// 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 edit.domain;

import 'dart:async';

import 'package:analysis_server/src/analysis_server.dart';
import 'package:analysis_server/src/constants.dart';
import 'package:analysis_server/src/protocol.dart' hide Element;
import 'package:analysis_server/src/services/correction/assist.dart';
import 'package:analysis_server/src/services/correction/fix.dart';
import 'package:analysis_server/src/services/correction/status.dart';
import 'package:analysis_server/src/services/refactoring/refactoring.dart';
import 'package:analysis_server/src/services/search/search_engine.dart';
import 'package:analyzer/src/generated/ast.dart';
import 'package:analyzer/src/generated/element.dart';
import 'package:analyzer/src/generated/engine.dart' as engine;
import 'package:analyzer/src/generated/error.dart' as engine;
import 'package:analyzer/src/generated/source.dart';


/**
 * Instances of the class [EditDomainHandler] implement a [RequestHandler]
 * that handles requests in the edit domain.
 */
class EditDomainHandler implements RequestHandler {
  /**
   * The analysis server that is using this handler to process requests.
   */
  final AnalysisServer server;

  /**
   * The [SearchEngine] for this server.
   */
  SearchEngine searchEngine;

  _RefactoringManager refactoringManager;

  /**
   * Initialize a newly created handler to handle requests for the given [server].
   */
  EditDomainHandler(this.server) {
    searchEngine = server.searchEngine;
    refactoringManager = new _RefactoringManager(server, searchEngine);
  }

  Response getAssists(Request request) {
    var params = new EditGetAssistsParams.fromRequest(request);
    List<SourceChange> changes = <SourceChange>[];
    List<CompilationUnit> units =
        server.getResolvedCompilationUnits(params.file);
    if (units.isNotEmpty) {
      CompilationUnit unit = units[0];
      List<Assist> assists =
          computeAssists(searchEngine, unit, params.offset, params.length);
      assists.forEach((Assist assist) {
        changes.add(assist.change);
      });
    }
    // respond
    return new EditGetAssistsResult(changes).toResponse(request.id);
  }

  Response getAvailableRefactorings(Request request) {
    var params = new EditGetAvailableRefactoringsParams.fromRequest(request);
    String file = params.file;
    int offset = params.offset;
    int length = params.length;
    // add refactoring kinds
    List<RefactoringKind> kinds = <RefactoringKind>[];
    // try EXTRACT_*
    if (length != 0) {
      kinds.add(RefactoringKind.EXTRACT_LOCAL_VARIABLE);
      kinds.add(RefactoringKind.EXTRACT_METHOD);
    }
    // try RENAME
    {
      List<Element> elements = server.getElementsAtOffset(file, offset);
      if (elements.isNotEmpty) {
        Element element = elements[0];
        RenameRefactoring renameRefactoring =
            new RenameRefactoring(searchEngine, element);
        if (renameRefactoring != null) {
          kinds.add(RefactoringKind.RENAME);
        }
      }
    }
    // respond
    return new EditGetAvailableRefactoringsResult(kinds).toResponse(request.id);
  }

  Response getFixes(Request request) {
    var params = new EditGetFixesParams.fromRequest(request);
    String file = params.file;
    int offset = params.offset;
    // add fixes
    List<ErrorFixes> errorFixesList = <ErrorFixes>[];
    List<CompilationUnit> units = server.getResolvedCompilationUnits(file);
    for (CompilationUnit unit in units) {
      engine.AnalysisErrorInfo errorInfo = server.getErrors(file);
      if (errorInfo != null) {
        LineInfo lineInfo = errorInfo.lineInfo;
        int requestLine = lineInfo.getLocation(offset).lineNumber;
        for (engine.AnalysisError error in errorInfo.errors) {
          int errorLine = lineInfo.getLocation(error.offset).lineNumber;
          if (errorLine == requestLine) {
            List<Fix> fixes = computeFixes(searchEngine, unit, error);
            if (fixes.isNotEmpty) {
              AnalysisError serverError =
                  new AnalysisError.fromEngine(lineInfo, error);
              ErrorFixes errorFixes = new ErrorFixes(serverError);
              errorFixesList.add(errorFixes);
              fixes.forEach((fix) {
                errorFixes.addFix(fix);
              });
            }
          }
        }
      }
    }
    // respond
    return new EditGetFixesResult(errorFixesList).toResponse(request.id);
  }

  @override
  Response handleRequest(Request request) {
    try {
      String requestName = request.method;
      if (requestName == EDIT_GET_ASSISTS) {
        return getAssists(request);
      } else if (requestName == EDIT_GET_AVAILABLE_REFACTORINGS) {
        return getAvailableRefactorings(request);
      } else if (requestName == EDIT_GET_FIXES) {
        return getFixes(request);
      } else if (requestName == EDIT_GET_REFACTORING) {
        refactoringManager.getRefactoring(request);
        return Response.DELAYED_RESPONSE;
      }
    } on RequestFailure catch (exception) {
      return exception.response;
    }
    return null;
  }
}


