use ruff_db::files::{File, FilePath};
use ruff_db::source::line_index;
use ruff_python_ast as ast;
use ruff_python_ast::{Expr, ExprRef, HasNodeIndex, name::Name};
use ruff_source_file::LineIndex;
use rustc_hash::FxHashMap;

use crate::Db;
use crate::module_name::ModuleName;
use crate::module_resolver::{KnownModule, Module, list_modules, resolve_module};
use crate::semantic_index::definition::Definition;
use crate::semantic_index::scope::FileScopeId;
use crate::semantic_index::semantic_index;
use crate::types::ide_support::all_declarations_and_bindings;
use crate::types::{Type, binding_type, infer_scope_types};

pub struct SemanticModel<'db> {
    db: &'db dyn Db,
    file: File,
}

impl<'db> SemanticModel<'db> {
    pub fn new(db: &'db dyn Db, file: File) -> Self {
        Self { db, file }
    }

    // TODO we don't actually want to expose the Db directly to lint rules, but we need to find a
    // solution for exposing information from types
    pub fn db(&self) -> &dyn Db {
        self.db
    }

    pub fn file_path(&self) -> &FilePath {
        self.file.path(self.db)
    }

    pub fn line_index(&self) -> LineIndex {
        line_index(self.db, self.file)
    }

    /// Returns a map from symbol name to that symbol's
    /// type and definition site (if available).
    ///
    /// The symbols are the symbols in scope at the given
    /// AST node.
    pub fn members_in_scope_at(
        &self,
        node: ast::AnyNodeRef<'_>,
    ) -> FxHashMap<Name, MemberDefinition<'db>> {
        let index = semantic_index(self.db, self.file);
        let mut members = FxHashMap::default();
        let Some(file_scope) = self.scope(node) else {
            return members;
        };

        for (file_scope, _) in index.ancestor_scopes(file_scope) {
            for memberdef in
                all_declarations_and_bindings(self.db, file_scope.to_scope_id(self.db, self.file))
            {
                members.insert(
                    memberdef.member.name,
                    MemberDefinition {
                        ty: memberdef.member.ty,
                        definition: memberdef.definition,
                    },
                );
            }
        }
        members
    }

    pub fn resolve_module(&self, module_name: &ModuleName) -> Option<Module<'_>> {
        resolve_module(self.db, module_name)
    }

    /// Returns completions for symbols available in a `import <CURSOR>` context.
    pub fn import_completions(&self) -> Vec<Completion<'db>> {
        list_modules(self.db)
            .into_iter()
            .map(|module| {
                let builtin = module.is_known(self.db, KnownModule::Builtins);
                let ty = Type::module_literal(self.db, self.file, module);
                Completion {
                    name: Name::new(module.name(self.db).as_str()),
                    ty: Some(ty),
                    builtin,
                }
            })
            .collect()
    }

    /// Returns completions for symbols available in a `from module import <CURSOR>` context.
    pub fn from_import_completions(
        &self,
        import: &ast::StmtImportFrom,
        _name: Option<usize>,
    ) -> Vec<Completion<'db>> {
        let module_name = match ModuleName::from_import_statement(self.db, self.file, import) {
            Ok(module_name) => module_name,
            Err(err) => {
                tracing::debug!(
                    "Could not extract module name from `{module:?}` with level {level}: {err:?}",
                    module = import.module,
                    level = import.level,
                );
                return vec![];
            }
        };
        self.module_completions(&module_name)
    }

    /// Returns completions only for submodules for the module
    /// identified by `name` in `import`.
    ///
    /// For example, `import re, os.<CURSOR>, zlib`.
    pub fn import_submodule_completions(
        &self,
        import: &ast::StmtImport,
        name: usize,
    ) -> Vec<Completion<'db>> {
        let module_ident = &import.names[name].name;
        let Some((parent_ident, _)) = module_ident.rsplit_once('.') else {
            return vec![];
        };
        let module_name =
            match ModuleName::from_identifier_parts(self.db, self.file, Some(parent_ident), 0) {
                Ok(module_name) => module_name,
                Err(err) => {
                    tracing::debug!(
                        "Could not extract module name from `{module:?}`: {err:?}",
                        module = module_ident,
                    );
                    return vec![];
                }
            };
        self.import_submodule_completions_for_name(&module_name)
    }

