package playback

import (
	"context"
	"errors"
	"reflect"
	"testing"
	"time"
)

func testRetryPolicy(maxAttempts int) RetryPolicy {
	return RetryPolicy{
		MaxAttempts:  maxAttempts,
		InitialDelay: 500 * time.Millisecond,
		MaxDelay:     10 * time.Second,
	}
}

func TestRunWithRetryFirstAttemptSucceeds(t *testing.T) {
	attempts := 0
	err := runWithRetry(
		context.Background(),
		testRetryPolicy(3),
		func(context.Context) (bool, error) {
			attempts++
			return false, nil
		},
		func(error) bool {
			t.Fatal("shouldRetry called after successful attempt")
			return false
		},
		func(context.Context, time.Duration) error {
			t.Fatal("wait called after successful attempt")
			return nil
		},
		nil,
	)

	if err != nil {
		t.Fatalf("runWithRetry() error = %v, want nil", err)
	}
	if attempts != 1 {
		t.Fatalf("attempt count = %d, want 1", attempts)
	}
}

func TestRunWithRetryFailuresThenSuccess(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	attempts := 0
	var delays []time.Duration

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(3),
		func(context.Context) (bool, error) {
			attempts++
			if attempts < 3 {
				return false, attemptErr
			}
			return false, nil
		},
		func(error) bool { return true },
		func(_ context.Context, delay time.Duration) error {
			delays = append(delays, delay)
			return nil
		},
		nil,
	)

	if err != nil {
		t.Fatalf("runWithRetry() error = %v, want nil", err)
	}
	if attempts != 3 {
		t.Errorf("attempt count = %d, want 3", attempts)
	}
	wantDelays := []time.Duration{500 * time.Millisecond, time.Second}
	if !reflect.DeepEqual(delays, wantDelays) {
		t.Errorf("retry delays = %v, want %v", delays, wantDelays)
	}
}

func TestRunWithRetryFiniteAttemptsExhausted(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	attempts := 0
	waits := 0

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(3),
		func(context.Context) (bool, error) {
			attempts++
			return false, attemptErr
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error {
			waits++
			return nil
		},
		nil,
	)

	if !errors.Is(err, attemptErr) {
		t.Fatalf("runWithRetry() error = %v, want %v", err, attemptErr)
	}
	if attempts != 3 {
		t.Errorf("attempt count = %d, want 3", attempts)
	}
	if waits != 2 {
		t.Errorf("wait count = %d, want 2", waits)
	}
}

func TestRunWithRetryUnlimitedEventuallySucceeds(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	attempts := 0

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(0),
		func(context.Context) (bool, error) {
			attempts++
			if attempts < 20 {
				return false, attemptErr
			}
			return false, nil
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		nil,
	)

	if err != nil {
		t.Fatalf("runWithRetry() error = %v, want nil", err)
	}
	if attempts != 20 {
		t.Fatalf("attempt count = %d, want 20", attempts)
	}
}

func TestRunWithRetryStopsWhenErrorIsNotRetryable(t *testing.T) {
	attemptErr := errors.New("invalid configuration")
	attempts := 0

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(0),
		func(context.Context) (bool, error) {
			attempts++
			return false, attemptErr
		},
		func(error) bool { return false },
		func(context.Context, time.Duration) error {
			t.Fatal("wait called for non-retryable error")
			return nil
		},
		nil,
	)

	if !errors.Is(err, attemptErr) {
		t.Fatalf("runWithRetry() error = %v, want %v", err, attemptErr)
	}
	if attempts != 1 {
		t.Fatalf("attempt count = %d, want 1", attempts)
	}
}

func TestRunWithRetryReturnsCancellationFromAttempt(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	attemptErr := errors.New("attempt failed")

	err := runWithRetry(
		ctx,
		testRetryPolicy(0),
		func(context.Context) (bool, error) {
			cancel()
			return false, attemptErr
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error {
			t.Fatal("wait called after cancellation")
			return nil
		},
		nil,
	)

	if !errors.Is(err, context.Canceled) {
		t.Fatalf("runWithRetry() error = %v, want context.Canceled", err)
	}
}

func TestRunWithRetryReturnsCancellationDuringBackoff(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	attemptErr := errors.New("attempt failed")

	err := runWithRetry(
		ctx,
		testRetryPolicy(0),
		func(context.Context) (bool, error) { return false, attemptErr },
		func(error) bool { return true },
		func(ctx context.Context, _ time.Duration) error {
			cancel()
			return ctx.Err()
		},
		nil,
	)

	if !errors.Is(err, context.Canceled) {
		t.Fatalf("runWithRetry() error = %v, want context.Canceled", err)
	}
}

func TestRunWithRetryReturnsWaitError(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	waitErr := errors.New("wait failed")

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(0),
		func(context.Context) (bool, error) { return false, attemptErr },
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return waitErr },
		nil,
	)

	if !errors.Is(err, waitErr) {
		t.Fatalf("runWithRetry() error = %v, want %v", err, waitErr)
	}
}

func TestWaitForRetryReturnsCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	err := waitForRetry(ctx, time.Hour)
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("waitForRetry() error = %v, want context.Canceled", err)
	}
}

func TestRetryObserverReportsFailuresBeforeSuccess(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	attempts := 0
	var events []retryEvent

