const render_recent_topics_body = require('../templates/recent_topics_table.hbs');
const render_recent_topic_row = require('../templates/recent_topic_row.hbs');
const render_recent_topics_filters = require('../templates/recent_topics_filters.hbs');
const topics = new Map(); // Key is stream-id:topic.
let topics_widget;
// Sets the number of avatars to display.
// Rest of the avatars, if present, are displayed as {+x}
const MAX_AVATAR = 4;
let filters = new Set();

// Use this to set the focused element.
//
// We set it's value to `table` in case the
// focus in one of the table rows, since the
// table rows are constantly updated and tracking
// the selected element in them would be tedious via
// jquery.
//
// So, we use table as a grid system and
// track the coordinates of the focus element via
// `row_focus` and `col_focus`.
let current_focus_elem;
let row_focus = 0;
// Start focus on the topic column, so Down+Enter works to visit a topic.
let col_focus = 1;

// The number of selectable actions in a recent_topics.  Used to
// implement wraparound of elements with the right/left keys.  Must be
// increased when we add new actions, or rethought if we add optional
// actions that only appear in some rows.
const MAX_SELECTABLE_COLS = 4;

function set_default_focus() {
    // If at any point we are confused about the currently
    // focused element, we switch focus to search.
    current_focus_elem = $("#recent_topics_search");
    current_focus_elem.focus();
}

function set_table_focus(row, col) {
    const topic_rows = $("#recent_topics_table table tbody tr");
    if (topic_rows.length === 0 || row < 0 || row >= topic_rows.length) {
        row_focus = 0;
        // return focus back to filters if we cannot focus on the table.
        set_default_focus();
        return true;
    }

    topic_rows.eq(row).find('.recent_topics_focusable').eq(col).children().focus();
    current_focus_elem = 'table';
    return true;
}

function revive_current_focus() {
    // After re-render, the current_focus_elem is no longer linked
    // to the focused element, this function attempts to revive the
    // link and focus to the element prior to the rerender.
    if (!current_focus_elem) {
        set_default_focus();
        return false;
    }

    if (current_focus_elem === 'table') {
        set_table_focus(row_focus, col_focus);
        return true;
    }

    const filter_button = current_focus_elem.data('filter');
    if (!filter_button) {
        set_default_focus();
    } else {
        current_focus_elem = $("#recent_topics_filter_buttons").find("[data-filter='" + filter_button + "']");
        current_focus_elem.focus();
    }
    return true;
}

function get_topic_key(stream_id, topic) {
    return stream_id + ":" + topic.toLowerCase();
}

exports.process_messages = function (messages) {
    // FIX: Currently, we do a complete_rerender everytime
    // we process a new message.
    // While this is inexpensive and handles all the cases itself,
    // the UX can be bad if user wants to scroll down the list as
    // the UI will be returned to the beginning of the list on every
    // update.
    for (const msg of messages) {
        exports.process_message(msg);
    }
    exports.complete_rerender();
};

exports.process_message = function (msg) {
    if (msg.type !== 'stream') {
        return false;
    }
    // Initialize topic data
    const key = get_topic_key(msg.stream_id, msg.topic);
    if (!topics.has(key)) {
        topics.set(key, {
            last_msg_id: -1,
            participated: false,
        });
    }
    // Update topic data
    const is_ours = people.is_my_user_id(msg.sender_id);
    const topic_data = topics.get(key);
    if (topic_data.last_msg_id < msg.id) {
        // NOTE: This also stores locally echoed msg_id which
        // has not been successfully received from the server.
        // We store it now and reify it when response is available
        // from server.
        topic_data.last_msg_id = msg.id;
    }
    // TODO: Add backend support for participated topics.
    // Currently participated === Recently Participated
    // i.e. Only those topics are participated for which we have the user's
    // message fetched in the topic. Ideally we would want this to be attached
    // to topic info fetched from backend, which is currently not a thing.
    topic_data.participated = is_ours || topic_data.participated;
    return true;
};

exports.reify_message_id_if_available = function (opts) {
    // We don't need to reify the message_id of the topic
    // if a new message arrives in the topic from another user,
    // since it replaces the last_msg_id of the topic which
    // we were trying to reify.
    for (const [, value] of topics.entries()) {
        if (value.last_msg_id === opts.old_id) {
            value.last_msg_id = opts.new_id;
            return true;
        }
    }
    return false;
};

