// Copyright (c) 2014, 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.optype;

import 'package:analysis_server/src/services/completion/completion_target.dart';
import 'package:analyzer/src/generated/ast.dart';
import 'package:analyzer/src/generated/scanner.dart';

/**
 * An [AstVisitor] for determining whether top level suggestions or invocation
 * suggestions should be made based upon the type of node in which the
 * suggestions were requested.
 */
class OpType {

  /**
   * Indicates whether constructor suggestions should be included.
   */
  bool includeConstructorSuggestions = false;

  /**
   * Indicates whether type names should be suggested.
   */
  bool includeTypeNameSuggestions = false;

  /**
   * Indicates whether setters along with methods and functions that
   * have a [void] return type should be suggested.
   */
  bool includeVoidReturnSuggestions = false;

  /**
   * Indicates whether fields and getters along with methods and functions that
   * have a non-[void] return type should be suggested.
   */
  bool includeReturnValueSuggestions = false;

  /**
   * Indicates whether statement labels should be suggested.
   */
  bool includeStatementLabelSuggestions = false;

  /**
   * Indicates whether case labels should be suggested.
   */
  bool includeCaseLabelSuggestions = false;

  /**
   * Indicates whether the completion target is prefixed.
   */
  bool isPrefixed = false;

  /**
   * Determine the suggestions that should be made based upon the given
   * [CompletionTarget] and [offset].
   */
  factory OpType.forCompletion(CompletionTarget target, int offset) {
    OpType optype = new OpType._();
    target.containingNode
        .accept(new _OpTypeAstVisitor(optype, target.entity, offset));
    return optype;
  }

  OpType._();

  /**
   * Indicate whether only type names should be suggested
   */
  bool get includeOnlyTypeNameSuggestions => includeTypeNameSuggestions &&
      !includeReturnValueSuggestions &&
      !includeVoidReturnSuggestions;
}

class _OpTypeAstVisitor extends GeneralizingAstVisitor {

  /**
   * The entity (AstNode or Token) which will be replaced or displaced by the
   * added text.
   */
  final Object entity;

  /**
   * The offset within the source at which the completion is requested.
   */
  final int offset;

  /**
   * The [OpType] being initialized
   */
  final OpType optype;

  _OpTypeAstVisitor(this.optype, this.entity, this.offset);

  @override
  void visitAnnotation(Annotation node) {
    if (identical(entity, node.name)) {
      optype.includeTypeNameSuggestions = true;
      optype.includeReturnValueSuggestions = true;
    } else if (identical(entity, node.constructorName)) {
      optype.includeTypeNameSuggestions = true;
      optype.includeReturnValueSuggestions = true;
      optype.isPrefixed = true;
    }
  }

  @override
  void visitArgumentList(ArgumentList node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitAsExpression(AsExpression node) {
    if (identical(entity, node.type)) {
      optype.includeTypeNameSuggestions = true;
      // TODO (danrubel) Possible future improvement:
      // on the RHS of an "is" or "as" expression, don't suggest types that are
      // guaranteed to pass or guaranteed to fail the cast.
      // See dartbug.com/18860
    }
  }

  void visitAssignmentExpression(AssignmentExpression node) {
    if (identical(entity, node.rightHandSide)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitAwaitExpression(AwaitExpression node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitBinaryExpression(BinaryExpression node) {
    if (identical(entity, node.rightOperand)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitBlock(Block node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
    optype.includeVoidReturnSuggestions = true;
  }

  @override
  void visitBreakStatement(BreakStatement node) {
    if (node.label == null || identical(entity, node.label)) {
      optype.includeStatementLabelSuggestions = true;
    }
  }

  @override
  void visitCascadeExpression(CascadeExpression node) {
    if (node.cascadeSections.contains(entity)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeVoidReturnSuggestions = true;
      optype.isPrefixed = true;
    }
  }

  @override
  void visitCatchClause(CatchClause node) {
    if (identical(entity, node.exceptionType)) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitClassDeclaration(ClassDeclaration node) {
    // Make suggestions in the body of the class declaration
    if (node.members.contains(entity) || identical(entity, node.rightBracket)) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitClassMember(ClassMember node) {}

  @override
  void visitCommentReference(CommentReference node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
    optype.includeVoidReturnSuggestions = true;
  }

  void visitCompilationUnit(CompilationUnit node) {
    if (entity is! CommentToken) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitConditionalExpression(ConditionalExpression node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  visitConstructorName(ConstructorName node) {
    // some PrefixedIdentifier nodes are transformed into
    // ConstructorName nodes during the resolution process.
    if (identical(entity, node.name)) {
      TypeName type = node.type;
      if (type != null) {
        SimpleIdentifier prefix = type.name;
        if (prefix != null) {
          optype.includeConstructorSuggestions = true;
          optype.isPrefixed = true;
        }
      }
    }
  }

