// Copyright (c) 2015, 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.

library services.completion.dart.sorter.common;

import 'dart:async';

import 'package:analysis_server/src/protocol_server.dart' as protocol;
import 'package:analysis_server/src/protocol_server.dart'
    show CompletionSuggestion, CompletionSuggestionKind;
import 'package:analysis_server/src/provisional/completion/completion_core.dart';
import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
import 'package:analysis_server/src/services/completion/dart/contribution_sorter.dart';
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/ast/ast.dart';
import 'package:analyzer_plugin/src/utilities/completion/completion_target.dart';

part 'common_usage_sorter.g.dart';

/// A computer for adjusting the relevance of completions computed by others
/// based upon common Dart usage patterns. This is a long-lived object
/// that should not maintain state between calls to it's [sort] method.
class CommonUsageSorter implements DartContributionSorter {
  /// A map of <library>.<classname> to an ordered list of method names,
  /// field names, getter names, and named constructors.
  /// The names are ordered from most relevant to least relevant.
  /// Names not listed are considered equally less relevant than those listed.
  final Map<String, List<String>> selectorRelevance;

  CommonUsageSorter([this.selectorRelevance = defaultSelectorRelevance]);

  @override
  Future sort(DartCompletionRequest request,
      Iterable<CompletionSuggestion> suggestions) {
    _update(request, suggestions);
    return Future.value();
  }

  CompletionTarget _getCompletionTarget(CompletionRequest request) =>
      CompletionTarget.forOffset(request.result.unit, request.offset);

  /// Adjusts the relevance based on the given completion context.
  /// The compilation unit and completion node
  /// in the given completion context may not be resolved.
  void _update(
      CompletionRequest request, Iterable<CompletionSuggestion> suggestions) {
    var target = _getCompletionTarget(request);
    if (target != null) {
      var visitor = _BestTypeVisitor(target.entity);
      var typeElem = target.containingNode.accept(visitor);
      if (typeElem != null) {
        var libElem = typeElem.library;
        if (libElem != null) {
          _updateInvocationRelevance(typeElem.name, libElem, suggestions);
        }
      }
    }
  }

  /// Adjusts the relevance of all method suggestions based upon the given
  /// target type and library.
  void _updateInvocationRelevance(String typeName, LibraryElement libElem,
      Iterable<CompletionSuggestion> suggestions) {
    var selectors = selectorRelevance['${libElem.name}.$typeName'];
    if (selectors != null) {
      for (var suggestion in suggestions) {
        var element = suggestion.element;
        if (element != null &&
            (element.kind == protocol.ElementKind.CONSTRUCTOR ||
                element.kind == protocol.ElementKind.FIELD ||
                element.kind == protocol.ElementKind.GETTER ||
                element.kind == protocol.ElementKind.METHOD ||
                element.kind == protocol.ElementKind.SETTER) &&
            suggestion.kind == CompletionSuggestionKind.INVOCATION &&
            suggestion.declaringType == typeName) {
          var index = selectors.indexOf(suggestion.completion);
          if (index != -1) {
            suggestion.relevance = DART_RELEVANCE_COMMON_USAGE - index;
          }
        }
      }
    }
  }
}

/// An [AstVisitor] used to determine the best defining type of a node.
class _BestTypeVisitor extends UnifyingAstVisitor<Element> {
  /// The entity which the completed text will replace (or which will be
  /// displaced once the completed text is inserted).  This may be an AstNode or
  /// a Token, or it may be `null` if the cursor is after all tokens in the
  /// file. See field of the same name in [CompletionTarget].
  final Object entity;

  _BestTypeVisitor(this.entity);

  @override
  Element visitConstructorName(ConstructorName node) {
    return node.period != null && node.name == entity
        ? node.type?.type?.element
        : null;
  }

  @override
  Element visitNamedExpression(NamedExpression node) {
    var parent = node.parent;
    if (parent is ArgumentListImpl) {
      var params = parent.correspondingStaticParameters;
      if (params != null) {
        var index = parent.arguments.indexOf(node);
        return params[index]?.type?.element;
      }
    }
    return super.visitNamedExpression(node);
  }

  @override
  Element visitNode(AstNode node) {
    return null;
  }

  @override
  Element visitPrefixedIdentifier(PrefixedIdentifier node) {
    if (node.identifier == entity) {
      var type = node.prefix.staticType;
      if (type is InterfaceType) {
        return type.element;
      }
      return node.prefix.staticElement;
    }
    return null;
  }

  @override
  Element visitPropertyAccess(PropertyAccess node) =>
      node.propertyName == entity ? node.realTarget?.staticType?.element : null;
}