import { createServer, type IncomingMessage, type ServerResponse } from "node:http";
import { buildSchema, graphql } from "graphql";
import { parseTelegramBusinessUpdate } from "./telegram";
import { enqueueTelegramInboundTask, enqueueTelegramOutboundTask } from "./hatchet/tasks";

const PORT = Number(process.env.PORT || 8080);
const MAX_BODY_SIZE_BYTES = Number(process.env.MAX_BODY_SIZE_BYTES || 1024 * 1024);
const WEBHOOK_SECRET = String(process.env.TELEGRAM_WEBHOOK_SECRET || "").trim();
const GRAPHQL_SHARED_SECRET = String(process.env.TELEGRAM_BACKEND_GRAPHQL_SHARED_SECRET || "").trim();

const schema = buildSchema(`
  type Query {
    health: Health!
  }

  type Health {
    ok: Boolean!
    service: String!
    now: String!
  }

  input TelegramOutboundTaskInput {
    omniMessageId: String!
    chatId: String!
    text: String!
    businessConnectionId: String
  }

  input TelegramSendMessageInput {
    chatId: String!
    text: String!
    businessConnectionId: String
  }

  type TaskEnqueueResult {
    ok: Boolean!
    message: String!
    runId: String
  }

  type TelegramSendResult {
    ok: Boolean!
    message: String!
    providerMessageId: String
    responseJson: String
  }

  type Mutation {
    enqueueTelegramOutbound(input: TelegramOutboundTaskInput!): TaskEnqueueResult!
    sendTelegramMessage(input: TelegramSendMessageInput!): TelegramSendResult!
  }
`);

function asString(value: unknown) {
  if (typeof value !== "string") return null;
  const v = value.trim();
  return v || null;
}

function writeJson(res: ServerResponse, statusCode: number, body: unknown) {
  res.statusCode = statusCode;
  res.setHeader("content-type", "application/json; charset=utf-8");
  res.end(JSON.stringify(body));
}

function isWebhookAuthorized(req: IncomingMessage) {
  if (!WEBHOOK_SECRET) return true;
  const incoming = String(req.headers["x-telegram-bot-api-secret-token"] || "").trim();
  return incoming !== "" && incoming === WEBHOOK_SECRET;
}

function isGraphqlAuthorized(req: IncomingMessage) {
  if (!GRAPHQL_SHARED_SECRET) return true;
  const incoming = String(req.headers["x-graphql-secret"] || "").trim();
  return incoming !== "" && incoming === GRAPHQL_SHARED_SECRET;
}

async function readJsonBody(req: IncomingMessage): Promise<unknown> {
  const chunks: Buffer[] = [];
  let total = 0;

  for await (const chunk of req) {
    const buf = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk);
    total += buf.length;
    if (total > MAX_BODY_SIZE_BYTES) {
      throw new Error(`payload_too_large:${MAX_BODY_SIZE_BYTES}`);
    }
    chunks.push(buf);
  }

  const raw = Buffer.concat(chunks).toString("utf8");
  if (!raw) return {};
  return JSON.parse(raw);
}

async function sendTelegramMessage(input: {
  chatId: string;
  text: string;
  businessConnectionId?: string | null;
}) {
  const token = asString(process.env.TELEGRAM_BOT_TOKEN);
  if (!token) {
    throw new Error("TELEGRAM_BOT_TOKEN is required");
  }

  const base = String(process.env.TELEGRAM_API_BASE || "https://api.telegram.org").replace(/\/+$/, "");
  const endpoint = `${base}/bot${token}/sendMessage`;

  const payload: Record<string, unknown> = {
    chat_id: input.chatId,
    text: input.text,
  };
  if (input.businessConnectionId) {
    payload.business_connection_id = input.businessConnectionId;
  }

  const response = await fetch(endpoint, {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify(payload),
  });

  const text = await response.text();
  const body = (() => {
    try {
      return JSON.parse(text) as Record<string, any>;
    } catch {
      return { raw: text };
    }
  })();

  if (!response.ok || body?.ok === false) {
    throw new Error(`telegram send failed: ${response.status} ${JSON.stringify(body)}`);
  }

  const providerMessageId =
    body?.result?.message_id != null
      ? String(body.result.message_id)
      : body?.message_id != null
        ? String(body.message_id)
        : null;

  return {
    ok: true,
    message: "sent",
    providerMessageId,
    responseJson: JSON.stringify(body),
  };
}

const root = {
  health: () => ({
    ok: true,
    service: "telegram_backend",
    now: new Date().toISOString(),
  }),

  enqueueTelegramOutbound: async ({ input }: { input: any }) => {
    const run = await enqueueTelegramOutboundTask({
      omniMessageId: String(input.omniMessageId ?? ""),
      chatId: String(input.chatId ?? ""),
      text: String(input.text ?? ""),
      businessConnectionId: input.businessConnectionId != null ? String(input.businessConnectionId) : null,
    });

    return {
      ok: true,
      message: "enqueued",
      runId: run.runId,
    };
  },

  sendTelegramMessage: async ({ input }: { input: any }) => {
    const result = await sendTelegramMessage({
      chatId: String(input.chatId ?? ""),
      text: String(input.text ?? ""),
      businessConnectionId: input.businessConnectionId != null ? String(input.businessConnectionId) : null,
    });

    return result;
  },
};

export function startServer() {
  const server = createServer(async (req, res) => {
    if (!req.url || !req.method) {
      writeJson(res, 404, { ok: false, error: "not_found" });
      return;
    }

    if (req.url === "/health" && req.method === "GET") {
      writeJson(res, 200, {
        ok: true,
        service: "telegram_backend",
        now: new Date().toISOString(),
      });
      return;
    }

    if (req.url === "/webhooks/telegram/business" && req.method === "POST") {
      if (!isWebhookAuthorized(req)) {
        writeJson(res, 401, { ok: false, error: "invalid_webhook_secret" });
        return;
      }

      try {
        const body = await readJsonBody(req);
        const envelope = parseTelegramBusinessUpdate(body);
        const run = await enqueueTelegramInboundTask(envelope);

        writeJson(res, 200, {
          ok: true,
          queued: true,
          runId: run.runId,
          providerEventId: envelope.providerEventId,
          idempotencyKey: envelope.idempotencyKey,
        });
      } catch (error) {
        const message = error instanceof Error ? error.message : String(error);
        const statusCode = message.startsWith("payload_too_large:") ? 413 : 503;
        writeJson(res, statusCode, {
          ok: false,
          error: "receiver_enqueue_failed",
          message,
        });
      }

      return;
    }

    if (req.url === "/graphql" && req.method === "POST") {
      if (!isGraphqlAuthorized(req)) {
        writeJson(res, 401, { errors: [{ message: "unauthorized" }] });
        return;
      }

      try {
        const body = (await readJsonBody(req)) as {
          query?: string;
          variables?: Record<string, unknown>;
          operationName?: string;
        };

        const result = await graphql({
          schema,
          source: String(body.query || ""),
          rootValue: root,
          variableValues: body.variables || {},
          operationName: body.operationName,
        });

        writeJson(res, 200, result);
      } catch (error) {
        const message = error instanceof Error ? error.message : String(error);
        const statusCode = message.startsWith("payload_too_large:") ? 413 : 400;
        writeJson(res, statusCode, { errors: [{ message }] });
      }

      return;
    }

    writeJson(res, 404, { ok: false, error: "not_found" });
  });

  server.listen(PORT, "0.0.0.0", () => {
    console.log(`[telegram_backend] listening on :${PORT}`);
  });

  return server;
}