define([
    'underscore',
    'backbone',
    'gettext',
    'edx-ui-toolkit/js/utils/html-utils',
    'edx-ui-toolkit/js/utils/string-utils',
    'text!templates/paging-header.underscore'
], function(_, Backbone, gettext, HtmlUtils, StringUtils, pagingHeaderTemplate) {
    'use strict';
    var PagingHeader = Backbone.View.extend({
        events: {
            'click .next-page-link': 'nextPage',
            'click .previous-page-link': 'previousPage'
        },

        initialize: function(options) {
            var view = options.view,
                collection = view.collection;
            this.view = view;
            collection.bind('add', _.bind(this.render, this));
            collection.bind('remove', _.bind(this.render, this));
            collection.bind('reset', _.bind(this.render, this));
        },

        render: function() {
            var view = this.view,
                collection = view.collection,
                currentPage = collection.getPageNumber(),
                lastPage = collection.getTotalPages(),
                messageHtml = this.messageHtml(),
                isNextDisabled = lastPage === 0 || currentPage === lastPage;

            HtmlUtils.setHtml(this.$el, HtmlUtils.template(pagingHeaderTemplate)({messageHtml: messageHtml}));
            this.$('.previous-page-link')
                    .toggleClass('is-disabled', currentPage === 1)
                    .attr('aria-disabled', currentPage === 1);
            this.$('.next-page-link')
                    .toggleClass('is-disabled', isNextDisabled)
                    .attr('aria-disabled', isNextDisabled);

            return this;
        },

        messageHtml: function() {
            var message = '',
                assetType = false;

            if (this.view.collection.assetType) {
                if (this.view.collection.sortDirection === 'asc') {
                        // Translators: sample result:
                        // "Showing 0-9 out of 25 total, filtered by Images, sorted by Date Added ascending"
                    message = gettext('Showing {currentItemRange} out of {totalItemsCount}, filtered by {assetType}, sorted by {sortName} ascending');  // eslint-disable-line max-len
                } else {
                        // Translators: sample result:
                        // "Showing 0-9 out of 25 total, filtered by Images, sorted by Date Added descending"
                    message = gettext('Showing {currentItemRange} out of {totalItemsCount}, filtered by {assetType}, sorted by {sortName} descending');  // eslint-disable-line max-len
                }
                assetType = this.filterNameLabel();
            } else {
                if (this.view.collection.sortDirection === 'asc') {
                        // Translators: sample result:
                        // "Showing 0-9 out of 25 total, sorted by Date Added ascending"
                    message = gettext('Showing {currentItemRange} out of {totalItemsCount}, sorted by {sortName} ascending');  // eslint-disable-line max-len
                } else {
                        // Translators: sample result:
                        // "Showing 0-9 out of 25 total, sorted by Date Added descending"
                    message = gettext('Showing {currentItemRange} out of {totalItemsCount}, sorted by {sortName} descending');  // eslint-disable-line max-len
                }
            }

            return HtmlUtils.interpolateHtml(message, {
                currentItemRange: this.currentItemRangeLabel(),
                totalItemsCount: this.totalItemsCountLabel(),
                assetType: assetType,
                sortName: this.sortNameLabel()
            });
        },

        currentItemRangeLabel: function() {
            var view = this.view,
                collection = view.collection,
                start = (collection.getPageNumber() - 1) * collection.getPageSize(),
                count = collection.size(),
                end = start + count,
                htmlMessage = HtmlUtils.HTML('<span class="count-current-shown">{start}-{end}</span>');

            return HtmlUtils.interpolateHtml(htmlMessage, {
                start: Math.min(start + 1, end),
                end: end
            });
        },

        totalItemsCountLabel: function() {
            var totalItemsLabel,
                htmlMessage = HtmlUtils.HTML('<span class="count-total">{totalItemsLabel}</span>');

                // Translators: turns into "25 total" to be used in other sentences, e.g. "Showing 0-9 out of 25 total".
            totalItemsLabel = StringUtils.interpolate(gettext('{totalItems} total'), {
                totalItems: this.view.collection.getTotalRecords()
            });

            return HtmlUtils.interpolateHtml(htmlMessage, {
                totalItemsLabel: totalItemsLabel
            });
        },

        sortNameLabel: function() {
            var htmlMessage = HtmlUtils.HTML('<span class="sort-order">{sortName}</span>');

            return HtmlUtils.interpolateHtml(htmlMessage, {
                sortName: this.view.sortDisplayName()
            });
        },

        filterNameLabel: function() {
            var htmlMessage = HtmlUtils.HTML('<span class="filter-column">{filterName}</span>');

            return HtmlUtils.interpolateHtml(htmlMessage, {
                filterName: this.view.filterDisplayName()
            });
        },

        nextPage: function() {
            this.view.nextPage();
        },

        previousPage: function() {
            this.view.previousPage();
        }
    });

    return PagingHeader;
});
