// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/visitor.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/nullability_suffix.dart';
import 'package:analyzer/dart/element/scope.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/dart/element/scope.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/element/type_system.dart';
import 'package:analyzer/src/summary2/function_type_builder.dart';
import 'package:analyzer/src/summary2/linked_element_factory.dart';
import 'package:analyzer/src/summary2/linking_node_scope.dart';
import 'package:analyzer/src/summary2/named_type_builder.dart';
import 'package:analyzer/src/summary2/reference.dart';
import 'package:analyzer/src/summary2/types_builder.dart';

/// Recursive visitor of [LinkedNode]s that resolves explicit type annotations
/// in outlines.  This includes resolving element references in identifiers
/// in type annotation, and setting [LinkedNodeType]s for corresponding type
/// annotation nodes.
///
/// Declarations that have type annotations, e.g. return types of methods, get
/// the corresponding type set (so, if there is an explicit type annotation,
/// the type is set, otherwise we keep it empty, so we will attempt to infer
/// it later).
class ReferenceResolver extends ThrowingAstVisitor<void> {
  final TypeSystemImpl _typeSystem;
  final NodesToBuildType nodesToBuildType;
  final LinkedElementFactory elementFactory;
  final Reference unitReference;

  /// Indicates whether the library is opted into NNBD.
  final bool isNNBD;

  /// The depth-first number of the next [GenericFunctionType] node.
  int _nextGenericFunctionTypeId = 0;

  Reference? reference;
  Scope scope;

  ReferenceResolver(
    this.nodesToBuildType,
    this.elementFactory,
    LibraryElementImpl libraryElement,
    this.unitReference,
    this.isNNBD,
    this.scope,
  )   : _typeSystem = libraryElement.typeSystem,
        reference = unitReference;

  @override
  void visitBlockFunctionBody(BlockFunctionBody node) {}

  @override
  void visitClassDeclaration(ClassDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ClassElementImpl;
    reference = element.reference!;
    element.accessors; // create elements
    element.constructors; // create elements
    element.methods; // create elements

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);

    node.typeParameters?.accept(this);
    node.extendsClause?.accept(this);
    node.implementsClause?.accept(this);
    node.withClause?.accept(this);

    scope = ClassScope(scope, element);
    LinkingNodeContext(node, scope);

    node.members.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitClassTypeAlias(ClassTypeAlias node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ClassElementImpl;
    reference = element.reference!;

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);
    LinkingNodeContext(node, scope);

    node.typeParameters?.accept(this);
    node.superclass.accept(this);
    node.withClause.accept(this);
    node.implementsClause?.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitCompilationUnit(CompilationUnit node) {
    LinkingNodeContext(node, scope);
    node.declarations.accept(this);
  }

  @override
  void visitConstructorDeclaration(ConstructorDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ConstructorElementImpl;
    reference = element.reference!;
    element.parameters; // create elements

    scope = TypeParameterScope(scope, element.typeParameters);
    LinkingNodeContext(node, scope);

    node.parameters.accept(this);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitDefaultFormalParameter(DefaultFormalParameter node) {
    node.parameter.accept(this);
  }

  @override
  void visitEnumDeclaration(EnumDeclaration node) {}

  @override
  void visitExpressionFunctionBody(ExpressionFunctionBody node) {}

  @override
  void visitExtendsClause(ExtendsClause node) {
    node.superclass.accept(this);
  }

  @override
  void visitExtensionDeclaration(ExtensionDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ExtensionElementImpl;
    reference = element.reference!;

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);

    node.typeParameters?.accept(this);
    node.extendedType.accept(this);

    scope = ExtensionScope(scope, element);
    LinkingNodeContext(node, scope);

    node.members.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitFieldDeclaration(FieldDeclaration node) {
    node.fields.accept(this);
  }

  @override
  void visitFieldFormalParameter(FieldFormalParameter node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as FieldFormalParameterElementImpl;
    reference = element.reference;
    element.parameters; // create elements

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);

    node.type?.accept(this);
    node.typeParameters?.accept(this);
    node.parameters?.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitFormalParameterList(FormalParameterList node) {
    node.parameters.accept(this);
  }

  @override
  void visitFunctionDeclaration(FunctionDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ExecutableElementImpl;
    reference = element.reference!;
    element.parameters; // create elements

    _createTypeParameterElements(
      element,
      node.functionExpression.typeParameters,
    );
    scope = TypeParameterScope(outerScope, element.typeParameters);
    LinkingNodeContext(node, scope);

    node.returnType?.accept(this);
    node.functionExpression.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitFunctionExpression(FunctionExpression node) {
    node.typeParameters?.accept(this);
    node.parameters?.accept(this);
  }

  @override
  void visitFunctionTypeAlias(FunctionTypeAlias node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as FunctionTypeAliasElementImpl;
    reference = element.reference!;

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(outerScope, element.typeParameters);

    node.returnType?.accept(this);
    node.typeParameters?.accept(this);

    var functionElement = element.function;
    reference = functionElement.reference!;
    functionElement.parameters; // create elements
    node.parameters.accept(this);

    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitFunctionTypedFormalParameter(FunctionTypedFormalParameter node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ParameterElementImpl;
    reference = element.reference;
    element.parameters; // create elements

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);

    node.returnType?.accept(this);
    node.typeParameters?.accept(this);
    node.parameters.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitGenericFunctionType(GenericFunctionType node) {
    var nodeImpl = node as GenericFunctionTypeImpl;
    var outerScope = scope;
    var outerReference = reference;

