import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";

import * as db from "./offlineStore";
import * as sync from "./syncEngine";
import type { NoteMeta, Notebook } from "./types";

/* A stub transport. `req()` only ever touches status, ok and json(), so a plain
 * object is enough and keeps the tests free of undici/jsdom differences. */
type Reply = { status: number; body?: unknown };
const reply = ({ status, body = {} }: Reply) => ({
  status,
  ok: status >= 200 && status < 300,
  json: async () => body,
});

let calls: Array<{ method: string; url: string; body: unknown }> = [];
let handler: (method: string, url: string, body: unknown) => Reply | Promise<Reply>;

function installFetch() {
  vi.stubGlobal(
    "fetch",
    vi.fn(async (url: string, opts: RequestInit = {}) => {
      const method = opts.method || "GET";
      const body = opts.body ? JSON.parse(opts.body as string) : undefined;
      calls.push({ method, url, body });
      return reply(await handler(method, url, body));
    })
  );
}

const succeed = () => {
  handler = () => ({ status: 200, body: { id: "server-id" } });
};
const failWith = (status: number, body: unknown = { error: "nope" }) => {
  handler = () => ({ status, body });
};
const respondWith = (body: unknown) => {
  handler = () => ({ status: 200, body });
};
const failTransport = () => {
  vi.stubGlobal(
    "fetch",
    vi.fn(async () => {
      throw new TypeError("Failed to fetch");
    })
  );
};

const note = (id: string, over: Partial<NoteMeta> = {}): NoteMeta => ({
  id,
  title: `Note ${id}`,
  folderId: "nb1",
  starred: false,
  trashed: false,
  createdAt: "2026-01-01T00:00:00.000Z",
  updatedAt: "2026-01-01T00:00:00.000Z",
  ...over,
});
const notebook = (id: string, over: Partial<Notebook> = {}): Notebook => ({
  id,
  name: `NB ${id}`,
  cover: 0,
  sortOrder: 0,
  ...over,
});

beforeEach(async () => {
  await db.clearAll();
  calls = [];
  succeed();
  installFetch();
  sync.__testing.setToken("test-token");
  sync.__testing.setOnline(true);
  sync.__testing.resetPendingWrites();
  vi.spyOn(console, "warn").mockImplementation(() => {});
  vi.spyOn(console, "error").mockImplementation(() => {});
  vi.spyOn(console, "info").mockImplementation(() => {});
});

afterEach(() => {
  // Restored here as well as in each test: a timed-out test never runs its own
  // cleanup, and leaked fake timers would hang every hook after it.
  vi.useRealTimers();
  vi.unstubAllGlobals();
  vi.restoreAllMocks();
});

/** Fakes only setTimeout, so IndexedDB keeps working while the debounce does not. */
const withFakeDebounce = async (fn: () => Promise<void>) => {
  vi.useFakeTimers({ toFake: ["setTimeout", "clearTimeout"] });
  try {
    await fn();
  } finally {
    vi.useRealTimers();
  }
};

describe("flushQueue", () => {
  it("removes an entry once the server accepted it", async () => {
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });
    await sync.__testing.flushQueue();
    expect(await db.getQueueSize()).toBe(0);
    expect(calls.map((c) => `${c.method} ${c.url}`)).toEqual(["DELETE /api/notes/n1"]);
  });

  it("keeps a failed entry queued and counts the attempt — losing it silently ate offline edits", async () => {
    failWith(500);
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });
    await sync.__testing.flushQueue();

    const [entry] = await db.peekQueue();
    expect(entry).toBeDefined();
    expect(entry!.attempts).toBe(1);
    expect(entry!.action).toBe("trashNote");
  });

  it("retries across flushes and gives up only after repeated failures", async () => {
    failWith(500);
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });

    for (let i = 1; i <= 4; i++) {
      await sync.__testing.flushQueue();
      const [entry] = await db.peekQueue();
      expect(entry!.attempts).toBe(i);
    }

    // Fifth failure hits the cap; the entry is dropped so it cannot wedge the queue.
    await sync.__testing.flushQueue();
    expect(await db.getQueueSize()).toBe(0);
  });

  it("stops at the first transport failure and keeps everything for later", async () => {
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });
    await db.enqueue({ action: "trashNote", data: { id: "n2" } });
    failTransport();

    await sync.__testing.flushQueue();

    expect(await db.getQueueSize()).toBe(2);
    const entries = await db.peekQueue();
    // Nothing is counted as a failed attempt: being offline is not the entry's fault.
    expect(entries.every((e) => e.attempts === undefined)).toBe(true);
  });

  it("propagates an auth failure and leaves the queue untouched", async () => {
    failWith(401);
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });

    await expect(sync.__testing.flushQueue()).rejects.toThrow("AUTH");
    expect(await db.getQueueSize()).toBe(1);
  });

