// 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.

library fn;

import 'dart:async';
import 'dart:collection';
import 'dart:sky' as sky;
import 'reflect.dart' as reflect;

final sky.Tracing _tracing = sky.window.tracing;

final bool _shouldLogRenderDuration = false;
final bool _shouldTrace = false;

class Style {
  final String _className;
  static final Map<String, Style> _cache = new HashMap<String, Style>();

  static int _nextStyleId = 1;

  static String _getNextClassName() { return "style${_nextStyleId++}"; }

  Style extend(Style other) {
    var className = "$_className ${other._className}";

    return _cache.putIfAbsent(className, () {
      return new Style._internal(className);
    });
  }

  factory Style(String styles) {
    return _cache.putIfAbsent(styles, () {
      var className = _getNextClassName();
      sky.Element styleNode = sky.document.createElement('style');
      styleNode.setChild(new sky.Text(".$className { $styles }"));
      sky.document.appendChild(styleNode);
      return new Style._internal(className);
    });
  }

  Style._internal(this._className);
}

void _parentInsertBefore(sky.ParentNode parent,
                         sky.Node node,
                         sky.Node ref) {
  if (ref != null) {
    ref.insertBefore([node]);
  } else {
    parent.appendChild(node);
  }
}

enum _SyncOperation { IDENTICAL, INSERTION, STATEFUL, STATELESS, REMOVAL }

/*
 * All Effen nodes derive from UINode. All nodes have a _parent, a _key and
 * can be sync'd.
 */
abstract class UINode {
  String _key;
  UINode _parent;
  UINode get parent => _parent;
  sky.Node _root;
  bool _defunct = false;

  UINode({ Object key }) {
    _key = key == null ? "$runtimeType" : "$runtimeType-$key";
  }

  // Subclasses which implements Nodes that become stateful may return true
  // if the |old| node has become stateful and should be retained.
  bool _willSync(UINode old) => false;

  void _sync(UINode old, sky.ParentNode host, sky.Node insertBefore);

  void _remove() {
    _defunct = true;
    _root = null;
    handleRemoved();
  }
  void handleRemoved() { }

  int _nodeDepth;
  void _ensureDepth() {
    if (_nodeDepth == null) {
      if (_parent != null) {
        _parent._ensureDepth();
        _nodeDepth = _parent._nodeDepth + 1;
      } else {
        _nodeDepth = 0;
      }
    }
  }

  void _trace(String message) {
    if (!_shouldTrace)
      return;

    _ensureDepth();
    print((' ' * _nodeDepth) + message);
  }

  void _traceSync(_SyncOperation op, String key) {
    if (!_shouldTrace)
      return;

    String opString = op.toString().toLowerCase();
    String outString = opString.substring(opString.indexOf('.') + 1);
    _trace('_sync($outString) $key');
  }

  void _removeChild(UINode node) {
    _traceSync(_SyncOperation.REMOVAL, node._key);
    node._remove();
  }

  // Returns the child which should be retained as the child of this node.
  UINode _syncChild(UINode node, UINode oldNode, sky.ParentNode host,
      sky.Node insertBefore) {

    assert(oldNode == null || node._key == oldNode._key);

    if (node == oldNode) {
      _traceSync(_SyncOperation.IDENTICAL, node._key);
      return node; // Nothing to do. Subtrees must be identical.
    }

    // TODO(rafaelw): This eagerly removes the old DOM. It may be that a
    // new component was built that could re-use some of it. Consider
    // syncing the new VDOM against the old one.
    if (oldNode != null && node._key != oldNode._key) {
      _removeChild(oldNode);
    }

    if (node._willSync(oldNode)) {
      _traceSync(_SyncOperation.STATEFUL, node._key);
      oldNode._sync(node, host, insertBefore);
      node._defunct = true;
      assert(oldNode._root is sky.Node);
      return oldNode;
    }

    node._parent = this;

    if (oldNode == null) {
      _traceSync(_SyncOperation.INSERTION, node._key);
    } else {
      _traceSync(_SyncOperation.STATELESS, node._key);
    }
    node._sync(oldNode, host, insertBefore);
    if (oldNode != null)
      oldNode._defunct = true;

    assert(node._root is sky.Node);
    return node;
  }
}

abstract class ContentNode extends UINode {
  UINode content;

