import { expect, test, vi } from 'vitest';
import { ExponentialBackoffExternallyAbortable } from '../../source/exponential-backoff/exponential-backoff-externally-aborted.ts';
import type { ExponentialBackoffExternallyAbortableOptions } from '../../source/exponential-backoff/exponential-backoff-externally-aborted.ts';
import {
    ExponentialBackoffNumberTooSmallError,
    ExponentialBackoffStoppedRetriesError,
    ExternallyAbortedExponentialBackoffExternalSignalAbortedError,
    ExternallyAbortedExponentialBackoffInternalSignalAbortedError,
} from '../../source/exponential-backoff/errors.ts';
import { testExponentialBackoff } from './exponential-backoff-run.shared.ts';

/**
 * Tests that invalid constructor options are still rejected by the inner ExponentialBackoff.
 */
const testExternallyAbortedExponentialBackoffConstructorValidatesOptions = (): void => {
    expect(() => new ExponentialBackoffExternallyAbortable({ maxAttempts: -1 })).toThrow(ExponentialBackoffNumberTooSmallError);
};

/**
 * Tests that {@link ExponentialBackoffExternallyAbortable.abort} before `run` prevents the task from
 * ever being invoked and rejects with a stopped-retries error whose cause is the internal abort error.
 */
const testExternallyAbortedExponentialBackoffAbortBeforeRun = async (): Promise<void> => {
    const taskFn = vi.fn(async () => 'should not run');
    const onError = vi.fn();
    const abortReason = 'stopped by abort()';

    const backoff = new ExponentialBackoffExternallyAbortable({
        baseDelay: 0,
        jitter: 0,
        maxAttempts: 3,
    });

    // Abort before any attempt so the wrapper should short-circuit on the first inner call.
    backoff.abort(abortReason);

    try {
        await backoff.run(taskFn, { onError });
        expect.fail('Expected ExponentialBackoffStoppedRetriesError to be thrown');
    } catch (error) {
        expect(error).toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        expect((error as ExponentialBackoffStoppedRetriesError).cause).toBeInstanceOf(ExternallyAbortedExponentialBackoffInternalSignalAbortedError);
        expect(((error as ExponentialBackoffStoppedRetriesError).cause as Error).cause).toEqual(new Error(abortReason));
    }

    // The user task must not run; the wrapper throws before forwarding to it.
    expect(taskFn).not.toHaveBeenCalled();

    expect(onError).not.toHaveBeenCalled();
};

/**
 * Tests that {@link ExponentialBackoffExternallyAbortable.abort} during a retry delay takes effect
 * immediately without calling the task again.
 */
const testExternallyAbortedExponentialBackoffAbortBetweenAttempts = async (): Promise<void> => {
    vi.useFakeTimers();

    try {
        const taskFn = vi.fn(async () => {
            throw new Error('retry me');
        });
        const onError = vi.fn();
        const abortReason = new Error('stopped between attempts');

        const backoff = new ExponentialBackoffExternallyAbortable({
            baseDelay: 1_000,
            jitter: 0,
            maxAttempts: 0,
        });

        const errorPromise = backoff.run(taskFn, { onError }).catch((error: unknown) => error);

        // First attempt runs immediately and fails, then a 1000ms delay is scheduled.
        await Promise.resolve();
        expect(taskFn).toHaveBeenCalledTimes(1);

        await vi.advanceTimersByTimeAsync(500);
        backoff.abort(abortReason);

        const error = await errorPromise;
        expect(error).toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        expect((error as ExponentialBackoffStoppedRetriesError).cause).toBeInstanceOf(ExternallyAbortedExponentialBackoffInternalSignalAbortedError);
        expect(((error as ExponentialBackoffStoppedRetriesError).cause as Error).cause).toBe(abortReason);

        // The user task ran only on the first attempt; the aborted second attempt never forwarded to it.
        expect(taskFn).toHaveBeenCalledTimes(1);

        expect(onError).toHaveBeenCalledOnce();
        expect(onError.mock.calls[0][0].message).toBe('retry me');
        expect(vi.getTimerCount()).toBe(0);
    } finally {
        vi.useRealTimers();
    }
};