    /// Returns completions only for submodules for the module
    /// used in a `from module import attribute` statement.
    ///
    /// For example, `from os.<CURSOR>`.
    pub fn from_import_submodule_completions(
        &self,
        import: &ast::StmtImportFrom,
    ) -> Vec<Completion<'db>> {
        let level = import.level;
        let Some(module_ident) = import.module.as_deref() else {
            return vec![];
        };
        let Some((parent_ident, _)) = module_ident.rsplit_once('.') else {
            return vec![];
        };
        let module_name = match ModuleName::from_identifier_parts(
            self.db,
            self.file,
            Some(parent_ident),
            level,
        ) {
            Ok(module_name) => module_name,
            Err(err) => {
                tracing::debug!(
                    "Could not extract module name from `{module:?}` with level {level}: {err:?}",
                    module = import.module,
                    level = import.level,
                );
                return vec![];
            }
        };
        self.import_submodule_completions_for_name(&module_name)
    }

    /// Returns submodule-only completions for the given module.
    fn import_submodule_completions_for_name(
        &self,
        module_name: &ModuleName,
    ) -> Vec<Completion<'db>> {
        let Some(module) = resolve_module(self.db, module_name) else {
            tracing::debug!("Could not resolve module from `{module_name:?}`");
            return vec![];
        };
        self.submodule_completions(&module)
    }

    /// Returns completions for symbols available in the given module as if
    /// it were imported by this model's `File`.
    fn module_completions(&self, module_name: &ModuleName) -> Vec<Completion<'db>> {
        let Some(module) = resolve_module(self.db, module_name) else {
            tracing::debug!("Could not resolve module from `{module_name:?}`");
            return vec![];
        };
        let ty = Type::module_literal(self.db, self.file, module);
        let builtin = module.is_known(self.db, KnownModule::Builtins);

        let mut completions = vec![];
        for crate::types::Member { name, ty } in crate::types::all_members(self.db, ty) {
            completions.push(Completion {
                name,
                ty: Some(ty),
                builtin,
            });
        }
        completions.extend(self.submodule_completions(&module));
        completions
    }

    /// Returns completions for submodules of the given module.
    fn submodule_completions(&self, module: &Module<'db>) -> Vec<Completion<'db>> {
        let builtin = module.is_known(self.db, KnownModule::Builtins);

        let mut completions = vec![];
        for submodule in module.all_submodules(self.db) {
            let ty = Type::module_literal(self.db, self.file, *submodule);
            let Some(base) = submodule.name(self.db).components().next_back() else {
                continue;
            };
            completions.push(Completion {
                name: Name::new(base),
                ty: Some(ty),
                builtin,
            });
        }
        completions
    }

    /// Returns completions for symbols available in a `object.<CURSOR>` context.
    pub fn attribute_completions(&self, node: &ast::ExprAttribute) -> Vec<Completion<'db>> {
        let ty = node.value.inferred_type(self);
        crate::types::all_members(self.db, ty)
            .into_iter()
            .map(|member| Completion {
                name: member.name,
                ty: Some(member.ty),
                builtin: false,
            })
            .collect()
    }