/**
 * An object managing a single [Refactoring] instance.
 *
 * The instance is identified by its kind, file, offset and length.
 * It is initialized when the a set of parameters is given for the first time.
 * All subsequent requests are performed on this [Refactoring] instance.
 *
 * Once new set of parameters is received, the previous [Refactoring] instance
 * is invalidated and a new one is created and initialized.
 */
class _RefactoringManager {
  final AnalysisServer server;
  final SearchEngine searchEngine;

  RefactoringKind kind;
  String file;
  int offset;
  int length;
  Refactoring refactoring;
  Object feedback;
  RefactoringStatus initStatus;
  RefactoringStatus optionsStatus;
  RefactoringStatus finalStatus;

  String requestId;
  EditGetRefactoringResult result;

  _RefactoringManager(this.server, this.searchEngine) {
    _reset();
  }

  bool get _hasFatalError {
    return initStatus.hasFatalError ||
        optionsStatus.hasFatalError ||
        finalStatus.hasFatalError;
  }

  void getRefactoring(Request request) {
    // prepare for processing the request
    requestId = request.id;
    result = new EditGetRefactoringResult(<RefactoringProblem>[]);
    // process the request
    var params = new EditGetRefactoringParams.fromRequest(request);
    _init(params.kind, params.file, params.offset, params.length).then((_) {
      if (_hasFatalError) {
        return _sendResultResponse();
      }
      // set options
      if (params.options == null) {
        return _sendResultResponse();
      }
      optionsStatus = _setOptions(params.options);
      if (_hasFatalError) {
        return _sendResultResponse();
      }
      // done if just validation
      if (params.validateOnly) {
        return _sendResultResponse();
      }
      // validation and create change
      refactoring.checkFinalConditions().then((_finalStatus) {
        finalStatus = _finalStatus;
        if (_hasFatalError) {
          return _sendResultResponse();
        }
        return refactoring.createChange().then((change) {
          result.change = new SourceChange(change.message, edits: change.edits);
          return _sendResultResponse();
        });
      });
    });
  }

  /**
   * Initializes this context to perform a refactoring with the specified
   * parameters. The existing [Refactoring] is reused or created as needed.
   */
  Future<RefactoringStatus> _init(RefactoringKind kind, String file, int offset,
      int length) {
    List<RefactoringProblem> problems = <RefactoringProblem>[];
    // check if we can continue with the existing Refactoring instance
    if (this.kind == kind &&
        this.file == file &&
        this.offset == offset &&
        this.length == length) {
      return new Future.value(initStatus);
    }
    _reset();
    this.kind = kind;
    this.file = file;
    this.offset = offset;
    this.length = length;
    // create a new Refactoring instance
    if (kind == RefactoringKind.RENAME) {
      List<AstNode> nodes = server.getNodesAtOffset(file, offset);
      List<Element> elements = server.getElementsAtOffset(file, offset);
      if (nodes.isNotEmpty && elements.isNotEmpty) {
        AstNode node = nodes[0];
        Element element = elements[0];
        refactoring = new RenameRefactoring(searchEngine, element);
        feedback = new RenameFeedback(node.offset, node.length);
      }
    }
    if (refactoring == null) {
      initStatus =
          new RefactoringStatus.fatal('Unable to create a refactoring');
      return new Future.value(initStatus);
    }
    // check initial conditions
    return refactoring.checkInitialConditions().then((status) {
      initStatus = status;
      return initStatus;
    });
  }

  void _reset() {
    refactoring = null;
    feedback = null;
    initStatus = new RefactoringStatus();
    optionsStatus = new RefactoringStatus();
    finalStatus = new RefactoringStatus();
  }

  void _sendResultResponse() {
    result.feedback = feedback;
    // set problems
    {
      RefactoringStatus status = new RefactoringStatus();
      status.addStatus(initStatus);
      status.addStatus(optionsStatus);
      status.addStatus(finalStatus);
      result.problems = status.problems;
    }
    // send the response
    server.sendResponse(result.toResponse(requestId));
    // done with this request
    requestId = null;
    result = null;
  }

  RefactoringStatus _setOptions(Object options) {
    if (refactoring is RenameRefactoring) {
      RenameRefactoring renameRefactoring = refactoring;
      RenameOptions renameOptions = options;
      String newName = renameOptions.newName;
      renameRefactoring.newName = newName;
      return renameRefactoring.checkNewName();
    }
    return new RefactoringStatus();
  }
}