define(['backbone', 'underscore', 'gettext', 'js/models/validation_helpers', 'js/utils/date_utils',
    'edx-ui-toolkit/js/utils/string-utils'
],
    function(Backbone, _, gettext, ValidationHelpers, DateUtils, StringUtils) {
        'use strict';
        var CourseDetails = Backbone.Model.extend({
            defaults: {
                org: '',
                course_id: '',
                run: '',
                language: '',
                start_date: null,	// maps to 'start'
                end_date: null,		// maps to 'end'
                certificate_available_date: null,
                enrollment_start: null,
                enrollment_end: null,
                syllabus: null,
                title: '',
                subtitle: '',
                duration: '',
                description: '',
                short_description: '',
                overview: '',
                intro_video: null,
                effort: null,	// an int or null,
                license: null,
                course_image_name: '', // the filename
                course_image_asset_path: '', // the full URL (/c4x/org/course/num/asset/filename)
                banner_image_name: '',
                banner_image_asset_path: '',
                video_thumbnail_image_name: '',
                video_thumbnail_image_asset_path: '',
                pre_requisite_courses: [],
                entrance_exam_enabled: '',
                entrance_exam_minimum_score_pct: '50',
                learning_info: [],
                instructor_info: {},
                self_paced: null
            },

            validate: function(newattrs) {
        // Returns either nothing (no return call) so that validate works or an object of {field: errorstring} pairs
        // A bit funny in that the video key validation is asynchronous; so, it won't stop the validation.
                var errors = {};
                newattrs = DateUtils.convertDateStringsToObjects(
                    newattrs,
                    ['start_date', 'end_date', 'certificate_available_date', 'enrollment_start', 'enrollment_end']
                );

                if (newattrs.start_date === null) {
                    errors.start_date = gettext('The course must have an assigned start date.');
                }

                if (newattrs.start_date && newattrs.end_date && newattrs.start_date >= newattrs.end_date) {
                    errors.end_date = gettext('The course end date must be later than the course start date.');
                }
                if (newattrs.start_date && newattrs.enrollment_start &&
                  newattrs.start_date < newattrs.enrollment_start) {
                    errors.enrollment_start = gettext(
                      'The course start date must be later than the enrollment start date.'
                    );
                }
                if (newattrs.enrollment_start && newattrs.enrollment_end &&
                  newattrs.enrollment_start >= newattrs.enrollment_end) {
                    errors.enrollment_end = gettext(
                      'The enrollment start date cannot be after the enrollment end date.'
                    );
                }
                if (newattrs.end_date && newattrs.enrollment_end && newattrs.end_date < newattrs.enrollment_end) {
                    errors.enrollment_end = gettext('The enrollment end date cannot be after the course end date.');
                }
                if (this.showCertificateAvailableDate && newattrs.end_date && newattrs.certificate_available_date &&
                    newattrs.certificate_available_date < newattrs.end_date) {
                    errors.certificate_available_date = gettext(
                        'The certificate available date must be later than the course end date.'
                    );
                }
                if (newattrs.intro_video && newattrs.intro_video !== this.get('intro_video')) {
                    if (this._videokey_illegal_chars.exec(newattrs.intro_video)) {
                        errors.intro_video = gettext('Key should only contain letters, numbers, _, or -');
                    }
            // TODO check if key points to a real video using google's youtube api
                }
                if (_.has(newattrs, 'entrance_exam_minimum_score_pct')) {
                    var range = {
                        min: 1,
                        max: 100
                    };
                    if (!ValidationHelpers.validateIntegerRange(newattrs.entrance_exam_minimum_score_pct, range)) {
                        errors.entrance_exam_minimum_score_pct = StringUtils.interpolate(gettext(
                          'Please enter an integer between %(min)s and %(max)s.'
                        ), range, true);
                    }
                }
                if (!_.isEmpty(errors)) return errors;
        // NOTE don't return empty errors as that will be interpreted as an error state
            },

            _videokey_illegal_chars: /[^a-zA-Z0-9_-]/g,

            set_videosource: function(newsource) {
        // newsource either is <video youtube="speed:key, *"/> or just the "speed:key, *" string
        // returns the videosource for the preview which iss the key whose speed is closest to 1
                if (_.isEmpty(newsource) &&
                  !_.isEmpty(this.get('intro_video'))) this.set({intro_video: null}, {validate: true});
        // TODO remove all whitespace w/in string
                else {
                    if (this.get('intro_video') !== newsource) this.set('intro_video', newsource, {validate: true});
                }

                return this.videosourceSample();
            },

            videosourceSample: function() {
                if (this.has('intro_video')) return '//www.youtube.com/embed/' + this.get('intro_video');
                else return '';
            },

    // Whether or not the course pacing can be toggled. If the course
    // has already started, returns false; otherwise, returns true.
            canTogglePace: function() {
                return new Date() <= new Date(this.get('start_date'));
            }
        });

        return CourseDetails;
    }); // end define()