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(3),
		func(context.Context) (bool, error) {
			attempts++
			if attempts < 3 {
				return false, attemptErr
			}
			return false, nil
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		func(event retryEvent) {
			events = append(events, event)
		},
	)

	if err != nil {
		t.Fatalf("runWithRetry() error = %v, want nil", err)
	}
	if len(events) != 2 {
		t.Fatalf("event count = %d, want 2", len(events))
	}

	wantDelays := []time.Duration{500 * time.Millisecond, time.Second}
	for i, event := range events {
		wantAttempts := i + 1
		if event.FailedAttempts != wantAttempts {
			t.Errorf("event %d failed attempts = %d, want %d", i, event.FailedAttempts, wantAttempts)
		}
		if !errors.Is(event.Err, attemptErr) {
			t.Errorf("event %d error = %v, want %v", i, event.Err, attemptErr)
		}
		if event.RetryIn != wantDelays[i] {
			t.Errorf("event %d retry delay = %s, want %s", i, event.RetryIn, wantDelays[i])
		}
		if !event.WillRetry {
			t.Errorf("event %d WillRetry = false, want true", i)
		}
	}
}

func TestRetryObserverReportsExhaustion(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	var events []retryEvent

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(2),
		func(context.Context) (bool, error) { return false, attemptErr },
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		func(event retryEvent) {
			events = append(events, event)
		},
	)

	if !errors.Is(err, attemptErr) {
		t.Fatalf("runWithRetry() error = %v, want %v", err, attemptErr)
	}
	if len(events) != 2 {
		t.Fatalf("event count = %d, want 2", len(events))
	}
	if !events[0].WillRetry || events[0].RetryIn != 500*time.Millisecond {
		t.Errorf("first event = %+v, want retry after 500ms", events[0])
	}
	final := events[1]
	if final.FailedAttempts != 2 {
		t.Errorf("final failed attempts = %d, want 2", final.FailedAttempts)
	}
	if final.WillRetry {
		t.Error("final WillRetry = true, want false")
	}
	if final.RetryIn != 0 {
		t.Errorf("final retry delay = %s, want 0", final.RetryIn)
	}
	if !errors.Is(final.Err, attemptErr) {
		t.Errorf("final error = %v, want %v", final.Err, attemptErr)
	}
}

func TestRetryObserverNotCalledOnImmediateSuccess(t *testing.T) {
	observerCalls := 0
	err := runWithRetry(
		context.Background(),
		testRetryPolicy(3),
		func(context.Context) (bool, error) { return false, nil },
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		func(retryEvent) { observerCalls++ },
	)

	if err != nil {
		t.Fatalf("runWithRetry() error = %v, want nil", err)
	}
	if observerCalls != 0 {
		t.Fatalf("observer call count = %d, want 0", observerCalls)
	}
}

func TestRetryObserverNotCalledWhenAttemptCancelsContext(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	observerCalls := 0

	err := runWithRetry(
		ctx,
		testRetryPolicy(0),
		func(context.Context) (bool, error) {
			cancel()
			return false, errors.New("attempt interrupted")
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		func(retryEvent) { observerCalls++ },
	)

	if !errors.Is(err, context.Canceled) {
		t.Fatalf("runWithRetry() error = %v, want context.Canceled", err)
	}
	if observerCalls != 0 {
		t.Fatalf("observer call count = %d, want 0", observerCalls)
	}
}

func TestRunWithRetryResetsFailuresAfterStableAttempt(t *testing.T) {
	attemptErr := errors.New("attempt failed")
	attempts := 0
	var events []retryEvent

	err := runWithRetry(
		context.Background(),
		testRetryPolicy(2),
		func(context.Context) (bool, error) {
			attempts++
			switch attempts {
			case 1:
				return false, attemptErr
			case 2:
				return true, attemptErr
			default:
				return false, attemptErr
			}
		},
		func(error) bool { return true },
		func(context.Context, time.Duration) error { return nil },
		func(event retryEvent) {
			events = append(events, event)
		},
	)

	if !errors.Is(err, attemptErr) {
		t.Fatalf("runWithRetry() error = %v, want %v", err, attemptErr)
	}
	if attempts != 3 {
		t.Fatalf("attempt count = %d, want 3", attempts)
	}
	if len(events) != 3 {
		t.Fatalf("event count = %d, want 3", len(events))
	}

	wantFailedAttempts := []int{1, 1, 2}
	wantWillRetry := []bool{true, true, false}
	for i, event := range events {
		if event.FailedAttempts != wantFailedAttempts[i] {
			t.Errorf(
				"event %d failed attempts = %d, want %d",
				i,
				event.FailedAttempts,
				wantFailedAttempts[i],
			)
		}
		if event.WillRetry != wantWillRetry[i] {
			t.Errorf(
				"event %d WillRetry = %t, want %t",
				i,
				event.WillRetry,
				wantWillRetry[i],
			)
		}
	}
}