var express = require('express');
var router = express.Router();

const DB = require("../mongoDB.js");
const { getUserId, getProfileId } = require("../utils/sessionUtils.js");
const { normalizeLanguageCode, translateText } = require("../utils/chatTranslation.js");

const ACTIVE_WINDOW_MS = 120000;
const MESSAGE_MAX_LENGTH = 500;
const activeUsers = new Map();
const translationInflight = new Map();

const toDisplayName = (profile, fallbackName) => {
    const firstName = profile?.profile?.firstName || "";
    const lastName = profile?.profile?.lastName || "";
    const displayName = (firstName + " " + lastName).trim();
    return displayName || fallbackName || "Anonymous";
};

const pruneActiveUsers = () => {
    const now = Date.now();
    for (const [profileId, entry] of activeUsers.entries()) {
        if (now - entry.lastSeen > ACTIVE_WINDOW_MS) {
            activeUsers.delete(profileId);
        }
    }
};

const getActiveUsersList = () => {
    pruneActiveUsers();
    return Array.from(activeUsers.values())
        .sort((a, b) => b.lastSeen - a.lastSeen)
        .map((entry) => ({
            profileId: entry.profileId,
            userId: entry.userId,
            displayName: entry.displayName,
            lastSeen: entry.lastSeen,
        }));
};

DB.getDB.then((DB) => {
    const resolveTargetLanguage = (req) => {
        const requested = req.query?.lang || req.headers["x-app-language"] || req.headers["accept-language"] || "en";
        return normalizeLanguageCode(requested);
    };

    const mapChatMessageForLanguage = async (message, targetLang) => {
        const normalizedTarget = normalizeLanguageCode(targetLang);
        const sourceLang = normalizeLanguageCode(message?.sourceLang || "auto");
        const originalText = message?.text || "";

        if (!originalText) {
            return {
                ...message,
                textOriginal: "",
                text: "",
                displayLang: sourceLang,
            };
        }

        if (sourceLang === normalizedTarget) {
            return {
                ...message,
                textOriginal: originalText,
                text: originalText,
                displayLang: sourceLang,
            };
        }

        const cachedTranslation = message?.translations?.[normalizedTarget]?.text;
        if (cachedTranslation) {
            return {
                ...message,
                textOriginal: originalText,
                text: cachedTranslation,
                displayLang: normalizedTarget,
            };
        }

        const translationKey = `${message?._id?.toString?.() || ""}:${normalizedTarget}`;
        if (translationInflight.has(translationKey)) {
            await translationInflight.get(translationKey);
            const refreshed = await DB.chatMessagesCol.findOne({ _id: message._id }).catch(() => null);
            const refreshedCached = refreshed?.translations?.[normalizedTarget]?.text;
            if (refreshedCached) {
                return {
                    ...message,
                    translations: refreshed.translations,
                    textOriginal: originalText,
                    text: refreshedCached,
                    displayLang: normalizedTarget,
                };
            }
            return {
                ...message,
                textOriginal: originalText,
                text: originalText,
                displayLang: sourceLang,
            };
        }

        const inFlightTask = (async () => {
            const translated = await translateText({
                text: originalText,
                sourceLang,
                targetLang: normalizedTarget,
            });
            if (!translated?.translatedText) return null;
            await DB.setChatMessageTranslation({
                messageId: message._id,
                targetLang: normalizedTarget,
                text: translated.translatedText,
                provider: translated.provider,
                model: translated.model,
            });
            return translated.translatedText;
        })();

        translationInflight.set(translationKey, inFlightTask);
        let translatedText = null;
        try {
            translatedText = await inFlightTask;
        } finally {
            translationInflight.delete(translationKey);
        }

        return {
            ...message,
            textOriginal: originalText,
            text: translatedText || originalText,
            displayLang: translatedText ? normalizedTarget : sourceLang,
        };
    };

    const markActiveUser = async (req) => {
        const userId = getUserId(req);
        const profileId = req.profileInfo?._id || getProfileId(req);
        if (!profileId || !userId) return null;
        const profile = await DB.getProfileCache(profileId);
        const displayName = toDisplayName(profile, req.userInfo?.username);
        activeUsers.set(profileId + "", {
            profileId: profileId + "",
            userId: userId + "",
            displayName,
            lastSeen: Date.now(),
        });
        return activeUsers.get(profileId + "");
    };

    router.get("/messages", async (req, res) => {
        try {
            await markActiveUser(req);
            const targetLang = resolveTargetLanguage(req);
            const messages = await DB.getRecentChatMessages(req.query.limit || 100);
            const translatedMessages = await Promise.all(messages.map((message) => mapChatMessageForLanguage(message, targetLang)));
            return res.json({
                status: "ok",
                requestedLang: targetLang,
                messages: translatedMessages,
            });
        } catch (error) {
            console.error("Error getting chat messages", error);
            return res.status(500).json({ status: "Internal server error", messages: [] });
        }
    });

    router.post("/messages", async (req, res) => {
        try {
            const userId = getUserId(req);
            const profileId = req.profileInfo?._id || getProfileId(req);
            const text = typeof req.body?.text === "string" ? req.body.text.trim() : "";
            const sourceLang = normalizeLanguageCode(req.body?.sourceLang || req.headers["x-app-language"] || "en");
            if (!text) {
                return res.status(400).json({ status: "Message text is required" });
            }
            if (text.length > MESSAGE_MAX_LENGTH) {
                return res.status(400).json({ status: `Message too long (${MESSAGE_MAX_LENGTH} max chars)` });
            }

            const profile = await DB.getProfileCache(profileId);
            const senderName = toDisplayName(profile, req.userInfo?.username);
            const message = await DB.addChatMessage({
                senderId: userId,
                senderProfileId: profileId,
                senderName,
                text,
                sourceLang,
            });
            if (!message) {
                return res.status(500).json({ status: "Could not save message" });
            }

            activeUsers.set(profileId + "", {
                profileId: profileId + "",
                userId: userId + "",
                displayName: senderName,
                lastSeen: Date.now(),
            });

            return res.json({
                status: "ok",
                message,
                activeUsers: getActiveUsersList(),
            });
        } catch (error) {
            console.error("Error posting chat message", error);
            return res.status(500).json({ status: "Internal server error" });
        }
    });

    router.get("/active", async (req, res) => {
        try {
            await markActiveUser(req);
            return res.json({
                status: "ok",
                activeUsers: getActiveUsersList(),
            });
        } catch (error) {
            console.error("Error getting active chat users", error);
            return res.status(500).json({ status: "Internal server error", activeUsers: [] });
        }
    });

    router.post("/ping", async (req, res) => {
        try {
            await markActiveUser(req);
            return res.json({
                status: "ok",
                activeUsers: getActiveUsersList(),
            });
        } catch (error) {
            console.error("Error updating chat presence", error);
            return res.status(500).json({ status: "Internal server error", activeUsers: [] });
        }
    });
});

module.exports = router;