import "dotenv/config";
import http from "node:http";
import express, { type Request, type Response } from "express";
import { Server as SocketIOServer } from "socket.io";
import { createClient } from "redis";
import { createAdapter } from "@socket.io/redis-adapter";
import { verifyToken } from "@clerk/backend";
import { db, sql } from "@fitai/database";

interface ThreadAccess {
  id: string;
  type: "gym" | "dm";
  gymId: string | null;
  trainerId: string | null;
  clientId: string | null;
}

interface IncomingChatMessagePayload {
  threadId?: string;
  body?: string;
  clientMessageId?: string;
  attachments?: unknown;
}

interface AuthenticatedSocketData {
  user: {
    id: string;
    role: "superAdmin" | "admin" | "trainer" | "client";
    gymId: string | null;
  };
}

const app = express();
const server = http.createServer(app);
const sendRateWindowByUser = new Map<string, number[]>();
const typingRateWindowByKey = new Map<string, number[]>();
const readRateWindowByKey = new Map<string, number[]>();
const SEND_LIMIT_PER_MINUTE = 30;
const TYPING_LIMIT_PER_10_SECONDS = 20;
const READ_LIMIT_PER_10_SECONDS = 30;
let redisRateClient: ReturnType<typeof createClient> | null = null;

const io = new SocketIOServer<
  Record<string, never>,
  Record<string, never>,
  Record<string, never>,
  AuthenticatedSocketData
>(server, {
  cors: {
    origin: process.env.REALTIME_CORS_ORIGIN?.split(",") ?? "*",
    credentials: true,
  },
  path: process.env.REALTIME_SOCKET_PATH ?? "/socket.io",
});

app.get("/healthz", (_req: Request, res: Response) => {
  res.json({ ok: true, service: "realtime" });
});

async function attachRedisAdapter(): Promise<void> {
  const redisUrl = process.env.REDIS_URL;
  if (!redisUrl) {
    return;
  }

  const pubClient = createClient({ url: redisUrl });
  const subClient = pubClient.duplicate();
  await pubClient.connect();
  await subClient.connect();

  redisRateClient = pubClient;
  io.adapter(createAdapter(pubClient, subClient));
}

io.use(async (socket: any, next: (err?: Error) => void) => {
  try {
    const token =
      typeof socket.handshake.auth?.token === "string"
        ? socket.handshake.auth.token
        : null;

    const userId = await verifyAndExtractUserId(token);
    if (!userId) {
      return next(new Error("Unauthorized"));
    }

    const rows = await db.all(sql`
      SELECT
        id,
        role,
        gym_id as gymId
      FROM users
      WHERE id = ${userId}
      LIMIT 1
    `);

    const user = rows?.[0] as
      | {
          id: string;
          role: "superAdmin" | "admin" | "trainer" | "client";
          gymId: string | null;
        }
      | undefined;

    if (!user) {
      return next(new Error("Unauthorized"));
    }

    socket.data.user = user;
    return next();
  } catch {
    return next(new Error("Unauthorized"));
  }
});

io.on("connection", (socket: any) => {
  socket.on("chat:subscribe", async (payload: { threadId?: string }) => {
    const threadId = payload?.threadId;
    if (!threadId) {
      socket.emit("chat:error", { code: "invalid_payload" });
      return;
    }

    const allowed = await canAccessThread(socket.data.user, threadId);
    if (!allowed) {
      socket.emit("chat:error", { code: "forbidden" });
      return;
    }

    await socket.join(`thread:${threadId}`);
    socket.emit("chat:subscribed", { threadId });
  });

  socket.on("chat:unsubscribe", async (payload: { threadId?: string }) => {
    const threadId = payload?.threadId;
    if (!threadId) {
      return;
    }

    await socket.leave(`thread:${threadId}`);
  });

  socket.on(
    "chat:typing",
    async (payload: { threadId?: string; isTyping?: boolean }) => {
      const threadId = payload?.threadId;
      if (!threadId) {
        return;
      }

      const typingAllowed = await checkRateLimit(
        typingRateWindowByKey,
        `typing:${socket.data.user.id}:${threadId}`,
        TYPING_LIMIT_PER_10_SECONDS,
        10,
      );
      if (!typingAllowed) {
        return;
      }

