var components = (function () {

var exports = {};

/* USAGE:
    Toggle x = components.toggle({
        selected: Integer selected_index,
        values: Array<Object> [
            { label: i18n.t(String title) }
        ],
        callback: function () {
            // .. on value change.
        },
    }).get();
*/

exports.toggle = function (opts) {
    var component = (function render_component(opts) {
        var _component = $("<div class='tab-switcher'></div>");
        opts.values.forEach(function (value, i) {
            // create a tab with a tab-id so they don't have to be referenced
            // by text value which can be inconsistent.
            var tab = $("<div class='ind-tab' data-tab-key='" + value.key + "' data-tab-id='" + i + "' tabindex='0'>" + value.label + "</div>");

            // add proper classes for styling in CSS.
            if (i === 0) {
                // this should be default selected unless otherwise specified.
                tab.addClass("first selected");
            } else if (i === opts.values.length - 1) {
                tab.addClass("last");
            } else {
                tab.addClass("middle");
            }
            _component.append(tab);
        });
        return _component;
    }(opts));

    var meta = {
        $ind_tab: component.find(".ind-tab"),
        idx: -1,
    };

    function select_tab(idx) {
        meta.$ind_tab.removeClass("selected");

        var elem = meta.$ind_tab.eq(idx);
        elem.addClass("selected");

        meta.idx = idx;
        if (opts.callback) {
            opts.callback(
                opts.values[idx].label,
                opts.values[idx].key
            );
        }

        if (!opts.child_wants_focus) {
            elem.focus();
        }
    }

    function maybe_go_left() {
        if (meta.idx > 0) {
            select_tab(meta.idx - 1);
            return true;
        }
    }

    function maybe_go_right() {
        if (meta.idx < opts.values.length - 1) {
            select_tab(meta.idx + 1);
            return true;
        }
    }

    (function () {
        meta.$ind_tab.click(function () {
            var idx = $(this).data("tab-id");
            select_tab(idx);
        });

        keydown_util.handle({
            elem: meta.$ind_tab,
            handlers: {
                left_arrow: maybe_go_left,
                right_arrow: maybe_go_right,
            },
        });

        // We should arguably default opts.selected to 0.
        if (typeof opts.selected === "number") {
            select_tab(opts.selected);
        }
    }());

    var prototype = {
        maybe_go_left: maybe_go_left,
        maybe_go_right: maybe_go_right,

        value: function () {
            if (meta.idx >= 0) {
                return opts.values[meta.idx].label;
            }
        },

        get: function () {
            return component;
        },
        // go through the process of finding the correct tab for a given name,
        // and when found, select that one and provide the proper callback.
        goto: function (name) {
            var value = _.find(opts.values, function (o) {
                return o.label === name || o.key === name;
            });

            var idx = opts.values.indexOf(value);

            if (idx >= 0) {
                select_tab(idx);
            }
        },
    };

    return prototype;
};

return exports;
}());

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