import {
    CallToPlayAsyncScope,
    type CallToPlayRetryCallback,
    type CallToPlayRetryScheduler,
} from '../src/lib/callToPlayOwnership.ts';
import { type AsyncCleanup } from '../src/lib/asyncOwnership.ts';

const assertEquals = <T>(actual: T, expected: T, message: string) => {
    if (actual !== expected) {
        throw new Error(`${message}: expected ${expected}, got ${actual}`);
    }
};

const assertArrayEquals = <T>(actual: T[], expected: T[], message: string) => {
    assertEquals(JSON.stringify(actual), JSON.stringify(expected), message);
};

const deferred = <T>() => {
    let resolve!: (value: T) => void;
    let reject!: (reason: unknown) => void;
    const promise = new Promise<T>((resolvePromise, rejectPromise) => {
        resolve = resolvePromise;
        reject = rejectPromise;
    });
    return { promise, resolve, reject };
};

interface ScheduledRetry {
    callback: CallToPlayRetryCallback;
    cancelled: boolean;
}

class ManualRetryScheduler {
    private readonly scheduled: ScheduledRetry[] = [];

    public readonly schedule: CallToPlayRetryScheduler = callback => {
        const retry = { callback, cancelled: false };
        this.scheduled.push(retry);
        return () => {
            retry.cancelled = true;
        };
    };

    public pendingCount(): number {
        return this.scheduled.filter(retry => !retry.cancelled).length;
    }

    public fireNext(): Promise<void> {
        const index = this.scheduled.findIndex(retry => !retry.cancelled);
        if (index < 0) throw new Error('no retry is scheduled');
        const [retry] = this.scheduled.splice(index, 1);
        return retry.callback();
    }
}

const noRetry: CallToPlayRetryScheduler = () => () => {};

Deno.test('queued listener callbacks are ignored and a late listener unlistens after disposal', async () => {
    const scope = new CallToPlayAsyncScope(noRetry);
    const listener = deferred<AsyncCleanup>();
    const cleanupDone = deferred<void>();
    const published: string[] = [];
    let callback: ((value: string) => void) | undefined;
    let unlistens = 0;

    const registration = scope.registerListener(() => {
        callback = scope.guard(value => published.push(value));
        return listener.promise;
    });

    const disposal = scope.dispose();
    callback?.('queued-after-dispose');
    listener.resolve(async () => {
        unlistens += 1;
        await cleanupDone.promise;
    });

    await Promise.resolve();
    assertEquals(unlistens, 1, 'the listener should unlisten as soon as registration resolves');
    cleanupDone.resolve();
    assertEquals(await registration, false, 'the late registration should report cancellation');
    await disposal;
    assertArrayEquals(published, [], 'a queued listener must not publish after disposal');
});

Deno.test('retry attempts never overlap and stop after readiness', async () => {
    const scheduler = new ManualRetryScheduler();
    const scope = new CallToPlayAsyncScope(scheduler.schedule);
    const first = deferred<boolean>();
    const second = deferred<boolean>();
    const firstStarted = deferred<void>();
    const secondStarted = deferred<void>();
    let attempts = 0;

    scope.startRetry(() => {
        attempts += 1;
        if (attempts === 1) {
            firstStarted.resolve();
            return first.promise;
        }
        secondStarted.resolve();
        return second.promise;
    }, 2_000);

    assertEquals(scheduler.pendingCount(), 1, 'starting retry should schedule one attempt');
    const firstRun = scheduler.fireNext();
    await firstStarted.promise;
    assertEquals(attempts, 1, 'the first retry should start');
    assertEquals(scheduler.pendingCount(), 0, 'no retry should queue while one is in flight');

    scope.startRetry(() => Promise.resolve(false), 2_000);
    assertEquals(scheduler.pendingCount(), 0, 'starting again must not overlap the in-flight retry');

    first.resolve(false);
    await firstRun;
    assertEquals(scheduler.pendingCount(), 1, 'a failed attempt should schedule its successor');

    const secondRun = scheduler.fireNext();
    await secondStarted.promise;
    assertEquals(attempts, 2, 'the successor should start only after the first settled');
    assertEquals(scheduler.pendingCount(), 0, 'the second in-flight retry must be exclusive');

    second.resolve(true);
    await secondRun;
    assertEquals(scheduler.pendingCount(), 0, 'readiness should stop the retry loop');
    await scope.dispose();
});

Deno.test('disposal waits for an in-flight retry attempt', async () => {
    const scheduler = new ManualRetryScheduler();
    const scope = new CallToPlayAsyncScope(scheduler.schedule);
    const attempt = deferred<boolean>();
    const started = deferred<void>();
    let disposalSettled = false;

    scope.startRetry(() => {
        started.resolve();
        return attempt.promise;
    }, 2_000);
    const retry = scheduler.fireNext();
    await started.promise;

    const disposal = scope.dispose().then(() => {
        disposalSettled = true;
    });
    await Promise.resolve();
    assertEquals(disposalSettled, false, 'disposal must join the running retry');

    attempt.resolve(false);
    await retry;
    await disposal;
    assertEquals(disposalSettled, true, 'disposal should settle after the retry exits');
    assertEquals(scheduler.pendingCount(), 0, 'a disposed retry must not schedule a successor');
});