function get_sorted_topics() {
    // Sort all recent topics by last message time.
    return new Map(
        Array.from(topics.entries()).sort((a, b) => b[1].last_msg_id - a[1].last_msg_id),
    );
}

exports.get = function () {
    return get_sorted_topics();
};


function format_topic(topic_data) {
    const last_msg = message_store.get(topic_data.last_msg_id);
    const stream = last_msg.stream;
    const stream_id = last_msg.stream_id;
    const stream_info = stream_data.get_sub_by_id(stream_id);
    if (stream_info === undefined) {
        // stream was deleted
        return {};
    }
    const topic = last_msg.topic;
    const time = new XDate(last_msg.timestamp * 1000);
    const last_msg_time = timerender.last_seen_status_from_date(time);
    const full_datetime = timerender.get_full_datetime(time);

    // We hide the row according to filters or if it's muted.
    // We only supply the data to the topic rows and let jquery
    // display / hide them according to filters instead of
    // doing complete re-render.
    const topic_muted = !!muting.is_topic_muted(stream_id, topic);
    const stream_muted = stream_data.is_muted(stream_id);
    const muted = topic_muted || stream_muted;
    const unread_count = unread.unread_topic_counter.get(stream_id, topic);

    // Display in most recent sender first order
    const all_senders = recent_senders.get_topic_recent_senders(stream_id, topic);
    const senders = all_senders.slice(-MAX_AVATAR);
    const senders_info = people.sender_info_with_small_avatar_urls_for_sender_ids(senders);

    return {
        // stream info
        stream_id: stream_id,
        stream: stream,
        stream_color: stream_info.color,
        invite_only: stream_info.invite_only,
        is_web_public: stream_info.is_web_public,
        stream_url: hash_util.by_stream_uri(stream_id),

        topic: topic,
        topic_key: get_topic_key(stream_id, topic),
        unread_count: unread_count,
        last_msg_time: last_msg_time,
        topic_url: hash_util.by_stream_topic_uri(stream_id, topic),
        senders: senders_info,
        other_senders_count: Math.max(0, all_senders.length - MAX_AVATAR),
        muted: muted,
        topic_muted: topic_muted,
        participated: topic_data.participated,
        full_last_msg_date_time: full_datetime.date + ' ' + full_datetime.time,
    };
}

function get_topic_row(topic_data) {
    const msg = message_store.get(topic_data.last_msg_id);
    const topic_key = get_topic_key(msg.stream_id, msg.topic);
    return $("#" + $.escapeSelector("recent_topic:" + topic_key));
}

exports.process_topic_edit = function (old_stream_id, old_topic, new_topic, new_stream_id) {
    // See `recent_senders.process_topic_edit` for
    // logic behind this and important notes on use of this function.
    topics.delete(get_topic_key(old_stream_id, old_topic));

    const old_topic_msgs = message_util.get_messages_in_topic(old_stream_id, old_topic);
    exports.process_messages(old_topic_msgs);

    new_stream_id = new_stream_id || old_stream_id;
    const new_topic_msgs = message_util.get_messages_in_topic(new_stream_id, new_topic);
    exports.process_messages(new_topic_msgs);
};

exports.topic_in_search_results = function (keyword, stream, topic) {
    if (keyword === "") {
        return true;
    }
    // Escape speacial characters from input.
    // https://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex
    keyword = keyword.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
    const text = (stream + ' ' + topic).toLowerCase().replace(/\s+/g, ' ');
    const search_words = keyword.toLowerCase().replace(/\s+/g, ' ').split(' ');
    return search_words.every((word) => {
        if (text.search(word) !== -1) {
            return true;
        }
        return false;
    });
};

exports.filters_should_hide_topic = function (topic_data) {
    const msg = message_store.get(topic_data.last_msg_id);

    if (stream_data.get_sub_by_id(msg.stream_id) === undefined) {
        // Never try to process deactivated streams.
        return true;
    }

    if (filters.has('unread')) {
        const unreadCount = unread.unread_topic_counter.get(msg.stream_id, msg.topic);
        if (unreadCount === 0) {
            return true;
        }
    }

