// 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/type.dart';
import 'package:analyzer/src/dart/element/builder.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/resolver/scope.dart';
import 'package:analyzer/src/generated/resolver.dart';
import 'package:analyzer/src/summary/format.dart';
import 'package:analyzer/src/summary/idl.dart';
import 'package:analyzer/src/summary/link.dart' as graph
    show DependencyWalker, Node;
import 'package:analyzer/src/summary2/ast_resolver.dart';
import 'package:analyzer/src/summary2/lazy_ast.dart';
import 'package:analyzer/src/summary2/link.dart';
import 'package:analyzer/src/summary2/linking_node_scope.dart';
import 'package:analyzer/src/task/strong_mode.dart';

DartType _dynamicIfNull(DartType type) {
  if (type == null || type.isBottom || type.isDartCoreNull) {
    return DynamicTypeImpl.instance;
  }
  return type;
}

AstNode _getLinkedNode(Element element) {
  return (element as ElementImpl).linkedNode;
}

/// Resolver for typed constant top-level variables and fields initializers.
///
/// Initializers of untyped variables are resolved during [TopLevelInference].
class ConstantInitializersResolver {
  final Linker linker;

  LibraryElement _library;
  Scope _scope;

  ConstantInitializersResolver(this.linker);

  DynamicTypeImpl get _dynamicType => DynamicTypeImpl.instance;

  void perform() {
    for (var builder in linker.builders.values) {
      _library = builder.element;
      for (var unitContext in builder.context.units) {
        for (var unitMember in unitContext.unit.declarations) {
          _scope = builder.scope;
          if (unitMember is TopLevelVariableDeclaration) {
            _variableDeclarationList(unitMember.variables);
          } else if (unitMember is ClassOrMixinDeclaration) {
            _scope = LinkingNodeContext.get(unitMember).scope;
            for (var classMember in unitMember.members) {
              if (classMember is FieldDeclaration) {
                _variableDeclarationList(classMember.fields);
              }
            }
          }
        }
      }
    }
  }

  void _variableDeclarationList(VariableDeclarationList node) {
    if (node.isConst && node.type != null) {
      for (var variable in node.variables) {
        if (variable.initializer != null) {
          var astResolver = AstResolver(linker, _library, _scope);
          astResolver.rewriteAst(variable.initializer);
          astResolver.resolve(variable.initializer);
        }
      }
    }
  }
}

class TopLevelInference {
  final Linker linker;

  TopLevelInference(this.linker);

  DynamicTypeImpl get _dynamicType => DynamicTypeImpl.instance;

  void infer() {
    var initializerInference = _InitializerInference(linker);
    initializerInference.createNodes();

    _performOverrideInference();
    initializerInference.perform();
    _inferConstructorFieldFormals();
  }

  void _inferConstructorFieldFormals() {
    for (var builder in linker.builders.values) {
      for (var unit in builder.element.units) {
        for (var class_ in unit.types) {
          var fields = <String, DartType>{};
          for (var field in class_.fields) {
            if (field.isSynthetic) continue;

            var name = field.name;
            var type = field.type;
            if (type == null) {
              throw StateError('Field $name should have a type.');
            }
            fields[name] ??= type;
          }

          for (var constructor in class_.constructors) {
            for (var parameter in constructor.parameters) {
              if (parameter is FieldFormalParameterElement) {
                var node = _getLinkedNode(parameter);
                if (node is DefaultFormalParameter) {
                  var defaultParameter = node as DefaultFormalParameter;
                  node = defaultParameter.parameter;
                }

                if (node is FieldFormalParameter &&
                    node.type == null &&
                    node.parameters == null) {
                  var name = parameter.name;
                  var type = fields[name] ?? _dynamicType;
                  LazyAst.setType(node, type);
                }
              }
            }
          }
        }
      }
    }
  }

  void _performOverrideInference() {
    var inferrer = new InstanceMemberInferrer(
      linker.typeProvider,
      linker.inheritance,
    );
    for (var builder in linker.builders.values) {
      for (var unit in builder.element.units) {
        inferrer.inferCompilationUnit(unit);
      }
    }
  }
}

class _FunctionElementForLink_Initializer implements FunctionElementImpl {
  final _InferenceNode _node;

  @override
  Element enclosingElement;

  _FunctionElementForLink_Initializer(this._node);

  @override
  DartType get returnType {
    if (!_node.isEvaluated) {
      _node._walker.walk(_node);
    }
    return LazyAst.getType(_node._node);
  }

  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
}

class _InferenceDependenciesCollector extends RecursiveAstVisitor<void> {
  final Set<PropertyInducingElement> _set = Set.identity();

