//! This module implements import-resolution/macro expansion algorithm.
//!
//! The result of this module is `CrateDefMap`: a data structure which contains:
//!
//!   * a tree of modules for the crate
//!   * for each module, a set of items visible in the module (directly declared
//!     or imported)
//!
//! Note that `CrateDefMap` contains fully macro expanded code.
//!
//! Computing `CrateDefMap` can be partitioned into several logically
//! independent "phases". The phases are mutually recursive though, there's no
//! strict ordering.
//!
//! ## Collecting RawItems
//!
//! This happens in the `raw` module, which parses a single source file into a
//! set of top-level items. Nested imports are desugared to flat imports in this
//! phase. Macro calls are represented as a triple of (Path, Option<Name>,
//! TokenTree).
//!
//! ## Collecting Modules
//!
//! This happens in the `collector` module. In this phase, we recursively walk
//! tree of modules, collect raw items from submodules, populate module scopes
//! with defined items (so, we assign item ids in this phase) and record the set
//! of unresolved imports and macros.
//!
//! While we walk tree of modules, we also record macro_rules definitions and
//! expand calls to macro_rules defined macros.
//!
//! ## Resolving Imports
//!
//! We maintain a list of currently unresolved imports. On every iteration, we
//! try to resolve some imports from this list. If the import is resolved, we
//! record it, by adding an item to current module scope and, if necessary, by
//! recursively populating glob imports.
//!
//! ## Resolving Macros
//!
//! macro_rules from the same crate use a global mutable namespace. We expand
//! them immediately, when we collect modules.
//!
//! Macros from other crates (including proc-macros) can be used with
//! `foo::bar!` syntax. We handle them similarly to imports. There's a list of
//! unexpanded macros. On every iteration, we try to resolve each macro call
//! path and, upon success, we run macro expansion and "collect module" phase on
//! the result

mod collector;
mod mod_resolution;
mod path_resolution;

#[cfg(test)]
mod tests;

use std::sync::Arc;

use arena::Arena;
use base_db::{CrateId, Edition, FileId};
use hir_expand::{diagnostics::DiagnosticSink, name::Name, InFile};
use rustc_hash::FxHashMap;
use stdx::format_to;
use syntax::ast;

use crate::{
    db::DefDatabase,
    item_scope::{BuiltinShadowMode, ItemScope},
    nameres::{diagnostics::DefDiagnostic, path_resolution::ResolveMode},
    path::ModPath,
    per_ns::PerNs,
    AstId, LocalModuleId, ModuleDefId, ModuleId,
};

/// Contains all top-level defs from a macro-expanded crate
#[derive(Debug, PartialEq, Eq)]
pub struct CrateDefMap {
    pub root: LocalModuleId,
    pub modules: Arena<ModuleData>,
    pub(crate) krate: CrateId,
    /// The prelude module for this crate. This either comes from an import
    /// marked with the `prelude_import` attribute, or (in the normal case) from
    /// a dependency (`std` or `core`).
    pub(crate) prelude: Option<ModuleId>,
    pub(crate) extern_prelude: FxHashMap<Name, ModuleDefId>,

    edition: Edition,
    diagnostics: Vec<DefDiagnostic>,
}

impl std::ops::Index<LocalModuleId> for CrateDefMap {
    type Output = ModuleData;
    fn index(&self, id: LocalModuleId) -> &ModuleData {
        &self.modules[id]
    }
}

#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
pub enum ModuleOrigin {
    CrateRoot {
        definition: FileId,
    },
    /// Note that non-inline modules, by definition, live inside non-macro file.
    File {
        is_mod_rs: bool,
        declaration: AstId<ast::Module>,
        definition: FileId,
    },
    Inline {
        definition: AstId<ast::Module>,
    },
}

impl Default for ModuleOrigin {
    fn default() -> Self {
        ModuleOrigin::CrateRoot { definition: FileId(0) }
    }
}

impl ModuleOrigin {
    fn declaration(&self) -> Option<AstId<ast::Module>> {
        match self {
            ModuleOrigin::File { declaration: module, .. }
            | ModuleOrigin::Inline { definition: module, .. } => Some(*module),
            ModuleOrigin::CrateRoot { .. } => None,
        }
    }

    pub fn file_id(&self) -> Option<FileId> {
        match self {
            ModuleOrigin::File { definition, .. } | ModuleOrigin::CrateRoot { definition } => {
                Some(*definition)
            }
            _ => None,
        }
    }

    pub fn is_inline(&self) -> bool {
        match self {
            ModuleOrigin::Inline { .. } => true,
            ModuleOrigin::CrateRoot { .. } | ModuleOrigin::File { .. } => false,
        }
    }

    /// Returns a node which defines this module.
    /// That is, a file or a `mod foo {}` with items.
    fn definition_source(&self, db: &dyn DefDatabase) -> InFile<ModuleSource> {
        match self {
            ModuleOrigin::File { definition, .. } | ModuleOrigin::CrateRoot { definition } => {
                let file_id = *definition;
                let sf = db.parse(file_id).tree();
                InFile::new(file_id.into(), ModuleSource::SourceFile(sf))
            }
            ModuleOrigin::Inline { definition } => InFile::new(
                definition.file_id,
                ModuleSource::Module(definition.to_node(db.upcast())),
            ),
        }
    }
}

