svgedit/editor/history.js

/**
 * Package: svedit.history
 *
 * Licensed under the MIT License
 *
 * Copyright(c) 2010 Jeff Schiller
 */

import {getHref, setHref, getRotationAngle} from './svgutils.js';
import {removeElementFromListMap} from './svgtransformlist.js';

// Group: Undo/Redo history management
export const HistoryEventTypes = {
  BEFORE_APPLY: 'before_apply',
  AFTER_APPLY: 'after_apply',
  BEFORE_UNAPPLY: 'before_unapply',
  AFTER_UNAPPLY: 'after_unapply'
};

// const removedElements = {};

/**
 * An interface that all command objects must implement.
 * @typedef svgedit.history.HistoryCommand
 * @type {Object}
 *   void apply(svgedit.history.HistoryEventHandler);
 *   void unapply(svgedit.history.HistoryEventHandler);
 *   Element[] elements();
 *   String getText();
 *
 *   static String type();
 * }
 *
 * Interface: svgedit.history.HistoryEventHandler
 * An interface for objects that will handle history events.
 *
 * interface svgedit.history.HistoryEventHandler {
 *   void handleHistoryEvent(eventType, command);
 * }
 *
 * eventType is a string conforming to one of the HistoryEvent types.
 * command is an object fulfilling the HistoryCommand interface.
 */

/**
 * @class svgedit.history.MoveElementCommand
 * @implements svgedit.history.HistoryCommand
 * History command for an element that had its DOM position changed
 * @param {Element} elem - The DOM element that was moved
 * @param {Element} oldNextSibling - The element's next sibling before it was moved
 * @param {Element} oldParent - The element's parent before it was moved
 * @param {string} [text] - An optional string visible to user related to this change
*/
export class MoveElementCommand {
  constructor (elem, oldNextSibling, oldParent, text) {
    this.elem = elem;
    this.text = text ? ('Move ' + elem.tagName + ' to ' + text) : ('Move ' + elem.tagName);
    this.oldNextSibling = oldNextSibling;
    this.oldParent = oldParent;
    this.newNextSibling = elem.nextSibling;
    this.newParent = elem.parentNode;
  }
  getText () {
    return this.text;
  }
  type () {
    return 'svgedit.history.MoveElementCommand';
  }

  /**
   * Re-positions the element
   * @param {handleHistoryEvent: function}
  */
  apply (handler) {
    // TODO(codedread): Refactor this common event code into a base HistoryCommand class.
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_APPLY, this);
    }

    this.elem = this.newParent.insertBefore(this.elem, this.newNextSibling);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_APPLY, this);
    }
  }

  /**
   * Positions the element back to its original location
   * @param {handleHistoryEvent: function}
  */
  unapply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_UNAPPLY, this);
    }

    this.elem = this.oldParent.insertBefore(this.elem, this.oldNextSibling);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_UNAPPLY, this);
    }
  }

  // Returns array with element associated with this command
  elements () {
    return [this.elem];
  }
}
MoveElementCommand.type = MoveElementCommand.prototype.type;

// implements svgedit.history.HistoryCommand
// History command for an element that was added to the DOM
//
// Parameters:
// elem - The newly added DOM element
// text - An optional string visible to user related to this change
export class InsertElementCommand {
  constructor (elem, text) {
    this.elem = elem;
    this.text = text || ('Create ' + elem.tagName);
    this.parent = elem.parentNode;
    this.nextSibling = this.elem.nextSibling;
  }

  type () {
    return 'svgedit.history.InsertElementCommand';
  }

  getText () {
    return this.text;
  }

  // Re-Inserts the new element
  apply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_APPLY, this);
    }

    this.elem = this.parent.insertBefore(this.elem, this.nextSibling);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_APPLY, this);
    }
  }

  // Removes the element
  unapply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_UNAPPLY, this);
    }

    this.parent = this.elem.parentNode;
    this.elem = this.elem.parentNode.removeChild(this.elem);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_UNAPPLY, this);
    }
  }

