//! Lookup hir elements using positions in the source code. This is a lossy
//! transformation: in general, a single source might correspond to several
//! modules, functions, etc, due to macros, cfgs and `#[path=]` attributes on
//! modules.
//!
//! So, this modules should not be used during hir construction, it exists
//! purely for "IDE needs".
use std::sync::Arc;

use either::Either;
use hir_def::{
    body::{
        scope::{ExprScopes, ScopeId},
        BodySourceMap,
    },
    expr::{ExprId, PatId},
    resolver::{self, resolver_for_scope, Resolver, TypeNs, ValueNs},
    DefWithBodyId, TraitId,
};
use hir_expand::{
    hygiene::Hygiene, name::AsName, AstId, HirFileId, InFile, MacroCallId, MacroCallKind,
};
use hir_ty::{InEnvironment, InferenceResult, TraitEnvironment};
use ra_syntax::{
    ast::{self, AstNode},
    AstPtr, SyntaxNode, SyntaxNodePtr, SyntaxToken, TextRange, TextUnit,
};
use rustc_hash::FxHashSet;

use crate::{
    db::HirDatabase, Adt, Const, DefWithBody, EnumVariant, Function, Local, MacroDef, Name, Path,
    ScopeDef, Static, Struct, Trait, Type, TypeAlias, TypeParam,
};

/// `SourceAnalyzer` is a convenience wrapper which exposes HIR API in terms of
/// original source files. It should not be used pinside the HIR itself.
#[derive(Debug)]
pub struct SourceAnalyzer {
    file_id: HirFileId,
    resolver: Resolver,
    body_owner: Option<DefWithBody>,
    body_source_map: Option<Arc<BodySourceMap>>,
    infer: Option<Arc<InferenceResult>>,
    scopes: Option<Arc<ExprScopes>>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum PathResolution {
    /// An item
    Def(crate::ModuleDef),
    /// A local binding (only value namespace)
    Local(Local),
    /// A generic parameter
    TypeParam(TypeParam),
    SelfType(crate::ImplBlock),
    Macro(MacroDef),
    AssocItem(crate::AssocItem),
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ScopeEntryWithSyntax {
    pub(crate) name: Name,
    pub(crate) ptr: Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>,
}

impl ScopeEntryWithSyntax {
    pub fn name(&self) -> &Name {
        &self.name
    }

    pub fn ptr(&self) -> Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>> {
        self.ptr
    }
}

#[derive(Debug)]
pub struct ReferenceDescriptor {
    pub range: TextRange,
    pub name: String,
}

#[derive(Debug)]
pub struct Expansion {
    macro_call_id: MacroCallId,
}

impl Expansion {
    pub fn map_token_down(
        &self,
        db: &impl HirDatabase,
        token: InFile<&SyntaxToken>,
    ) -> Option<InFile<SyntaxToken>> {
        let exp_info = self.file_id().expansion_info(db)?;
        exp_info.map_token_down(token)
    }

    pub fn file_id(&self) -> HirFileId {
        self.macro_call_id.as_file()
    }
}

impl SourceAnalyzer {
    pub fn new(
        db: &impl HirDatabase,
        node: InFile<&SyntaxNode>,
        offset: Option<TextUnit>,
    ) -> SourceAnalyzer {
        crate::source_binder::SourceBinder::default().analyze(db, node, offset)
    }

    pub(crate) fn new_for_body(
        db: &impl HirDatabase,
        def: DefWithBodyId,
        node: InFile<&SyntaxNode>,
        offset: Option<TextUnit>,
    ) -> SourceAnalyzer {
        let (_body, source_map) = db.body_with_source_map(def);
        let scopes = db.expr_scopes(def);
        let scope = match offset {
            None => scope_for(&scopes, &source_map, node),
            Some(offset) => scope_for_offset(&scopes, &source_map, node.with_value(offset)),
        };
        let resolver = resolver_for_scope(db, def, scope);
        SourceAnalyzer {
            resolver,
            body_owner: Some(def.into()),
            body_source_map: Some(source_map),
            infer: Some(db.infer(def)),
            scopes: Some(scopes),
            file_id: node.file_id,
        }
    }

