history.js

'use strict';

var _ = require('lodash');
var LocalStorage = require('node-localstorage').LocalStorage;
var path = require('path');
var os = require('os');

// Number of command histories kept in persistent storage
var HISTORY_SIZE = 500;

var temp = path.normalize(path.join(os.tmpdir(), '/.local_storage'));
var DEFAULT_STORAGE_PATH = temp;

var History = function History() {
  this._storageKey = undefined;

  // Prompt Command History
  // Histctr moves based on number of times 'up' (+= ctr)
  //  or 'down' (-= ctr) was pressed in traversing
  // command history.
  this._hist = [];
  this._histCtr = 0;

  // When in a 'mode', we reset the
  // history and store it in a cache until
  // exiting the 'mode', at which point we
  // resume the original history.
  this._histCache = [];
  this._histCtrCache = 0;
};

/**
 * Initialize the history with local storage data
 * Called from setId when history id is set
 */

History.prototype._init = function () {
  if (!this._storageKey) {
    return;
  }

  // Load history from local storage
  var persistedHistory = JSON.parse(this._localStorage.getItem(this._storageKey));
  if (_.isArray(persistedHistory)) {
    Array.prototype.push.apply(this._hist, persistedHistory);
  }
};

/**
 * Set id for this history instance.
 * Calls init internally to initialize
 * the history with the id.
 */

History.prototype.setId = function (id) {
  // Initialize a localStorage instance with default
  // path if it is not initialized
  if (!this._localStorage) {
    this._localStorage = new LocalStorage(DEFAULT_STORAGE_PATH);
  }
  this._storageKey = 'cmd_history_' + id;
  this._init();
};

/**
 * Initialize a local storage instance with
 * the path if not already initialized.
 *
 * @param path
 */

History.prototype.setStoragePath = function (path) {
  if (!this._localStorage) {
    this._localStorage = new LocalStorage(path);
  }
};

/**
 * Get previous history. Called when up is pressed.
 *
 * @return {String}
 */

History.prototype.getPreviousHistory = function () {
  this._histCtr++;
  this._histCtr = this._histCtr > this._hist.length ? this._hist.length : this._histCtr;
  return this._hist[this._hist.length - this._histCtr];
};

/**
 * Get next history. Called when down is pressed.
 *
 * @return {String}
 */

History.prototype.getNextHistory = function () {
  this._histCtr--;

  // Return empty prompt if the we dont have any history to show
  if (this._histCtr < 1) {
    this._histCtr = 0;
    return '';
  }

  return this._hist[this._hist.length - this._histCtr];
};

/**
 * Peek into history, without changing state
 *
 * @return {String}
 */

History.prototype.peek = function (depth) {
  depth = depth || 0;
  return this._hist[this._hist.length - 1 - depth];
};

/**
 * A new command was submitted. Called when enter is pressed and the prompt is not empty.
 *
 * @param cmd
 */

History.prototype.newCommand = function (cmd) {
  // Always reset history when new command is executed.
  this._histCtr = 0;

  // Don't store command in history if it's a duplicate.
  if (this._hist[this._hist.length - 1] === cmd) {
    return;
  }

  // Push into history.
  this._hist.push(cmd);

  // Only persist history when not in mode
  if (this._storageKey && !this._inMode) {
    var persistedHistory = this._hist;
    var historyLen = this._hist.length;
    if (historyLen > HISTORY_SIZE) {
      persistedHistory = this._hist.slice(historyLen - HISTORY_SIZE - 1, historyLen - 1);
    }

    // Add to local storage
    this._localStorage.setItem(this._storageKey, JSON.stringify(persistedHistory));
  }
};

/**
 * Called when entering a mode
 */

History.prototype.enterMode = function () {
  // Reassign the command history to a
  // cache, replacing it with a blank
  // history for the mode.
  this._histCache = _.clone(this._hist);
  this._histCtrCache = parseFloat(this._histCtr);
  this._hist = [];
  this._histCtr = 0;
  this._inMode = true;
};

/**
 * Called when exiting a mode
 */

History.prototype.exitMode = function () {
  this._hist = this._histCache;
  this._histCtr = this._histCtrCache;
  this._histCache = [];
  this._histCtrCache = 0;
  this._inMode = false;
};

/**
 * Clears the command history
 * (Currently only used in unit test)
 */

History.prototype.clear = function () {
  if (this._storageKey) {
    this._localStorage.removeItem(this._storageKey);
  }
};

module.exports = History;