  // Returns array with element associated with this command
  elements () {
    return [this.elem];
  }
}
InsertElementCommand.type = InsertElementCommand.prototype.type;

// implements svgedit.history.HistoryCommand
// History command for an element removed from the DOM
//
// Parameters:
// elem - The removed DOM element
// oldNextSibling - the DOM element's nextSibling when it was in the DOM
// oldParent - The DOM element's parent
// text - An optional string visible to user related to this change
export class RemoveElementCommand {
  constructor (elem, oldNextSibling, oldParent, text) {
    this.elem = elem;
    this.text = text || ('Delete ' + elem.tagName);
    this.nextSibling = oldNextSibling;
    this.parent = oldParent;

    // special hack for webkit: remove this element's entry in the svgTransformLists map
    removeElementFromListMap(elem);
  }
  type () {
    return 'svgedit.history.RemoveElementCommand';
  }

  getText () {
    return this.text;
  }

  // Re-removes the new element
  apply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_APPLY, this);
    }

    removeElementFromListMap(this.elem);
    this.parent = this.elem.parentNode;
    this.elem = this.parent.removeChild(this.elem);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_APPLY, this);
    }
  }

  // Re-adds the new element
  unapply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_UNAPPLY, this);
    }

    removeElementFromListMap(this.elem);
    if (this.nextSibling == null) {
      if (window.console) {
        console.log('Error: reference element was lost');
      }
    }
    this.parent.insertBefore(this.elem, this.nextSibling);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_UNAPPLY, this);
    }
  }

  // Function: RemoveElementCommand.elements
  // Returns array with element associated with this command
  elements () {
    return [this.elem];
  }
}
RemoveElementCommand.type = RemoveElementCommand.prototype.type;

// implements svgedit.history.HistoryCommand
// History command to make a change to an element.
// Usually an attribute change, but can also be textcontent.
//
// Parameters:
// elem - The DOM element that was changed
// attrs - An object with the attributes to be changed and the values they had *before* the change
// text - An optional string visible to user related to this change
export class ChangeElementCommand {
  constructor (elem, attrs, text) {
    this.elem = elem;
    this.text = text ? ('Change ' + elem.tagName + ' ' + text) : ('Change ' + elem.tagName);
    this.newValues = {};
    this.oldValues = attrs;
    for (const attr in attrs) {
      if (attr === '#text') {
        this.newValues[attr] = elem.textContent;
      } else if (attr === '#href') {
        this.newValues[attr] = getHref(elem);
      } else {
        this.newValues[attr] = elem.getAttribute(attr);
      }
    }
  }
  type () {
    return 'svgedit.history.ChangeElementCommand';
  }

  getText () {
    return this.text;
  }

  // Performs the stored change action
  apply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_APPLY, this);
    }

    let bChangedTransform = false;
    for (const attr in this.newValues) {
      if (this.newValues[attr]) {
        if (attr === '#text') {
          this.elem.textContent = this.newValues[attr];
        } else if (attr === '#href') {
          setHref(this.elem, this.newValues[attr]);
        } else {
          this.elem.setAttribute(attr, this.newValues[attr]);
        }
      } else {
        if (attr === '#text') {
          this.elem.textContent = '';
        } else {
          this.elem.setAttribute(attr, '');
          this.elem.removeAttribute(attr);
        }
      }

      if (attr === 'transform') { bChangedTransform = true; }
    }

    // relocate rotational transform, if necessary
    if (!bChangedTransform) {
      const angle = getRotationAngle(this.elem);
      if (angle) {
        const bbox = this.elem.getBBox();
        const cx = bbox.x + bbox.width / 2,
          cy = bbox.y + bbox.height / 2;
        const rotate = ['rotate(', angle, ' ', cx, ',', cy, ')'].join('');
        if (rotate !== this.elem.getAttribute('transform')) {
          this.elem.setAttribute('transform', rotate);
        }
      }
    }

