var server_events = (function () {

var exports = {};

var waiting_on_homeview_load = true;

var events_stored_during_tutorial = [];
var events_stored_while_loading = [];

var get_events_xhr;
var get_events_timeout;
var get_events_failures = 0;
var get_events_params = {};

function get_events_success(events) {
    var messages = [];
    var messages_to_update = [];
    var new_pointer;

    _.each(events, function (event) {
        get_events_params.last_event_id = Math.max(get_events_params.last_event_id,
                                                   event.id);
    });

    if (tutorial.is_running()) {
        events_stored_during_tutorial = events_stored_during_tutorial.concat(events);
        return;
    }

    if (events_stored_during_tutorial.length > 0) {
        events = events_stored_during_tutorial.concat(events);
        events_stored_during_tutorial = [];
    }

    if (waiting_on_homeview_load) {
        events_stored_while_loading = events_stored_while_loading.concat(events);
        return;
    }

    if (events_stored_while_loading.length > 0) {
        events = events_stored_while_loading.concat(events);
        events_stored_while_loading = [];
    }

    _.each(events, function (event) {
        switch (event.type) {
        case 'message':
            var msg = event.message;
            msg.flags = event.flags;
            if (event.local_message_id !== undefined) {
                msg.local_id = event.local_message_id;
            }
            messages.push(msg);
            break;
        case 'pointer':
            new_pointer = event.pointer;
            break;
        case 'restart':
            reload.initiate({message: "The application has been updated; reloading!"});
            break;
        case 'update_message':
            messages_to_update.push(event);
            break;
        case 'realm_user':
            if (event.op === 'add') {
                people.add_in_realm(event.person);
            } else if (event.op === 'remove') {
                people.remove(event.person);
            } else if (event.op === 'update') {
                people.update(event.person);
            }
            break;
        case 'stream':
            if (event.op === 'update') {
                // Legacy: Stream properties are still managed by subs.js on the client side.
                subs.update_subscription_properties(event.name, event.property, event.value);
            }
            break;
        case 'subscriptions':
            if (event.op === 'add') {
                _.each(event.subscriptions, function (subscription) {
                    $(document).trigger($.Event('subscription_add.zulip',
                                                {subscription: subscription}));
                });
            } else if (event.op === 'remove') {
                _.each(event.subscriptions, function (subscription) {
                    $(document).trigger($.Event('subscription_remove.zulip',
                                                {subscription: subscription}));
                });
            } else if (event.op === 'update') {
                subs.update_subscription_properties(event.name, event.property, event.value);
            } else if (event.op === 'peer_add' || event.op === 'peer_remove') {
                _.each(event.subscriptions, function (sub) {
                    var js_event_type;
                    if (event.op === 'peer_add') {
                        js_event_type = 'peer_subscribe.zulip';

                        stream_data.add_subscriber(sub, event.user_email);
                    } else if (event.op === 'peer_remove') {
                        js_event_type = 'peer_unsubscribe.zulip';

                        stream_data.remove_subscriber(sub, event.user_email);
                    }

                    $(document).trigger(js_event_type, {stream_name: sub,
                                                        user_email: event.user_email});
                });

            }
            break;
        case 'presence':
            var users = {};
            users[event.email] = event.presence;
            activity.set_user_statuses(users, event.server_timestamp);
            break;
        case 'update_message_flags':
            var new_value = event.operation === "add";
            switch(event.flag) {
            case 'starred':
                _.each(event.messages, function (message_id) {
                    ui.update_starred(message_id, new_value);
                });
                break;
            case 'read':
                var msgs_to_update = _.map(event.messages, function (message_id) {
                    return message_store.msg_metadata_cache[message_id];
                });
                unread.mark_messages_as_read(msgs_to_update, {from: "server"});
                break;
            }
            break;
        case 'referral':
            referral.update_state(event.referrals.granted, event.referrals.used);
            break;
        case 'realm_emoji':
            emoji.update_emojis(event.realm_emoji);
            break;
        case 'alert_words':
            alert_words.words = event.alert_words;
            break;
        case 'muted_topics':
            muting_ui.handle_updates(event.muted_topics);
            break;
        case 'realm_filters':
            page_params.realm_filters = event.realm_filters;
            echo.set_realm_filters(page_params.realm_filters);
            break;
        }
    });

