::from_ast(self, ast)
    }
}

pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<N>, Self>;
    fn from_ast(ctx: LocationCtx<&impl DefDatabase>, ast: &N) -> Self {
        let items = ctx.db.ast_id_map(ctx.file_id);
        let item_id = items.ast_id(ast);
        Self::from_ast_id(ctx, item_id)
    }
    fn from_ast_id(ctx: LocationCtx<&impl DefDatabase>, ast_id: FileAstId<N>) -> Self {
        let loc = ItemLoc { module: ctx.module, ast_id: ast_id.with_file_id(ctx.file_id) };
        Self::interner(ctx.db.as_ref()).loc2id(&loc)
    }
    fn source(self, db: &impl DefDatabase) -> (HirFileId, TreeArc<N>) {
        let int = Self::interner(db.as_ref());
        let loc = int.id2loc(self);
        let ast = loc.ast_id.to_node(db);
        (loc.ast_id.file_id(), ast)
    }
    fn module(self, db: &impl DefDatabase) -> Module {
        let int = Self::interner(db.as_ref());
        let loc = int.id2loc(self);
        loc.module
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct FunctionId(RawId);
impl_arena_id!(FunctionId);
impl AstItemDef<ast::FnDef> for FunctionId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::FnDef>, Self> {
        &interner.fns
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct StructId(RawId);
impl_arena_id!(StructId);
impl AstItemDef<ast::StructDef> for StructId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StructDef>, Self> {
        &interner.structs
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct EnumId(RawId);
impl_arena_id!(EnumId);
impl AstItemDef<ast::EnumDef> for EnumId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::EnumDef>, Self> {
        &interner.enums
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct ConstId(RawId);
impl_arena_id!(ConstId);
impl AstItemDef<ast::ConstDef> for ConstId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::ConstDef>, Self> {
        &interner.consts
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct StaticId(RawId);
impl_arena_id!(StaticId);
impl AstItemDef<ast::StaticDef> for StaticId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StaticDef>, Self> {
        &interner.statics
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct TraitId(RawId);
impl_arena_id!(TraitId);
impl AstItemDef<ast::TraitDef> for TraitId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TraitDef>, Self> {
        &interner.traits
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub(crate) struct TypeAliasId(RawId);
impl_arena_id!(TypeAliasId);
impl AstItemDef<ast::TypeAliasDef> for TypeAliasId {
    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TypeAliasDef>, Self> {
        &interner.types
    }
}