#[derive(Default, Debug, PartialEq, Eq)]
pub struct ModuleData {
    pub parent: Option<LocalModuleId>,
    pub children: FxHashMap<Name, LocalModuleId>,
    pub scope: ItemScope,

    /// Where does this module come from?
    pub origin: ModuleOrigin,
}

impl CrateDefMap {
    pub(crate) fn crate_def_map_query(db: &dyn DefDatabase, krate: CrateId) -> Arc<CrateDefMap> {
        let _p = profile::span("crate_def_map_query").detail(|| {
            db.crate_graph()[krate].display_name.as_deref().unwrap_or_default().to_string()
        });
        let def_map = {
            let edition = db.crate_graph()[krate].edition;
            let mut modules: Arena<ModuleData> = Arena::default();
            let root = modules.alloc(ModuleData::default());
            CrateDefMap {
                krate,
                edition,
                extern_prelude: FxHashMap::default(),
                prelude: None,
                root,
                modules,
                diagnostics: Vec::new(),
            }
        };
        let def_map = collector::collect_defs(db, def_map);
        Arc::new(def_map)
    }

    pub fn add_diagnostics(
        &self,
        db: &dyn DefDatabase,
        module: LocalModuleId,
        sink: &mut DiagnosticSink,
    ) {
        self.diagnostics.iter().for_each(|it| it.add_to(db, module, sink))
    }

    pub fn modules_for_file(&self, file_id: FileId) -> impl Iterator<Item = LocalModuleId> + '_ {
        self.modules
            .iter()
            .filter(move |(_id, data)| data.origin.file_id() == Some(file_id))
            .map(|(id, _data)| id)
    }

    pub(crate) fn resolve_path(
        &self,
        db: &dyn DefDatabase,
        original_module: LocalModuleId,
        path: &ModPath,
        shadow: BuiltinShadowMode,
    ) -> (PerNs, Option<usize>) {
        let res =
            self.resolve_path_fp_with_macro(db, ResolveMode::Other, original_module, path, shadow);
        (res.resolved_def, res.segment_index)
    }

    // FIXME: this can use some more human-readable format (ideally, an IR
    // even), as this should be a great debugging aid.
    pub fn dump(&self) -> String {
        let mut buf = String::new();
        go(&mut buf, self, "crate", self.root);
        return buf;

        fn go(buf: &mut String, map: &CrateDefMap, path: &str, module: LocalModuleId) {
            format_to!(buf, "{}\n", path);

            let mut entries: Vec<_> = map.modules[module].scope.resolutions().collect();
            entries.sort_by_key(|(name, _)| name.clone());

            for (name, def) in entries {
                format_to!(buf, "{}:", name.map_or("_".to_string(), |name| name.to_string()));

                if def.types.is_some() {
                    buf.push_str(" t");
                }
                if def.values.is_some() {
                    buf.push_str(" v");
                }
                if def.macros.is_some() {
                    buf.push_str(" m");
                }
                if def.is_none() {
                    buf.push_str(" _");
                }

                buf.push_str("\n");
            }

            for (name, child) in map.modules[module].children.iter() {
                let path = format!("{}::{}", path, name);
                buf.push('\n');
                go(buf, map, &path, *child);
            }
        }
    }
}

impl ModuleData {
    /// Returns a node which defines this module. That is, a file or a `mod foo {}` with items.
    pub fn definition_source(&self, db: &dyn DefDatabase) -> InFile<ModuleSource> {
        self.origin.definition_source(db)
    }

    /// Returns a node which declares this module, either a `mod foo;` or a `mod foo {}`.
    /// `None` for the crate root or block.
    pub fn declaration_source(&self, db: &dyn DefDatabase) -> Option<InFile<ast::Module>> {
        let decl = self.origin.declaration()?;
        let value = decl.to_node(db.upcast());
        Some(InFile { file_id: decl.file_id, value })
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ModuleSource {
    SourceFile(ast::SourceFile),
    Module(ast::Module),
}

mod diagnostics {
    use cfg::{CfgExpr, CfgOptions};
    use hir_expand::diagnostics::DiagnosticSink;
    use hir_expand::hygiene::Hygiene;
    use hir_expand::{InFile, MacroCallKind};
    use syntax::{ast, AstPtr, SyntaxNodePtr};

    use crate::path::ModPath;
    use crate::{db::DefDatabase, diagnostics::*, nameres::LocalModuleId, AstId};

    #[derive(Debug, PartialEq, Eq)]
    enum DiagnosticKind {
        UnresolvedModule { declaration: AstId<ast::Module>, candidate: String },