  @override
  void visitSimpleIdentifier(SimpleIdentifier node) {
    var element = node.staticElement;
    if (element is PropertyAccessorElement && element.isGetter) {
      _set.add(element.variable);
    }
  }
}

class _InferenceNode extends graph.Node<_InferenceNode> {
  final _InferenceWalker _walker;
  final LibraryElement _library;
  final Scope _scope;
  final PropertyInducingElementImpl _element;
  final VariableDeclaration _node;

  @override
  bool isEvaluated = false;

  _InferenceNode(
    this._walker,
    this._library,
    this._scope,
    this._element,
    this._node,
  );

  bool get isImplicitlyTypedInstanceField {
    VariableDeclarationList variables = _node.parent;
    if (variables.type == null) {
      var parent = variables.parent;
      return parent is FieldDeclaration && !parent.isStatic;
    }
    return false;
  }

  @override
  List<_InferenceNode> computeDependencies() {
    _buildLocalElements();
    _resolveInitializer();

    var collector = _InferenceDependenciesCollector();
    _node.initializer.accept(collector);

    if (collector._set.isEmpty) {
      return const <_InferenceNode>[];
    }

    var dependencies = collector._set
        .map(_walker.getNode)
        .where((node) => node != null)
        .toList();

    for (var node in dependencies) {
      if (node.isImplicitlyTypedInstanceField) {
        LazyAst.setType(_node, DynamicTypeImpl.instance);
        isEvaluated = true;
        return const <_InferenceNode>[];
      }
    }

    return dependencies;
  }

  void evaluate() {
    _resolveInitializer();

    if (LazyAst.getType(_node) == null) {
      var initializerType = _node.initializer.staticType;
      initializerType = _dynamicIfNull(initializerType);
      LazyAst.setType(_node, initializerType);
    }

    isEvaluated = true;
  }

  void markCircular(List<_InferenceNode> cycle) {
    LazyAst.setType(_node, DynamicTypeImpl.instance);

    var cycleNames = Set<String>();
    for (var inferenceNode in cycle) {
      var node = inferenceNode._node;
      if (node is VariableDeclaration) {
        cycleNames.add(node.name.name);
      } else {
        cycleNames.add('<unknown>');
      }
    }

    LazyAst.setTypeInferenceError(
      _node,
      TopLevelInferenceErrorBuilder(
        kind: TopLevelInferenceErrorKind.dependencyCycle,
        arguments: cycleNames.toList(),
      ),
    );

    isEvaluated = true;
  }

  void _buildLocalElements() {
    var holder = ElementHolder();
    _node.initializer.accept(LocalElementBuilder(holder, null));
    _element.encloseElements(holder.functions);
  }

  void _resolveInitializer() {
    var astResolver = AstResolver(_walker._linker, _library, _scope);
    astResolver.rewriteAst(_node.initializer);
    astResolver.resolve(_node.initializer);
  }
}

class _InferenceWalker extends graph.DependencyWalker<_InferenceNode> {
  final Linker _linker;
  final Map<Element, _InferenceNode> _nodes = Map.identity();

  _InferenceWalker(this._linker);

  @override
  void evaluate(_InferenceNode v) {
    v.evaluate();
  }

  @override
  void evaluateScc(List<_InferenceNode> scc) {
    for (var node in scc) {
      node.markCircular(scc);
    }
  }

  _InferenceNode getNode(Element element) {
    return _nodes[element];
  }

  void walkNodes() {
    for (var node in _nodes.values) {
      if (!node.isEvaluated) {
        walk(node);
      }
    }
  }
}

class _InitializerInference {
  final Linker _linker;
  final _InferenceWalker _walker;

  LibraryElement _library;
  Scope _scope;

  _InitializerInference(this._linker) : _walker = _InferenceWalker(_linker);

  void createNodes() {
    for (var builder in _linker.builders.values) {
      _library = builder.element;
      for (var unit in _library.units) {
        unit.types.forEach(_addClassElementFields);
        unit.mixins.forEach(_addClassElementFields);

        _scope = builder.scope;
        for (var element in unit.topLevelVariables) {
          _addNode(element);
        }
      }
    }
  }

  void perform() {
    _walker.walkNodes();
  }

  void _addClassElementFields(ClassElement class_) {
    var node = _getLinkedNode(class_);
    _scope = LinkingNodeContext.get(node).scope;
    for (var element in class_.fields) {
      _addNode(element);
    }
  }

  void _addNode(PropertyInducingElement element) {
    if (element.isSynthetic) return;

    VariableDeclaration node = _getLinkedNode(element);
    if (LazyAst.getType(node) != null) return;

    if (node.initializer != null) {
      var inferenceNode =
          _InferenceNode(_walker, _library, _scope, element, node);
      _walker._nodes[element] = inferenceNode;
      (element as PropertyInducingElementImpl).initializer =
          _FunctionElementForLink_Initializer(inferenceNode);
    } else {
      LazyAst.setType(node, DynamicTypeImpl.instance);
    }
  }
}