define(["backbone", "underscore", "js/models/chapter", "js/collections/chapter", "backbone.associations"],
    function(Backbone, _, ChapterModel, ChapterCollection) {

    var Textbook = Backbone.AssociatedModel.extend({
        defaults: function() {
            return {
                name: "",
                chapters: new ChapterCollection([{}]),
                showChapters: false,
                editing: false
            };
        },
        relations: [{
            type: Backbone.Many,
            key: "chapters",
            relatedModel: ChapterModel,
            collectionType: ChapterCollection
        }],
        initialize: function() {
            this.setOriginalAttributes();
            return this;
        },
        setOriginalAttributes: function() {
            this._originalAttributes = this.parse(this.toJSON());
        },
        reset: function() {
            this.set(this._originalAttributes, {parse: true});
        },
        isDirty: function() {
            return !_.isEqual(this._originalAttributes, this.parse(this.toJSON()));
        },
        isEmpty: function() {
            return !this.get('name') && this.get('chapters').isEmpty();
        },
        url: function() {
            if(this.isNew()) {
                return CMS.URL.TEXTBOOKS + "/new";
            } else {
                return CMS.URL.TEXTBOOKS + "/" + this.id;
            }
        },
        parse: function(response) {
            var ret = $.extend(true, {}, response);
            if("tab_title" in ret && !("name" in ret)) {
                ret.name = ret.tab_title;
                delete ret.tab_title;
            }
            if("url" in ret && !("chapters" in ret)) {
                ret.chapters = {"url": ret.url};
                delete ret.url;
            }
            _.each(ret.chapters, function(chapter, i) {
                chapter.order = chapter.order || i+1;
            });
            return ret;
        },
        toJSON: function() {
            return {
                tab_title: this.get('name'),
                chapters: this.get('chapters').toJSON()
            };
        },
        // NOTE: validation functions should return non-internationalized error
        // messages. The messages will be passed through gettext in the template.
        validate: function(attrs, options) {
            if (!attrs.name) {
                return {
                    message: "Textbook name is required",
                    attributes: {name: true}
                };
            }
            if (attrs.chapters.length === 0) {
                return {
                    message: "Please add at least one chapter",
                    attributes: {chapters: true}
                };
            } else {
                // validate all chapters
                var invalidChapters = [];
                attrs.chapters.each(function(chapter) {
                    if(!chapter.isValid()) {
                        invalidChapters.push(chapter);
                    }
                });
                if(!_.isEmpty(invalidChapters)) {
                    return {
                        message: "All chapters must have a name and asset",
                        attributes: {chapters: invalidChapters}
                    };
                }
            }
        }
    });
    return Textbook;
});