      const allowed = await canAccessThread(socket.data.user, threadId);
      if (!allowed) {
        return;
      }

      socket.to(`thread:${threadId}`).emit("chat:typing", {
        threadId,
        userId: socket.data.user.id,
        isTyping: Boolean(payload?.isTyping),
      });
    },
  );

  socket.on("chat:send", async (payload: IncomingChatMessagePayload) => {
    try {
      const threadId =
        typeof payload?.threadId === "string" ? payload.threadId : null;
      const body = typeof payload?.body === "string" ? payload.body.trim() : "";

      if (!threadId || !body) {
        socket.emit("chat:error", {
          code: "invalid_payload",
          message: "threadId and body are required",
        });
        return;
      }

      const sendAllowed = await checkRateLimit(
        sendRateWindowByUser,
        `send:${socket.data.user.id}`,
        SEND_LIMIT_PER_MINUTE,
        60,
      );
      if (!sendAllowed) {
        socket.emit("chat:error", {
          code: "rate_limited",
          message: "Too many messages. Please slow down.",
        });
        return;
      }

      if (body.length > 2000) {
        socket.emit("chat:error", {
          code: "message_too_long",
          message: "Message is too long",
        });
        return;
      }

      const access = await getThreadAccess(socket.data.user, threadId);
      if (!access) {
        socket.emit("chat:error", { code: "forbidden", message: "Forbidden" });
        return;
      }

      await ensureThreadMembership(
        threadId,
        socket.data.user.id,
        socket.data.user.role,
      );

      const clientMessageId =
        typeof payload.clientMessageId === "string" &&
        payload.clientMessageId.trim().length > 0
          ? payload.clientMessageId.trim()
          : null;

      if (clientMessageId) {
        const existingRows = await db.all(sql`
          SELECT
            id,
            thread_id as threadId,
            sender_user_id as senderUserId,
            body,
            kind,
            attachments_json as attachmentsJson,
            client_message_id as clientMessageId,
            created_at as createdAt,
            edited_at as editedAt,
            deleted_at as deletedAt
          FROM chat_messages
          WHERE sender_user_id = ${socket.data.user.id}
            AND client_message_id = ${clientMessageId}
          LIMIT 1
        `);

        if (existingRows?.[0]) {
          const message = mapMessageRow(existingRows[0] as MessageRow);
          socket.emit("chat:message:ack", {
            threadId,
            clientMessageId,
            message,
            duplicate: true,
          });
          return;
        }
      }

      const attachments = normalizeAttachments(payload.attachments);
      const now = nowEpochSeconds();
      const messageId = generateId("msg");

      await db.run(sql`
        INSERT INTO chat_messages (
          id,
          thread_id,
          sender_user_id,
          body,
          kind,
          attachments_json,
          client_message_id,
          created_at
        ) VALUES (
          ${messageId},
          ${threadId},
          ${socket.data.user.id},
          ${body},
          ${"text"},
          ${attachments.length > 0 ? JSON.stringify(attachments) : null},
          ${clientMessageId},
          ${now}
        )
      `);

      await db.run(sql`
        UPDATE chat_threads
        SET
          last_message_at = ${now},
          updated_at = ${now}
        WHERE id = ${threadId}
      `);

      const createdRows = await db.all(sql`
        SELECT
          id,
          thread_id as threadId,
          sender_user_id as senderUserId,
          body,
          kind,
          attachments_json as attachmentsJson,
          client_message_id as clientMessageId,
          created_at as createdAt,
          edited_at as editedAt,
          deleted_at as deletedAt
        FROM chat_messages
        WHERE id = ${messageId}
        LIMIT 1
      `);

      const createdRow = createdRows?.[0] as MessageRow | undefined;
      if (!createdRow) {
        socket.emit("chat:error", {
          code: "send_failed",
          message: "Failed to persist message",
        });
        return;
      }

      const message = mapMessageRow(createdRow);

      await socket.join(`thread:${threadId}`);

      io.to(`thread:${threadId}`).emit("chat:message:new", {
        threadId,
        message,
      });

      io.to(`thread:${threadId}`).emit("chat:read:update", {
        threadId,
        userId: socket.data.user.id,
        lastReadMessageId: message.id,
      });