Deno.test('late snapshots and actions cannot publish after their scope is disposed', async () => {
    const scope = new CallToPlayAsyncScope(noRetry);
    const snapshot = deferred<string>();
    const action = deferred<boolean>();
    const publications: string[] = [];
    let snapshotStarts = 0;
    let actionStarts = 0;

    const pendingSnapshot = scope.applyIfActive(
        () => {
            snapshotStarts += 1;
            return snapshot.promise;
        },
        value => publications.push(`snapshot:${value}`),
    );
    const pendingAction = scope.applyIfActive(
        () => {
            actionStarts += 1;
            return action.promise;
        },
        value => publications.push(`action:${value}`),
    );

    const disposal = scope.dispose();
    snapshot.resolve('stale');
    action.resolve(true);

    assertEquals(await pendingSnapshot, false, 'the late snapshot should report cancellation');
    assertEquals(await pendingAction, false, 'the late action should report cancellation');
    await disposal;
    assertArrayEquals(publications, [], 'late work must not publish into a disposed hook');

    const postDisposeAction = await scope.applyIfActive(
        () => {
            actionStarts += 1;
            return Promise.resolve(true);
        },
        value => publications.push(`post-dispose:${value}`),
    );
    assertEquals(postDisposeAction, false, 'an action must not start after disposal');
    assertEquals(snapshotStarts, 1, 'the snapshot should start exactly once');
    assertEquals(actionStarts, 1, 'only the pre-disposal action should start');
    assertArrayEquals(publications, [], 'post-disposal actions must not publish');
});

Deno.test('an older action completion cannot overwrite a newer action status', async () => {
    const scope = new CallToPlayAsyncScope(noRetry);
    const older = deferred<boolean>();
    const newer = deferred<boolean>();
    const statuses: string[] = [];

    const publishOlder = scope.guardLatestAction((accepted: boolean) => {
        statuses.push(`older:${accepted}`);
    });
    const olderAction = scope.applyIfActive(
        () => older.promise,
        accepted => publishOlder(accepted),
    );

    const publishNewer = scope.guardLatestAction((accepted: boolean) => {
        statuses.push(`newer:${accepted}`);
    });
    const newerAction = scope.applyIfActive(
        () => newer.promise,
        accepted => publishNewer(accepted),
    );

    newer.resolve(true);
    assertEquals(await newerAction, true, 'the newer action should complete normally');
    older.resolve(false);
    assertEquals(await olderAction, true, 'the older action result should still complete');

    assertArrayEquals(statuses, ['newer:true'], 'only the newest action may publish status');
    await scope.dispose();
});

Deno.test('backend mutations start in user order even when the first invoke is delayed', async () => {
    const scope = new CallToPlayAsyncScope(noRetry);
    const first = deferred<string>();
    const second = deferred<string>();
    const started: string[] = [];
    const applied: string[] = [];

    const firstMutation = scope.applyMutationIfActive(
        () => {
            started.push('display-name:older');
            return first.promise;
        },
        value => applied.push(value),
    );
    const secondMutation = scope.applyMutationIfActive(
        () => {
            started.push('action:newer');
            return second.promise;
        },
        value => applied.push(value),
    );

    await Promise.resolve();
    assertArrayEquals(started, ['display-name:older'], 'the newer mutation must remain queued');

    first.resolve('older-applied');
    assertEquals(await firstMutation, true, 'the first mutation should publish while active');
    await Promise.resolve();
    assertArrayEquals(
        started,
        ['display-name:older', 'action:newer'],
        'the second backend invoke must start after the first settles',
    );

    second.resolve('newer-applied');
    assertEquals(await secondMutation, true, 'the second mutation should publish while active');
    assertArrayEquals(
        applied,
        ['older-applied', 'newer-applied'],
        'mutation results should publish in backend order',
    );
    await scope.dispose();
});

Deno.test('disposal drains admitted mutations and rejects later admission', async () => {
    const scope = new CallToPlayAsyncScope(noRetry);
    const first = deferred<void>();
    const second = deferred<void>();
    const started: string[] = [];
    const publications: string[] = [];

    const firstMutation = scope.applyMutationIfActive(
        () => {
            started.push('first');
            return first.promise;
        },
        () => publications.push('first'),
    );
    const secondMutation = scope.applyMutationIfActive(
        () => {
            started.push('second');
            return second.promise;
        },
        () => publications.push('second'),
    );
    await Promise.resolve();

    let disposed = false;
    const disposal = scope.dispose().then(() => {
        disposed = true;
    });
    const rejected = await scope.applyMutationIfActive(
        () => {
            started.push('rejected');
            return Promise.resolve();
        },
        () => publications.push('rejected'),
    );
    assertEquals(rejected, false, 'a mutation submitted after disposal must be rejected');
    assertEquals(disposed, false, 'disposal must wait for admitted mutations');

    first.resolve();
    assertEquals(await firstMutation, false, 'disposed scopes suppress the first result');
    await Promise.resolve();
    assertArrayEquals(started, ['first', 'second'], 'the admitted successor must still run');
    assertEquals(disposed, false, 'disposal must also wait for the admitted successor');

    second.resolve();
    assertEquals(await secondMutation, false, 'disposed scopes suppress the second result');
    await disposal;
    assertEquals(disposed, true, 'disposal should settle after the admitted queue drains');
    assertArrayEquals(started, ['first', 'second'], 'no post-disposal mutation may start');
    assertArrayEquals(publications, [], 'disposed mutation results must not publish');
});