    if (!topic_data.participated && filters.has('participated')) {
        return true;
    }

    if (!filters.has('include_muted')) {
        const topic_muted = !!muting.is_topic_muted(msg.stream_id, msg.topic);
        const stream_muted = stream_data.is_muted(msg.stream_id);
        if (topic_muted || stream_muted) {
            return true;
        }
    }

    const search_keyword = $("#recent_topics_search").val();
    if (!recent_topics.topic_in_search_results(search_keyword, msg.stream, msg.topic)) {
        return true;
    }

    return false;
};

exports.inplace_rerender = function (topic_key) {
    if (!overlays.recent_topics_open()) {
        return false;
    }
    if (!topics.has(topic_key)) {
        return false;
    }

    const topic_data = topics.get(topic_key);
    topics_widget.render_item(topic_data);
    const topic_row = get_topic_row(topic_data);

    if (exports.filters_should_hide_topic(topic_data)) {
        topic_row.hide();
    } else {
        topic_row.show();
    }
    revive_current_focus();
    return true;
};

exports.update_topic_is_muted = function (stream_id, topic) {
    const key = get_topic_key(stream_id, topic);
    if (!topics.has(key)) {
        // we receive mute request for a topic we are
        // not tracking currently
        return false;
    }

    exports.inplace_rerender(key);
    return true;
};

exports.update_topic_unread_count = function (message) {
    const topic_key = get_topic_key(message.stream_id, message.topic);
    exports.inplace_rerender(topic_key);
};

exports.set_filter = function (filter) {
    // This function updates the `filters` variable
    // after user clicks on one of the filter buttons
    // based on `btn-recent-selected` class and current
    // set `filters`.

    // Get the button which was clicked.
    const filter_elem = $('#recent_topics_filter_buttons')
        .find('[data-filter="' + filter + '"]');

    // If user clicks `All`, we clear all filters.
    if (filter === 'all' && filters.size !== 0) {
        filters = new Set();
    // If the button was already selected, remove the filter.
    } else if (filter_elem.hasClass('btn-recent-selected')) {
        filters.delete(filter);
    // If the button was not selected, we add the filter.
    } else {
        filters.add(filter);
    }
};

function show_selected_filters() {
    // Add `btn-selected-filter` to the buttons to show
    // which filters are applied.
    if (filters.size === 0) {
        $('#recent_topics_filter_buttons')
            .find('[data-filter="all"]')
            .addClass('btn-recent-selected');
    } else {
        for (const filter of filters) {
            $('#recent_topics_filter_buttons')
                .find('[data-filter="' + filter + '"]')
                .addClass('btn-recent-selected');
        }
    }
}

exports.update_filters_view = function () {
    const rendered_filters = render_recent_topics_filters({
        filter_participated: filters.has('participated'),
        filter_unread: filters.has('unread'),
        filter_muted: filters.has('include_muted'),
    });
    $("#recent_filters_group").html(rendered_filters);
    show_selected_filters();

    topics_widget.hard_redraw();
    revive_current_focus();
};

function stream_sort(a, b) {
    const a_stream = message_store.get(a.last_msg_id).stream;
    const b_stream = message_store.get(b.last_msg_id).stream;
    if (a_stream > b_stream) {
        return 1;
    } else if (a_stream === b_stream) {
        return 0;
    }
    return -1;
}

function topic_sort(a, b) {
    const a_topic = message_store.get(a.last_msg_id).topic;
    const b_topic = message_store.get(b.last_msg_id).topic;
    if (a_topic > b_topic) {
        return 1;
    } else if (a_topic === b_topic) {
        return 0;
    }
    return -1;
}

exports.complete_rerender = function () {
    if (!overlays.recent_topics_open()) {
        return false;
    }
    // Prepare header
    const rendered_body = render_recent_topics_body({
        filter_participated: filters.has('participated'),
        filter_unread: filters.has('unread'),
        filter_muted: filters.has('include_muted'),
        search_val: $("#recent_topics_search").val() || "",
    });
    $('#recent_topics_table').html(rendered_body);
    show_selected_filters();