        UnresolvedExternCrate { ast: AstId<ast::ExternCrate> },

        UnresolvedImport { ast: AstId<ast::Use>, index: usize },

        UnconfiguredCode { ast: AstId<ast::Item>, cfg: CfgExpr, opts: CfgOptions },

        UnresolvedProcMacro { ast: MacroCallKind },

        MacroError { ast: MacroCallKind, message: String },
    }

    #[derive(Debug, PartialEq, Eq)]
    pub(super) struct DefDiagnostic {
        in_module: LocalModuleId,
        kind: DiagnosticKind,
    }

    impl DefDiagnostic {
        pub(super) fn unresolved_module(
            container: LocalModuleId,
            declaration: AstId<ast::Module>,
            candidate: String,
        ) -> Self {
            Self {
                in_module: container,
                kind: DiagnosticKind::UnresolvedModule { declaration, candidate },
            }
        }

        pub(super) fn unresolved_extern_crate(
            container: LocalModuleId,
            declaration: AstId<ast::ExternCrate>,
        ) -> Self {
            Self {
                in_module: container,
                kind: DiagnosticKind::UnresolvedExternCrate { ast: declaration },
            }
        }

        pub(super) fn unresolved_import(
            container: LocalModuleId,
            ast: AstId<ast::Use>,
            index: usize,
        ) -> Self {
            Self { in_module: container, kind: DiagnosticKind::UnresolvedImport { ast, index } }
        }

        pub(super) fn unconfigured_code(
            container: LocalModuleId,
            ast: AstId<ast::Item>,
            cfg: CfgExpr,
            opts: CfgOptions,
        ) -> Self {
            Self { in_module: container, kind: DiagnosticKind::UnconfiguredCode { ast, cfg, opts } }
        }

        pub(super) fn unresolved_proc_macro(container: LocalModuleId, ast: MacroCallKind) -> Self {
            Self { in_module: container, kind: DiagnosticKind::UnresolvedProcMacro { ast } }
        }

        pub(super) fn macro_error(
            container: LocalModuleId,
            ast: MacroCallKind,
            message: String,
        ) -> Self {
            Self { in_module: container, kind: DiagnosticKind::MacroError { ast, message } }
        }

        pub(super) fn add_to(
            &self,
            db: &dyn DefDatabase,
            target_module: LocalModuleId,
            sink: &mut DiagnosticSink,
        ) {
            if self.in_module != target_module {
                return;
            }

            match &self.kind {
                DiagnosticKind::UnresolvedModule { declaration, candidate } => {
                    let decl = declaration.to_node(db.upcast());
                    sink.push(UnresolvedModule {
                        file: declaration.file_id,
                        decl: AstPtr::new(&decl),
                        candidate: candidate.clone(),
                    })
                }

                DiagnosticKind::UnresolvedExternCrate { ast } => {
                    let item = ast.to_node(db.upcast());
                    sink.push(UnresolvedExternCrate {
                        file: ast.file_id,
                        item: AstPtr::new(&item),
                    });
                }

                DiagnosticKind::UnresolvedImport { ast, index } => {
                    let use_item = ast.to_node(db.upcast());
                    let hygiene = Hygiene::new(db.upcast(), ast.file_id);
                    let mut cur = 0;
                    let mut tree = None;
                    ModPath::expand_use_item(
                        InFile::new(ast.file_id, use_item),
                        &hygiene,
                        |_mod_path, use_tree, _is_glob, _alias| {
                            if cur == *index {
                                tree = Some(use_tree.clone());
                            }

                            cur += 1;
                        },
                    );

                    if let Some(tree) = tree {
                        sink.push(UnresolvedImport { file: ast.file_id, node: AstPtr::new(&tree) });
                    }
                }

                DiagnosticKind::UnconfiguredCode { ast, cfg, opts } => {
                    let item = ast.to_node(db.upcast());
                    sink.push(InactiveCode {
                        file: ast.file_id,
                        node: AstPtr::new(&item).into(),
                        cfg: cfg.clone(),
                        opts: opts.clone(),
                    });
                }

                DiagnosticKind::UnresolvedProcMacro { ast } => {
                    let (file, ast, name) = match ast {
                        MacroCallKind::FnLike(ast) => {
                            let node = ast.to_node(db.upcast());
                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
                        }
                        MacroCallKind::Attr(ast, name) => {
                            let node = ast.to_node(db.upcast());
                            (
                                ast.file_id,
                                SyntaxNodePtr::from(AstPtr::new(&node)),
                                Some(name.to_string()),
                            )
                        }
                    };
                    sink.push(UnresolvedProcMacro { file, node: ast, macro_name: name });
                }

                DiagnosticKind::MacroError { ast, message } => {
                    let (file, ast) = match ast {
                        MacroCallKind::FnLike(ast) => {
                            let node = ast.to_node(db.upcast());
                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                        }
                        MacroCallKind::Attr(ast, _) => {
                            let node = ast.to_node(db.upcast());
                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                        }
                    };
                    sink.push(MacroError { file, node: ast, message: message.clone() });
                }
            }
        }
    }
}