    // TODO(scheglov) remove reference
    var id = _nextGenericFunctionTypeId++;
    var containerRef = unitReference.getChild('@genericFunctionType');
    reference = containerRef.getChild('$id');

    var element = GenericFunctionTypeElementImpl.forLinkedNode(
      unitReference.element as CompilationUnitElementImpl,
      reference!,
      node,
    );
    element.parameters; // create elements

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(outerScope, element.typeParameters);

    node.returnType?.accept(this);
    node.typeParameters?.accept(this);
    node.parameters.accept(this);

    var nullabilitySuffix = _getNullabilitySuffix(node.question != null);
    var builder = FunctionTypeBuilder.of(isNNBD, nodeImpl, nullabilitySuffix);
    nodeImpl.type = builder;
    nodesToBuildType.addTypeBuilder(builder);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitGenericTypeAlias(GenericTypeAlias node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as TypeAliasElementImpl;
    reference = element.reference!;

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(outerScope, element.typeParameters);

    node.typeParameters?.accept(this);
    node.type.accept(this);
    nodesToBuildType.addDeclaration(node);

    var aliasedType = node.type;
    if (aliasedType is GenericFunctionTypeImpl) {
      element.encloseElement(
        aliasedType.declaredElement as GenericFunctionTypeElementImpl,
      );
    }

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitImplementsClause(ImplementsClause node) {
    node.interfaces.accept(this);
  }

  @override
  void visitMethodDeclaration(MethodDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as ExecutableElementImpl;
    reference = element.reference!;
    element.parameters; // create elements

    _createTypeParameterElements(element, node.typeParameters);

    scope = TypeParameterScope(scope, element.typeParameters);
    LinkingNodeContext(node, scope);

    node.returnType?.accept(this);
    node.typeParameters?.accept(this);
    node.parameters?.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitMixinDeclaration(MixinDeclaration node) {
    var outerScope = scope;
    var outerReference = reference;

    var element = node.declaredElement as MixinElementImpl;
    reference = element.reference!;
    element.accessors; // create elements
    element.constructors; // create elements
    element.methods; // create elements

    _createTypeParameterElements(element, node.typeParameters);
    scope = TypeParameterScope(scope, element.typeParameters);

    node.typeParameters?.accept(this);
    node.onClause?.accept(this);
    node.implementsClause?.accept(this);

    scope = ClassScope(scope, element);
    LinkingNodeContext(node, scope);

    node.members.accept(this);
    nodesToBuildType.addDeclaration(node);

    scope = outerScope;
    reference = outerReference;
  }

  @override
  void visitOnClause(OnClause node) {
    node.superclassConstraints.accept(this);
  }

  @override
  void visitSimpleFormalParameter(SimpleFormalParameter node) {
    node.type?.accept(this);
    nodesToBuildType.addDeclaration(node);
  }

  @override
  void visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
    node.variables.accept(this);
  }

  @override
  void visitTypeArgumentList(TypeArgumentList node) {
    node.arguments.accept(this);
  }

  @override
  void visitTypeName(TypeName node) {
    var typeIdentifier = node.name;

    Element? element;
    if (typeIdentifier is PrefixedIdentifier) {
      var prefix = typeIdentifier.prefix;
      var prefixName = prefix.name;
      var prefixElement = scope.lookup(prefixName).getter;
      prefix.staticElement = prefixElement;

      if (prefixElement is PrefixElement) {
        var nameNode = typeIdentifier.identifier;
        var name = nameNode.name;

        element = prefixElement.scope.lookup(name).getter;
        nameNode.staticElement = element;
      }
    } else {
      var nameNode = typeIdentifier as SimpleIdentifier;
      var name = nameNode.name;

      if (name == 'void') {
        node.type = VoidTypeImpl.instance;
        return;
      }

      element = scope.lookup(name).getter;
      nameNode.staticElement = element;
    }

    node.typeArguments?.accept(this);

    var nullabilitySuffix = _getNullabilitySuffix(node.question != null);
    if (element == null) {
      node.type = DynamicTypeImpl.instance;
    } else if (element is TypeParameterElement) {
      node.type = TypeParameterTypeImpl(
        element: element,
        nullabilitySuffix: nullabilitySuffix,
      );
    } else {
      var builder = NamedTypeBuilder.of(
        _typeSystem,
        node,
        element,
        nullabilitySuffix,
      );
      node.type = builder;
      nodesToBuildType.addTypeBuilder(builder);
    }
  }

  @override
  void visitTypeParameter(TypeParameter node) {
    node.bound?.accept(this);
  }

  @override
  void visitTypeParameterList(TypeParameterList node) {
    node.typeParameters.accept(this);
  }

  @override
  void visitVariableDeclarationList(VariableDeclarationList node) {
    node.type?.accept(this);
    nodesToBuildType.addDeclaration(node);
  }

  @override
  void visitWithClause(WithClause node) {
    node.mixinTypes.accept(this);
  }

  void _createTypeParameterElement(
    ElementImpl enclosingElement,
    TypeParameter node,
  ) {
    var element = TypeParameterElementImpl.forLinkedNode(
      enclosingElement,
      node,
    );
    node.name.staticElement = element;
  }

  void _createTypeParameterElements(
    ElementImpl enclosingElement,
    TypeParameterList? typeParameterList,
  ) {
    if (typeParameterList == null) return;

    for (var typeParameter in typeParameterList.typeParameters) {
      _createTypeParameterElement(enclosingElement, typeParameter);
    }
  }

  NullabilitySuffix _getNullabilitySuffix(bool hasQuestion) {
    if (isNNBD) {
      if (hasQuestion) {
        return NullabilitySuffix.question;
      } else {
        return NullabilitySuffix.none;
      }
    } else {
      return NullabilitySuffix.star;
    }
  }
}