  ContentNode(UINode content) : this.content = content, super(key: content._key);

  void _sync(UINode old, sky.ParentNode host, sky.Node insertBefore) {
    UINode oldContent = old == null ? null : (old as ContentNode).content;
    content = _syncChild(content, oldContent, host, insertBefore);
    _root = content._root;
  }

  void _remove() {
    _removeChild(content);
    super._remove();
  }
}

class StyleNode extends ContentNode {
  final Style style;

  StyleNode(UINode content, this.style): super(content);
}

/*
 * SkyNodeWrappers correspond to a desired state of a sky.Node. They are fully
 * immutable, with one exception: A UINode which is a Component which lives within
 * an SkyElementWrapper's children list, may be replaced with the "old" instance if it
 * has become stateful.
 */
abstract class SkyNodeWrapper extends UINode {

  static final Map<sky.Node, SkyNodeWrapper> _nodeMap =
      new HashMap<sky.Node, SkyNodeWrapper>();

  static SkyNodeWrapper _getMounted(sky.Node node) => _nodeMap[node];

  SkyNodeWrapper({ Object key }) : super(key: key);

  SkyNodeWrapper get _emptyNode;

  sky.Node _createNode();

  void _sync(UINode old, sky.ParentNode host, sky.Node insertBefore) {
    if (old == null) {
      _root = _createNode();
      _parentInsertBefore(host, _root, insertBefore);
      old = _emptyNode;
    } else {
      _root = old._root;
    }

    _nodeMap[_root] = this;
    _syncNode(old);
  }

  void _syncNode(SkyNodeWrapper old);

  void _remove() {
    assert(_root != null);
    _root.remove();
    _nodeMap.remove(_root);
    super._remove();
  }
}

typedef GestureEventListener(sky.GestureEvent e);
typedef PointerEventListener(sky.PointerEvent e);
typedef EventListener(sky.Event e);

class EventListenerNode extends ContentNode  {
  final Map<String, sky.EventListener> listeners;

  static final Set<String> _registeredEvents = new HashSet<String>();

  static Map<String, sky.EventListener> _createListeners({
    EventListener onWheel,
    GestureEventListener onGestureFlingCancel,
    GestureEventListener onGestureFlingStart,
    GestureEventListener onGestureScrollStart,
    GestureEventListener onGestureScrollUpdate,
    GestureEventListener onGestureTap,
    GestureEventListener onGestureTapDown,
    PointerEventListener onPointerCancel,
    PointerEventListener onPointerDown,
    PointerEventListener onPointerMove,
    PointerEventListener onPointerUp,
    Map<String, sky.EventListener> custom
  }) {
    var listeners = custom != null ?
        new HashMap<String, sky.EventListener>.from(custom) :
        new HashMap<String, sky.EventListener>();

    if (onWheel != null)
      listeners['wheel'] = onWheel;
    if (onGestureFlingCancel != null)
      listeners['gestureflingcancel'] = onGestureFlingCancel;
    if (onGestureFlingStart != null)
      listeners['gestureflingstart'] = onGestureFlingStart;
    if (onGestureScrollStart != null)
      listeners['gesturescrollstart'] = onGestureScrollStart;
    if (onGestureScrollUpdate != null)
      listeners['gesturescrollupdate'] = onGestureScrollUpdate;
    if (onGestureTap != null)
      listeners['gesturetap'] = onGestureTap;
    if (onGestureTapDown != null)
      listeners['gesturetapdown'] = onGestureTapDown;
    if (onPointerCancel != null)
      listeners['pointercancel'] = onPointerCancel;
    if (onPointerDown != null)
      listeners['pointerdown'] = onPointerDown;
    if (onPointerMove != null)
      listeners['pointermove'] = onPointerMove;
    if (onPointerUp != null)
      listeners['pointerup'] = onPointerUp;