/**
 * Tests that a constructor `abortSignal` that is already aborted prevents the task from running.
 */
const testExternallyAbortedExponentialBackoffAbortSignalAlreadyAborted = async (): Promise<void> => {
    const taskFn = vi.fn(async () => 'should not run');
    const onError = vi.fn();
    const abortReason = 'signal already aborted';

    const abortController = new AbortController();
    abortController.abort(abortReason);

    const backoff = new ExponentialBackoffExternallyAbortable({
        abortSignal: abortController.signal,
        baseDelay: 0,
        jitter: 0,
        maxAttempts: 3,
    });

    try {
        await backoff.run(taskFn, { onError });
        expect.fail('Expected ExponentialBackoffStoppedRetriesError to be thrown');
    } catch (error) {
        expect(error).toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        expect((error as ExponentialBackoffStoppedRetriesError).cause).toBeInstanceOf(ExternallyAbortedExponentialBackoffExternalSignalAbortedError);
        expect(((error as ExponentialBackoffStoppedRetriesError).cause as Error).cause).toEqual(new Error(abortReason));
    }

    expect(taskFn).not.toHaveBeenCalled();
    expect(onError).not.toHaveBeenCalled();
};

/**
 * Tests that aborting the constructor `abortSignal` interrupts the current retry delay.
 */
const testExternallyAbortedExponentialBackoffAbortSignalBetweenAttempts = async (): Promise<void> => {
    vi.useFakeTimers();

    try {
        const taskFn = vi.fn(async () => {
            throw new Error('retry me');
        });
        const onError = vi.fn();
        const abortReason = new Error('signal aborted between attempts');

        const abortController = new AbortController();
        const backoff = new ExponentialBackoffExternallyAbortable({
            abortSignal: abortController.signal,
            baseDelay: 1_000,
            jitter: 0,
            maxAttempts: 0,
        });

        const errorPromise = backoff.run(taskFn, { onError }).catch((error: unknown) => error);

        await Promise.resolve();
        expect(taskFn).toHaveBeenCalledTimes(1);

        await vi.advanceTimersByTimeAsync(500);
        abortController.abort(abortReason);

        const error = await errorPromise;
        expect(error).toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        expect((error as ExponentialBackoffStoppedRetriesError).cause).toBeInstanceOf(ExternallyAbortedExponentialBackoffExternalSignalAbortedError);
        expect(((error as ExponentialBackoffStoppedRetriesError).cause as Error).cause).toBe(abortReason);

        expect(taskFn).toHaveBeenCalledTimes(1);
        expect(onError).toHaveBeenCalledOnce();
        expect(onError.mock.calls[0][0].message).toBe('retry me');
        expect(vi.getTimerCount()).toBe(0);
    } finally {
        vi.useRealTimers();
    }
};

/**
 * Tests that a single {@link ExponentialBackoffExternallyAbortable.abort} stops every concurrent `run` on that instance.
 */
const testExternallyAbortedExponentialBackoffAbortStopsConcurrentRuns = async (): Promise<void> => {
    vi.useFakeTimers();

    try {
        const firstTaskFn = vi.fn(async () => {
            throw new Error('first run failed');
        });
        const secondTaskFn = vi.fn(async () => {
            throw new Error('second run failed');
        });
        const abortReason = new Error('stop all runs');

        // One instance is shared across concurrent runs, matching the class remark that abort stops all of them.
        const backoff = new ExponentialBackoffExternallyAbortable({
            baseDelay: 1_000,
            jitter: 0,
            maxAttempts: 0,
        });

        // Handle both rejections before aborting the shared instance.
        const firstErrorPromise = backoff.run(firstTaskFn).catch((error: unknown) => error);
        const secondErrorPromise = backoff.run(secondTaskFn).catch((error: unknown) => error);

        await Promise.resolve();
        expect(firstTaskFn).toHaveBeenCalledTimes(1);
        expect(secondTaskFn).toHaveBeenCalledTimes(1);

        backoff.abort(abortReason);

        await expect(firstErrorPromise).resolves.toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        await expect(secondErrorPromise).resolves.toBeInstanceOf(ExponentialBackoffStoppedRetriesError);

        expect(firstTaskFn).toHaveBeenCalledTimes(1);
        expect(secondTaskFn).toHaveBeenCalledTimes(1);
        expect(vi.getTimerCount()).toBe(0);
    } finally {
        vi.useRealTimers();
    }
};