      socket.emit("chat:message:ack", {
        threadId,
        clientMessageId,
        message,
      });
    } catch (error) {
      socket.emit("chat:error", {
        code: "internal_error",
        message: error instanceof Error ? error.message : "Failed to send",
      });
    }
  });

  socket.on(
    "chat:read",
    async (payload: { threadId?: string; lastReadMessageId?: string }) => {
      const threadId = payload?.threadId;
      if (!threadId) {
        return;
      }

      const readAllowed = await checkRateLimit(
        readRateWindowByKey,
        `read:${socket.data.user.id}:${threadId}`,
        READ_LIMIT_PER_10_SECONDS,
        10,
      );
      if (!readAllowed) {
        return;
      }

      const allowed = await canAccessThread(socket.data.user, threadId);
      if (!allowed) {
        return;
      }

      await ensureThreadMembership(
        threadId,
        socket.data.user.id,
        socket.data.user.role,
      );

      const now = Math.floor(Date.now() / 1000);
      await db.run(sql`
        UPDATE chat_thread_members
        SET
          last_read_message_id = ${payload?.lastReadMessageId ?? null},
          last_read_at = ${now}
        WHERE thread_id = ${threadId}
          AND user_id = ${socket.data.user.id}
      `);

      io.to(`thread:${threadId}`).emit("chat:read:update", {
        threadId,
        userId: socket.data.user.id,
        lastReadMessageId: payload?.lastReadMessageId ?? null,
      });
    },
  );
});

async function canAccessThread(
  user: AuthenticatedSocketData["user"],
  threadId: string,
): Promise<boolean> {
  const access = await getThreadAccess(user, threadId);
  return Boolean(access);
}

async function getThreadAccess(
  user: AuthenticatedSocketData["user"],
  threadId: string,
): Promise<ThreadAccess | null> {
  const rows = await db.all(sql`
    SELECT
      id,
      type,
      gym_id as gymId,
      trainer_id as trainerId,
      client_id as clientId,
      archived_at as archivedAt
    FROM chat_threads
    WHERE id = ${threadId}
    LIMIT 1
  `);

  const thread = rows?.[0] as
    | {
        id: string;
        type: "gym" | "dm";
        gymId: string | null;
        trainerId: string | null;
        clientId: string | null;
        archivedAt: number | null;
      }
    | undefined;

  if (!thread || thread.archivedAt) {
    return null;
  }

  if (user.role === "superAdmin") {
    return {
      id: thread.id,
      type: thread.type,
      gymId: thread.gymId,
      trainerId: thread.trainerId,
      clientId: thread.clientId,
    };
  }

  if (thread.type === "gym") {
    if (!user.gymId || user.gymId !== thread.gymId) {
      return null;
    }

    return {
      id: thread.id,
      type: thread.type,
      gymId: thread.gymId,
      trainerId: thread.trainerId,
      clientId: thread.clientId,
    };
  }

  const isParticipant =
    user.id === thread.trainerId || user.id === thread.clientId;
  if (!isParticipant) {
    return null;
  }

  if (thread.trainerId && thread.clientId) {
    const assignmentRows = await db.all(sql`
      SELECT id
      FROM trainer_client_assignments
      WHERE trainer_id = ${thread.trainerId}
        AND client_id = ${thread.clientId}
        AND is_active = 1
      LIMIT 1
    `);

    if (!assignmentRows?.[0]) {
      return null;
    }
  }

  return {
    id: thread.id,
    type: thread.type,
    gymId: thread.gymId,
    trainerId: thread.trainerId,
    clientId: thread.clientId,
  };
}

async function verifyAndExtractUserId(
  token: string | null,
): Promise<string | null> {
  if (!token) {
    return null;
  }

  const secretKey = process.env.CLERK_SECRET_KEY;
  if (!secretKey) {
    return null;
  }

  try {
    const verified = await verifyToken(token, {
      secretKey,
      clockSkewInMs: 5000,
    });
    if (typeof verified.sub === "string" && verified.sub.trim().length > 0) {
      return verified.sub;
    }

