Rationalize Dart mojo and sky package structure

sky/framework/editing/editable_string.dart

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:mojom/keyboard/keyboard.mojom.dart';
-
-typedef void StringUpdated();
-
-class TextRange {
-  final int start;
-  final int end;
-
-  TextRange({this.start, this.end});
-  TextRange.collapsed(int position)
-      : start = position,
-        end = position;
-  const TextRange.empty()
-      : start = -1,
-        end = -1;
-
-  bool get isValid => start >= 0 && end >= 0;
-  bool get isCollapsed => start == end;
-}
-
-class EditableString implements KeyboardClient {
-  String text;
-  TextRange composing = const TextRange.empty();
-  TextRange selection = const TextRange.empty();
-
-  final StringUpdated onUpdated;
-
-  KeyboardClientStub stub;
-
-  EditableString({this.text: '', this.onUpdated}) {
-    stub = new KeyboardClientStub.unbound()..impl = this;
-  }
-
-  String textBefore(TextRange range) {
-    return text.substring(0, range.start);
-  }
-
-  String textAfter(TextRange range) {
-    return text.substring(range.end);
-  }
-
-  String textInside(TextRange range) {
-    return text.substring(range.start, range.end);
-  }
-
-  void _delete(TextRange range) {
-    if (range.isCollapsed || !range.isValid) return;
-    text = textBefore(range) + textAfter(range);
-  }
-
-  TextRange _append(String newText) {
-    int start = text.length;
-    text += newText;
-    return new TextRange(start: start, end: start + newText.length);
-  }
-
-  TextRange _replace(TextRange range, String newText) {
-    assert(range.isValid);
-
-    String before = textBefore(range);
-    String after = textAfter(range);
-
-    text = before + newText + after;
-    return new TextRange(
-        start: before.length, end: before.length + newText.length);
-  }
-
-  TextRange _replaceOrAppend(TextRange range, String newText) {
-    if (!range.isValid) return _append(newText);
-    return _replace(range, newText);
-  }
-
-  void commitCompletion(CompletionData completion) {
-    // TODO(abarth): Not implemented.
-  }
-
-  void commitCorrection(CorrectionData correction) {
-    // TODO(abarth): Not implemented.
-  }
-
-  void commitText(String text, int newCursorPosition) {
-    // TODO(abarth): Why is |newCursorPosition| always 1?
-    TextRange committedRange = _replaceOrAppend(composing, text);
-    selection = new TextRange.collapsed(committedRange.end);
-    composing = const TextRange.empty();
-    onUpdated();
-  }
-
-  void deleteSurroundingText(int beforeLength, int afterLength) {
-    TextRange beforeRange = new TextRange(
-        start: selection.start - beforeLength, end: selection.start);
-    TextRange afterRange =
-        new TextRange(start: selection.end, end: selection.end + afterLength);
-    _delete(afterRange);
-    _delete(beforeRange);
-    selection = new TextRange(
-        start: selection.start - beforeLength,
-        end: selection.end - beforeLength);
-    onUpdated();
-  }
-
-  void setComposingRegion(int start, int end) {
-    composing = new TextRange(start: start, end: end);
-    onUpdated();
-  }
-
-  void setComposingText(String text, int newCursorPosition) {
-    // TODO(abarth): Why is |newCursorPosition| always 1?
-    composing = _replaceOrAppend(composing, text);
-    selection = new TextRange.collapsed(composing.end);
-    onUpdated();
-  }
-
-  void setSelection(int start, int end) {
-    selection = new TextRange(start: start, end: end);
-    onUpdated();
-  }
-}