import crypto from "node:crypto";
import type { IncomingMessage, ServerResponse } from "node:http";
import { describe, expect, it, vi } from "vitest";
import { createLineNodeWebhookHandler } from "./webhook-node.js";

const sign = (body: string, secret: string) =>
  crypto.createHmac("SHA256", secret).update(body).digest("base64");

function createRes() {
  const headers: Record<string, string> = {};
  const resObj = {
    statusCode: 0,
    headersSent: false,
    setHeader: (k: string, v: string) => {
      headers[k.toLowerCase()] = v;
    },
    end: vi.fn((data?: unknown) => {
      resObj.headersSent = true;
      // Keep payload available for assertions
      resObj.body = data;
    }),
    body: undefined as unknown,
  };
  const res = resObj as unknown as ServerResponse & { body?: unknown };
  return { res, headers };
}

function createPostWebhookTestHarness(rawBody: string, secret = "secret") {
  const bot = { handleWebhook: vi.fn(async () => {}) };
  const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
  const handler = createLineNodeWebhookHandler({
    channelSecret: secret,
    bot,
    runtime,
    readBody: async () => rawBody,
  });
  return { bot, handler, secret };
}

const runSignedPost = async (params: {
  handler: (req: IncomingMessage, res: ServerResponse) => Promise<void>;
  rawBody: string;
  secret: string;
  res: ServerResponse;
}) =>
  await params.handler(
    {
      method: "POST",
      headers: { "x-line-signature": sign(params.rawBody, params.secret) },
    } as unknown as IncomingMessage,
    params.res,
  );

describe("createLineNodeWebhookHandler", () => {
  it("returns 200 for GET", async () => {
    const bot = { handleWebhook: vi.fn(async () => {}) };
    const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
    const handler = createLineNodeWebhookHandler({
      channelSecret: "secret",
      bot,
      runtime,
      readBody: async () => "",
    });

    const { res } = createRes();
    await handler({ method: "GET", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(200);
    expect(res.body).toBe("OK");
  });

  it("returns 204 for HEAD", async () => {
    const bot = { handleWebhook: vi.fn(async () => {}) };
    const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
    const handler = createLineNodeWebhookHandler({
      channelSecret: "secret",
      bot,
      runtime,
      readBody: async () => "",
    });

    const { res } = createRes();
    await handler({ method: "HEAD", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(204);
    expect(res.body).toBeUndefined();
  });

  it("returns 200 for verification request (empty events, no signature)", async () => {
    const rawBody = JSON.stringify({ events: [] });
    const { bot, handler } = createPostWebhookTestHarness(rawBody);

    const { res, headers } = createRes();
    await handler({ method: "POST", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(200);
    expect(headers["content-type"]).toBe("application/json");
    expect(res.body).toBe(JSON.stringify({ status: "ok" }));
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });

  it("returns 405 for non-GET/HEAD/POST methods", async () => {
    const { bot, handler } = createPostWebhookTestHarness(JSON.stringify({ events: [] }));

    const { res, headers } = createRes();
    await handler({ method: "PUT", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(405);
    expect(headers.allow).toBe("GET, HEAD, POST");
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });

  it("rejects missing signature when events are non-empty", async () => {
    const rawBody = JSON.stringify({ events: [{ type: "message" }] });
    const { bot, handler } = createPostWebhookTestHarness(rawBody);

    const { res } = createRes();
    await handler({ method: "POST", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(400);
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });

  it("uses a tight body-read limit for unsigned POST requests", async () => {
    const bot = { handleWebhook: vi.fn(async () => {}) };
    const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
    const readBody = vi.fn(async (_req: IncomingMessage, maxBytes: number) => {
      expect(maxBytes).toBe(4096);
      return JSON.stringify({ events: [{ type: "message" }] });
    });
    const handler = createLineNodeWebhookHandler({
      channelSecret: "secret",
      bot,
      runtime,
      readBody,
    });

    const { res } = createRes();
    await handler({ method: "POST", headers: {} } as unknown as IncomingMessage, res);

    expect(res.statusCode).toBe(400);
    expect(readBody).toHaveBeenCalledTimes(1);
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });

  it("uses strict pre-auth limits for signed POST requests", async () => {
    const rawBody = JSON.stringify({ events: [{ type: "message" }] });
    const bot = { handleWebhook: vi.fn(async () => {}) };
    const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
    const readBody = vi.fn(async (_req: IncomingMessage, maxBytes: number, timeoutMs?: number) => {
      expect(maxBytes).toBe(64 * 1024);
      expect(timeoutMs).toBe(5_000);
      return rawBody;
    });
    const handler = createLineNodeWebhookHandler({
      channelSecret: "secret",
      bot,
      runtime,
      readBody,
      maxBodyBytes: 1024 * 1024,
    });

    const { res } = createRes();
    await runSignedPost({ handler, rawBody, secret: "secret", res });

    expect(res.statusCode).toBe(200);
    expect(readBody).toHaveBeenCalledTimes(1);
    expect(bot.handleWebhook).toHaveBeenCalledTimes(1);
  });

  it("rejects invalid signature", async () => {
    const rawBody = JSON.stringify({ events: [{ type: "message" }] });
    const { bot, handler } = createPostWebhookTestHarness(rawBody);

    const { res } = createRes();
    await handler(
      { method: "POST", headers: { "x-line-signature": "bad" } } as unknown as IncomingMessage,
      res,
    );

    expect(res.statusCode).toBe(401);
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });

  it("accepts valid signature and dispatches events", async () => {
    const rawBody = JSON.stringify({ events: [{ type: "message" }] });
    const { bot, handler, secret } = createPostWebhookTestHarness(rawBody);

    const { res } = createRes();
    await runSignedPost({ handler, rawBody, secret, res });

    expect(res.statusCode).toBe(200);
    expect(bot.handleWebhook).toHaveBeenCalledWith(
      expect.objectContaining({ events: expect.any(Array) }),
    );
  });

  it("returns 500 when event processing fails and does not acknowledge with 200", async () => {
    const rawBody = JSON.stringify({ events: [{ type: "message" }] });
    const { secret } = createPostWebhookTestHarness(rawBody);
    const failingBot = {
      handleWebhook: vi.fn(async () => {
        throw new Error("transient failure");
      }),
    };
    const runtime = { log: vi.fn(), error: vi.fn(), exit: vi.fn() };
    const failingHandler = createLineNodeWebhookHandler({
      channelSecret: secret,
      bot: failingBot,
      runtime,
      readBody: async () => rawBody,
    });

    const { res } = createRes();
    await runSignedPost({ handler: failingHandler, rawBody, secret, res });

    expect(res.statusCode).toBe(500);
    expect(res.body).toBe(JSON.stringify({ error: "Internal server error" }));
    expect(failingBot.handleWebhook).toHaveBeenCalledTimes(1);
    expect(runtime.error).toHaveBeenCalledTimes(1);
  });

  it("returns 400 for invalid JSON payload even when signature is valid", async () => {
    const rawBody = "not json";
    const { bot, handler, secret } = createPostWebhookTestHarness(rawBody);

    const { res } = createRes();
    await runSignedPost({ handler, rawBody, secret, res });

    expect(res.statusCode).toBe(400);
    expect(bot.handleWebhook).not.toHaveBeenCalled();
  });
});