    return listeners;
  }

  EventListenerNode(UINode content, {
    EventListener onWheel,
    GestureEventListener onGestureFlingCancel,
    GestureEventListener onGestureFlingStart,
    GestureEventListener onGestureScrollStart,
    GestureEventListener onGestureScrollUpdate,
    GestureEventListener onGestureTap,
    GestureEventListener onGestureTapDown,
    PointerEventListener onPointerCancel,
    PointerEventListener onPointerDown,
    PointerEventListener onPointerMove,
    PointerEventListener onPointerUp,
    Map<String, sky.EventListener> custom
  }) : listeners = _createListeners(
         onWheel: onWheel,
         onGestureFlingCancel: onGestureFlingCancel,
         onGestureFlingStart: onGestureFlingStart,
         onGestureScrollUpdate: onGestureScrollUpdate,
         onGestureScrollStart: onGestureScrollStart,
         onGestureTap: onGestureTap,
         onGestureTapDown: onGestureTapDown,
         onPointerCancel: onPointerCancel,
         onPointerDown: onPointerDown,
         onPointerMove: onPointerMove,
         onPointerUp: onPointerUp,
         custom: custom
       ),
       super(content);

  void _handleEvent(sky.Event e) {
    sky.EventListener listener = listeners[e.type];
    if (listener != null) {
      listener(e);
    }
  }

  static void _dispatchEvent(sky.Event e) {
    UINode target = SkyNodeWrapper._getMounted(e.target);

    // TODO(rafaelw): StopPropagation?
    while (target != null) {
      if (target is EventListenerNode) {
        (target as EventListenerNode)._handleEvent(e);
      }

      target = target._parent;
    }
  }

  static void _ensureDocumentListener(String eventType) {
    if (_registeredEvents.add(eventType)) {
      sky.document.addEventListener(eventType, _dispatchEvent);
    }
  }

  void _sync(UINode old, sky.ParentNode host, sky.Node insertBefore) {
    for (var type in listeners.keys) {
      _ensureDocumentListener(type);
    }

    super._sync(old, host, insertBefore);
  }
}

class Text extends SkyNodeWrapper {
  final String data;

  // Text nodes are special cases of having non-unique keys (which don't need
  // to be assigned as part of the API). Since they are unique in not having
  // children, there's little point to reordering, so we always just re-assign
  // the data.
  Text(this.data) : super(key:'*text*');

  static final Text _emptyText = new Text(null);

  SkyNodeWrapper get _emptyNode => _emptyText;

  static final Style _displayParagraph = new Style('display:paragraph');

  sky.Node _createNode() {
    return sky.document.createElement('div')
                           ..setChild(new sky.Text(this.data))
                           ..setAttribute('class', _displayParagraph._className);
  }

  void _syncNode(SkyNodeWrapper old) {
    if (old == _emptyText)
      return; // we set inside _createNode();

    (_root.firstChild as sky.Text).data = data;
  }
}

final List<UINode> _emptyList = new List<UINode>();

abstract class SkyElementWrapper extends SkyNodeWrapper {

  String get _tagName;

  sky.Node _createNode() => sky.document.createElement(_tagName);

  final List<UINode> children;
  final Style style;
  final String inlineStyle;

  String _class;

  SkyElementWrapper({
    Object key,
    List<UINode> children,
    this.style,
    this.inlineStyle
  }) : this.children = children == null ? _emptyList : children,
       super(key:key) {

    assert(!_debugHasDuplicateIds());
  }

  void _remove() {
    super._remove();
    if (children != null) {
      for (var child in children) {
        _removeChild(child);
      }
    }
  }

  bool _debugHasDuplicateIds() {
    var idSet = new HashSet<String>();
    for (var child in children) {
      if (child is Text) {
        continue; // Text nodes all have the same key and are never reordered.
      }

      if (!idSet.add(child._key)) {
        throw '''If multiple (non-Text) nodes of the same type exist as children
                 of another node, they must have unique keys.''';
      }
    }
    return false;
  }

  void _ensureClass() {
    if (_class == null) {
      List<Style> styles = new List<Style>();
      if (style != null) {
        styles.add(style);
      }

      UINode parent = _parent;
      while (parent != null && parent is! SkyNodeWrapper) {
        if (parent is StyleNode && (parent as StyleNode).style != null)
          styles.add((parent as StyleNode).style);

        parent = parent._parent;
      }

      _class = styles.map((s) => s._className).join(' ');
    }
  }

  void _syncNode(SkyNodeWrapper old) {
    SkyElementWrapper oldSkyElementWrapper = old as SkyElementWrapper;
    sky.Element root = _root as sky.Element;