    // Show topics list
    const container = $('.recent_topics_table table tbody');
    container.empty();
    const mapped_topic_values = Array.from(exports.get().values()).map((value) => value);

    topics_widget = list_render.create(container, mapped_topic_values, {
        name: "recent_topics_table",
        parent_container: $("#recent_topics_table"),
        modifier: function (item) {
            return render_recent_topic_row(format_topic(item));
        },
        filter: {
            // We use update_filters_view & filters_should_hide_topic to do all the
            // filtering for us, which is called using click_handlers.
            predicate: function (topic_data) {
                return !exports.filters_should_hide_topic(topic_data);
            },
        },
        sort_fields: {
            stream_sort: stream_sort,
            topic_sort: topic_sort,
        },
        html_selector: get_topic_row,
    });
    revive_current_focus();
};

exports.launch = function () {
    overlays.open_overlay({
        name: 'recent_topics',
        overlay: $('#recent_topics_overlay'),
        on_close: function () {
            hashchange.exit_overlay();
        },
    });
    exports.complete_rerender();
};

exports.change_focused_element = function (e, input_key) {
    // Called from hotkeys.js; like all logic in that module,
    // returning true will cause the caller to do
    // preventDefault/stopPropagation; false will let the browser
    // handle the key.
    if (input_key === 'tab') {
        input_key = 'right_arrow';
    } else if (input_key === 'shift_tab') {
        input_key = 'left_arrow';
    }

    const $elem = $(e.target);

    if ($("#recent_topics_table").find(':focus').length === 0) {
        // This is a failsafe to return focus back to recent topics overlay,
        // in case it loses focus due to some unknown reason.
        set_default_focus();
        return false;
    }

    if (e.target.id === 'recent_topics_search') {
        // Since the search box a text area, we want the browser to handle
        // Left/Right and selection within the widget; but if the user
        // arrows off the edges, we should move focus to the adjacent widgets..
        const textInput = $("#recent_topics_search").get(0);
        const start = textInput.selectionStart;
        const end = textInput.selectionEnd;
        const text_length = textInput.value.length;
        let is_selected = false;
        if (end - start > 0) {
            is_selected = true;
        }

        switch (input_key) {
        case 'left_arrow':
            if (start !== 0 || is_selected) {
                return false;
            }
            current_focus_elem = $elem.prev().children().last();
            break;
        case 'right_arrow':
            if (end !== text_length || is_selected) {
                return false;
            }
            current_focus_elem = $elem.prev().children().first();
            break;
        case 'down_arrow':
            set_table_focus(row_focus, col_focus);
            return true;
        case 'click':
            // Note: current_focus_elem can be different here, so we just
            // set current_focus_elem to the input box, we don't want .focus() on
            // it since it is already focused.
            // We only do this for search beacuse we don't want the focus to
            // go away from the input box when `revive_current_focus` is called
            // on rerender when user is typing.
            current_focus_elem = $("#recent_topics_search");
            return true;
        }
    } else if ($elem.hasClass('btn-recent-filters')) {
        switch (input_key) {
        case 'left_arrow':
            if ($elem.parent().children().first()[0] === $elem[0]) {
                current_focus_elem = $("#recent_topics_search");
            } else {
                current_focus_elem = $elem.prev();
            }
            break;
        case 'right_arrow':
            if ($elem.parent().children().last()[0] === $elem[0]) {
                current_focus_elem = $("#recent_topics_search");
            } else {
                current_focus_elem = $elem.next();
            }
            break;
        case 'down_arrow':
            set_table_focus(row_focus, col_focus);
            return true;
        }
    } else if (current_focus_elem === 'table') {
        // For arrowing around the table of topics, we implement left/right
        // wraparound.  Going off the top or the bottom takes one
        // to the navigation at the top (see set_table_focus).
        switch (input_key) {
        case 'left_arrow':
            col_focus -= 1;
            if (col_focus < 0) {
                col_focus = MAX_SELECTABLE_COLS - 1;
            }
            break;
        case 'right_arrow':
            col_focus += 1;
            if (col_focus >= MAX_SELECTABLE_COLS) {
                col_focus = 0;
            }
            break;
        case 'down_arrow':
            row_focus += 1;
            break;
        case 'up_arrow':
            row_focus -= 1;
        }
        set_table_focus(row_focus, col_focus);
        return true;
    }
    if (current_focus_elem) {
        current_focus_elem.focus();
    }

    return true;
};

window.recent_topics = exports;