/src/extensions/paginator/backgrid-paginator.js

/*
  backgrid-paginator
  http://github.com/wyuenho/backgrid

  Copyright (c) 2013 Jimmy Yuen Ho Wong and contributors
  Licensed under the MIT @license.
*/

(function (_, Backbone, Backgrid) {

  "use strict";

  /**
     PageHandle is a class that renders the actual page handles and reacts to
     click events for pagination.

     This class acts in two modes - control or discrete page handle modes. If
     one of the `is*` flags is `true`, an instance of this class is under
     control page handle mode. Setting a `pageIndex` to an instance of this
     class under control mode has no effect and the correct page index will
     always be inferred from the `is*` flag. Only one of the `is*` flags should
     be set to `true` at a time. For example, an instance of this class cannot
     simultaneously be a rewind control and a fast forward control. A `label`
     and a `title` template or a string are required to be passed to the
     constuctor under this mode. If a `title` template is provided, it __MUST__
     accept a parameter `label`. When the `label` is provided to the `title`
     template function, its result will be used to render the generated anchor's
     title attribute.

     If all of the `is*` flags is set to `false`, which is the default, an
     instance of this class will be in discrete page handle mode. An instance
     under this mode requires the `pageIndex` to be passed from the constructor
     as an option and it __MUST__ be a 0-based index of the list of page numbers
     to render. The constuctor will normalize the base to the same base the
     underlying PageableCollection collection instance uses. A `label` is not
     required under this mode, which will default to the equivalent 1-based page
     index calculated from `pageIndex` and the underlying PageableCollection
     instance. A provided `label` will still be honored however. The `title`
     parameter is also not required under this mode, in which case the default
     `title` template will be used. You are encouraged to provide your own
     `title` template however if you wish to localize the title strings.

     If this page handle represents the current page, an `active` class will be
     placed on the root list element.

     if this page handle is at the border of the list of pages, a `disabled`
     class will be placed on the root list element.

     Only page handles that are neither `active` nor `disabled` will respond to
     click events and triggers pagination.

     @class Backgrid.Extension.PageHandle
  */
  var PageHandle = Backgrid.Extension.PageHandle = Backbone.View.extend({

    /** @property */
    tagName: "li",

    /** @property */
    events: {
      "click a": "changePage"
    },

    /**
       @property {string|function(Object.<string, string>): string} title
       The title to use for the `title` attribute of the generated page handle
       anchor elements. It can be a string or an Underscore template function
       that takes a mandatory `label` parameter.
    */
    title: _.template('Page <%- label %>'),

    /**
       @property {boolean} isRewind Whether this handle represents a rewind
       control
    */
    isRewind: false,

    /**
       @property {boolean} isBack Whether this handle represents a back
       control
    */
    isBack: false,

    /**
       @property {boolean} isForward Whether this handle represents a forward
       control
    */
    isForward: false,

    /**
       @property {boolean} isFastForward Whether this handle represents a fast
       forward control
    */
    isFastForward: false,

    /**
       Initializer.

       @param {Object} options
       @param {Backbone.Collection} options.collection
       @param {number} pageIndex 0-based index of the page number this handle
       handles. This parameter will be normalized to the base the underlying
       PageableCollection uses.
       @param {string} [options.label] If provided it is used to render the
       anchor text, otherwise the normalized pageIndex will be used
       instead. Required if any of the `is*` flags is set to `true`.
       @param {string} [options.title]
       @param {boolean} [options.isRewind=false]
       @param {boolean} [options.isBack=false]
       @param {boolean} [options.isForward=false]
       @param {boolean} [options.isFastForward=false]
    */
    initialize: function (options) {
      Backbone.View.prototype.initialize.apply(this, arguments);

      var collection = this.collection;
      var state = collection.state;
      var currentPage = state.currentPage;
      var firstPage = state.firstPage;
      var lastPage = state.lastPage;

      _.extend(this, _.pick(options,
                            ["isRewind", "isBack", "isForward", "isFastForward"]));

      var pageIndex;
      if (this.isRewind) pageIndex = firstPage;
      else if (this.isBack) pageIndex = Math.max(firstPage, currentPage - 1);
      else if (this.isForward) pageIndex = Math.min(lastPage, currentPage + 1);
      else if (this.isFastForward) pageIndex = lastPage;
      else {
        pageIndex = +options.pageIndex;
        pageIndex = (firstPage ? pageIndex + 1 : pageIndex);
      }
      this.pageIndex = pageIndex;

      if (((this.isRewind || this.isBack) && currentPage == firstPage) ||
          ((this.isForward || this.isFastForward) && currentPage == lastPage)) {
        this.$el.addClass("disabled");
      }
      else if (!(this.isRewind ||
                 this.isBack ||
                 this.isForward ||
                 this.isFastForward) &&
               currentPage == pageIndex) {
        this.$el.addClass("active");
      }

      this.label = (options.label || (firstPage ? pageIndex : pageIndex + 1)) + '';
      var title = options.title || this.title;
      this.title = _.isFunction(title) ? title({label: this.label}) : title;
    },