  @override
  void visitContinueStatement(ContinueStatement node) {
    if (node.label == null || identical(entity, node.label)) {
      optype.includeStatementLabelSuggestions = true;
      optype.includeCaseLabelSuggestions = true;
    }
  }

  @override
  void visitDefaultFormalParameter(DefaultFormalParameter node) {
    if (identical(entity, node.defaultValue)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitDoStatement(DoStatement node) {
    if (identical(entity, node.condition)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitEmptyStatement(EmptyStatement node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
    optype.includeVoidReturnSuggestions = true;
  }

  @override
  void visitExpression(Expression node) {
    // This should never be called; we should always dispatch to the visitor
    // for a particular kind of expression.
    assert(false);
  }

  @override
  void visitExpressionFunctionBody(ExpressionFunctionBody node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitExpressionStatement(ExpressionStatement node) {
    // Given f[], the parser drops the [] from the expression statement
    // but the [] token is the CompletionTarget entity
    if (entity is Token) {
      Token token = entity;
      if (token.lexeme == '[]' && offset == token.offset + 1) {
        optype.includeReturnValueSuggestions = true;
        optype.includeTypeNameSuggestions = true;
      }
    }
  }

  @override
  void visitExtendsClause(ExtendsClause node) {
    if (identical(entity, node.superclass)) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitForEachStatement(ForEachStatement node) {
    if (identical(entity, node.identifier)) {
      optype.includeTypeNameSuggestions = true;
    }
    if (identical(entity, node.loopVariable)) {
      optype.includeTypeNameSuggestions = true;
    }
    if (identical(entity, node.inKeyword) && offset <= node.inKeyword.offset) {
      if (node.identifier == null && node.loopVariable == null) {
        optype.includeTypeNameSuggestions = true;
      }
    }
    if (identical(entity, node.iterable)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitFormalParameterList(FormalParameterList node) {
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitForStatement(ForStatement node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
    optype.includeVoidReturnSuggestions = true;
    // TODO (danrubel) void return suggestions only belong after
    // the 2nd semicolon.  Return value suggestions only belong after the
    // e1st or second semicolon.
  }

  @override
  void visitFunctionDeclaration(FunctionDeclaration node) {
    if (identical(entity, node.returnType) ||
        identical(entity, node.name) && node.returnType == null) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitFunctionExpression(FunctionExpression node) {}

  @override
  void visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {}

  @override
  void visitFunctionTypeAlias(FunctionTypeAlias node) {
    if (identical(entity, node.returnType) ||
        identical(entity, node.name) && node.returnType == null) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitIfStatement(IfStatement node) {
    if (identical(entity, node.condition)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    } else if (identical(entity, node.thenStatement) ||
        identical(entity, node.elseStatement)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
      optype.includeVoidReturnSuggestions = true;
    }
  }

  @override
  void visitImplementsClause(ImplementsClause node) {
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitIndexExpression(IndexExpression node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitInstanceCreationExpression(InstanceCreationExpression node) {
    if (identical(entity, node.constructorName)) {
      optype.includeConstructorSuggestions = true;
    }
  }

  @override
  void visitInterpolationExpression(InterpolationExpression node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      // Only include type names in a ${ } expression
      optype.includeTypeNameSuggestions =
          node.leftBracket != null && node.leftBracket.length > 1;
    }
  }

  @override
  void visitIsExpression(IsExpression node) {
    if (identical(entity, node.type)) {
      optype.includeTypeNameSuggestions = true;
      // TODO (danrubel) Possible future improvement:
      // on the RHS of an "is" or "as" expression, don't suggest types that are
      // guaranteed to pass or guaranteed to fail the cast.
      // See dartbug.com/18860
    }
  }

  void visitLibraryIdentifier(LibraryIdentifier node) {
    // No suggestions.
  }

  @override
  void visitMapLiteralEntry(MapLiteralEntry node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitMethodDeclaration(MethodDeclaration node) {
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitMethodInvocation(MethodInvocation node) {
    bool isThis = node.target is ThisExpression;
    if (identical(entity, node.operator) && offset > node.operator.offset) {
      // The cursor is between the two dots of a ".." token, so we need to
      // generate the completions we would generate after a "." token.
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = !isThis;
      optype.includeVoidReturnSuggestions = true;
      optype.isPrefixed = true;
    } else if (identical(entity, node.methodName)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = !isThis;
      optype.includeVoidReturnSuggestions = true;
      optype.isPrefixed = true;
    }
  }