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_APPLY, this);
    }

    return true;
  }

  // Reverses the stored change action
  unapply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_UNAPPLY, this);
    }

    let bChangedTransform = false;
    for (const attr in this.oldValues) {
      if (this.oldValues[attr]) {
        if (attr === '#text') {
          this.elem.textContent = this.oldValues[attr];
        } else if (attr === '#href') {
          setHref(this.elem, this.oldValues[attr]);
        } else {
          this.elem.setAttribute(attr, this.oldValues[attr]);
        }
      } else {
        if (attr === '#text') {
          this.elem.textContent = '';
        } else {
          this.elem.removeAttribute(attr);
        }
      }
      if (attr === 'transform') { bChangedTransform = true; }
    }
    // relocate rotational transform, if necessary
    if (!bChangedTransform) {
      const angle = getRotationAngle(this.elem);
      if (angle) {
        const bbox = this.elem.getBBox();
        const cx = bbox.x + bbox.width / 2,
          cy = bbox.y + bbox.height / 2;
        const rotate = ['rotate(', angle, ' ', cx, ',', cy, ')'].join('');
        if (rotate !== this.elem.getAttribute('transform')) {
          this.elem.setAttribute('transform', rotate);
        }
      }
    }

    // Remove transformlist to prevent confusion that causes bugs like 575.
    removeElementFromListMap(this.elem);

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_UNAPPLY, this);
    }

    return true;
  }

  // Returns array with element associated with this command
  elements () {
    return [this.elem];
  }
}
ChangeElementCommand.type = ChangeElementCommand.prototype.type;

// TODO: create a 'typing' command object that tracks changes in text
// if a new Typing command is created and the top command on the stack is also a Typing
// and they both affect the same element, then collapse the two commands into one

// implements svgedit.history.HistoryCommand
// History command that can contain/execute multiple other commands
//
// Parameters:
// text - An optional string visible to user related to this change
export class BatchCommand {
  constructor (text) {
    this.text = text || 'Batch Command';
    this.stack = [];
  }

  type () {
    return 'svgedit.history.BatchCommand';
  }

  getText () {
    return this.text;
  }

  // Runs "apply" on all subcommands
  apply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_APPLY, this);
    }

    const len = this.stack.length;
    for (let i = 0; i < len; ++i) {
      this.stack[i].apply(handler);
    }

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_APPLY, this);
    }
  }

  // Runs "unapply" on all subcommands
  unapply (handler) {
    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.BEFORE_UNAPPLY, this);
    }

    for (let i = this.stack.length - 1; i >= 0; i--) {
      this.stack[i].unapply(handler);
    }

    if (handler) {
      handler.handleHistoryEvent(HistoryEventTypes.AFTER_UNAPPLY, this);
    }
  }

  // Iterate through all our subcommands and returns all the elements we are changing
  elements () {
    const elems = [];
    let cmd = this.stack.length;
    while (cmd--) {
      const thisElems = this.stack[cmd].elements();
      let elem = thisElems.length;
      while (elem--) {
        if (!elems.includes(thisElems[elem])) { elems.push(thisElems[elem]); }
      }
    }
    return elems;
  }

  // Adds a given command to the history stack
  //
  // Parameters:
  // cmd - The undo command object to add
  addSubCommand (cmd) {
    this.stack.push(cmd);
  }

  // Returns a boolean indicating whether or not the batch command is empty
  isEmpty () {
    return !this.stack.length;
  }
}
BatchCommand.type = BatchCommand.prototype.type;

// Parameters:
// historyEventHandler - an object that conforms to the HistoryEventHandler interface
// (see above)
export class UndoManager {
  constructor (historyEventHandler) {
    this.handler_ = historyEventHandler || null;
    this.undoStackPointer = 0;
    this.undoStack = [];

