/**
 * The Session boundary.
 *
 * Phase 1 of `docs/architecture/multiplayer.md` moved the page off `game.ts` and onto a `Session`,
 * so that a server can later be substituted for the local engine without the page noticing. The
 * whole point of the change is that nothing about solitaire changed, which is a hard thing to prove
 * by playing — hence this file: the same seed driven the same way through both routes must land in
 * the same position, card for card.
 *
 * The rest of the suite covers what a remote session will have to reproduce exactly: which calls
 * fire the redraw, which signals drain, and what `capabilities` admits a local session can do that a
 * server cannot.
 */

import { describe, it } from 'node:test';
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import { join } from 'node:path';

import { actionGroups, currentActor, handPlayable, newGame, overHandLimit, submit, toSave, view } from '../src/web/game.ts';
import { createLocalSession } from '../src/web/session.ts';

/**
 * Drive a session by always taking the first offered action.
 *
 * `menu().options` and `actionGroups(game).options` are the same `legalActions` list in the same
 * order, so taking index 0 on either side is the same rule — which is what makes the two routes
 * comparable below.
 */
async function playSession(seed: number, maxTurns = 20_000) {
  const session = createLocalSession(seed);
  let turns = 0;
  for (; turns < maxTurns; turns++) {
    if (session.actor() === null) break;
    const options = session.menu().options;
    if (options.length === 0) break;
    if (!(await session.submit(options[0]!))) break;
  }
  return { session, turns };
}

/** One action through the session, first option, for tests that just need the game to move. */
async function step(session: ReturnType<typeof createLocalSession>): Promise<boolean> {
  const options = session.menu().options;
  if (options.length === 0) return false;
  return session.submit(options[0]!);
}

describe('a local session plays the same game as the calls it replaced', () => {
  it('reaches an identical position from the same seed', async () => {
    // The equivalence proof. `game.ts` directly on the left, the Session on the right, same seed and
    // same tie-breaking rule — if the boundary leaked anything the boards diverge.
    const game = newGame(77);
    for (let i = 0; i < 20_000; i++) {
      if (currentActor(game) === null) break;
      const { options } = actionGroups(game);
      if (options.length === 0) break;
      if (!submit(game, options[0]!)) break;
    }

    const { session, turns } = await playSession(77);
    assert.ok(turns > 50, `only ${turns} decisions — the game stalled`);

    const f = session.view();
    assert.equal(f.status, 'finished');
    assert.equal(f.status, view(game).status);
    assert.equal(f.day, view(game).day);
    assert.deepEqual(f.cells, view(game).cells, 'the board differs across the boundary');
    assert.deepEqual(session.save(), toSave(game), 'the histories differ across the boundary');
  });

  it('reports the same seat, actor and hand as the underlying game', () => {
    const session = createLocalSession(31);
    assert.equal(session.seat(), 0);
    assert.equal(session.actor(), currentActor(session.game));
    assert.deepEqual(session.handPlayable(), handPlayable(session.game));
    assert.equal(session.overHandLimit(), overHandLimit(session.game));
  });
});

describe('a session tells the page when to redraw', () => {
  it('notifies on an accepted intent and not on a refused one', async () => {
    const session = createLocalSession(404);
    let redraws = 0;
    session.subscribe(() => {
      redraws++;
    });

    assert.ok(await step(session));
    assert.equal(redraws, 1);

    // A refused intent leaves the game where it was, so there is nothing to redraw. This matters
    // more than it looks: a remote session will push on state change, and a page that redrew on
    // every submit would flicker on every rejection the server sends back.
    assert.equal(await session.submit({ type: 'turn.end', player: 0 } as never), false);
    assert.equal(redraws, 1);
  });

  it('stops notifying after unsubscribe', async () => {
    const session = createLocalSession(404);
    let redraws = 0;
    const off = session.subscribe(() => {
      redraws++;
    });
    assert.ok(await step(session));
    off();
    await step(session);
    assert.equal(redraws, 1);
  });
});

describe('the transient signals drain', () => {
  it('hands out cues once', async () => {
    // Cues are a moment, not a state — the Frame can be rebuilt any number of times per render, and
    // a sound that replayed on each rebuild would stutter. So they are taken, not read.
    const session = createLocalSession(88);
    for (let i = 0; i < 40; i++) {
      if (session.actor() === null) break;
      if (!(await step(session))) break;
      if (session.takeCues().length > 0) {
        assert.deepEqual(session.takeCues(), [], 'a cue was handed out twice');
        return;
      }
    }
    assert.fail('no cue was earned in 40 actions — the driver never reached a sounding event');
  });