/**
 * Tests that a signal supplied for one run composes with the instance-wide abort sources.
 */
const testExternallyAbortedExponentialBackoffRunSignalInterruptsDelay = async (): Promise<void> => {
    vi.useFakeTimers();

    try {
        const abortReason = new Error('stop this run');
        const abortController = new AbortController();
        const taskFn = vi.fn().mockRejectedValue(new Error('retry me'));
        const backoff = new ExponentialBackoffExternallyAbortable({
            baseDelay: 1_000,
            jitter: 0,
            maxAttempts: 0,
        });

        const errorPromise = backoff.run(taskFn, { signal: abortController.signal }).catch((error: unknown) => error);

        await Promise.resolve();
        expect(taskFn).toHaveBeenCalledOnce();

        abortController.abort(abortReason);

        const error = await errorPromise;
        expect(error).toBeInstanceOf(ExponentialBackoffStoppedRetriesError);
        expect((error as ExponentialBackoffStoppedRetriesError).cause).toBe(abortReason);
        expect(taskFn).toHaveBeenCalledOnce();
        expect(vi.getTimerCount()).toBe(0);
    } finally {
        vi.useRealTimers();
    }
};

/**
 * Tests that a successful run is unaffected by a later abort of the shared instance.
 */
const testExternallyAbortedExponentialBackoffSuccessfulRunIgnoresLaterAbort = async (): Promise<void> => {
    const taskFn = vi.fn(async () => 'success');

    const backoff = new ExponentialBackoffExternallyAbortable({
        baseDelay: 0,
        jitter: 0,
    });

    const result = await backoff.run(taskFn);

    expect(result).toBe('success');
    expect(taskFn).toHaveBeenCalledOnce();

    // Aborting after success must not throw retroactively; it only affects subsequent runs.
    backoff.abort(new Error('too late'));
};

const runTests = async (): Promise<void> => {
    const factory = (options?: Partial<ExponentialBackoffExternallyAbortableOptions>): ExponentialBackoffExternallyAbortable => {
        return new ExponentialBackoffExternallyAbortable(options);
    };

    // Shared retry/delay/stopRetries contract, run against an adapter around instance run.
    testExponentialBackoff('ExternallyAbortedExponentialBackoff', factory);

    // Behavior that only exists on the externally-aborted wrapper.
    test(
        'ExternallyAbortedExponentialBackoff: constructor still validates options',
        testExternallyAbortedExponentialBackoffConstructorValidatesOptions,
    );
    test(
        'ExternallyAbortedExponentialBackoff: abort before run stops without calling the task',
        testExternallyAbortedExponentialBackoffAbortBeforeRun,
    );
    test(
        'ExternallyAbortedExponentialBackoff: abort between attempts interrupts the delay',
        testExternallyAbortedExponentialBackoffAbortBetweenAttempts,
    );
    test(
        'ExternallyAbortedExponentialBackoff: abortSignal already aborted stops without calling the task',
        testExternallyAbortedExponentialBackoffAbortSignalAlreadyAborted,
    );
    test(
        'ExternallyAbortedExponentialBackoff: abortSignal between attempts interrupts the delay',
        testExternallyAbortedExponentialBackoffAbortSignalBetweenAttempts,
    );
    test('ExternallyAbortedExponentialBackoff: abort stops every concurrent run', testExternallyAbortedExponentialBackoffAbortStopsConcurrentRuns);
    test(
        'ExternallyAbortedExponentialBackoff: a per-run signal interrupts the delay',
        testExternallyAbortedExponentialBackoffRunSignalInterruptsDelay,
    );
    test(
        'ExternallyAbortedExponentialBackoff: successful run is unaffected by a later abort',
        testExternallyAbortedExponentialBackoffSuccessfulRunIgnoresLaterAbort,
    );
};

await runTests();