package delivery_test

import (
	"context"
	"errors"
	"orchestra/internal/delivery"
	"orchestra/internal/domain"
	"testing"
	"time"
)

type fakeSender struct {
	fail bool
	sent []string
}

func (f *fakeSender) Send(_ context.Context, msg string) error {
	if f.fail {
		return errors.New("boom")
	}
	f.sent = append(f.sent, msg)
	return nil
}

// TestFanoutContinuesAfterSendError guards S4: a single sender error must
// not kill the fanout goroutine or stall the cursor for the other senders.
func TestFanoutContinuesAfterSendError(t *testing.T) {
	failing := &fakeSender{fail: true}
	ok := &fakeSender{}
	var gotErrs int
	var savedCursor uint64
	f := &delivery.Fanout{
		Senders:    []delivery.Sender{failing, ok},
		Retry:      time.Millisecond,
		OnError:    func(error) { gotErrs++ },
		SaveCursor: func(c uint64) { savedCursor = c },
	}
	events := []domain.Event{{Seq: 1, Type: "TaskCompleted", TaskID: "t1"}}
	served := false
	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Millisecond)
	defer cancel()
	err := f.Run(ctx, func(cursor uint64) []domain.Event {
		if served {
			return nil
		}
		served = true
		return events
	})
	if !errors.Is(err, context.DeadlineExceeded) {
		t.Fatalf("Run returned %v, want deadline exceeded (goroutine must survive send errors)", err)
	}
	if gotErrs == 0 {
		t.Fatal("expected OnError to be called for the failing sender")
	}
	if len(ok.sent) != 1 {
		t.Fatalf("healthy sender got %d messages, want 1", len(ok.sent))
	}
	if savedCursor != 1 {
		t.Fatalf("cursor=%d, want 1 (must advance despite the other sender's error)", savedCursor)
	}
}