    const fallback =
      typeof verified.sid === "string" && verified.sid.trim().length > 0
        ? verified.sid
        : null;
    if (fallback) {
      const rows = await db.all(sql`
        SELECT id
        FROM users
        WHERE id = ${fallback}
        LIMIT 1
      `);
      if (rows?.[0]) {
        return fallback;
      }
    }

    const payload = JSON.parse(
      Buffer.from(token.split(".")[1], "base64url").toString(),
    );
    if (typeof payload.sub === "string" && payload.sub.trim().length > 0) {
      return payload.sub;
    }

    return null;
  } catch {
    return null;
  }
}

async function main() {
  await attachRedisAdapter();
  const port = Number(process.env.REALTIME_PORT ?? 3001);
  server.listen(port, () => {
    console.log(`[realtime] listening on :${port}`);
  });
}

async function ensureThreadMembership(
  threadId: string,
  userId: string,
  role: AuthenticatedSocketData["user"]["role"],
): Promise<void> {
  const now = nowEpochSeconds();
  await db.run(sql`
    INSERT OR IGNORE INTO chat_thread_members (
      id,
      thread_id,
      user_id,
      role_in_thread,
      joined_at,
      muted
    ) VALUES (
      ${generateId("member")},
      ${threadId},
      ${userId},
      ${role},
      ${now},
      ${0}
    )
  `);

  await db.run(sql`
    UPDATE chat_thread_members
    SET left_at = NULL
    WHERE thread_id = ${threadId}
      AND user_id = ${userId}
  `);
}

function normalizeAttachments(
  raw: unknown,
): Array<{ url: string; type: string; name?: string }> {
  if (!Array.isArray(raw)) {
    return [];
  }

  return raw
    .filter(
      (item): item is { url: string; type: string; name?: string } =>
        item !== null &&
        typeof item === "object" &&
        typeof (item as { url?: unknown }).url === "string" &&
        typeof (item as { type?: unknown }).type === "string",
    )
    .map((item) => ({
      url: item.url,
      type: item.type,
      name: typeof item.name === "string" ? item.name : undefined,
    }));
}

function parseAttachments(
  value: string | null,
): Array<{ url: string; type: string; name?: string }> {
  if (!value) {
    return [];
  }

  try {
    return normalizeAttachments(JSON.parse(value));
  } catch {
    return [];
  }
}

function mapMessageRow(row: MessageRow) {
  return {
    id: row.id,
    threadId: row.threadId,
    senderUserId: row.senderUserId,
    body: row.body,
    kind: row.kind,
    attachments: parseAttachments(row.attachmentsJson),
    clientMessageId: row.clientMessageId,
    createdAt: new Date(Number(row.createdAt) * 1000).toISOString(),
    editedAt: row.editedAt
      ? new Date(Number(row.editedAt) * 1000).toISOString()
      : null,
    deletedAt: row.deletedAt
      ? new Date(Number(row.deletedAt) * 1000).toISOString()
      : null,
  };
}

function generateId(prefix: string): string {
  return `${prefix}_${Date.now()}_${Math.random().toString(36).slice(2, 10)}`;
}

function nowEpochSeconds(): number {
  return Math.floor(Date.now() / 1000);
}

export async function checkRateLimit(
  windows: Map<string, number[]>,
  key: string,
  limit: number,
  windowSeconds: number,
): Promise<boolean> {
  if (redisRateClient) {
    try {
      const redisKey = `fitai:chat:rl:${key}`;
      const count = await redisRateClient.incr(redisKey);
      if (count === 1) {
        await redisRateClient.expire(redisKey, windowSeconds);
      }

      return count <= limit;
    } catch {
      // Continue with in-memory fallback below.
    }
  }

  const now = Date.now();
  const current = windows.get(key) ?? [];
  const windowMs = windowSeconds * 1000;
  const withinWindow = current.filter(
    (timestamp) => now - timestamp < windowMs,
  );

  if (withinWindow.length >= limit) {
    windows.set(key, withinWindow);
    return false;
  }

  withinWindow.push(now);
  windows.set(key, withinWindow);
  return true;
}

interface MessageRow {
  id: string;
  threadId: string;
  senderUserId: string;
  body: string;
  kind: "text" | "system";
  attachmentsJson: string | null;
  clientMessageId: string | null;
  createdAt: number;
  editedAt: number | null;
  deletedAt: number | null;
}

void main();