//! FIXME: write short doc here

use rustc_hash::FxHashMap;
use std::sync::Arc;

use ra_arena::{impl_arena_id, map::ArenaMap, Arena, RawId};
use ra_cfg::CfgOptions;
use ra_syntax::{
    ast::{self, AstNode},
    AstPtr,
};

use crate::{
    attr::Attr,
    code_model::{Module, ModuleSource},
    db::{AstDatabase, DefDatabase, HirDatabase},
    generics::HasGenericParams,
    ids::LocationCtx,
    ids::MacroCallLoc,
    resolve::Resolver,
    ty::Ty,
    type_ref::TypeRef,
    AssocItem, AstId, Const, Function, HasSource, HirFileId, MacroFileKind, Path, Source, TraitRef,
    TypeAlias,
};

#[derive(Debug, Default, PartialEq, Eq)]
pub struct ImplSourceMap {
    map: ArenaMap<ImplId, Source<AstPtr<ast::ImplBlock>>>,
}

impl ImplSourceMap {
    fn insert(&mut self, impl_id: ImplId, file_id: HirFileId, impl_block: &ast::ImplBlock) {
        let source = Source { file_id, ast: AstPtr::new(impl_block) };
        self.map.insert(impl_id, source)
    }

    pub fn get(&self, db: &impl AstDatabase, impl_id: ImplId) -> Source<ast::ImplBlock> {
        let src = self.map[impl_id];
        let root = src.file_syntax(db);
        src.map(|ptr| ptr.to_node(&root))
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ImplBlock {
    module: Module,
    impl_id: ImplId,
}

impl HasSource for ImplBlock {
    type Ast = ast::ImplBlock;
    fn source(self, db: &(impl DefDatabase + AstDatabase)) -> Source<ast::ImplBlock> {
        let source_map = db.impls_in_module_with_source_map(self.module).1;
        source_map.get(db, self.impl_id)
    }
}

impl ImplBlock {
    pub(crate) fn containing(
        module_impl_blocks: Arc<ModuleImplBlocks>,
        item: AssocItem,
    ) -> Option<ImplBlock> {
        let impl_id = *module_impl_blocks.impls_by_def.get(&item)?;
        Some(ImplBlock { module: module_impl_blocks.module, impl_id })
    }

    pub(crate) fn from_id(module: Module, impl_id: ImplId) -> ImplBlock {
        ImplBlock { module, impl_id }
    }

    pub fn id(&self) -> ImplId {
        self.impl_id
    }

    pub fn module(&self) -> Module {
        self.module
    }

    pub fn target_trait(&self, db: &impl DefDatabase) -> Option<TypeRef> {
        db.impls_in_module(self.module).impls[self.impl_id].target_trait().cloned()
    }

    pub fn target_type(&self, db: &impl DefDatabase) -> TypeRef {
        db.impls_in_module(self.module).impls[self.impl_id].target_type().clone()
    }

    pub fn target_ty(&self, db: &impl HirDatabase) -> Ty {
        Ty::from_hir(db, &self.resolver(db), &self.target_type(db))
    }

    pub fn target_trait_ref(&self, db: &impl HirDatabase) -> Option<TraitRef> {
        let target_ty = self.target_ty(db);
        TraitRef::from_hir(db, &self.resolver(db), &self.target_trait(db)?, Some(target_ty))
    }

    pub fn items(&self, db: &impl DefDatabase) -> Vec<AssocItem> {
        db.impls_in_module(self.module).impls[self.impl_id].items().to_vec()
    }

    pub fn is_negative(&self, db: &impl DefDatabase) -> bool {
        db.impls_in_module(self.module).impls[self.impl_id].negative
    }

    pub(crate) fn resolver(&self, db: &impl DefDatabase) -> Resolver {
        let r = self.module().resolver(db);
        // add generic params, if present
        let p = self.generic_params(db);
        let r = if !p.params.is_empty() { r.push_generic_params_scope(p) } else { r };
        let r = r.push_impl_block_scope(self.clone());
        r
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ImplData {
    target_trait: Option<TypeRef>,
    target_type: TypeRef,
    items: Vec<AssocItem>,
    negative: bool,
}

impl ImplData {
    pub(crate) fn from_ast(
        db: &(impl DefDatabase + AstDatabase),
        file_id: HirFileId,
        module: Module,
        node: &ast::ImplBlock,
    ) -> Self {
        let target_trait = node.target_trait().map(TypeRef::from_ast);
        let target_type = TypeRef::from_ast_opt(node.target_type());
        let ctx = LocationCtx::new(db, module, file_id);
        let negative = node.is_negative();
        let items = if let Some(item_list) = node.item_list() {
            item_list
                .impl_items()
                .map(|item_node| match item_node {
                    ast::ImplItem::FnDef(it) => Function { id: ctx.to_def(&it) }.into(),
                    ast::ImplItem::ConstDef(it) => Const { id: ctx.to_def(&it) }.into(),
                    ast::ImplItem::TypeAliasDef(it) => TypeAlias { id: ctx.to_def(&it) }.into(),
                })
                .collect()
        } else {
            Vec::new()
        };
        ImplData { target_trait, target_type, items, negative }
    }

    pub fn target_trait(&self) -> Option<&TypeRef> {
        self.target_trait.as_ref()
    }

    pub fn target_type(&self) -> &TypeRef {
        &self.target_type
    }

    pub fn items(&self) -> &[AssocItem] {
        &self.items
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ImplId(pub RawId);
impl_arena_id!(ImplId);

