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

import { createCursorPaginationRuntime } from "../../src/adapters/query-cache/cursor-pagination-runtime.ts";

const profile = {
  profileId: "bounded-cursor-v1",
  maxPages: 3,
  maxTotalItems: 4,
  maxEstimatedBytes: 1_024,
  maxCursorBytes: 64,
  allowSparsePage: false,
} as const;

describe("bounded cursor pagination runtime", () => {
  it("loads a stable finite chain without exposing cursors in its value", async () => {
    const loadPage = vi
      .fn()
      .mockResolvedValueOnce({
        ok: true,
        value: {
          items: ["one"],
          nextCursor: "cursor-2",
          hasMore: true,
          snapshotToken: "snapshot-a",
        },
      })
      .mockResolvedValueOnce({
        ok: true,
        value: {
          items: ["two"],
          nextCursor: null,
          hasMore: false,
          snapshotToken: "snapshot-a",
        },
      });
    const runtime = createCursorPaginationRuntime({
      definitionId: "LIST_ALL",
      profile,
      loadPage,
    });

    await expect(runtime.loadAll({})).resolves.toEqual({
      ok: true,
      value: ["one", "two"],
    });
    expect(loadPage.mock.calls.map(([cursor]) => cursor)).toEqual([
      null,
      "cursor-2",
    ]);
  });

  it.each([
    {
      page: {
        items: [],
        nextCursor: "next",
        hasMore: true,
        snapshotToken: null,
      },
      code: "PAGINATION_PAGE_INVALID",
    },
    {
      page: {
        items: ["one"],
        nextCursor: null,
        hasMore: true,
        snapshotToken: null,
      },
      code: "PAGINATION_PAGE_INVALID",
    },
  ])("rejects invalid page invariants", async ({ page, code }) => {
    const runtime = createCursorPaginationRuntime({
      definitionId: "LIST_ALL",
      profile,
      loadPage: async () => ({ ok: true, value: page }),
    });
    await expect(runtime.loadAll({})).resolves.toMatchObject({
      ok: false,
      error: { kind: "PAGINATION_CONTRACT_VIOLATION", code },
    });
  });

  it("rejects cursor loops and snapshot drift", async () => {
    const loop = createCursorPaginationRuntime({
      definitionId: "LIST_ALL",
      profile,
      loadPage: async () => ({
        ok: true,
        value: {
          items: ["one"],
          nextCursor: "same",
          hasMore: true,
          snapshotToken: null,
        },
      }),
    });
    await expect(loop.loadAll({})).resolves.toMatchObject({
      ok: false,
      error: { code: "PAGINATION_CURSOR_LOOP" },
    });

    let page = 0;
    const drift = createCursorPaginationRuntime({
      definitionId: "LIST_ALL",
      profile,
      loadPage: async () => ({
        ok: true,
        value: {
          items: [String(page)],
          nextCursor: page++ === 0 ? "next" : null,
          hasMore: page === 1,
          snapshotToken: page === 1 ? "snapshot-a" : "snapshot-b",
        },
      }),
    });
    await expect(drift.loadAll({})).resolves.toMatchObject({
      ok: false,
      error: { code: "PAGINATION_SNAPSHOT_CHANGED" },
    });
  });
});