// 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/element/element.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/src/generated/source.dart';
import 'package:nnbd_migration/instrumentation.dart';
import 'package:nnbd_migration/src/edit_plan.dart';
import 'package:nnbd_migration/src/front_end/instrumentation_information.dart';
import 'package:nnbd_migration/src/front_end/migration_summary.dart';

/// A listener used to gather instrumentation information from the migration
/// engine.
class InstrumentationListener implements NullabilityMigrationInstrumentation {
  final MigrationSummary migrationSummary;

  /// The instrumentation information being gathered.
  InstrumentationInformation data = InstrumentationInformation();

  /// Initialize a newly created listener.
  InstrumentationListener({this.migrationSummary});

  @override
  void changes(Source source, Map<int, List<AtomicEdit>> changes) {
    assert(_sourceInfo(source).changes == null);
    _sourceInfo(source).changes = changes;
    migrationSummary?.recordChanges(source, changes);
  }

  @override
  void explicitTypeNullability(
      Source source, TypeAnnotation typeAnnotation, NullabilityNodeInfo node) {
    data.nodeInformation[node] =
        NodeInformation(_filePathForSource(source), typeAnnotation, null);
    _sourceInfo(source).explicitTypeNullability[typeAnnotation] = node;
  }

  @override
  void externalDecoratedType(Element element, DecoratedTypeInfo decoratedType) {
    _storeNodeInformation(decoratedType, element.source, null, element);
  }

  @override
  void externalDecoratedTypeParameterBound(
      TypeParameterElement typeParameter, DecoratedTypeInfo decoratedType) {
    _storeNodeInformation(
        decoratedType, typeParameter.source, null, typeParameter);
  }

  @override
  void graphEdge(EdgeInfo edge, EdgeOriginInfo originInfo) {
    data.edgeOrigin[edge] = originInfo;
  }

  @override
  void immutableNodes(NullabilityNodeInfo never, NullabilityNodeInfo always) {
    data.never = never;
    data.always = always;
  }

  @override
  void implicitReturnType(
      Source source, AstNode node, DecoratedTypeInfo decoratedReturnType) {
    _storeNodeInformation(decoratedReturnType, source, node, null);
  }

  @override
  void implicitType(
      Source source, AstNode node, DecoratedTypeInfo decoratedType) {
    _storeNodeInformation(decoratedType, source, node, null);
  }

  @override
  void implicitTypeArguments(
      Source source, AstNode node, Iterable<DecoratedTypeInfo> types) {
    for (var type in types) {
      _storeNodeInformation(type, source, node, null);
    }
  }

  @override
  void prepareForUpdate() {
    for (var source in data.sourceInformation.keys) {
      _sourceInfo(source).changes = null;
    }
  }

  String _filePathForSource(Source source) {
    return source.fullName;
  }

  /// Return the source information associated with the given [source], creating
  /// it if there has been no previous information for that source.
  SourceInformation _sourceInfo(Source source) =>
      data.sourceInformation.putIfAbsent(source, () => SourceInformation());

  // TODO(srawlins): This code is completely untested.
  void _storeNodeInformation(DecoratedTypeInfo decoratedType, Source source,
      AstNode astNode, Element element) {
    // Make sure source info exists for the given source.
    _sourceInfo(source);
    data.nodeInformation[decoratedType.node] =
        NodeInformation(_filePathForSource(source), astNode, element);
    var dartType = decoratedType.type;
    if (dartType is InterfaceType) {
      for (var i = 0; i < dartType.typeArguments.length; i++) {
        _storeNodeInformation(
            decoratedType.typeArgument(i), source, astNode, element);
      }
    } else if (dartType is FunctionType) {
      _storeNodeInformation(
        decoratedType.returnType,
        source,
        astNode,
        element,
      );
      var i = 0;
      for (var parameter in dartType.parameters) {
        if (parameter.isNamed) {
          var name = parameter.name;
          _storeNodeInformation(
              decoratedType.namedParameter(name), source, astNode, element);
        } else {
          _storeNodeInformation(
              decoratedType.positionalParameter(i), source, astNode, element);
          i++;
        }
      }
    }
  }

  @override
  void finished() {
    migrationSummary?.write();
  }
}