    _ensureClass();
    if (_class != oldSkyElementWrapper._class && _class != '')
      root.setAttribute('class', _class);

    if (inlineStyle != oldSkyElementWrapper.inlineStyle)
      root.setAttribute('style', inlineStyle);

    _syncChildren(oldSkyElementWrapper);
  }

  void _syncChildren(SkyElementWrapper oldSkyElementWrapper) {
    sky.Element root = _root as sky.Element;
    assert(root != null);

    var startIndex = 0;
    var endIndex = children.length;

    var oldChildren = oldSkyElementWrapper.children;
    var oldStartIndex = 0;
    var oldEndIndex = oldChildren.length;

    sky.Node nextSibling = null;
    UINode currentNode = null;
    UINode oldNode = null;

    void sync(int atIndex) {
      children[atIndex] = _syncChild(currentNode, oldNode, _root, nextSibling);
    }

    // Scan backwards from end of list while nodes can be directly synced
    // without reordering.
    while (endIndex > startIndex && oldEndIndex > oldStartIndex) {
      currentNode = children[endIndex - 1];
      oldNode = oldChildren[oldEndIndex - 1];

      if (currentNode._key != oldNode._key) {
        break;
      }

      endIndex--;
      oldEndIndex--;
      sync(endIndex);
      nextSibling = currentNode._root;
    }

    HashMap<String, UINode> oldNodeIdMap = null;

    bool oldNodeReordered(String key) {
      return oldNodeIdMap != null &&
             oldNodeIdMap.containsKey(key) &&
             oldNodeIdMap[key] == null;
    }

    void advanceOldStartIndex() {
      oldStartIndex++;
      while (oldStartIndex < oldEndIndex &&
             oldNodeReordered(oldChildren[oldStartIndex]._key)) {
        oldStartIndex++;
      }
    }

    void ensureOldIdMap() {
      if (oldNodeIdMap != null)
        return;

      oldNodeIdMap = new HashMap<String, UINode>();
      for (int i = oldStartIndex; i < oldEndIndex; i++) {
        var node = oldChildren[i];
        if (node is! Text) {
          oldNodeIdMap.putIfAbsent(node._key, () => node);
        }
      }
    }

    bool searchForOldNode() {
      if (currentNode is Text)
        return false; // Never re-order Text nodes.

      ensureOldIdMap();
      oldNode = oldNodeIdMap[currentNode._key];
      if (oldNode == null)
        return false;

      oldNodeIdMap[currentNode._key] = null; // mark it reordered.
      _parentInsertBefore(root, oldNode._root, nextSibling);
      return true;
    }

    // Scan forwards, this time we may re-order;
    nextSibling = root.firstChild;
    while (startIndex < endIndex && oldStartIndex < oldEndIndex) {
      currentNode = children[startIndex];
      oldNode = oldChildren[oldStartIndex];

      if (currentNode._key == oldNode._key) {
        assert(currentNode.runtimeType == oldNode.runtimeType);
        nextSibling = nextSibling.nextSibling;
        sync(startIndex);
        startIndex++;
        advanceOldStartIndex();
        continue;
      }

      oldNode = null;
      searchForOldNode();
      sync(startIndex);
      startIndex++;
    }

    // New insertions
    oldNode = null;
    while (startIndex < endIndex) {
      currentNode = children[startIndex];
      sync(startIndex);
      startIndex++;
    }

    // Removals
    currentNode = null;
    while (oldStartIndex < oldEndIndex) {
      oldNode = oldChildren[oldStartIndex];
      _removeChild(oldNode);
      advanceOldStartIndex();
    }
  }
}

class Container extends SkyElementWrapper {

  String get _tagName => 'div';

  static final Container _emptyContainer = new Container();

  SkyNodeWrapper get _emptyNode => _emptyContainer;