  it("processes entries in the order they were queued", async () => {
    await db.enqueue({ action: "trashNote", data: { id: "first" } });
    await db.enqueue({ action: "trashNote", data: { id: "second" } });
    await sync.__testing.flushQueue();
    expect(calls.map((c) => c.url)).toEqual(["/api/notes/first", "/api/notes/second"]);
  });

  it("does nothing while signed out", async () => {
    sync.__testing.setToken(null);
    await db.enqueue({ action: "trashNote", data: { id: "n1" } });
    await sync.__testing.flushQueue();
    expect(calls.length).toBe(0);
    expect(await db.getQueueSize()).toBe(1);
  });

  it("repoints notes at the server id when a queued notebook is finally created", async () => {
    await db.putNotebook(notebook("nb_local", { _pendingCreate: true }));
    await db.putNote(note("n1", { folderId: "nb_local" }));
    await db.enqueue({
      action: "createNotebook",
      data: { localId: "nb_local", name: "Later", cover: 0, sortOrder: 0 },
    });

    await sync.__testing.flushQueue();

    expect((await db.getNote("n1"))?.folderId).toBe("server-id");
    expect((await db.getAllNotebooks()).map((n) => n.id)).toEqual(["server-id"]);
  });
});

describe("fullSync", () => {
  const serverState = (notes: unknown[], notebooks: unknown[]) => {
    handler = (_method, url) => {
      if (url.endsWith("/notebooks")) return { status: 200, body: notebooks };
      if (url.endsWith("/notes/trash")) return { status: 200, body: [] };
      if (url.endsWith("/notes")) return { status: 200, body: notes };
      return { status: 200, body: {} };
    };
  };

  it("mirrors the server's notes and notebooks", async () => {
    serverState(
      [{ id: "s1", title: "Server note", notebook_id: "snb", created_at: "t", updated_at: "t" }],
      [{ id: "snb", name: "Server book", cover_index: 2, sort_order: 1 }]
    );
    await sync.fullSync();

    expect((await db.getAllNotes()).map((n) => n.id)).toEqual(["s1"]);
    const [nb] = await db.getAllNotebooks();
    expect(nb).toMatchObject({ id: "snb", name: "Server book", cover: 2, sortOrder: 1 });
  });

  it("keeps notes created offline that the server has never seen", async () => {
    await db.putNote(note("local_1", { _pendingCreate: true }));
    await db.putNote(note("stale_1")); // synced earlier, since deleted elsewhere
    serverState([], []);

    await sync.fullSync();

    const ids = (await db.getAllNotes()).map((n) => n.id);
    expect(ids).toContain("local_1");
    expect(ids).not.toContain("stale_1");
  });

  it("keeps notebooks created offline", async () => {
    await db.putNotebook(notebook("nb_local", { _pendingCreate: true }));
    serverState([], []);

    await sync.fullSync();

    expect((await db.getAllNotebooks()).map((n) => n.id)).toContain("nb_local");
  });

  it("drops the local-only flag once the server reports the same id", async () => {
    await db.putNote(note("s1", { _pendingCreate: true }));
    serverState(
      [{ id: "s1", title: "Now on server", notebook_id: null, created_at: "t", updated_at: "t" }],
      []
    );

    await sync.fullSync();

    const [n] = await db.getAllNotes();
    expect(n!._pendingCreate).toBeUndefined();
    expect(n!.title).toBe("Now on server");
  });

  it("leaves the local mirror intact when a server read fails midway", async () => {
    await db.putNote(note("keep"));
    await db.putNotebook(notebook("keep_nb"));
    handler = (_method, url) => {
      if (url.endsWith("/notebooks")) return { status: 200, body: [] };
      return { status: 500, body: { error: "boom" } }; // the notes read fails
    };

    await sync.fullSync();

    expect((await db.getAllNotes()).map((n) => n.id)).toEqual(["keep"]);
    expect((await db.getAllNotebooks()).map((n) => n.id)).toEqual(["keep_nb"]);
  });

  it("does nothing while signed out", async () => {
    sync.__testing.setToken(null);
    await sync.fullSync();
    expect(calls.length).toBe(0);
  });
});

describe("hasPendingWrites", () => {
  it("is false without an id", () => {
    expect(sync.hasPendingWrites(null)).toBe(false);
    expect(sync.hasPendingWrites(undefined)).toBe(false);
    expect(sync.hasPendingWrites("")).toBe(false);
  });

  it("is false for a note nobody is writing", () => {
    expect(sync.hasPendingWrites("n1")).toBe(false);
  });

  it("reports a write that is in flight — the guard that stops stale reads winning", () => {
    sync.__testing.beginWrite("n1");
    expect(sync.hasPendingWrites("n1")).toBe(true);
    expect(sync.hasPendingWrites("n2")).toBe(false);
    sync.__testing.endWrite("n1");
    expect(sync.hasPendingWrites("n1")).toBe(false);
  });

  it("stays true until the last of several overlapping writes finishes", () => {
    sync.__testing.beginWrite("n1");
    sync.__testing.beginWrite("n1");
    sync.__testing.endWrite("n1");
    expect(sync.hasPendingWrites("n1")).toBe(true);
    sync.__testing.endWrite("n1");
    expect(sync.hasPendingWrites("n1")).toBe(false);
  });

