// This module just manages data.  See activity.js for
// the UI of our buddy list.

// The following Maps have user_id as the key.  Some of the
// user_ids may not yet be registered in people.js.
// See the long comment in `set_info` below for details.

// In future commits we'll use raw_info to facilitate
// handling server events and/or timeout events.
const raw_info = new Map();
exports.presence_info = new Map();

/* Mark users as offline after 140 seconds since their last checkin,
 * Keep in sync with zerver/tornado/event_queue.py:receiver_is_idle
 */
const OFFLINE_THRESHOLD_SECS = 140;

const BIG_REALM_COUNT = 250;

exports.is_active = function (user_id) {
    if (exports.presence_info.has(user_id)) {
        const status = exports.presence_info.get(user_id).status;
        if (status === "active") {
            return true;
        }
    }
    return false;
};

exports.get_status = function (user_id) {
    if (people.is_my_user_id(user_id)) {
        return "active";
    }
    if (exports.presence_info.has(user_id)) {
        return exports.presence_info.get(user_id).status;
    }
    return "offline";
};

exports.get_user_ids = function () {
    return Array.from(exports.presence_info.keys());
};

function status_from_timestamp(baseline_time, info) {
    let status = 'offline';
    let last_active = 0;

    for (const [device, device_presence] of Object.entries(info)) {
        const age = baseline_time - device_presence.timestamp;
        if (last_active < device_presence.timestamp) {
            last_active = device_presence.timestamp;
        }
        if (age < OFFLINE_THRESHOLD_SECS) {
            switch (device_presence.status) {
            case 'active':
                status = device_presence.status;
                break;
            case 'idle':
                if (status !== 'active') {
                    status = device_presence.status;
                }
                break;
            case 'offline':
                if (status !== 'active' && status !== 'idle') {
                    status = device_presence.status;
                }
                break;
            default:
                blueslip.error('Unexpected status', {presence_object: device_presence, device: device}, undefined);
            }
        }
    }
    return {status: status,
            last_active: last_active };
}

// For testing
exports._status_from_timestamp = status_from_timestamp;

exports.update_info_from_event = function (user_id, info, server_time) {
    raw_info.set(user_id, {
        info: info,
        server_time: server_time,
    });

    const status = status_from_timestamp(server_time, info);
    exports.presence_info.set(user_id, status);
};

exports.set_info = function (presences, server_timestamp) {
    raw_info.clear();
    exports.presence_info.clear();
    for (const [user_id_str, info] of Object.entries(presences)) {
        const user_id = parseInt(user_id_str, 10);

        // Note: In contrast with all other state updates received
        // receive from the server, presence data is updated via a
        // polling process rather than the events system
        // (server_events_dispatch.js).
        //
        // This means that if we're coming back from being offline and
        // new users were created in the meantime, we may see user IDs
        // not yet present in people.js if server_events doesn't have
        // current data (or we've been offline, our event queue was
        // GC'ed, and we're about to reload).  Such user_ids being
        // present could, in turn, create spammy downstream exceptions
        // when rendering the buddy list.  To address this, we check
        // if the user ID is not yet present in people.js, and if it
        // is, we skip storing that user (we'll see them again in the
        // next presence request in 1 minute anyway).
        //
        // It's important to check both suspect_offline and
        // reload_state.is_in_progress, because races where presence
        // returns data on users not yet received via the server_events
        // system are common in both situations.
        const person = people.get_by_user_id(user_id, true);
        if (person === undefined) {
            if (!(server_events.suspect_offline || reload_state.is_in_progress())) {
                // If we're online, and we get a user who we don't
                // know about in the presence data, throw an error.
                blueslip.error('Unknown user ID in presence data: ' + user_id);
            }
            // Either way, we deal by skipping this user and
            // continuing with processing everyone else.
            continue;
        }

        raw_info.set(user_id, {
            info: info,
            server_time: server_timestamp,
        });

        const status = status_from_timestamp(server_timestamp,
                                             info);

        exports.presence_info.set(user_id, status);
    }
    exports.update_info_for_small_realm();
};

exports.update_info_for_small_realm = function () {
    if (people.get_active_human_count() >= BIG_REALM_COUNT) {
        // For big realms, we don't want to bloat our buddy
        // lists with lots of long-time-inactive users.
        return;
    }

    // For small realms, we create presence info for users
    // that the server didn't include in its presence update.
    const persons = people.get_realm_users();

    for (const person of persons) {
        const user_id = person.user_id;
        let status = "offline";

        if (exports.presence_info.has(user_id)) {
            // this is normal, we have data for active
            // users that we don't want to clobber.
            continue;
        }

        if (person.is_bot) {
            // we don't show presence for bots
            continue;
        }

        if (people.is_my_user_id(user_id)) {
            status = "active";
        }

        exports.presence_info.set(user_id, {
            status: status,
            last_active: undefined,
        });
    }
};

exports.last_active_date = function (user_id) {
    const info = exports.presence_info.get(user_id);

    if (!info || !info.last_active) {
        return;
    }

    const date = new XDate(info.last_active * 1000);
    return date;
};

exports.initialize = function (params) {
    presence.set_info(params.presences,
                      params.initial_servertime);
};

window.presence = exports;