    // this is the stack that stores the original values, the elements and
    // the attribute name for begin/finish
    this.undoChangeStackPointer = -1;
    this.undoableChangeStack = [];
  }

  // Resets the undo stack, effectively clearing the undo/redo history
  resetUndoStack () {
    this.undoStack = [];
    this.undoStackPointer = 0;
  }

  // Returns:
  // Integer with the current size of the undo history stack
  getUndoStackSize () {
    return this.undoStackPointer;
  }

  // Returns:
  // Integer with the current size of the redo history stack
  getRedoStackSize () {
    return this.undoStack.length - this.undoStackPointer;
  }

  // Returns:
  // String associated with the next undo command
  getNextUndoCommandText () {
    return this.undoStackPointer > 0 ? this.undoStack[this.undoStackPointer - 1].getText() : '';
  }

  // Returns:
  // String associated with the next redo command
  getNextRedoCommandText () {
    return this.undoStackPointer < this.undoStack.length ? this.undoStack[this.undoStackPointer].getText() : '';
  }

  // Performs an undo step
  undo () {
    if (this.undoStackPointer > 0) {
      const cmd = this.undoStack[--this.undoStackPointer];
      cmd.unapply(this.handler_);
    }
  }

  // Performs a redo step
  redo () {
    if (this.undoStackPointer < this.undoStack.length && this.undoStack.length > 0) {
      const cmd = this.undoStack[this.undoStackPointer++];
      cmd.apply(this.handler_);
    }
  }

  /**
  * Adds a command object to the undo history stack
  * @param cmd - The command object to add
  */
  addCommandToHistory (cmd) {
    // FIXME: we MUST compress consecutive text changes to the same element
    // (right now each keystroke is saved as a separate command that includes the
    // entire text contents of the text element)
    // TODO: consider limiting the history that we store here (need to do some slicing)

    // if our stack pointer is not at the end, then we have to remove
    // all commands after the pointer and insert the new command
    if (this.undoStackPointer < this.undoStack.length && this.undoStack.length > 0) {
      this.undoStack = this.undoStack.splice(0, this.undoStackPointer);
    }
    this.undoStack.push(cmd);
    this.undoStackPointer = this.undoStack.length;
  }

  // This function tells the canvas to remember the old values of the
  // attrName attribute for each element sent in.  The elements and values
  // are stored on a stack, so the next call to finishUndoableChange() will
  // pop the elements and old values off the stack, gets the current values
  // from the DOM and uses all of these to construct the undo-able command.
  //
  // Parameters:
  // attrName - The name of the attribute being changed
  // elems - Array of DOM elements being changed
  beginUndoableChange (attrName, elems) {
    const p = ++this.undoChangeStackPointer;
    let i = elems.length;
    const oldValues = new Array(i), elements = new Array(i);
    while (i--) {
      const elem = elems[i];
      if (elem == null) { continue; }
      elements[i] = elem;
      oldValues[i] = elem.getAttribute(attrName);
    }
    this.undoableChangeStack[p] = {
      attrName,
      oldValues,
      elements
    };
  }

  // This function returns a BatchCommand object which summarizes the
  // change since beginUndoableChange was called.  The command can then
  // be added to the command history
  //
  // Returns:
  // Batch command object with resulting changes
  finishUndoableChange () {
    const p = this.undoChangeStackPointer--;
    const changeset = this.undoableChangeStack[p];
    const {attrName} = changeset;
    const batchCmd = new BatchCommand('Change ' + attrName);
    let i = changeset.elements.length;
    while (i--) {
      const elem = changeset.elements[i];
      if (elem == null) { continue; }
      const changes = {};
      changes[attrName] = changeset.oldValues[i];
      if (changes[attrName] !== elem.getAttribute(attrName)) {
        batchCmd.addSubCommand(new ChangeElementCommand(elem, changes, attrName));
      }
    }
    this.undoableChangeStack[p] = null;
    return batchCmd;
  }
}