import { test, expect } from '@playwright/test';

/**
 * Full Phase-3 gate scenario:
 *   preset-toggle → Scholar's Mate play → undo → save/reload → export → import → checkmate
 *
 * Undo is exercised on the *original* page before reload, where moveHistoryRef
 * still holds all moves since start (loadEngine resets history, so undo is only
 * meaningful there). Export/import is verified by restoring that same 8-move
 * position in a fresh browser context, then completing the Scholar's Mate.
 */
test("full game flow: preset toggle, Scholar's Mate, save/reload, export/import, undo, checkmate", async ({ page, browser }) => {

  // ── Step 1: Preset toggles ─────────────────────────────────────────────────
  await page.goto('/rules');
  // pawns-move-backward: incompatibleWith ["double-pawn-sprint"] only
  await page.locator('[data-preset="pawns-move-backward"] [data-role="toggle"]').click();
  // knights-leap-twice: incompatibleWith []
  await page.locator('[data-preset="knights-leap-twice"] [data-role="toggle"]').click();
  // These two presets are compatible — no compat warning
  await expect(page.locator('[data-testid="compat-warning"]')).not.toBeVisible();

  await page.locator('[data-action="start-new-game"]').click();
  await page.waitForURL('**/game');

  // ── Step 2: Play all 8 moves before any reload ────────────────────────────
  //
  // We play ALL 8 moves here on the pristine page so that moveHistoryRef still
  // holds the full sequence. loadEngine() resets moveHistoryRef to [], so any
  // subsequent reload/import invalidates the undo chain; doing undo NOW (before
  // the first reload) is the only way to test it correctly without source changes.
  //
  // Targeting `[data-square="${from}"] [data-piece]` places the drag origin on
  // the draggable piece element so that dragstart fires on it. The target is the
  // square div that has onDrop/onDragOver.
  const drag = async (from: string, to: string) => {
    await page
      .locator(`[data-square="${from}"] [data-piece]`)
      .dragTo(page.locator(`[data-square="${to}"]`));
  };

  // Scholar's Mate setup — moves 1-5
  await drag('e2', 'e4'); // 1. e4
  await drag('e7', 'e5'); // 1...e5
  await drag('f1', 'c4'); // 2. Bc4
  await drag('b8', 'c6'); // 2...Nc6
  await drag('d1', 'h5'); // 3. Qh5

  await expect(page.locator('[data-testid="turn-indicator"]')).toContainText('Black');

  // Continuation — moves 6-8
  await drag('d7', 'd6'); // 3...d6  (random; Qf7 still covers d7 via rank-7)
  await drag('a2', 'a3'); // 4. a3   (random)
  await drag('g8', 'f6'); // 4...Nf6?? — will be undone

  // ── Step 3: Undo Nf6, verify knight back on g8 ────────────────────────────
  // History = [e4,e5,Bc4,Nc6,Qh5,d6,a3,Nf6] → pop → [e4,e5,Bc4,Nc6,Qh5,d6,a3]
  // Rebuild replays all 7 moves from initial; g8 kingside knight is untouched
  // (only the b8 queenside knight moved to c6 in move 4).
  await page.locator('[data-action="undo"]').click();
  await expect(page.locator('[data-square="g8"] [data-piece="black-knight"]')).toBeVisible();

  // Re-play Nf6 to restore the 8-move export state (White's turn)
  await drag('g8', 'f6'); // 4...Nf6?? again

  // ── Step 4: Save named slot ────────────────────────────────────────────────
  await page.goto('/save');
  await page.fill('input[type="text"]', 'scholars-test');
  await page.locator('[data-action="save"]').click();
  await expect(page.locator('[data-testid="save-slot-scholars-test"]')).toBeVisible();

  // ── Step 5: Reload → autosave restore ─────────────────────────────────────
  // Each applyMove() calls saveAutoSave(); App.useEffect restores it on mount.
  // The last applyMove was Nf6 → autosave = 8-move state.
  // Queen on h5 and bishop on c4 are present in that state (neither moved
  // during moves 6-8).
  await page.reload();
  await page.goto('/game');
  await expect(page.locator('[data-square="h5"] [data-piece="white-queen"]')).toBeVisible();
  await expect(page.locator('[data-square="c4"] [data-piece="white-bishop"]')).toBeVisible();

  // ── Step 6: Export JSON (8-move state, White's turn) ──────────────────────
  await page.goto('/save');
  const downloadPromise = page.waitForEvent('download');
  await page.locator('[data-action="export"]').click();
  const download = await downloadPromise;
  const exportPath = `/tmp/chess-export-${Date.now()}.json`;
  await download.saveAs(exportPath);

  // ── Step 7: Import in a fresh browser context ──────────────────────────────
  const freshContext = await browser.newContext();
  const freshPage = await freshContext.newPage();
  await freshPage.goto('http://localhost:5173/save');

  // setInputFiles works on hidden inputs; onChange → FileReader → onLoad(facts)
  // → handleLoad in SaveWrapper → loadEngine → saveAutoSave → navigate('/game')
  const fileInput = freshPage.locator('input[type="file"]');
  await fileInput.setInputFiles(exportPath);
  await freshPage.waitForURL('**/game');

  // Verify the 8-move position was restored in the fresh context
  await expect(freshPage.locator('[data-square="h5"] [data-piece="white-queen"]')).toBeVisible();
  await expect(freshPage.locator('[data-square="c4"] [data-piece="white-bishop"]')).toBeVisible();

  // ── Step 8: Scholar's Mate — Qxf7# ───────────────────────────────────────
  // It is White's turn (after Black's Nf6 in the imported 8-move state).
  // h5→f7 is a 2-square diagonal via empty g6. f7 has the black f7 pawn.
  // Queen on f7 is defended by Bc4 (c4-d5-e6-f7 diagonal).
  // Black king on e8 cannot escape:
  //   d8 = own queen (occupied),  d7 = attacked by Qf7 along rank-7,
  //   e7 = attacked by Qf7 (adjacent on rank-7),  f8 = own bishop (occupied),
  //   f7 = queen (defended by Bc4).
  // Nf6 cannot capture f7 (not an L-shaped jump from f6).
  await freshPage
    .locator('[data-square="h5"] [data-piece]')
    .dragTo(freshPage.locator('[data-square="f7"]'));

  // ── Step 9: Assert checkmate ──────────────────────────────────────────────
  await expect(freshPage.locator('[data-testid="game-over"]')).toBeVisible();

  await freshContext.close();
});