@wordpress/undo-manager/build/index.js

A small package to manage undo/redo.

"use strict";

var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.createUndoManager = createUndoManager;
var _isShallowEqual = _interopRequireDefault(require("@wordpress/is-shallow-equal"));
/**
 * WordPress dependencies
 */

/**
 * Internal dependencies
 */

/**
 * Represents a single change in history.
 */

/**
 * Represents changes for a single item.
 */

/**
 * Represents a record of history changes.
 */

/**
 * The undo manager interface.
 */

/**
 * Merge changes for a single item into a record of changes.
 *
 * @param changes1 Previous changes
 * @param changes2 Next changes
 *
 * @return Merged changes
 */
function mergeHistoryChanges(changes1, changes2) {
  const newChanges = {
    ...changes1
  };
  Object.entries(changes2).forEach(([key, value]) => {
    if (newChanges[key]) {
      newChanges[key] = {
        ...newChanges[key],
        to: value.to
      };
    } else {
      newChanges[key] = value;
    }
  });
  return newChanges;
}

/**
 * Adds history changes for a single item into a record of changes.
 *
 * @param record  The record to merge into.
 * @param changes The changes to merge.
 */
const addHistoryChangesIntoRecord = (record, changes) => {
  const existingChangesIndex = record?.findIndex(({
    id: recordIdentifier
  }) => {
    return typeof recordIdentifier === 'string' ? recordIdentifier === changes.id : (0, _isShallowEqual.default)(recordIdentifier, changes.id);
  });
  const nextRecord = [...record];
  if (existingChangesIndex !== -1) {
    // If the edit is already in the stack leave the initial "from" value.
    nextRecord[existingChangesIndex] = {
      id: changes.id,
      changes: mergeHistoryChanges(nextRecord[existingChangesIndex].changes, changes.changes)
    };
  } else {
    nextRecord.push(changes);
  }
  return nextRecord;
};

/**
 * Creates an undo manager.
 *
 * @return Undo manager.
 */
function createUndoManager() {
  let history = [];
  let stagedRecord = [];
  let offset = 0;
  const dropPendingRedos = () => {
    history = history.slice(0, offset || undefined);
    offset = 0;
  };
  const appendStagedRecordToLatestHistoryRecord = () => {
    var _history$index;
    const index = history.length === 0 ? 0 : history.length - 1;
    let latestRecord = (_history$index = history[index]) !== null && _history$index !== void 0 ? _history$index : [];
    stagedRecord.forEach(changes => {
      latestRecord = addHistoryChangesIntoRecord(latestRecord, changes);
    });
    stagedRecord = [];
    history[index] = latestRecord;
  };

  /**
   * Checks whether a record is empty.
   * A record is considered empty if it the changes keep the same values.
   * Also updates to function values are ignored.
   *
   * @param record The record to check.
   * @return Whether the record is empty.
   */
  const isRecordEmpty = record => {
    const filteredRecord = record.filter(({
      changes
    }) => {
      return Object.values(changes).some(({
        from,
        to
      }) => typeof from !== 'function' && typeof to !== 'function' && !(0, _isShallowEqual.default)(from, to));
    });
    return !filteredRecord.length;
  };
  return {
    addRecord(record, isStaged = false) {
      const isEmpty = !record || isRecordEmpty(record);
      if (isStaged) {
        if (isEmpty) {
          return;
        }
        record.forEach(changes => {
          stagedRecord = addHistoryChangesIntoRecord(stagedRecord, changes);
        });
      } else {
        dropPendingRedos();
        if (stagedRecord.length) {
          appendStagedRecordToLatestHistoryRecord();
        }
        if (isEmpty) {
          return;
        }
        history.push(record);
      }
    },
    undo() {
      if (stagedRecord.length) {
        dropPendingRedos();
        appendStagedRecordToLatestHistoryRecord();
      }
      const undoRecord = history[history.length - 1 + offset];
      if (!undoRecord) {
        return;
      }
      offset -= 1;
      return undoRecord;
    },
    redo() {
      const redoRecord = history[history.length + offset];
      if (!redoRecord) {
        return;
      }
      offset += 1;
      return redoRecord;
    },
    hasUndo() {
      return !!history[history.length - 1 + offset];
    },
    hasRedo() {
      return !!history[history.length + offset];
    }
  };
}
//# sourceMappingURL=index.js.map