  it("covers the debounce window before a save even starts", async () => {
    await db.putNote(note("n1"));
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "typing…");
      // The request has not been sent yet, but the note must already count as busy.
      expect(sync.hasPendingWrites("n1")).toBe(true);
      await vi.runAllTimersAsync();
    });
    expect(sync.hasPendingWrites("n1")).toBe(false);
  });
});

describe("updateNoteContent", () => {
  it("writes locally before anything reaches the network", async () => {
    await db.putNote(note("n1"));
    await sync.updateNoteContent("n1", "body text");
    expect((await db.getNoteContent("n1"))?.content).toBe("body text");
    expect(calls.length).toBe(0); // still inside the debounce window
  });

  it("sends links along with the body, since the server cannot read it", async () => {
    await db.putNote(note("n1"));
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "body", ["target-1"]);
      await vi.runAllTimersAsync();
    });
    const put = calls.find((c) => c.method === "PUT");
    expect(put?.body).toMatchObject({ content: "body", links: ["target-1"] });
  });

  it("omits the links field when the caller passes none", async () => {
    await db.putNote(note("n1"));
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "body");
      await vi.runAllTimersAsync();
    });
    const put = calls.find((c) => c.method === "PUT");
    expect(put?.body).toMatchObject({ content: "body" });
    expect(put?.body).not.toHaveProperty("links");
  });

  it("sends the revision the edit was based on, so the server can spot a conflict", async () => {
    await db.putNote(note("n1"));
    await db.putNoteContent("n1", "old", null, null, "2026-01-01T10:00:00.000Z");
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "body");
      await vi.runAllTimersAsync();
    });
    const put = calls.find((c) => c.method === "PUT");
    expect((put?.body as Record<string, unknown>).baseUpdatedAt).toBe("2026-01-01T10:00:00.000Z");
  });

  it("adopts the revision the server reports, so the next save is not taken for a conflict", async () => {
    await db.putNote(note("n1"));
    await db.putNoteContent("n1", "old", null, null, "2026-01-01T10:00:00.000Z");
    respondWith({ success: true, updatedAt: "2026-01-01T11:00:00.000Z" });
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "body");
      await vi.runAllTimersAsync();
    });
    expect((await db.getNoteContent("n1"))?.updatedAt).toBe("2026-01-01T11:00:00.000Z");
  });

  it("queues the change when the request fails", async () => {
    failWith(500);
    await db.putNote(note("n1"));
    await withFakeDebounce(async () => {
      await sync.updateNoteContent("n1", "body");
      await vi.runAllTimersAsync();
    });
    const [entry] = await db.peekQueue();
    expect(entry?.action).toBe("updateNote");
  });
});

describe("loadNoteContent", () => {
  it("returns the cached body without waiting for the server", async () => {
    await db.putNoteContent("n1", "cached", null);
    const c = await sync.loadNoteContent("n1");
    expect(c.content).toBe("cached");
  });

  it("does not refresh from the server while a write is in flight", async () => {
    await db.putNoteContent("n1", "cached", null);
    sync.__testing.beginWrite("n1");
    await sync.loadNoteContent("n1");
    expect(calls.length).toBe(0);
    sync.__testing.endWrite("n1");
  });

  it("falls back to the cache when the server read fails", async () => {
    await db.putNoteContent("n1", "cached", null);
    failWith(500);
    const c = await sync.loadNoteContent("n1", { forceRemote: true });
    expect(c.content).toBe("cached");
  });

  it("returns an empty shape for a note with nothing cached and no connection", async () => {
    sync.__testing.setOnline(false);
    const c = await sync.loadNoteContent("missing");
    expect(c).toEqual({ content: "", drawingData: null, drawingStrokes: null, updatedAt: null });
    sync.__testing.setOnline(true);
  });
});

describe("offline behaviour", () => {
  beforeEach(() => sync.__testing.setOnline(false));
  afterEach(() => sync.__testing.setOnline(true));

  it("creates a note locally and queues it", async () => {
    const n = await sync.createNote("nb1");
    expect(n._pendingCreate).toBe(true);
    expect(calls.length).toBe(0);
    const [entry] = await db.peekQueue();
    expect(entry?.action).toBe("createNote");
  });

  it("creates a notebook locally, flagged so fullSync will not drop it", async () => {
    const nb = await sync.createNotebook({ name: "Later", cover: 1 });
    expect(nb._pendingCreate).toBe(true);
    expect((await db.getAllNotebooks())[0]?._pendingCreate).toBe(true);
  });

  it("queues a star toggle instead of losing it", async () => {
    await db.putNote(note("n1"));
    expect(await sync.toggleNoteStar("n1")).toBe(true);
    const [entry] = await db.peekQueue();
    expect(entry?.action).toBe("updateNote");
    expect((await db.getNote("n1"))?.starred).toBe(true);
  });
});