/// The collection of impl blocks is a two-step process: first we collect the
/// blocks per-module; then we build an index of all impl blocks in the crate.
/// This way, we avoid having to do this process for the whole crate whenever
/// a file is changed; as long as the impl blocks in the file don't change,
/// we don't need to do the second step again.
#[derive(Debug, PartialEq, Eq)]
pub struct ModuleImplBlocks {
    pub(crate) module: Module,
    pub(crate) impls: Arena<ImplId, ImplData>,
    impls_by_def: FxHashMap<AssocItem, ImplId>,
}

impl ModuleImplBlocks {
    pub(crate) fn impls_in_module_with_source_map_query(
        db: &(impl DefDatabase + AstDatabase),
        module: Module,
    ) -> (Arc<ModuleImplBlocks>, Arc<ImplSourceMap>) {
        let mut source_map = ImplSourceMap::default();
        let crate_graph = db.crate_graph();
        let cfg_options = crate_graph.cfg_options(module.krate.crate_id());

        let result = ModuleImplBlocks::collect(db, cfg_options, module, &mut source_map);
        (Arc::new(result), Arc::new(source_map))
    }

    pub(crate) fn impls_in_module_query(
        db: &impl DefDatabase,
        module: Module,
    ) -> Arc<ModuleImplBlocks> {
        db.impls_in_module_with_source_map(module).0
    }

    fn collect(
        db: &(impl DefDatabase + AstDatabase),
        cfg_options: &CfgOptions,
        module: Module,
        source_map: &mut ImplSourceMap,
    ) -> Self {
        let mut m = ModuleImplBlocks {
            module,
            impls: Arena::default(),
            impls_by_def: FxHashMap::default(),
        };

        let src = m.module.definition_source(db);
        match &src.ast {
            ModuleSource::SourceFile(node) => {
                m.collect_from_item_owner(db, cfg_options, source_map, node, src.file_id)
            }
            ModuleSource::Module(node) => {
                let item_list = node.item_list().expect("inline module should have item list");
                m.collect_from_item_owner(db, cfg_options, source_map, &item_list, src.file_id)
            }
        };
        m
    }

    fn collect_from_item_owner(
        &mut self,
        db: &(impl DefDatabase + AstDatabase),
        cfg_options: &CfgOptions,
        source_map: &mut ImplSourceMap,
        owner: &dyn ast::ModuleItemOwner,
        file_id: HirFileId,
    ) {
        for item in owner.items_with_macros() {
            match item {
                ast::ItemOrMacro::Item(ast::ModuleItem::ImplBlock(impl_block_ast)) => {
                    let attrs = Attr::from_attrs_owner(file_id, &impl_block_ast, db);
                    if attrs.map_or(false, |attrs| {
                        attrs.iter().any(|attr| attr.is_cfg_enabled(cfg_options) == Some(false))
                    }) {
                        continue;
                    }

                    let impl_block = ImplData::from_ast(db, file_id, self.module, &impl_block_ast);
                    let id = self.impls.alloc(impl_block);
                    for &impl_item in &self.impls[id].items {
                        self.impls_by_def.insert(impl_item, id);
                    }

                    source_map.insert(id, file_id, &impl_block_ast);
                }
                ast::ItemOrMacro::Item(_) => (),
                ast::ItemOrMacro::Macro(macro_call) => {
                    let attrs = Attr::from_attrs_owner(file_id, &macro_call, db);
                    if attrs.map_or(false, |attrs| {
                        attrs.iter().any(|attr| attr.is_cfg_enabled(cfg_options) == Some(false))
                    }) {
                        continue;
                    }

                    //FIXME: we should really cut down on the boilerplate required to process a macro
                    let ast_id = AstId::new(file_id, db.ast_id_map(file_id).ast_id(&macro_call));
                    if let Some(path) = macro_call
                        .path()
                        .and_then(|path| Path::from_src(Source { ast: path, file_id }, db))
                    {
                        if let Some(def) = self.module.resolver(db).resolve_path_as_macro(db, &path)
                        {
                            let call_id = db.intern_macro(MacroCallLoc { def: def.id, ast_id });
                            let file_id = call_id.as_file(MacroFileKind::Items);
                            if let Some(item_list) =
                                db.parse_or_expand(file_id).and_then(ast::MacroItems::cast)
                            {
                                self.collect_from_item_owner(
                                    db,
                                    cfg_options,
                                    source_map,
                                    &item_list,
                                    file_id,
                                )
                            }
                        }
                    }
                }
            }
        }
    }
}