Remove the unused operations queue

pkg/analysis_server/lib/src/operation/operation_queue.dart

-// 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.
-
-import 'dart:collection';
-
-import 'package:analysis_server/src/analysis_server.dart';
-import 'package:analysis_server/src/operation/operation.dart';
-import 'package:analyzer/src/generated/engine.dart';
-import 'package:analyzer/src/generated/source.dart';
-
-/**
- * A queue of operations in an [AnalysisServer].
- */
-class ServerOperationQueue {
-  final List<Queue<ServerOperation>> _queues = <Queue<ServerOperation>>[];
-
-  ServerOperationQueue() {
-    for (int i = 0; i < ServerOperationPriority.COUNT; i++) {
-      var queue = new DoubleLinkedQueue<ServerOperation>();
-      _queues.add(queue);
-    }
-  }
-
-  /**
-   * Returns `true` if there are no queued [ServerOperation]s.
-   */
-  bool get isEmpty {
-    return _queues.every((queue) => queue.isEmpty);
-  }
-
-  /**
-   * Adds the given operation to this queue. The exact position in the queue
-   * depends on the priority of the given operation relative to the priorities
-   * of the other operations in the queue.
-   */
-  void add(ServerOperation operation) {
-    int queueIndex = operation.priority.ordinal;
-    Queue<ServerOperation> queue = _queues[queueIndex];
-    // try to merge into an existing operation
-    for (ServerOperation existingOperation in queue) {
-      if (existingOperation is MergeableOperation &&
-          existingOperation.merge(operation)) {
-        return;
-      }
-    }
-    // add it
-    queue.addLast(operation);
-  }
-
-  /**
-   * Removes all elements in the queue.
-   */
-  void clear() {
-    for (Queue<ServerOperation> queue in _queues) {
-      queue.clear();
-    }
-  }
-
-  /**
-   * The given [context] has been removed, so all pending operations that refer
-   * to it should be removed from the queue.
-   */
-  void contextRemoved(AnalysisContext context) {
-    for (Queue<ServerOperation> queue in _queues) {
-      queue.removeWhere((operation) => operation.context == context);
-    }
-  }
-
-  /**
-   * Return the next operation to perform, or `null` if the queue is empty.
-   * This method does not change the queue.
-   */
-  ServerOperation peek() {
-    for (Queue<ServerOperation> queue in _queues) {
-      if (!queue.isEmpty) {
-        return queue.first;
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Reschedules queued operations according their current priorities.
-   */
-  void reschedule() {
-    // prepare all operations
-    List<ServerOperation> operations = <ServerOperation>[];
-    for (Queue<ServerOperation> queue in _queues) {
-      operations.addAll(queue);
-      queue.clear();
-    }
-    // add all operations
-    operations.forEach(add);
-  }
-
-  /**
-   * The given [source] if about to changed.
-   */
-  void sourceAboutToChange(Source source) {
-    for (Queue<ServerOperation> queue in _queues) {
-      queue.removeWhere((operation) {
-        if (operation is SourceSensitiveOperation) {
-          return operation.shouldBeDiscardedOnSourceChange(source);
-        }
-        return false;
-      });
-    }
-  }
-
-  /**
-   * Returns the next operation to perform or `null` if empty.
-   */
-  ServerOperation take() {
-    for (Queue<ServerOperation> queue in _queues) {
-      if (!queue.isEmpty) {
-        return queue.removeFirst();
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Returns an operation that satisfies the given [test] or `null`.
-   */
-  ServerOperation takeIf(bool test(ServerOperation operation)) {
-    for (Queue<ServerOperation> queue in _queues) {
-      for (ServerOperation operation in queue) {
-        if (test(operation)) {
-          queue.remove(operation);
-          return operation;
-        }
-      }
-    }
-    return null;
-  }
-}