  Container({
    Object key,
    List<UINode> children,
    Style style,
    String inlineStyle
  }) : super(
    key: key,
    children: children,
    style: style,
    inlineStyle: inlineStyle
  );
}

abstract class LayoutContainer extends Container {

  LayoutContainer({
    Object key,
    List<UINode> children,
    Style style,
    String inlineStyle
  }) : super(
    key: key,
    children: children,
    style: style,
    inlineStyle: inlineStyle
  );

  sky.Node _createNode() {
    var result = super._createNode();
    result.setLayoutManager(() => layout(_root));
    return result;
  }

  // If we ever reuse sky nodes for different classes, then we should 
  // call _root.setLayoutManager(null) during _remove() here.

  void _syncNode(SkyNodeWrapper old) {
    super._syncNode(old);
    _root.setLayoutManager(() => layout(_root));
    _root.setNeedsLayout();
  }

  void layout(sky.Element skyNode);
  // set skyNode.width (e.g., set it to skyNode.parentNode.width)
  // for each skyNode.getChildNodes()[i]:
  //   call .layout()
  //   set .x, .y
  //   set .width if you want to force a width
  //   set .height if you want to force a height
  // set skyNode.height

}

class Image extends SkyElementWrapper {

  String get _tagName => 'img';

  static final Image _emptyImage = new Image();

  SkyNodeWrapper get _emptyNode => _emptyImage;

  final String src;
  final int width;
  final int height;

  Image({
    Object key,
    List<UINode> children,
    Style style,
    String inlineStyle,
    this.width,
    this.height,
    this.src
  }) : super(
    key: key,
    children: children,
    style: style,
    inlineStyle: inlineStyle
  );

  void _syncNode(UINode old) {
    super._syncNode(old);

    Image oldImage = old as Image;
    sky.HTMLImageElement skyImage = _root as sky.HTMLImageElement;

    if (src != oldImage.src)
      skyImage.src = src;

    if (width != oldImage.width)
      skyImage.style['width'] = '${width}px';

    if (height != oldImage.height)
      skyImage.style['height'] = '${height}px';
  }
}

class Anchor extends SkyElementWrapper {

  String get _tagName => 'a';

  static final Anchor _emptyAnchor = new Anchor();

  UINode get _emptyNode => _emptyAnchor;

  final String href;
  final int width;
  final int height;

  Anchor({
    Object key,
    List<UINode> children,
    Style style,
    String inlineStyle,
    this.width,
    this.height,
    this.href
  }) : super(
    key: key,
    children: children,
    style: style,
    inlineStyle: inlineStyle
  );

  void _syncNode(UINode old) {
    super._syncNode(old);

    Anchor oldAnchor = old as Anchor;
    sky.HTMLAnchorElement skyAnchor = _root as sky.HTMLAnchorElement;

    if (href != oldAnchor.href)
      skyAnchor.href = href;
  }
}


Set<Component> _mountedComponents = new HashSet<Component>();
Set<Component> _unmountedComponents = new HashSet<Component>();

void _enqueueDidMount(Component c) {
  assert(!_notifingMountStatus);
  _mountedComponents.add(c);
}

void _enqueueDidUnmount(Component c) {
  assert(!_notifingMountStatus);
  _unmountedComponents.add(c);
}

bool _notifingMountStatus = false;

void _notifyMountStatusChanged() {
  try {
    _notifingMountStatus = true;
    _unmountedComponents.forEach((c) => c._didUnmount());
    _mountedComponents.forEach((c) => c._didMount());
    _mountedComponents.clear();
    _unmountedComponents.clear();
  } finally {
    _notifingMountStatus = false;
  }
}

List<Component> _dirtyComponents = new List<Component>();
bool _buildScheduled = false;
bool _inRenderDirtyComponents = false;

void _buildDirtyComponents() {
  _tracing.begin('fn::_buildDirtyComponents');

  Stopwatch sw;
  if (_shouldLogRenderDuration)
    sw = new Stopwatch()..start();

  try {
    _inRenderDirtyComponents = true;

    _dirtyComponents.sort((a, b) => a._order - b._order);
    for (var comp in _dirtyComponents) {
      comp._buildIfDirty();
    }

    _dirtyComponents.clear();
    _buildScheduled = false;
  } finally {
    _inRenderDirtyComponents = false;
  }

  _notifyMountStatusChanged();

  if (_shouldLogRenderDuration) {
    sw.stop();
    print('Render took ${sw.elapsedMicroseconds} microseconds');
  }