  @override
  void visitNamedExpression(NamedExpression node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitNode(AstNode node) {
    // no suggestion by default
  }

  @override
  void visitFieldFormalParameter(FieldFormalParameter node) {
    if (entity == node.identifier) {
      optype.isPrefixed = true;
    } else {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitNormalFormalParameter(NormalFormalParameter node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  void visitParenthesizedExpression(ParenthesizedExpression node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitPostfixExpression(PostfixExpression node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitPrefixedIdentifier(PrefixedIdentifier node) {
    if (identical(entity, node.identifier)) {
      optype.isPrefixed = true;
      if (node.parent is TypeName && node.parent.parent is ConstructorName) {
        optype.includeConstructorSuggestions = true;
      } else {
        optype.includeReturnValueSuggestions = true;
        optype.includeTypeNameSuggestions = true;
        optype.includeVoidReturnSuggestions =
            node.parent is ExpressionStatement;
      }
    }
  }

  @override
  void visitPrefixExpression(PrefixExpression node) {
    if (identical(entity, node.operand)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitPropertyAccess(PropertyAccess node) {
    bool isThis = node.target is ThisExpression;
    if (node.realTarget is SimpleIdentifier && node.realTarget.isSynthetic) {
      // If the access has no target (empty string)
      // then don't suggest anything
      return;
    }
    if (identical(entity, node.operator) && offset > node.operator.offset) {
      // The cursor is between the two dots of a ".." token, so we need to
      // generate the completions we would generate after a "." token.
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = !isThis;
      optype.includeVoidReturnSuggestions = true;
      optype.isPrefixed = true;
    } else if (identical(entity, node.propertyName)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions =
          !isThis && (node.parent is! CascadeExpression);
      optype.includeVoidReturnSuggestions = true;
      optype.isPrefixed = true;
    }
  }

  @override
  void visitReturnStatement(ReturnStatement node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitSimpleIdentifier(SimpleIdentifier node) {
    // This should never happen; the containingNode will always be some node
    // higher up in the parse tree, and the SimpleIdentifier will be the
    // entity.
    assert(false);
  }

  @override
  void visitStringLiteral(StringLiteral node) {
    // no suggestions
  }

  @override
  void visitSwitchCase(SwitchCase node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitSwitchStatement(SwitchStatement node) {
    if (identical(entity, node.expression)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
    if (identical(entity, node.rightBracket)) {
      if (node.members.isNotEmpty) {
        optype.includeReturnValueSuggestions = true;
        optype.includeTypeNameSuggestions = true;
        optype.includeVoidReturnSuggestions = true;
      }
    }
    if (entity is SwitchMember && entity != node.members.first) {
      SwitchMember member = entity as SwitchMember;
      if (offset <= member.offset) {
          optype.includeReturnValueSuggestions = true;
          optype.includeTypeNameSuggestions = true;
          optype.includeVoidReturnSuggestions = true;
      }
    }
  }

  @override
  void visitThrowExpression(ThrowExpression node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitTypeArgumentList(TypeArgumentList node) {
    NodeList<TypeName> arguments = node.arguments;
    for (TypeName typeName in arguments) {
      if (identical(entity, typeName)) {
        optype.includeTypeNameSuggestions = true;
        break;
      }
    }
  }

  @override
  void visitTypedLiteral(TypedLiteral node) {
    optype.includeReturnValueSuggestions = true;
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitTypeName(TypeName node) {
    // The entity won't be the first child entity (node.name), since
    // CompletionTarget would have chosen an edge higher in the parse tree.  So
    // it must be node.typeArguments, meaning that the cursor is between the
    // type name and the "<" that starts the type arguments.  In this case,
    // we have no completions to offer.
    assert(identical(entity, node.typeArguments));
  }

  @override
  void visitTypeParameter(TypeParameter node) {
    optype.includeTypeNameSuggestions = true;
  }

  @override
  void visitVariableDeclaration(VariableDeclaration node) {
    // Make suggestions for the RHS of a variable declaration
    if (identical(entity, node.initializer)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitVariableDeclarationList(VariableDeclarationList node) {
    if ((node.keyword == null || node.keyword.lexeme != 'var') &&
        (node.type == null || identical(entity, node.type))) {
      optype.includeTypeNameSuggestions = true;
    }
  }

  @override
  void visitVariableDeclarationStatement(VariableDeclarationStatement node) {}

  @override
  void visitWhileStatement(WhileStatement node) {
    if (identical(entity, node.condition)) {
      optype.includeReturnValueSuggestions = true;
      optype.includeTypeNameSuggestions = true;
    }
  }
}