    pub(crate) fn new_for_resolver(
        resolver: Resolver,
        node: InFile<&SyntaxNode>,
    ) -> SourceAnalyzer {
        SourceAnalyzer {
            resolver,
            body_owner: None,
            body_source_map: None,
            infer: None,
            scopes: None,
            file_id: node.file_id,
        }
    }

    pub fn module(&self) -> Option<crate::code_model::Module> {
        Some(crate::code_model::Module { id: self.resolver.module()? })
    }

    fn expr_id(&self, expr: &ast::Expr) -> Option<ExprId> {
        let src = InFile { file_id: self.file_id, value: expr };
        self.body_source_map.as_ref()?.node_expr(src)
    }

    fn pat_id(&self, pat: &ast::Pat) -> Option<PatId> {
        let src = InFile { file_id: self.file_id, value: pat };
        self.body_source_map.as_ref()?.node_pat(src)
    }

    fn expand_expr(
        &self,
        db: &impl HirDatabase,
        expr: InFile<&ast::Expr>,
    ) -> Option<InFile<ast::Expr>> {
        let macro_call = ast::MacroCall::cast(expr.value.syntax().clone())?;
        let macro_file =
            self.body_source_map.as_ref()?.node_macro_file(expr.with_value(&macro_call))?;
        let expanded = db.parse_or_expand(macro_file)?;
        let kind = expanded.kind();
        let expr = InFile::new(macro_file, ast::Expr::cast(expanded)?);

        if ast::MacroCall::can_cast(kind) {
            self.expand_expr(db, expr.as_ref())
        } else {
            Some(expr)
        }
    }

    pub fn type_of(&self, db: &impl HirDatabase, expr: &ast::Expr) -> Option<Type> {
        let expr_id = if let Some(expr) = self.expand_expr(db, InFile::new(self.file_id, expr)) {
            self.body_source_map.as_ref()?.node_expr(expr.as_ref())?
        } else {
            self.expr_id(expr)?
        };

        let ty = self.infer.as_ref()?[expr_id].clone();
        let environment = TraitEnvironment::lower(db, &self.resolver);
        Some(Type { krate: self.resolver.krate()?, ty: InEnvironment { value: ty, environment } })
    }

    pub fn type_of_pat(&self, db: &impl HirDatabase, pat: &ast::Pat) -> Option<Type> {
        let pat_id = self.pat_id(pat)?;
        let ty = self.infer.as_ref()?[pat_id].clone();
        let environment = TraitEnvironment::lower(db, &self.resolver);
        Some(Type { krate: self.resolver.krate()?, ty: InEnvironment { value: ty, environment } })
    }

    pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
        let expr_id = self.expr_id(&call.clone().into())?;
        self.infer.as_ref()?.method_resolution(expr_id).map(Function::from)
    }

    pub fn resolve_field(&self, field: &ast::FieldExpr) -> Option<crate::StructField> {
        let expr_id = self.expr_id(&field.clone().into())?;
        self.infer.as_ref()?.field_resolution(expr_id).map(|it| it.into())
    }

    pub fn resolve_record_field(&self, field: &ast::RecordField) -> Option<crate::StructField> {
        let expr_id = match field.expr() {
            Some(it) => self.expr_id(&it)?,
            None => {
                let src = InFile { file_id: self.file_id, value: field };
                self.body_source_map.as_ref()?.field_init_shorthand_expr(src)?
            }
        };
        self.infer.as_ref()?.record_field_resolution(expr_id).map(|it| it.into())
    }

    pub fn resolve_record_literal(&self, record_lit: &ast::RecordLit) -> Option<crate::VariantDef> {
        let expr_id = self.expr_id(&record_lit.clone().into())?;
        self.infer.as_ref()?.variant_resolution_for_expr(expr_id).map(|it| it.into())
    }

    pub fn resolve_record_pattern(&self, record_pat: &ast::RecordPat) -> Option<crate::VariantDef> {
        let pat_id = self.pat_id(&record_pat.clone().into())?;
        self.infer.as_ref()?.variant_resolution_for_pat(pat_id).map(|it| it.into())
    }

