import { afterEach, describe, expect, it, vi } from 'vitest';
// Import from source (not the built barrel/dist) for consistency with the rest
// of the docmost-client test wave and to avoid running stale compiled output.
import { collectRecentSince } from '../packages/docmost-client/src/client.js';

/**
 * Edge-case unit tests for `collectRecentSince`, complementing
 * `test/recent-since.test.ts` (which covers the happy / cap / dedup / order
 * paths). These tests target the defensive `!= null` guards, the exact cutoff
 * boundary, and a mid-walk null cursor — none of which the existing suite
 * exercises. `fetchPage` is always faked; no network is involved.
 *
 * Imported `from 'docmost-client'` (the built barrel) to match the behaviour
 * the existing suite asserts against.
 */

// An item may be malformed (missing id and/or updatedAt), so every field is
// optional here on purpose — that is exactly what these tests probe.
type Item = { id?: string; updatedAt?: string };

/**
 * Build a fake `fetchPage` from an ordered list of pages. Page i's nextCursor
 * points at page i+1; the last page has no cursor (null). Tracks the call
 * count and the sequence of cursors the function asked for, so we can assert
 * the walk stopped where we expect.
 */
function fakeServer(pages: Item[][]) {
  let calls = 0;
  const cursorsRequested: (string | null)[] = [];
  const cursorFor = (i: number) => (i < pages.length - 1 ? `c${i}` : null);
  const fetchPage = async (cursor: string | null) => {
    // null -> page 0, "cN" -> page N+1 (mirrors the existing suite's helper).
    const idx = cursor === null ? 0 : Number(cursor.slice(1)) + 1;
    calls++;
    cursorsRequested.push(cursor);
    const items = pages[idx] ?? [];
    return { items, nextCursor: cursorFor(idx) };
  };
  return {
    fetchPage,
    get calls() {
      return calls;
    },
    get cursorsRequested() {
      return cursorsRequested;
    },
  };
}

afterEach(() => {
  vi.restoreAllMocks();
});

describe('collectRecentSince — malformed items (the `!= null` guards)', () => {
  it('keeps an item with no updatedAt without tripping the cutoff', async () => {
    // The item with no `updatedAt` must skip the `<= cutoff` comparison
    // entirely (guard: item.updatedAt != null) and therefore be collected
    // rather than terminating the scan. The genuinely-old 'old' item that
    // follows it is what stops the walk.
    const server = fakeServer([
      [
        { id: 'a', updatedAt: '2026-06-16T10:00:00Z' },
        { id: 'no-ts' }, // no updatedAt -> cutoff check skipped, still collected
        { id: 'b', updatedAt: '2026-06-16T09:00:00Z' },
        { id: 'old', updatedAt: '2026-06-16T01:00:00Z' }, // <= cutoff -> stop
        { id: 'after', updatedAt: '2026-06-16T00:30:00Z' },
      ],
    ]);

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T05:00:00Z',
    );

    // 'no-ts' survives between the two newer items; 'old' and everything after
    // it is excluded once the cutoff is hit.
    expect(out.map((i) => i.id)).toEqual(['a', 'no-ts', 'b']);
  });

  it('keeps an item with no id and never dedups it', async () => {
    // Items without an `id` are never added to the `seen` set (guard:
    // item.id != null), so they are never deduped: every no-id item — even
    // identical ones — is collected. A no-id item must not throw on the
    // `seen.has(undefined)` path either.
    const server = fakeServer([
      [
        { id: 'a', updatedAt: '2026-06-16T10:00:00Z' },
        { updatedAt: '2026-06-16T09:30:00Z' }, // no id
        { updatedAt: '2026-06-16T09:30:00Z' }, // identical, no id -> NOT deduped
        { id: 'b', updatedAt: '2026-06-16T09:00:00Z' },
      ],
    ]);

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T01:00:00Z',
    );

    // Both no-id items are kept (length 4), proving no-id items bypass dedup.
    expect(out).toHaveLength(4);
    expect(out.map((i) => i.id)).toEqual(['a', undefined, undefined, 'b']);
  });

  it('does not let a malformed item break id-based dedup of real items', async () => {
    // A malformed (no id, no updatedAt) item appears alongside a real id that
    // overlaps across pages. The real id 'b' must still be deduped exactly
    // once, and the malformed item must not interfere with that bookkeeping.
    const server = fakeServer([
      [
        { id: 'a', updatedAt: '2026-06-16T10:00:00Z' },
        {}, // fully malformed: no id, no updatedAt
        { id: 'b', updatedAt: '2026-06-16T09:00:00Z' },
      ],
      [
        { id: 'b', updatedAt: '2026-06-16T09:00:00Z' }, // overlap -> deduped
        { id: 'c', updatedAt: '2026-06-16T08:00:00Z' },
      ],
    ]);

