package transport

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

func TestDefaultRetryPolicy(t *testing.T) {
	p := DefaultRetryPolicy()
	if p.Initial != RetryInitial {
		t.Errorf("Initial = %v, want %v", p.Initial, RetryInitial)
	}
	if p.Max != RetryMax {
		t.Errorf("Max = %v, want %v", p.Max, RetryMax)
	}
	if p.MaxAttempts != RetryMaxAttempts {
		t.Errorf("MaxAttempts = %d, want %d", p.MaxAttempts, RetryMaxAttempts)
	}
}

func TestRetrySucceedsFirstAttempt(t *testing.T) {
	calls := 0
	got, err := Do(context.Background(), DefaultRetryPolicy(),
		func(_ context.Context, attempt int) (string, bool, error) {
			calls++
			if attempt != 1 {
				t.Errorf("attempt = %d, want 1", attempt)
			}
			return "ok", true, nil
		})
	if err != nil {
		t.Fatalf("Do: %v", err)
	}
	if got != "ok" {
		t.Errorf("got = %q, want ok", got)
	}
	if calls != 1 {
		t.Errorf("calls = %d, want 1", calls)
	}
}

func TestRetryIdempotentVerbRetries(t *testing.T) {
	calls := 0
	_, err := Do(context.Background(), DefaultRetryPolicy(),
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", true, errors.New("connection refused")
		})
	if err == nil {
		t.Fatal("expected error after exhausting attempts")
	}
	if calls != RetryMaxAttempts {
		t.Errorf("calls = %d, want %d", calls, RetryMaxAttempts)
	}
}

func TestRetryWithIdempotencyKeyRetries(t *testing.T) {
	calls := 0
	ctx := WithIdempotencyKey(context.Background(), "key-1")
	_, err := Do(ctx, DefaultRetryPolicy(),
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", false, errors.New("i/o timeout")
		})
	if err == nil {
		t.Fatal("expected error after exhausting attempts")
	}
	if calls != RetryMaxAttempts {
		t.Errorf("calls = %d, want %d (idempotency key enables retry)", calls, RetryMaxAttempts)
	}
}

func TestRetryMaxAttemptsReached(t *testing.T) {
	p := RetryPolicy{Initial: time.Millisecond, Max: 5 * time.Millisecond, MaxAttempts: 3}
	calls := 0
	_, err := Do(context.Background(), p,
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", true, errors.New("EOF")
		})
	if err == nil {
		t.Fatal("expected error")
	}
	if !IsTransient(err) {
		t.Errorf("expected transient error, got %v", err)
	}
	if calls != 3 {
		t.Errorf("calls = %d, want 3", calls)
	}
}

func TestRetryZeroMaxAttemptsDefaults(t *testing.T) {
	calls := 0
	p := RetryPolicy{}
	_, err := Do(context.Background(), p,
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "ok", true, nil
		})
	if err != nil {
		t.Fatalf("Do: %v", err)
	}
	if calls != 1 {
		t.Errorf("calls = %d, want 1", calls)
	}
}

func TestRetryNonTransientIdempotentRetries(t *testing.T) {
	calls := 0
	_, err := Do(context.Background(), DefaultRetryPolicy(),
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", true, errors.New("invalid spec")
		})
	if err == nil {
		t.Fatal("expected error")
	}
	if calls != RetryMaxAttempts {
		t.Errorf("calls = %d, want %d (non-transient idempotent still retries)", calls, RetryMaxAttempts)
	}
}

func TestRetryTransientNonIdempotentNoKeyBails(t *testing.T) {
	calls := 0
	_, err := Do(context.Background(), DefaultRetryPolicy(),
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", false, errors.New("connection refused")
		})
	if err == nil {
		t.Fatal("expected error")
	}
	if calls != 1 {
		t.Errorf("calls = %d, want 1 (transient+non-idempotent+no key = bail)", calls)
	}
}

func TestRetryContextCancelledMidBackoff(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	p := RetryPolicy{Initial: 100 * time.Millisecond, Max: time.Second, MaxAttempts: 5}
	calls := 0
	go func() {
		time.Sleep(20 * time.Millisecond)
		cancel()
	}()
	_, err := Do(ctx, p,
		func(_ context.Context, _ int) (string, bool, error) {
			calls++
			return "", true, errors.New("connection refused")
		})
	if err == nil {
		t.Fatal("expected error")
	}
	if !errors.Is(err, context.Canceled) {
		t.Errorf("expected context.Canceled, got %v", err)
	}
}

func TestBackoffGrowsExponentially(t *testing.T) {
	initial := 10 * time.Millisecond
	max := 1 * time.Second
	d1 := backoff(initial, max, 1)
	d2 := backoff(initial, max, 2)
	d3 := backoff(initial, max, 3)
	if d1 < 0 {
		t.Errorf("backoff(1) = %v, want >= 0", d1)
	}
	if d2 < d1 {
		t.Errorf("backoff(2)=%v < backoff(1)=%v (should grow)", d2, d1)
	}
	if d3 < d2 {
		t.Errorf("backoff(3)=%v < backoff(2)=%v (should grow)", d3, d2)
	}
}

func TestBackoffCapsAtMax(t *testing.T) {
	initial := 100 * time.Millisecond
	max := 200 * time.Millisecond
	d := backoff(initial, max, 10)
	if d > max+max/2 {
		t.Errorf("backoff(10) = %v, want <= ~max=%v", d, max)
	}
}

func TestContains(t *testing.T) {
	cases := []struct {
		s, sub string
		want   bool
	}{
		{"hello world", "world", true},
		{"hello", "xyz", false},
		{"hello", "", true},
		{"", "", true},
		{"abc", "abcd", false},
	}
	for _, c := range cases {
		if got := contains(c.s, c.sub); got != c.want {
			t.Errorf("contains(%q, %q) = %v, want %v", c.s, c.sub, got, c.want)
		}
	}
}