    pub fn resolve_macro_call(
        &self,
        db: &impl HirDatabase,
        macro_call: InFile<&ast::MacroCall>,
    ) -> Option<MacroDef> {
        let hygiene = Hygiene::new(db, macro_call.file_id);
        let path = macro_call.value.path().and_then(|ast| Path::from_src(ast, &hygiene))?;
        self.resolver.resolve_path_as_macro(db, path.mod_path()).map(|it| it.into())
    }

    pub fn resolve_hir_path(
        &self,
        db: &impl HirDatabase,
        path: &crate::Path,
    ) -> Option<PathResolution> {
        let types =
            self.resolver.resolve_path_in_type_ns_fully(db, path.mod_path()).map(|ty| match ty {
                TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
                TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
                TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
                    PathResolution::Def(Adt::from(it).into())
                }
                TypeNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
                TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
                TypeNs::BuiltinType(it) => PathResolution::Def(it.into()),
                TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
            });
        let values =
            self.resolver.resolve_path_in_value_ns_fully(db, path.mod_path()).and_then(|val| {
                let res = match val {
                    ValueNs::LocalBinding(pat_id) => {
                        let var = Local { parent: self.body_owner?, pat_id };
                        PathResolution::Local(var)
                    }
                    ValueNs::FunctionId(it) => PathResolution::Def(Function::from(it).into()),
                    ValueNs::ConstId(it) => PathResolution::Def(Const::from(it).into()),
                    ValueNs::StaticId(it) => PathResolution::Def(Static::from(it).into()),
                    ValueNs::StructId(it) => PathResolution::Def(Struct::from(it).into()),
                    ValueNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
                };
                Some(res)
            });

        let items = self
            .resolver
            .resolve_module_path_in_items(db, path.mod_path())
            .take_types()
            .map(|it| PathResolution::Def(it.into()));
        types.or(values).or(items).or_else(|| {
            self.resolver
                .resolve_path_as_macro(db, path.mod_path())
                .map(|def| PathResolution::Macro(def.into()))
        })
    }

    pub fn resolve_path(&self, db: &impl HirDatabase, path: &ast::Path) -> Option<PathResolution> {
        if let Some(path_expr) = path.syntax().parent().and_then(ast::PathExpr::cast) {
            let expr_id = self.expr_id(&path_expr.into())?;
            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_expr(expr_id) {
                return Some(PathResolution::AssocItem(assoc.into()));
            }
        }
        if let Some(path_pat) = path.syntax().parent().and_then(ast::PathPat::cast) {
            let pat_id = self.pat_id(&path_pat.into())?;
            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_pat(pat_id) {
                return Some(PathResolution::AssocItem(assoc.into()));
            }
        }
        // This must be a normal source file rather than macro file.
        let hir_path = crate::Path::from_ast(path.clone())?;
        self.resolve_hir_path(db, &hir_path)
    }

    fn resolve_local_name(&self, name_ref: &ast::NameRef) -> Option<ScopeEntryWithSyntax> {
        let name = name_ref.as_name();
        let source_map = self.body_source_map.as_ref()?;
        let scopes = self.scopes.as_ref()?;
        let scope = scope_for(scopes, source_map, InFile::new(self.file_id, name_ref.syntax()))?;
        let entry = scopes.resolve_name_in_scope(scope, &name)?;
        Some(ScopeEntryWithSyntax {
            name: entry.name().clone(),
            ptr: source_map.pat_syntax(entry.pat())?.value,
        })
    }

    pub fn process_all_names(&self, db: &impl HirDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
        self.resolver.process_all_names(db, &mut |name, def| {
            let def = match def {
                resolver::ScopeDef::PerNs(it) => it.into(),
                resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
                resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
                resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(TypeParam { id }),
                resolver::ScopeDef::Local(pat_id) => {
                    let parent = self.resolver.body_owner().unwrap().into();
                    ScopeDef::Local(Local { parent, pat_id })
                }
            };
            f(name, def)
        })
    }

