// 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 computer.navigation;

import 'package:analysis_server/src/protocol_server.dart' as protocol;
import 'package:analyzer/src/generated/ast.dart';
import 'package:analyzer/src/generated/element.dart';
import 'package:analyzer/src/generated/scanner.dart';


/**
 * A computer for navigation regions in a Dart [CompilationUnit].
 */
class DartUnitNavigationComputer {
  final CompilationUnit _unit;

  final List<protocol.NavigationRegion> _regions = <protocol.NavigationRegion>[
      ];

  DartUnitNavigationComputer(this._unit);

  /**
   * Returns the computed navigation regions, not `null`.
   */
  List<protocol.NavigationRegion> compute() {
    _unit.accept(new _DartUnitNavigationComputerVisitor(this));
    return new List.from(_regions);
  }

  void _addRegion(int offset, int length, Element element) {
    if (element is FieldFormalParameterElement) {
      element = (element as FieldFormalParameterElement).field;
    }
    if (element == null || element == DynamicElementImpl.instance) {
      return;
    }
    if (element.location == null) {
      return;
    }
    protocol.Element target = protocol.newElement_fromEngine(element);
    _regions.add(new protocol.NavigationRegion(offset, length, [target]));
  }

  void _addRegion_nodeStart_nodeEnd(AstNode a, AstNode b, Element element) {
    int offset = a.offset;
    int length = b.end - offset;
    _addRegion(offset, length, element);
  }

  void _addRegion_nodeStart_nodeStart(AstNode a, AstNode b, Element element,
      {bool excludeLastChar: false}) {
    int offset = a.offset;
    int length = b.offset - offset;
    if (excludeLastChar) {
      length--;
    }
    _addRegion(offset, length, element);
  }

  void _addRegion_tokenStart_nodeEnd(Token a, AstNode b, Element element) {
    int offset = a.offset;
    int length = b.end - offset;
    _addRegion(offset, length, element);
  }

  void _addRegionForNode(AstNode node, Element element) {
    int offset = node.offset;
    int length = node.length;
    _addRegion(offset, length, element);
  }

  void _addRegionForToken(Token token, Element element) {
    int offset = token.offset;
    int length = token.length;
    _addRegion(offset, length, element);
  }
}


class _DartUnitNavigationComputerVisitor extends RecursiveAstVisitor {
  final DartUnitNavigationComputer computer;

  _DartUnitNavigationComputerVisitor(this.computer);

  @override
  visitAssignmentExpression(AssignmentExpression node) {
    _safelyVisit(node.leftHandSide);
    computer._addRegionForToken(node.operator, node.bestElement);
    _safelyVisit(node.rightHandSide);
  }

  @override
  visitBinaryExpression(BinaryExpression node) {
    _safelyVisit(node.leftOperand);
    computer._addRegionForToken(node.operator, node.bestElement);
    _safelyVisit(node.rightOperand);
  }

  @override
  visitCompilationUnit(CompilationUnit unit) {
    // prepare top-level nodes sorted by their offsets
    List<AstNode> nodes = <AstNode>[];
    nodes.addAll(unit.directives);
    nodes.addAll(unit.declarations);
    nodes.sort((a, b) {
      return a.offset - b.offset;
    });
    // visit sorted nodes
    for (AstNode node in nodes) {
      node.accept(this);
    }
  }

  @override
  visitConstructorDeclaration(ConstructorDeclaration node) {
    // associate constructor with "T" or "T.name"
    {
      AstNode firstNode = node.returnType;
      AstNode lastNode = node.name;
      if (lastNode == null) {
        lastNode = firstNode;
      }
      if (firstNode != null && lastNode != null) {
        computer._addRegion_nodeStart_nodeEnd(
            firstNode,
            lastNode,
            node.element);
      }
    }
    super.visitConstructorDeclaration(node);
  }

  @override
  visitExportDirective(ExportDirective node) {
    ExportElement exportElement = node.element;
    if (exportElement != null) {
      Element element = exportElement.exportedLibrary;
      computer._addRegion_tokenStart_nodeEnd(node.keyword, node.uri, element);
    }
    super.visitExportDirective(node);
  }

  @override
  visitImportDirective(ImportDirective node) {
    ImportElement importElement = node.element;
    if (importElement != null) {
      Element element = importElement.importedLibrary;
      computer._addRegion_tokenStart_nodeEnd(node.keyword, node.uri, element);
    }
    super.visitImportDirective(node);
  }

  @override
  visitIndexExpression(IndexExpression node) {
    super.visitIndexExpression(node);
    computer._addRegionForToken(node.rightBracket, node.bestElement);
  }

  @override
  visitInstanceCreationExpression(InstanceCreationExpression node) {
    Element element = node.staticElement;
    ConstructorName constructorName = node.constructorName;
    if (element != null && constructorName != null) {
      ClassElement classElement = element.enclosingElement;
      if (element.isSynthetic) {
        element = classElement;
        computer._addRegion_nodeStart_nodeStart(
            node,
            node.argumentList,
            element);
      } else {
        // "new ", excluding last character
        computer._addRegion_nodeStart_nodeStart(
            node,
            constructorName.type,
            element,
            excludeLastChar: true);
        // "ClassName"
        computer._addRegionForNode(constructorName.type, classElement);
        // optional ".name"
        if (constructorName.period != null) {
          computer._addRegion_tokenStart_nodeEnd(
              constructorName.period,
              constructorName,
              element);
        }
      }
    }
    _safelyVisit(node.argumentList);
  }

  @override
  visitPartDirective(PartDirective node) {
    computer._addRegion_tokenStart_nodeEnd(
        node.keyword,
        node.uri,
        node.element);
    super.visitPartDirective(node);
  }

  @override
  visitPartOfDirective(PartOfDirective node) {
    computer._addRegion_tokenStart_nodeEnd(
        node.keyword,
        node.libraryName,
        node.element);
    super.visitPartOfDirective(node);
  }

  @override
  visitPostfixExpression(PostfixExpression node) {
    super.visitPostfixExpression(node);
    computer._addRegionForToken(node.operator, node.bestElement);
  }

  @override
  visitPrefixExpression(PrefixExpression node) {
    computer._addRegionForToken(node.operator, node.bestElement);
    super.visitPrefixExpression(node);
  }

  @override
  visitSimpleIdentifier(SimpleIdentifier node) {
    if (node.parent is ConstructorDeclaration) {
      return;
    }
    Element element = node.bestElement;
    computer._addRegionForNode(node, element);
  }

  void _safelyVisit(AstNode node) {
    if (node != null) {
      node.accept(this);
    }
  }
}