    /// Returns completions for symbols available in the scope containing the
    /// given expression.
    ///
    /// If a scope could not be determined, then completions for the global
    /// scope of this model's `File` are returned.
    pub fn scoped_completions(&self, node: ast::AnyNodeRef<'_>) -> Vec<Completion<'db>> {
        let index = semantic_index(self.db, self.file);

        let Some(file_scope) = self.scope(node) else {
            return vec![];
        };
        let mut completions = vec![];
        for (file_scope, _) in index.ancestor_scopes(file_scope) {
            completions.extend(
                all_declarations_and_bindings(self.db, file_scope.to_scope_id(self.db, self.file))
                    .map(|memberdef| Completion {
                        name: memberdef.member.name,
                        ty: Some(memberdef.member.ty),
                        builtin: false,
                    }),
            );
        }
        // Builtins are available in all scopes.
        let builtins = ModuleName::new("builtins").expect("valid module name");
        completions.extend(self.module_completions(&builtins));
        completions
    }

    fn scope(&self, node: ast::AnyNodeRef<'_>) -> Option<FileScopeId> {
        let index = semantic_index(self.db, self.file);

        match node {
            ast::AnyNodeRef::Identifier(identifier) => index.try_expression_scope_id(identifier),
            node => match node.as_expr_ref() {
                // If we couldn't identify a specific
                // expression that we're in, then just
                // fall back to the global scope.
                None => Some(FileScopeId::global()),
                Some(expr) => index.try_expression_scope_id(&expr),
            },
        }
    }
}

/// The type and definition (if available) of a symbol.
#[derive(Clone, Debug)]
pub struct MemberDefinition<'db> {
    pub ty: Type<'db>,
    pub definition: Option<Definition<'db>>,
}

/// A classification of symbol names.
///
/// The ordering here is used for sorting completions.
///
/// This sorts "normal" names first, then dunder names and finally
/// single-underscore names. This matches the order of the variants defined for
/// this enum, which is in turn picked up by the derived trait implementation
/// for `Ord`.
#[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord)]
pub enum NameKind {
    Normal,
    Dunder,
    Sunder,
}

impl NameKind {
    pub fn classify(name: &Name) -> NameKind {
        // Dunder needs a prefix and suffix double underscore.
        // When there's only a prefix double underscore, this
        // results in explicit name mangling. We let that be
        // classified as-if they were single underscore names.
        //
        // Ref: <https://docs.python.org/3/reference/lexical_analysis.html#reserved-classes-of-identifiers>
        if name.starts_with("__") && name.ends_with("__") {
            NameKind::Dunder
        } else if name.starts_with('_') {
            NameKind::Sunder
        } else {
            NameKind::Normal
        }
    }
}

/// A suggestion for code completion.
#[derive(Clone, Debug)]
pub struct Completion<'db> {
    /// The label shown to the user for this suggestion.
    pub name: Name,
    /// The type of this completion, if available.
    ///
    /// Generally speaking, this is always available
    /// *unless* this was a completion corresponding to
    /// an unimported symbol. In that case, computing the
    /// type of all such symbols could be quite expensive.
    pub ty: Option<Type<'db>>,
    /// Whether this suggestion came from builtins or not.
    ///
    /// At time of writing (2025-06-26), this information
    /// doesn't make it into the LSP response. Instead, we
    /// use it mainly in tests so that we can write less
    /// noisy tests.
    pub builtin: bool,
}

pub trait HasType {
    /// Returns the inferred type of `self`.
    ///
    /// ## Panics
    /// May panic if `self` is from another file than `model`.
    fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db>;
}

pub trait HasDefinition {
    /// Returns the inferred type of `self`.
    ///
    /// ## Panics
    /// May panic if `self` is from another file than `model`.
    fn definition<'db>(&self, model: &SemanticModel<'db>) -> Definition<'db>;
}

impl HasType for ast::ExprRef<'_> {
    fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
        let index = semantic_index(model.db, model.file);
        let file_scope = index.expression_scope_id(self);
        let scope = file_scope.to_scope_id(model.db, model.file);

        infer_scope_types(model.db, scope).expression_type(*self)
    }
}

macro_rules! impl_expression_has_type {
    ($ty: ty) => {
        impl HasType for $ty {
            #[inline]
            fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
                let expression_ref = ExprRef::from(self);
                expression_ref.inferred_type(model)
            }
        }
    };
}