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T01:00:00Z',
    );

    // Real ids appear once each; the malformed item is kept once (it counts as
    // a new item, so it does not stall progress between pages).
    expect(out.map((i) => i.id)).toEqual(['a', undefined, 'b', 'c']);
    expect(server.calls).toBe(2);
  });
});

describe('collectRecentSince — exact cutoff boundary (updatedAt === sinceIso)', () => {
  it('EXCLUDES an item whose updatedAt equals sinceIso (<= is inclusive on the boundary)', async () => {
    // The comparison is `item.updatedAt <= sinceIso`, so an item exactly AT
    // the cutoff satisfies it and is treated as the stop point: that item and
    // everything after it is excluded.
    const server = fakeServer([
      [
        { id: 'a', updatedAt: '2026-06-16T06:00:00Z' },
        { id: 'boundary', updatedAt: '2026-06-16T05:00:00Z' }, // === sinceIso
        { id: 'after', updatedAt: '2026-06-16T04:00:00Z' },
      ],
      [{ id: 'never', updatedAt: '2026-06-16T03:00:00Z' }], // must not be fetched
    ]);

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T05:00:00Z',
    );

    // Only the strictly-newer 'a'; the boundary item is the cutoff and is
    // excluded, and the walk stops without fetching page 1.
    expect(out.map((i) => i.id)).toEqual(['a']);
    expect(server.calls).toBe(1);
  });

  it('returns an empty array when the very first item is exactly at the cutoff', async () => {
    // Boundary item is first on the page: the loop hits the cutoff immediately
    // and collects nothing.
    const server = fakeServer([
      [
        { id: 'boundary', updatedAt: '2026-06-16T05:00:00Z' }, // === sinceIso
        { id: 'after', updatedAt: '2026-06-16T04:00:00Z' },
      ],
    ]);

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T05:00:00Z',
    );

    expect(out).toEqual([]);
    expect(server.calls).toBe(1);
  });
});

describe('collectRecentSince — nextCursor null mid-walk before cutoff', () => {
  it('stops and returns what it has when the cursor runs out before the cutoff', async () => {
    // Both pages are entirely newer than the cutoff (so `reachedCutoff` stays
    // false), but the last page has nextCursor === null. The `if
    // (!data.nextCursor) break` must end the walk gracefully and return the
    // accumulated items — no extra fetch, no warning (cap not hit).
    const server = fakeServer([
      [
        { id: 'a', updatedAt: '2026-06-16T10:00:00Z' },
        { id: 'b', updatedAt: '2026-06-16T09:00:00Z' },
      ],
      [
        { id: 'c', updatedAt: '2026-06-16T08:00:00Z' },
        { id: 'd', updatedAt: '2026-06-16T07:00:00Z' }, // still all newer
      ],
    ]);

    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});

    const out = await collectRecentSince(
      server.fetchPage,
      '2026-06-16T01:00:00Z',
      50, // generous cap: the null cursor, not the cap, must stop the walk
    );

    // Everything from both pages, in server order; the null cursor ends it.
    expect(out.map((i) => i.id)).toEqual(['a', 'b', 'c', 'd']);
    // Exactly the two real pages were fetched (page 0 via null, page 1 via c0).
    expect(server.calls).toBe(2);
    expect(server.cursorsRequested).toEqual([null, 'c0']);
    // The cutoff was never reached, but we exhausted the feed naturally, so no
    // truncation warning is emitted.
    expect(warn).not.toHaveBeenCalled();
  });
});

describe('collectRecentSince — hardPageCap warning (re-confirm)', () => {
  it('warns once when the cap is hit before the cutoff is reached', async () => {
    // Endless feed of unique, all-newer items with a perpetual nextCursor: the
    // only stop condition is the cap, which must emit exactly one truncation
    // warning naming the cap value.
    let n = 0;
    const fetchPage = async (_cursor: string | null) => {
      const id = `id${n++}`;
      return {
        items: [{ id, updatedAt: '2026-06-16T10:00:00Z' }] as Item[],
        nextCursor: 'next', // never runs out
      };
    };

    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});

    const cap = 3;
    const out = await collectRecentSince(fetchPage, '2020-01-01T00:00:00Z', cap);

    expect(out).toHaveLength(cap);
    expect(warn).toHaveBeenCalledTimes(1);
    expect(String(warn.mock.calls[0][0])).toContain('hardPageCap=3');
  });
});