import assert from "minimalistic-assert";

import * as buddy_data from "./buddy_data.ts";
import * as hash_util from "./hash_util.ts";
import * as narrow_state from "./narrow_state.ts";
import * as people from "./people.ts";
import * as pm_conversations from "./pm_conversations.ts";
import * as unread from "./unread.ts";
import * as user_status from "./user_status.ts";
import type {UserStatusEmojiInfo} from "./user_status.ts";

// Maximum number of conversation threads to show in default view.
const max_conversations_to_show = 8;

// Maximum number of conversation threads to show in default view with unreads.
const max_conversations_to_show_with_unreads = 15;

export function get_active_user_ids_string(): string | undefined {
    const filter = narrow_state.filter();

    if (!filter) {
        return undefined;
    }

    const emails = filter.operands("dm")[0];

    if (!emails) {
        return undefined;
    }

    const users_ids_array = people.emails_strings_to_user_ids_array(emails);
    if (!users_ids_array || users_ids_array.length === 0) {
        return undefined;
    }
    return people.sorted_other_user_ids(users_ids_array).join(",");
}

type DisplayObject = {
    recipients: string;
    user_ids_string: string;
    unread: number;
    is_zero: boolean;
    is_active: boolean;
    url: string;
    status_emoji_info: UserStatusEmojiInfo | undefined;
    user_circle_class: string | undefined;
    is_group: boolean;
    is_bot: boolean;
};

export function get_conversations(search_string = ""): DisplayObject[] {
    const conversations = pm_conversations.recent.get();
    const display_objects = [];

    // The user_ids_string for the current view, if any.
    const active_user_ids_string = get_active_user_ids_string();

    if (
        active_user_ids_string !== undefined &&
        !conversations
            .map((conversation) => conversation.user_ids_string)
            .includes(active_user_ids_string)
    ) {
        conversations.unshift({user_ids_string: active_user_ids_string, max_message_id: -1});
    }

    for (const conversation of conversations) {
        const user_ids_string = conversation.user_ids_string;

        const users = people.get_users_from_ids(
            people.user_ids_string_to_ids_array(user_ids_string),
        );
        if (!people.dm_matches_search_string(users, search_string)) {
            // Skip adding the conversation to the display_objects array if it does
            // not match the search_term.
            continue;
        }

        const reply_to = people.user_ids_string_to_emails_string(user_ids_string);
        assert(reply_to !== undefined);
        const recipients_string = people.get_recipients(user_ids_string);

        const num_unread = unread.num_unread_for_user_ids_string(user_ids_string);
        const is_group = user_ids_string.includes(",");
        const is_active = user_ids_string === active_user_ids_string;

        let user_circle_class;
        let status_emoji_info;
        let is_bot = false;

        if (!is_group) {
            const user_id = Number.parseInt(user_ids_string, 10);
            user_circle_class = buddy_data.get_user_circle_class(user_id);
            const recipient_user_obj = people.get_by_user_id(user_id);

            if (recipient_user_obj.is_bot) {
                // We display the bot icon rather than a user circle for bots.
                is_bot = true;
            } else {
                status_emoji_info = user_status.get_status_emoji(user_id);
            }
        }

        const display_object = {
            recipients: recipients_string,
            user_ids_string,
            unread: num_unread,
            is_zero: num_unread === 0,
            is_active,
            url: hash_util.pm_with_url(reply_to),
            status_emoji_info,
            user_circle_class,
            is_group,
            is_bot,
        };
        display_objects.push(display_object);
    }

    return display_objects;
}

// Designed to closely match topic_list_data.get_list_info().
export function get_list_info(
    zoomed: boolean,
    search_term = "",
): {
    conversations_to_be_shown: DisplayObject[];
    more_conversations_unread_count: number;
} {
    const conversations = get_conversations(search_term);

    if (zoomed || conversations.length <= max_conversations_to_show) {
        return {
            conversations_to_be_shown: conversations,
            more_conversations_unread_count: 0,
        };
    }

    const conversations_to_be_shown = [];
    let more_conversations_unread_count = 0;
    function should_show_conversation(idx: number, conversation: DisplayObject): boolean {
        // We always show the active conversation; see the similar
        // comment in topic_list_data.ts.
        if (conversation.is_active) {
            return true;
        }

        // We don't need to filter muted users here, because
        // pm_conversations.js takes care of this for us.

        // We include the most recent max_conversations_to_show
        // conversations, regardless of whether they have unread
        // messages.
        if (idx < max_conversations_to_show) {
            return true;
        }

        // We include older conversations with unread messages up
        // until max_conversations_to_show_with_unreads total
        // topics have been included.
        if (
            conversation.unread > 0 &&
            conversations_to_be_shown.length < max_conversations_to_show_with_unreads
        ) {
            return true;
        }

        // Otherwise, this conversation should only be visible in
        // the unzoomed view.
        return false;
    }
    for (const [idx, conversation] of conversations.entries()) {
        if (should_show_conversation(idx, conversation)) {
            conversations_to_be_shown.push(conversation);
        } else {
            more_conversations_unread_count += conversation.unread;
        }
    }

    return {
        conversations_to_be_shown,
        more_conversations_unread_count,
    };
}