impl_expression_has_type!(ast::ExprBoolOp);
impl_expression_has_type!(ast::ExprNamed);
impl_expression_has_type!(ast::ExprBinOp);
impl_expression_has_type!(ast::ExprUnaryOp);
impl_expression_has_type!(ast::ExprLambda);
impl_expression_has_type!(ast::ExprIf);
impl_expression_has_type!(ast::ExprDict);
impl_expression_has_type!(ast::ExprSet);
impl_expression_has_type!(ast::ExprListComp);
impl_expression_has_type!(ast::ExprSetComp);
impl_expression_has_type!(ast::ExprDictComp);
impl_expression_has_type!(ast::ExprGenerator);
impl_expression_has_type!(ast::ExprAwait);
impl_expression_has_type!(ast::ExprYield);
impl_expression_has_type!(ast::ExprYieldFrom);
impl_expression_has_type!(ast::ExprCompare);
impl_expression_has_type!(ast::ExprCall);
impl_expression_has_type!(ast::ExprFString);
impl_expression_has_type!(ast::ExprTString);
impl_expression_has_type!(ast::ExprStringLiteral);
impl_expression_has_type!(ast::ExprBytesLiteral);
impl_expression_has_type!(ast::ExprNumberLiteral);
impl_expression_has_type!(ast::ExprBooleanLiteral);
impl_expression_has_type!(ast::ExprNoneLiteral);
impl_expression_has_type!(ast::ExprEllipsisLiteral);
impl_expression_has_type!(ast::ExprAttribute);
impl_expression_has_type!(ast::ExprSubscript);
impl_expression_has_type!(ast::ExprStarred);
impl_expression_has_type!(ast::ExprName);
impl_expression_has_type!(ast::ExprList);
impl_expression_has_type!(ast::ExprTuple);
impl_expression_has_type!(ast::ExprSlice);
impl_expression_has_type!(ast::ExprIpyEscapeCommand);

impl HasType for ast::Expr {
    fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
        match self {
            Expr::BoolOp(inner) => inner.inferred_type(model),
            Expr::Named(inner) => inner.inferred_type(model),
            Expr::BinOp(inner) => inner.inferred_type(model),
            Expr::UnaryOp(inner) => inner.inferred_type(model),
            Expr::Lambda(inner) => inner.inferred_type(model),
            Expr::If(inner) => inner.inferred_type(model),
            Expr::Dict(inner) => inner.inferred_type(model),
            Expr::Set(inner) => inner.inferred_type(model),
            Expr::ListComp(inner) => inner.inferred_type(model),
            Expr::SetComp(inner) => inner.inferred_type(model),
            Expr::DictComp(inner) => inner.inferred_type(model),
            Expr::Generator(inner) => inner.inferred_type(model),
            Expr::Await(inner) => inner.inferred_type(model),
            Expr::Yield(inner) => inner.inferred_type(model),
            Expr::YieldFrom(inner) => inner.inferred_type(model),
            Expr::Compare(inner) => inner.inferred_type(model),
            Expr::Call(inner) => inner.inferred_type(model),
            Expr::FString(inner) => inner.inferred_type(model),
            Expr::TString(inner) => inner.inferred_type(model),
            Expr::StringLiteral(inner) => inner.inferred_type(model),
            Expr::BytesLiteral(inner) => inner.inferred_type(model),
            Expr::NumberLiteral(inner) => inner.inferred_type(model),
            Expr::BooleanLiteral(inner) => inner.inferred_type(model),
            Expr::NoneLiteral(inner) => inner.inferred_type(model),
            Expr::EllipsisLiteral(inner) => inner.inferred_type(model),
            Expr::Attribute(inner) => inner.inferred_type(model),
            Expr::Subscript(inner) => inner.inferred_type(model),
            Expr::Starred(inner) => inner.inferred_type(model),
            Expr::Name(inner) => inner.inferred_type(model),
            Expr::List(inner) => inner.inferred_type(model),
            Expr::Tuple(inner) => inner.inferred_type(model),
            Expr::Slice(inner) => inner.inferred_type(model),
            Expr::IpyEscapeCommand(inner) => inner.inferred_type(model),
        }
    }
}