    /**
       Renders a clickable anchor element under a list item.
    */
    render: function () {
      this.$el.empty();
      var anchor = document.createElement("a");
      anchor.href = '#';
      if (this.title) anchor.title = this.title;
      anchor.innerHTML = this.label;
      this.el.appendChild(anchor);
      this.delegateEvents();
      return this;
    },

    /**
       jQuery click event handler. Goes to the page this PageHandle instance
       represents. No-op if this page handle is currently active or disabled.
    */
    changePage: function (e) {
      e.preventDefault();
      var $el = this.$el;
      if (!$el.hasClass("active") && !$el.hasClass("disabled")) {
        this.collection.getPage(this.pageIndex);
      }
      return this;
    }

  });

  /**
     Paginator is a Backgrid extension that renders a series of configurable
     pagination handles. This extension is best used for splitting a large data
     set across multiple pages. If the number of pages is larger then a
     threshold, which is set to 10 by default, the page handles are rendered
     within a sliding window, plus the rewind, back, forward and fast forward
     control handles. The individual control handles can be turned off.

     @class Backgrid.Extension.Paginator
  */
  Backgrid.Extension.Paginator = Backbone.View.extend({

    /** @property */
    className: "backgrid-paginator",

    /** @property */
    windowSize: 10,

    /**
       @property {Object.<string, Object.<string, string>>} controls You can
       disable specific control handles by omitting certain keys.
    */
    controls: {
      rewind: {
        label: "《",
        title: "First"
      },
      back: {
        label: "〈",
        title: "Previous"
      },
      forward: {
        label: "〉",
        title: "Next"
      },
      fastForward: {
        label: "》",
        title: "Last"
      }
    },

    /**
       @property {Backgrid.Extension.PageHandle} pageHandle. The PageHandle
       class to use for rendering individual handles
    */
    pageHandle: PageHandle,

    /** @property */
    goBackFirstOnSort: true,

    /**
       Initializer.

       @param {Object} options
       @param {Backbone.Collection} options.collection
       @param {boolean} [options.controls]
       @param {boolean} [options.pageHandle=Backgrid.Extension.PageHandle]
       @param {boolean} [options.goBackFirstOnSort=true]
    */
    initialize: function (options) {
      Backgrid.requireOptions(options, ["collection"]);

      this.controls = options.controls || this.controls;
      this.pageHandle = options.pageHandle || this.pageHandle;

      var collection = this.collection;
      this.listenTo(collection, "add", this.render);
      this.listenTo(collection, "remove", this.render);
      this.listenTo(collection, "reset", this.render);
      if ((options.goBackFirstOnSort || this.goBackFirstOnSort) &&
          collection.fullCollection) {
        this.listenTo(collection.fullCollection, "sort", function () {
          collection.getFirstPage();
        });
      }
    },

    _calculateWindow: function () {
      var collection = this.collection;
      var state = collection.state;

      // convert all indices to 0-based here
      var firstPage = state.firstPage;
      var lastPage = +state.lastPage;
      lastPage = Math.max(0, firstPage ? lastPage - 1 : lastPage);
      var currentPage = Math.max(state.currentPage, state.firstPage);
      currentPage = firstPage ? currentPage - 1 : currentPage;
      var windowStart = Math.floor(currentPage / this.windowSize) * this.windowSize;
      var windowEnd = Math.min(lastPage + 1, windowStart + this.windowSize);
      return [windowStart, windowEnd];
    },

    /**
       Creates a list of page handle objects for rendering.

       @return {Array.<Object>} an array of page handle objects hashes
    */
    makeHandles: function () {

      var handles = [];
      var collection = this.collection;

      var window = this._calculateWindow();
      var winStart = window[0], winEnd = window[1];

      for (var i = winStart; i < winEnd; i++) {
        handles.push(new PageHandle({
          collection: collection,
          pageIndex: i
        }));
      }

      var controls = this.controls;
      _.each(["back", "rewind", "forward", "fastForward"], function (key) {
        var value = controls[key];
        if (value) {
          var handleCtorOpts = {
            collection: collection,
            title: value.title,
            label: value.label
          };
          handleCtorOpts["is" + key.slice(0, 1).toUpperCase() + key.slice(1)] = true;
          var handle = new PageHandle(handleCtorOpts);
          if (key == "rewind" || key == "back") handles.unshift(handle);
          else handles.push(handle);
        }
      });

      return handles;
    },

    /**
       Render the paginator handles inside an unordered list.
    */
    render: function () {
      this.$el.empty();

      if (this.handles) {
        for (var i = 0, l = this.handles.length; i < l; i++) {
          this.handles[i].remove();
        }
      }

      var handles = this.handles = this.makeHandles();

      var ul = document.createElement("ul");
      for (var i = 0; i < handles.length; i++) {
        ul.appendChild(handles[i].render().el);
      }

      this.el.appendChild(ul);

      return this;
    }

  });

}(_, Backbone, Backgrid));