import Fastify, { type FastifyInstance, type FastifyReply, type FastifyRequest } from "fastify";
import { readFileSync } from "node:fs";
import { join, dirname } from "node:path";
import { fileURLToPath } from "node:url";
import { MailboxStore, RenameError, rowToMessage } from "./db.js";
import type { DaemonConfig } from "./config.js";
import { registerMcp } from "./mcp.js";

export const HEADER_NAME = "x-mailbox";

declare module "fastify" {
  interface FastifyRequest {
    mailboxName?: string;
  }
}

function readVersion(): string {
  try {
    const here = dirname(fileURLToPath(import.meta.url));
    const pkg = JSON.parse(readFileSync(join(here, "..", "package.json"), "utf8")) as {
      version?: string;
    };
    return pkg.version ?? "unknown";
  } catch {
    return "unknown";
  }
}

const ANONYMOUS_PATHS = new Set(["/v1/list", "/v1/peek"]);

export async function buildServer(cfg: DaemonConfig, store: MailboxStore): Promise<FastifyInstance> {
  const app = Fastify({
    logger: true,
    connectionTimeout: 310_000,
  });
  const version = readVersion();

  app.addHook("onRequest", async (req: FastifyRequest, reply: FastifyReply) => {
    const url = req.url.split("?")[0] ?? "/";
    if (url === "/health" || url === "/mcp" || url.startsWith("/mcp/")) return;

    const headerValue = req.headers[HEADER_NAME];
    const name = (Array.isArray(headerValue) ? headerValue[0] : headerValue ?? "").trim();

    if (!name) {
      if (ANONYMOUS_PATHS.has(url)) return;
      reply.code(400).send({ error: `Missing ${HEADER_NAME} header.` });
      return reply;
    }

    req.mailboxName = name;
    store.upsertMailbox(name);
  });

  app.get("/health", async () => ({
    status: "ok",
    version,
    dbPath: cfg.dbPath,
  }));

  app.post<{ Body: { to?: string; body?: string } }>("/v1/send", async (req, reply) => {
    const { to, body } = req.body ?? {};
    if (!to || !body) {
      reply.code(400);
      return { error: "to and body are required" };
    }
    const from = req.mailboxName!;
    const result = store.send(from, to, body);
    return { id: result.id, queuedAt: result.queuedAt.toISOString() };
  });

  app.get<{ Querystring: { name?: string } }>("/v1/peek", async (req, reply) => {
    const name = (req.query.name ?? "").trim();
    if (!name) {
      reply.code(400);
      return { error: "name is required" };
    }
    const status = store.peek(name);
    return {
      pending: status.pending,
      oldestAt: status.oldestAt?.toISOString() ?? null,
    };
  });

  app.post<{ Querystring: { name?: string } }>("/v1/check-inbox", async (req, reply) => {
    const name = (req.query.name ?? "").trim();
    if (name !== req.mailboxName) {
      reply.code(403);
      return { error: "X-Mailbox header must match name." };
    }
    return store.checkInbox(name).map((m) => {
      const msg = rowToMessage(m);
      return { ...msg, sentAt: msg.sentAt.toISOString() };
    });
  });

  app.get("/v1/list", async (req) => {
    const name = req.mailboxName;
    return store
      .listMailboxes(name, { hideAfterMinutes: cfg.hideAfterMinutes })
      .map((m) => ({
        name: m.name,
        lastSeenAt: m.lastSeenAt.toISOString(),
        pendingForYou: m.pendingForYou,
      }));
  });

  app.post<{ Body: { to?: string } }>("/v1/rename", async (req, reply) => {
    const from = req.mailboxName!;
    const to = (req.body?.to ?? "").trim();
    if (!to) {
      reply.code(400);
      return { error: "to is required" };
    }
    try {
      const r = store.rename(from, to);
      return { from: r.from, to: r.to, messagesTransferred: r.messagesTransferred };
    } catch (err) {
      if (err instanceof RenameError) {
        reply.code(err.reason === "target-exists" ? 409 : 400);
        return { error: err.message, reason: err.reason };
      }
      throw err;
    }
  });

  const WATCH_DEFAULT_TIMEOUT_S = 25;
  const WATCH_MAX_TIMEOUT_S = 300;

  app.get<{ Querystring: { name?: string; timeout?: string } }>(
    "/v1/watch",
    async (req, reply) => {
      const name = (req.query.name ?? "").trim();
      if (!name) {
        reply.code(400);
        return { error: "name is required" };
      }
      if (name !== req.mailboxName) {
        reply.code(403);
        return { error: "X-Mailbox header must match name." };
      }

      const rawTimeout = req.query.timeout;
      const timeoutS = rawTimeout != null ? parseInt(rawTimeout, 10) : WATCH_DEFAULT_TIMEOUT_S;
      if (!Number.isFinite(timeoutS) || timeoutS <= 0 || timeoutS > WATCH_MAX_TIMEOUT_S) {
        reply.code(400);
        return { error: `timeout must be 1..${WATCH_MAX_TIMEOUT_S} seconds` };
      }

      const ac = new AbortController();
      const onClose = (): void => ac.abort();
      req.raw.once("close", onClose);
      try {
        const result = await store.waitForMessage(name, timeoutS * 1000, ac.signal);

        if (result.kind === "message") {
          const msg = rowToMessage(result.message);
          reply.code(200);
          return { ...msg, sentAt: msg.sentAt.toISOString() };
        }
        if (result.kind === "renamed") {
          reply.code(409);
          return { reason: "renamed", to: result.to };
        }
        if (result.kind === "timeout") {
          reply.code(204);
          return reply.send();
        }
        // aborted — client gone; hand control to Fastify without writing to the dead socket.
        reply.hijack();
        return;
      } finally {
        req.raw.off("close", onClose);
      }
    },
  );

  await registerMcp(app, store, cfg.hideAfterMinutes);

  return app;
}

function startSweep(
  store: MailboxStore,
  cfg: DaemonConfig,
  log: FastifyInstance["log"],
): NodeJS.Timeout | null {
  if (cfg.sweepIntervalMinutes <= 0 || cfg.deleteAfterMinutes <= 0) return null;
  const runOnce = (): void => {
    try {
      const r = store.pruneStale(cfg.deleteAfterMinutes);
      if (r.deletedMailboxes > 0 || r.deletedMessages > 0) {
        log.info(
          r,
          `Pruned ${r.deletedMailboxes} stale mailbox(es) and ${r.deletedMessages} delivered message(s)`,
        );
      }
    } catch (err) {
      log.error({ err }, "Stale-mailbox sweep failed");
    }
  };
  runOnce();
  const timer = setInterval(runOnce, cfg.sweepIntervalMinutes * 60_000);
  timer.unref?.();
  return timer;
}

export async function startServer(
  cfg: DaemonConfig,
): Promise<{ app: FastifyInstance; store: MailboxStore; sweepTimer: NodeJS.Timeout | null }> {
  const store = new MailboxStore(cfg.dbPath);
  const app = await buildServer(cfg, store);
  const timerRef: { current: NodeJS.Timeout | null } = { current: null };
  app.addHook("onClose", async () => {
    if (timerRef.current) clearInterval(timerRef.current);
  });
  await app.listen({ host: cfg.bind, port: cfg.port });
  timerRef.current = startSweep(store, cfg, app.log);
  return { app, store, sweepTimer: timerRef.current };
}