    if (messages.length !== 0) {
        messages = echo.process_from_server(messages);
        message_store.insert_new_messages(messages);
    }

    if (new_pointer !== undefined
        && new_pointer > furthest_read)
    {
        furthest_read = new_pointer;
        server_furthest_read = new_pointer;
        home_msg_list.select_id(new_pointer, {then_scroll: true, use_closest: true});
    }

    if ((home_msg_list.selected_id() === -1) && !home_msg_list.empty()) {
        home_msg_list.select_id(home_msg_list.first().id, {then_scroll: false});
    }

    if (messages_to_update.length !== 0) {
        message_store.update_messages(messages_to_update);
    }
}

function get_events(options) {
    options = _.extend({dont_block: false}, options);

    get_events_params.dont_block = options.dont_block || get_events_failures > 0;
    if (get_events_params.queue_id === undefined) {
        get_events_params.queue_id = page_params.event_queue_id;
        get_events_params.last_event_id = page_params.last_event_id;
    }

    if (get_events_xhr !== undefined) {
        get_events_xhr.abort();
    }
    if (get_events_timeout !== undefined) {
        clearTimeout(get_events_timeout);
    }
    get_events_timeout = undefined;
    get_events_xhr = channel.post({
        url:      '/json/get_events',
        data:     get_events_params,
        idempotent: true,
        timeout:  page_params.poll_timeout,
        success: function (data) {
            get_events_xhr = undefined;
            get_events_failures = 0;
            $('#connection-error').hide();

            get_events_success(data.events);
            get_events_timeout = setTimeout(get_events, 0);
        },
        error: function (xhr, error_type, exn) {
            get_events_xhr = undefined;
            // If we are old enough to have messages outside of the
            // Tornado cache or if we're old enough that our message
            // queue has been garbage collected, immediately reload.
            if ((xhr.status === 400) &&
                ($.parseJSON(xhr.responseText).msg.indexOf("too old") !== -1 ||
                 $.parseJSON(xhr.responseText).msg.indexOf("Bad event queue id") !== -1)) {
                page_params.event_queue_expired = true;
                reload.initiate({immediate: true});
            }

            if (error_type === 'abort') {
                // Don't restart if we explicitly aborted
                return;
            } else if (error_type === 'timeout') {
                // Retry indefinitely on timeout.
                get_events_failures = 0;
                $('#connection-error').hide();
            } else {
                get_events_failures += 1;
            }

            if (get_events_failures >= 5) {
                $('#connection-error').show();
            } else {
                $('#connection-error').hide();
            }

            var retry_sec = Math.min(90, Math.exp(get_events_failures/2));
            get_events_timeout = setTimeout(get_events, retry_sec*1000);
        }
    });
}

exports.assert_get_events_running = function assert_get_events_running(error_message) {
    if (get_events_xhr === undefined && get_events_timeout === undefined) {
        exports.restart_get_events({dont_block: true});
        blueslip.error(error_message);
    }
};

exports.restart_get_events = function restart_get_events(options) {
    get_events(options);
};

exports.force_get_events = function force_get_events() {
    get_events_timeout = setTimeout(get_events, 0);
};

exports.home_view_loaded = function home_view_loaded() {
    waiting_on_homeview_load = false;
    get_events_success([]);
    $(document).trigger("home_view_loaded.zulip");
};

var watchdog_time = $.now();
setInterval(function () {
    var new_time = $.now();
    if ((new_time - watchdog_time) > 20000) { // 20 seconds.
        // Defensively reset watchdog_time here in case there's an
        // exception in one of the event handlers
        watchdog_time = new_time;
        // Our app's JS wasn't running, which probably means the machine was
        // asleep.
        $(document).trigger($.Event('unsuspend'));
    }
    watchdog_time = new_time;
}, 5000);

$(function () {
    $(document).on('unsuspend', function () {
        // Immediately poll for new events on unsuspend
        blueslip.log("Restarting get_events due to unsuspend");
        get_events_failures = 0;
        exports.restart_get_events({dont_block: true});
    });
    get_events();
});

function cleanup_event_queue() {
    // Submit a request to the server to cleanup our event queue
    if (page_params.event_queue_expired === true) {
        return;
    }
    channel.del({
        url:      '/json/events',
        data:     {queue_id: page_params.event_queue_id}
    });
}

window.addEventListener("beforeunload", function (event) {
    cleanup_event_queue();
});


return exports;

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