macro_rules! impl_binding_has_ty_def {
    ($ty: ty) => {
        impl HasDefinition for $ty {
            #[inline]
            fn definition<'db>(&self, model: &SemanticModel<'db>) -> Definition<'db> {
                let index = semantic_index(model.db, model.file);
                index.expect_single_definition(self)
            }
        }

        impl HasType for $ty {
            #[inline]
            fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
                let binding = HasDefinition::definition(self, model);
                binding_type(model.db, binding)
            }
        }
    };
}

impl_binding_has_ty_def!(ast::StmtFunctionDef);
impl_binding_has_ty_def!(ast::StmtClassDef);
impl_binding_has_ty_def!(ast::Parameter);
impl_binding_has_ty_def!(ast::ParameterWithDefault);
impl_binding_has_ty_def!(ast::ExceptHandlerExceptHandler);

impl HasType for ast::Alias {
    fn inferred_type<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
        if &self.name == "*" {
            return Type::Never;
        }
        let index = semantic_index(model.db, model.file);
        binding_type(model.db, index.expect_single_definition(self))
    }
}

/// Implemented by types for which the semantic index tracks their scope.
pub(crate) trait HasTrackedScope: HasNodeIndex {}

impl HasTrackedScope for ast::Expr {}

impl HasTrackedScope for ast::ExprRef<'_> {}
impl HasTrackedScope for &ast::ExprRef<'_> {}

// See https://github.com/astral-sh/ty/issues/572 why this implementation exists
// even when we never register identifiers during semantic index building.
impl HasTrackedScope for ast::Identifier {}

#[cfg(test)]
mod tests {
    use ruff_db::files::system_path_to_file;
    use ruff_db::parsed::parsed_module;

    use crate::db::tests::TestDbBuilder;
    use crate::{HasType, SemanticModel};

    #[test]
    fn function_type() -> anyhow::Result<()> {
        let db = TestDbBuilder::new()
            .with_file("/src/foo.py", "def test(): pass")
            .build()?;

        let foo = system_path_to_file(&db, "/src/foo.py").unwrap();

        let ast = parsed_module(&db, foo).load(&db);

        let function = ast.suite()[0].as_function_def_stmt().unwrap();
        let model = SemanticModel::new(&db, foo);
        let ty = function.inferred_type(&model);

        assert!(ty.is_function_literal());

        Ok(())
    }

    #[test]
    fn class_type() -> anyhow::Result<()> {
        let db = TestDbBuilder::new()
            .with_file("/src/foo.py", "class Test: pass")
            .build()?;

        let foo = system_path_to_file(&db, "/src/foo.py").unwrap();

        let ast = parsed_module(&db, foo).load(&db);

        let class = ast.suite()[0].as_class_def_stmt().unwrap();
        let model = SemanticModel::new(&db, foo);
        let ty = class.inferred_type(&model);

        assert!(ty.is_class_literal());

        Ok(())
    }

    #[test]
    fn alias_type() -> anyhow::Result<()> {
        let db = TestDbBuilder::new()
            .with_file("/src/foo.py", "class Test: pass")
            .with_file("/src/bar.py", "from foo import Test")
            .build()?;

        let bar = system_path_to_file(&db, "/src/bar.py").unwrap();

        let ast = parsed_module(&db, bar).load(&db);

        let import = ast.suite()[0].as_import_from_stmt().unwrap();
        let alias = &import.names[0];
        let model = SemanticModel::new(&db, bar);
        let ty = alias.inferred_type(&model);

        assert!(ty.is_class_literal());

        Ok(())
    }
}