import { beforeEach, describe, expect, it, vi } from "vitest";
import type { Mock } from "vitest";
import type { Session } from "next-auth";

// Mirrors tests/requests.test.ts's @/auth mocking pattern — see that file's
// comment for why auth() (which reads cookies via next/headers) can't be
// exercised directly when tests import and call GET()/POST() outside of
// Next's own request-handling machinery.
vi.mock("@/auth", () => ({ auth: vi.fn() }));

import { GET, POST } from "@/app/api/employees/route";
import { prisma } from "@/lib/prisma";
import { auth } from "@/auth";

const mockedAuth = auth as unknown as Mock<() => Promise<Session | null>>;

const testSession: Session = {
  user: { id: "test-user-id" },
  expires: new Date(Date.now() + 60 * 60 * 1000).toISOString(),
};

function postRequest(body: unknown): Request {
  return new Request("http://localhost/api/employees", {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify(body),
  });
}

beforeEach(async () => {
  // Each test starts from an empty table so listing/order assertions are
  // deterministic.
  await prisma.employee.deleteMany();
  // Default to a logged-in session — the tests below exercise business
  // logic, not auth gating (that's covered by the "auth gating" describe
  // block further down).
  mockedAuth.mockResolvedValue(testSession);
});

describe("POST /api/employees", () => {
  it("creates an employee with no manager on valid input", async () => {
    const res = await POST(postRequest({ name: "Alice Nguyen", department: "IT" }));

    expect(res.status).toBe(201);
    const body = await res.json();

    expect(body).toMatchObject({
      name: "Alice Nguyen",
      department: "IT",
      manager_id: null,
    });
    expect(typeof body.id).toBe("string");
    expect(body.id.length).toBeGreaterThan(0);
    expect(typeof body.created_at).toBe("string");
    expect(Number.isNaN(Date.parse(body.created_at))).toBe(false);
  });

  it("creates an employee with a valid managerId reference", async () => {
    const managerRes = await POST(postRequest({ name: "Bob Tran", department: "IT" }));
    const manager = await managerRes.json();

    const res = await POST(
      postRequest({ name: "Alice Nguyen", department: "IT", managerId: manager.id })
    );

    expect(res.status).toBe(201);
    const body = await res.json();
    expect(body.manager_id).toBe(manager.id);
  });

  it("rejects an empty name", async () => {
    const res = await POST(postRequest({ name: "", department: "IT" }));

    expect(res.status).toBe(400);
    const body = await res.json();
    expect(typeof body.error).toBe("string");
    expect(body.error.length).toBeGreaterThan(0);
  });

  it("rejects an empty department", async () => {
    const res = await POST(postRequest({ name: "Alice Nguyen", department: "" }));

    expect(res.status).toBe(400);
    const body = await res.json();
    expect(typeof body.error).toBe("string");
    expect(body.error.length).toBeGreaterThan(0);
  });

  it("rejects a managerId that is not a valid UUID", async () => {
    const res = await POST(
      postRequest({ name: "Alice Nguyen", department: "IT", managerId: "not-a-uuid" })
    );

    expect(res.status).toBe(400);
    const body = await res.json();
    expect(body.error).toMatch(/managerId/i);
  });

  it("rejects a managerId that is a well-formed UUID but doesn't reference an existing employee", async () => {
    const res = await POST(
      postRequest({
        name: "Alice Nguyen",
        department: "IT",
        managerId: "00000000-0000-0000-0000-000000000000",
      })
    );

    expect(res.status).toBe(400);
    const body = await res.json();
    expect(body.error).toMatch(/managerId/i);
    expect(body.error).toMatch(/does not reference an existing employee/i);
  });

  it("allows an employee to reference itself as manager (not disallowed by the data model)", async () => {
    // Two-step: create the row first (no self-FK possible on insert since
    // the id doesn't exist yet), then verify the FK accepts an update to
    // point at itself, directly via Prisma (no PATCH endpoint exists yet —
    // this is a data-model sanity check, not an API contract test).
    const created = await prisma.employee.create({
      data: { name: "Self Manager", department: "IT" },
    });
    const updated = await prisma.employee.update({
      where: { id: created.id },
      data: { managerId: created.id },
    });
    expect(updated.managerId).toBe(created.id);
  });
});

describe("GET /api/employees", () => {
  it("lists created employees, newest first", async () => {
    await POST(postRequest({ name: "Alice Nguyen", department: "IT" }));
    // Ensure a distinct created_at ordering even on fast filesystems/clocks.
    await new Promise((resolve) => setTimeout(resolve, 5));
    await POST(postRequest({ name: "Bob Tran", department: "Finance" }));

    const res = await GET();
    expect(res.status).toBe(200);

    const body = await res.json();
    expect(Array.isArray(body)).toBe(true);
    expect(body).toHaveLength(2);

    // newest first
    expect(body[0]).toMatchObject({ name: "Bob Tran", department: "Finance" });
    expect(body[1]).toMatchObject({ name: "Alice Nguyen", department: "IT" });
  });

  it("returns an empty list when there are no employees", async () => {
    const res = await GET();
    expect(res.status).toBe(200);
    const body = await res.json();
    expect(body).toEqual([]);
  });
});

describe("auth gating on /api/employees", () => {
  // Mirrors tests/requests.test.ts's "auth gating" block — only checks
  // session presence, per the flat permission model (no role/permission
  // logic).
  it("POST /api/employees returns 401 without a session", async () => {
    mockedAuth.mockResolvedValue(null);

    const res = await POST(postRequest({ name: "Alice Nguyen", department: "IT" }));

    expect(res.status).toBe(401);
    const body = await res.json();
    expect(body).toEqual({ error: "Unauthorized" });

    // And it must not have created anything.
    const remaining = await prisma.employee.findMany();
    expect(remaining).toHaveLength(0);
  });

  it("GET /api/employees returns 401 without a session", async () => {
    mockedAuth.mockResolvedValue(null);

    const res = await GET();

    expect(res.status).toBe(401);
    const body = await res.json();
    expect(body).toEqual({ error: "Unauthorized" });
  });
});