var upload_widget = (function () {

    var exports = {};

    function is_image_format(file) {
        var type = file.type;
        if (!type) {
            return false;
        }

        var supported_types = [
            'image/jpeg',
            'image/png',
            'image/gif',
            'image/tiff',
        ];
        return _.indexOf(supported_types, type) >= 0;
    }

    exports.build_widget = function (
        get_file_input, // function returns a jQuery file input object
        file_name_field, // jQuery object to show file name
        input_error, // jQuery object for error text
        clear_button, // jQuery button to clear last upload choice
        upload_button // jQuery button to open file dialog
    ) {

        function accept(file) {
            file_name_field.text(file.name);
            input_error.hide();
            clear_button.show();
            upload_button.hide();
        }

        function clear() {
            var control = get_file_input();
            var new_control = control.clone(true);
            control.replaceWith(new_control);
            file_name_field.text('');
            clear_button.hide();
            upload_button.show();
        }

        clear_button.on('click', function (e) {
            clear();
            e.preventDefault();
        });

        upload_button.on('drop', function (e) {
            var files = e.dataTransfer.files;
            if (files === null || files === undefined || files.length === 0) {
                return false;
            }
            get_file_input().get(0).files = files;
            e.preventDefault();
            return false;
        });

        get_file_input().on('change', function (e) {
            if (e.target.files.length === 0) {
                input_error.hide();
            } else if (e.target.files.length === 1) {
                var file = e.target.files[0];
                if (file.size > 5 * 1024 * 1024) {
                    input_error.text('File size must be < 5Mb.');
                    input_error.show();
                    clear();
                } else if (!is_image_format(file)) {
                    input_error.text('File type is not supported.');
                    input_error.show();
                    clear();
                } else {
                    accept(file);
                }
            } else {
                input_error.text('Please just upload one file.');
            }
        });

        upload_button.on('click', function (e) {
            get_file_input().trigger('click');
            e.preventDefault();
        });

        function close() {
            clear();
            clear_button.off('click');
            upload_button.off('drop');
            get_file_input().off('change');
            upload_button.off('click');
        }

        return {
            // Call back to clear() in situations like adding bots, when
            // we want to use the same widget over and over again.
            clear: clear,
            // Call back to close() when you are truly done with the widget,
            // so you can release handlers.
            close: close,
        };
    };
    exports.build_direct_upload_widget = function (
        get_file_input, // function returns a jQuery file input object
        input_error, // jQuery object for error text
        upload_button, // jQuery button to open file dialog
        upload_function) {

        function accept() {
            input_error.hide();
            upload_function(get_file_input());
        }

        function clear() {
            var control = get_file_input();
            var new_control = control.clone(true);
            control.replaceWith(new_control);
        }

        upload_button.on('drop', function (e) {
            var files = e.dataTransfer.files;
            if (files === null || files === undefined || files.length === 0) {
                return false;
            }
            get_file_input().get(0).files = files;
            e.preventDefault();
            return false;
        });

        get_file_input().on('change', function (e) {
            if (e.target.files.length === 0) {
                input_error.hide();
            } else if (e.target.files.length === 1) {
                var file = e.target.files[0];
                if (file.size > 5 * 1024 * 1024) {
                    input_error.text('File size must be < 5Mb.');
                    input_error.show();
                    clear();
                } else if (!is_image_format(file)) {
                    input_error.text('File type is not supported.');
                    input_error.show();
                    clear();
                } else {
                    accept(file);
                }
            } else {
                input_error.text('Please just upload one file.');
            }
        });

        upload_button.on('click', function (e) {
            get_file_input().trigger('click');
            e.preventDefault();
        });
    };

    return exports;

}());

if (typeof module !== 'undefined') {
    module.exports = upload_widget;
}