    // FIXME: we only use this in `inline_local_variable` assist, ideally, we
    // should switch to general reference search infra there.
    pub fn find_all_refs(&self, pat: &ast::BindPat) -> Vec<ReferenceDescriptor> {
        let fn_def = pat.syntax().ancestors().find_map(ast::FnDef::cast).unwrap();
        let ptr = Either::Left(AstPtr::new(&ast::Pat::from(pat.clone())));
        fn_def
            .syntax()
            .descendants()
            .filter_map(ast::NameRef::cast)
            .filter(|name_ref| match self.resolve_local_name(&name_ref) {
                None => false,
                Some(entry) => entry.ptr() == ptr,
            })
            .map(|name_ref| ReferenceDescriptor {
                name: name_ref.text().to_string(),
                range: name_ref.syntax().text_range(),
            })
            .collect()
    }

    /// Note: `FxHashSet<TraitId>` should be treated as an opaque type, passed into `Type
    pub fn traits_in_scope(&self, db: &impl HirDatabase) -> FxHashSet<TraitId> {
        self.resolver.traits_in_scope(db)
    }

    pub fn expand(
        &self,
        db: &impl HirDatabase,
        macro_call: InFile<&ast::MacroCall>,
    ) -> Option<Expansion> {
        let def = self.resolve_macro_call(db, macro_call)?.id;
        let ast_id = AstId::new(
            macro_call.file_id,
            db.ast_id_map(macro_call.file_id).ast_id(macro_call.value),
        );
        Some(Expansion { macro_call_id: def.as_call_id(db, MacroCallKind::FnLike(ast_id)) })
    }
}

fn scope_for(
    scopes: &ExprScopes,
    source_map: &BodySourceMap,
    node: InFile<&SyntaxNode>,
) -> Option<ScopeId> {
    node.value
        .ancestors()
        .filter_map(ast::Expr::cast)
        .filter_map(|it| source_map.node_expr(InFile::new(node.file_id, &it)))
        .find_map(|it| scopes.scope_for(it))
}

fn scope_for_offset(
    scopes: &ExprScopes,
    source_map: &BodySourceMap,
    offset: InFile<TextUnit>,
) -> Option<ScopeId> {
    scopes
        .scope_by_expr()
        .iter()
        .filter_map(|(id, scope)| {
            let source = source_map.expr_syntax(*id)?;
            // FIXME: correctly handle macro expansion
            if source.file_id != offset.file_id {
                return None;
            }
            let syntax_node_ptr =
                source.value.either(|it| it.syntax_node_ptr(), |it| it.syntax_node_ptr());
            Some((syntax_node_ptr, scope))
        })
        // find containing scope
        .min_by_key(|(ptr, _scope)| {
            (
                !(ptr.range().start() <= offset.value && offset.value <= ptr.range().end()),
                ptr.range().len(),
            )
        })
        .map(|(ptr, scope)| {
            adjust(scopes, source_map, ptr, offset.file_id, offset.value).unwrap_or(*scope)
        })
}

// XXX: during completion, cursor might be outside of any particular
// expression. Try to figure out the correct scope...
fn adjust(
    scopes: &ExprScopes,
    source_map: &BodySourceMap,
    ptr: SyntaxNodePtr,
    file_id: HirFileId,
    offset: TextUnit,
) -> Option<ScopeId> {
    let r = ptr.range();
    let child_scopes = scopes
        .scope_by_expr()
        .iter()
        .filter_map(|(id, scope)| {
            let source = source_map.expr_syntax(*id)?;
            // FIXME: correctly handle macro expansion
            if source.file_id != file_id {
                return None;
            }
            let syntax_node_ptr =
                source.value.either(|it| it.syntax_node_ptr(), |it| it.syntax_node_ptr());
            Some((syntax_node_ptr, scope))
        })
        .map(|(ptr, scope)| (ptr.range(), scope))
        .filter(|(range, _)| range.start() <= offset && range.is_subrange(&r) && *range != r);

    child_scopes
        .max_by(|(r1, _), (r2, _)| {
            if r2.is_subrange(&r1) {
                std::cmp::Ordering::Greater
            } else if r1.is_subrange(&r2) {
                std::cmp::Ordering::Less
            } else {
                r1.start().cmp(&r2.start())
            }
        })
        .map(|(_ptr, scope)| *scope)
}