  it('hands out a scheduled slot once', () => {
    const session = createLocalSession(88);
    session.game.scheduled = 3;
    assert.equal(session.takeScheduled(), 3);
    assert.equal(session.takeScheduled(), null, 'the timetable flash fired twice');
  });

  it('keeps the newest card badged until another draw replaces it', () => {
    // Unlike the other two this one PERSISTS: it says which card is new, not that something just
    // happened, so it survives redraws and is superseded rather than consumed.
    const session = createLocalSession(88);
    session.game.justDrawn = 'card-a';
    assert.equal(session.justDrawn(), 'card-a');
    assert.equal(session.justDrawn(), 'card-a');
  });
});

describe('undo and restore rebuild the game without leaking the replay', () => {
  it('steps back one action and refuses at the start', async () => {
    const session = createLocalSession(909);
    assert.equal(session.steps(), 0);
    assert.equal(session.undo(), false, 'undo at the start must be a no-op');

    // Cloned: `toSave` hands back the game's own history array, so holding the object would watch it
    // grow rather than record where the game was.
    const before = structuredClone(session.save());
    await step(session);
    assert.equal(session.steps(), 1);

    assert.equal(session.undo(), true);
    assert.equal(session.steps(), 0);
    assert.deepEqual(session.save(), before, 'undo did not return to the previous position');
  });

  it('drops the rebuilt game’s cues and draws', async () => {
    // Undo replays the history from the start, which re-earns every cue and re-records every draw
    // along the way. None of that is news to a player who just stepped back, so a page that read it
    // would replay a whole game of sounds and badge whichever card the replay ended on.
    const session = createLocalSession(909);
    for (let i = 0; i < 12; i++) {
      if (session.actor() === null) break;
      if (!(await step(session))) break;
    }
    session.takeCues();

    assert.equal(session.undo(), true);
    assert.deepEqual(session.takeCues(), [], 'undo replayed the game’s sounds');
    assert.equal(session.takeScheduled(), null);
    assert.equal(session.justDrawn(), null, 'undo badged a card from the replay');
  });

  it('restores to the same position with nothing badged', async () => {
    const session = createLocalSession(909);
    for (let i = 0; i < 30; i++) {
      if (session.actor() === null) break;
      if (!(await step(session))) break;
    }
    const save = session.save();
    const cells = session.view().cells;

    const fresh = createLocalSession(1);
    fresh.restore(save);
    assert.equal(fresh.seed(), save.seed, 'restore kept the session’s original seed');
    assert.equal(fresh.steps(), save.history.length);
    assert.deepEqual(fresh.view().cells, cells, 'the board differs after restore');
    assert.equal(fresh.justDrawn(), null, 'restore badged a card from the replay');
  });
});

describe('the page stays on the near side of the boundary', () => {
  const main = readFileSync(join(import.meta.dirname, '..', 'src', 'web', 'main.ts'), 'utf8');

  it('never reaches through to GameState', () => {
    // There were eleven of these, and each one was a place the page knew something a server would
    // never send it — the deck order, another player's hand, the RNG. They all had to go before a
    // `RemoteSession` could be dropped in, and the cheapest way to keep them gone is to say so here:
    // a reader that comes back is a failing test rather than a bug found in Phase 2.
    const reaches = main.match(/\b(session\.game|game)\.state\b/g) ?? [];
    assert.deepEqual(reaches, [], 'main.ts reached through the Session into GameState');
  });

  it('imports only types from game.ts', () => {
    // Everything the page DOES now goes through `session`. Values from `game.ts` — `submit`, `view`,
    // `undo` — are the local engine by another name, and importing one is how the boundary gets
    // quietly reopened. Types are fine: `Frame` and `Menu` are what a server sends.
    const lines = main.split('\n').filter((l) => l.includes("from './game.ts'"));
    assert.ok(lines.length > 0, 'the check found no game.ts import at all — it has stopped checking');
    for (const l of lines) {
      assert.match(l, /^import type /, `main.ts imports values from game.ts: ${l.trim()}`);
    }
  });
});

describe('capabilities say what only a local session can do', () => {
  it('offers undo, a local save and a new deal', () => {
    // The page hides these rather than calling them and failing. A server can offer none of them: it
    // cannot un-see what other players have already seen, it is itself the store, and dealing is the
    // lobby's job. The page reads this object instead of assuming it is local.
    assert.deepEqual(createLocalSession(1).capabilities, {
      undo: true,
      saveLocal: true,
      newGame: true,
    });
  });
});