  _tracing.end('fn::_buildDirtyComponents');
}

void _scheduleComponentForRender(Component c) {
  assert(!_inRenderDirtyComponents);
  _dirtyComponents.add(c);

  if (!_buildScheduled) {
    _buildScheduled = true;
    new Future.microtask(_buildDirtyComponents);
  }
}

abstract class Component extends UINode {
  bool get _isBuilding => _currentlyBuilding == this;
  bool _dirty = true;

  sky.Node get _host => _root.parentNode;
  sky.Node get _insertionPoint => _root == null ? _root : _root.nextSibling;

  UINode _built;
  final int _order;
  static int _currentOrder = 0;
  bool _stateful;
  static Component _currentlyBuilding;
  List<Function> _mountCallbacks;
  List<Function> _unmountCallbacks;

  void onDidMount(Function fn) {
    if (_mountCallbacks == null)
      _mountCallbacks = new List<Function>();

    _mountCallbacks.add(fn);
  }

  void onDidUnmount(Function fn) {
    if (_unmountCallbacks == null)
      _unmountCallbacks = new List<Function>();

    _unmountCallbacks.add(fn);
  }


  Component({ Object key, bool stateful })
      : _stateful = stateful != null ? stateful : false,
        _order = _currentOrder + 1,
        super(key:key);

  Component.fromArgs(Object key, bool stateful)
      : this(key: key, stateful: stateful);

  void _didMount() {
    if (_mountCallbacks != null)
      _mountCallbacks.forEach((fn) => fn());
  }

  void _didUnmount() {
    if (_unmountCallbacks != null)
      _unmountCallbacks.forEach((fn) => fn());
  }

  // TODO(rafaelw): It seems wrong to expose DOM at all. This is presently
  // needed to get sizing info.
  sky.Node getRoot() => _root;

  void _remove() {
    assert(_built != null);
    assert(_root != null);
    _removeChild(_built);
    _built = null;
    _enqueueDidUnmount(this);
    super._remove();
  }

  bool _willSync(UINode old) {
    Component oldComponent = old as Component;
    if (oldComponent == null || !oldComponent._stateful)
      return false;

    // Make |this| the "old" Component
    _stateful = false;
    _built = oldComponent._built;
    assert(_built != null);

    // Make |oldComponent| the "new" component
    reflect.copyPublicFields(this, oldComponent);
    oldComponent._built = null;
    oldComponent._dirty = true;
    return true;
  }

  /* There are three cases here:
   * 1) Building for the first time:
   *      assert(_built == null && old == null)
   * 2) Re-building (because a dirty flag got set):
   *      assert(_built != null && old == null)
   * 3) Syncing against an old version
   *      assert(_built == null && old != null)
   */
  void _sync(UINode old, sky.ParentNode host, sky.Node insertBefore) {
    assert(!_defunct);
    assert(_built == null || old == null);

    Component oldComponent = old as Component;

    var oldBuilt;
    if (oldComponent == null) {
      oldBuilt = _built;
    } else {
      assert(_built == null);
      oldBuilt = oldComponent._built;
    }

    if (oldBuilt == null)
      _enqueueDidMount(this);

    int lastOrder = _currentOrder;
    _currentOrder = _order;
    _currentlyBuilding = this;
    _built = build();
    _currentlyBuilding = null;
    _currentOrder = lastOrder;

    _built = _syncChild(_built, oldBuilt, host, insertBefore);
    _dirty = false;
    _root = _built._root;
  }

  void _buildIfDirty() {
    if (!_dirty || _defunct)
      return;

    assert(_host != null);
    _trace('$_key rebuilding...');
    _sync(null, _host, _insertionPoint);
  }

  void scheduleBuild() {
    setState(() {});
  }

  void setState(Function fn()) {
    _stateful = true;
    fn();
    if (_isBuilding || _dirty || _defunct)
      return;

    _dirty = true;
    _scheduleComponentForRender(this);
  }

  UINode build();
}

abstract class App extends Component {
  sky.Node _host;

  App() : super(stateful: true) {
    _host = sky.document.createElement('div');
    sky.document.appendChild(_host);
    _scheduleComponentForRender(this);
  }
}