package shareser

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"

	"go.mongodb.org/mongo-driver/bson/primitive"
)

type fakeRecommendShareDeduper struct {
	mu   sync.Mutex
	keys map[string]bool
	ttls []time.Duration
	err  error
}

func (f *fakeRecommendShareDeduper) SetNXContext(
	_ context.Context,
	key string,
	_ interface{},
	expiration time.Duration,
) (bool, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	if f.err != nil {
		return false, f.err
	}
	f.ttls = append(f.ttls, expiration)
	if f.keys == nil {
		f.keys = make(map[string]bool)
	}
	if f.keys[key] {
		return false, nil
	}
	f.keys[key] = true
	return true, nil
}

func (f *fakeRecommendShareDeduper) DelContext(
	_ context.Context,
	keys ...string,
) (int64, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	var removed int64
	for _, key := range keys {
		if f.keys[key] {
			delete(f.keys, key)
			removed++
		}
	}
	return removed, nil
}

func TestIncrementRecommendShareOnceDeduplicatesEvent(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	now := time.Date(2026, 7, 31, 8, 0, 0, 0, time.UTC)
	calls := 0
	increment := func(context.Context, primitive.ObjectID) error {
		calls++
		return nil
	}
	for i := 0; i < 2; i++ {
		if err := incrementRecommendShareOnceWith(
			context.Background(), store, 123, id, "event-1", now, increment,
		); err != nil {
			t.Fatal(err)
		}
	}
	if calls != 1 {
		t.Fatalf("increment calls = %d, want 1", calls)
	}
	if len(store.ttls) != 3 ||
		store.ttls[0] != recommendShareDailyDedupTTL ||
		store.ttls[1] != recommendShareEventDedupTTL ||
		store.ttls[2] != recommendShareDailyDedupTTL {
		t.Fatalf("dedupe TTL calls = %v", store.ttls)
	}
}

func TestIncrementRecommendShareOnceCapsDifferentEventsPerDay(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	now := time.Date(2026, 7, 31, 8, 0, 0, 0, time.UTC)
	calls := 0
	increment := func(context.Context, primitive.ObjectID) error {
		calls++
		return nil
	}
	for _, eventID := range []string{"event-1", "event-2", "event-3"} {
		if err := incrementRecommendShareOnceWith(
			context.Background(), store, 123, id, eventID, now, increment,
		); err != nil {
			t.Fatal(err)
		}
	}
	if calls != 1 {
		t.Fatalf("increment calls = %d, want one per user/video/day", calls)
	}
}

func TestIncrementRecommendShareOnceEventRetryDoesNotConsumeNextDayQuota(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	first := time.Date(2026, 7, 31, 15, 59, 0, 0, time.UTC)
	nextDay := first.Add(2 * time.Minute)
	calls := 0
	increment := func(context.Context, primitive.ObjectID) error {
		calls++
		return nil
	}
	for _, step := range []struct {
		eventID string
		now     time.Time
	}{
		{eventID: "event-1", now: first},
		{eventID: "event-1", now: nextDay},
		{eventID: "event-2", now: nextDay},
	} {
		if err := incrementRecommendShareOnceWith(
			context.Background(), store, 123, id, step.eventID, step.now, increment,
		); err != nil {
			t.Fatal(err)
		}
	}
	if calls != 2 {
		t.Fatalf("increment calls = %d, want one on each day", calls)
	}
}

func TestIncrementRecommendShareOnceLegacyScopesByCSTDay(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	incremented := 0
	increment := func(context.Context, primitive.ObjectID) error {
		incremented++
		return nil
	}
	first := time.Date(2026, 7, 31, 15, 59, 0, 0, time.UTC)
	second := first.Add(2 * time.Minute)
	for _, now := range []time.Time{first, first, second} {
		if err := incrementRecommendShareOnceWith(
			context.Background(), store, 123, id, "", now, increment,
		); err != nil {
			t.Fatal(err)
		}
	}
	if incremented != 2 {
		t.Fatalf("increment calls = %d, want 2 days", incremented)
	}
}

func TestIncrementRecommendShareOnceRedisFailureDoesNotIncrement(t *testing.T) {
	wantErr := errors.New("redis unavailable")
	store := &fakeRecommendShareDeduper{err: wantErr}
	calls := 0
	err := incrementRecommendShareOnceWith(
		context.Background(),
		store,
		123,
		primitive.NewObjectID(),
		"event",
		time.Now(),
		func(context.Context, primitive.ObjectID) error {
			calls++
			return nil
		},
	)
	if !errors.Is(err, wantErr) {
		t.Fatalf("error = %v, want %v", err, wantErr)
	}
	if calls != 0 {
		t.Fatalf("increment calls = %d, want 0", calls)
	}
}

func TestIncrementRecommendShareOnceReleasesKeyAfterFailure(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	wantErr := errors.New("injected")
	calls := 0
	increment := func(context.Context, primitive.ObjectID) error {
		calls++
		if calls == 1 {
			return wantErr
		}
		return nil
	}
	if err := incrementRecommendShareOnceWith(
		context.Background(), store, 123, id, "event", time.Now(), increment,
	); !errors.Is(err, wantErr) {
		t.Fatalf("first error = %v, want injected", err)
	}
	if err := incrementRecommendShareOnceWith(
		context.Background(), store, 123, id, "event", time.Now(), increment,
	); err != nil {
		t.Fatalf("retry error = %v", err)
	}
	if calls != 2 {
		t.Fatalf("increment calls = %d, want 2", calls)
	}
}

func TestIncrementRecommendShareOnceConcurrent(t *testing.T) {
	store := &fakeRecommendShareDeduper{}
	id := primitive.NewObjectID()
	var mu sync.Mutex
	calls := 0
	increment := func(context.Context, primitive.ObjectID) error {
		mu.Lock()
		calls++
		mu.Unlock()
		return nil
	}
	var wg sync.WaitGroup
	for i := 0; i < 32; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if err := incrementRecommendShareOnceWith(
				context.Background(), store, 123, id, "event", time.Now(), increment,
			); err != nil {
				t.Errorf("increment error = %v", err)
			}
		}()
	}
	wg.Wait()
	if calls != 1 {
		t.Fatalf("increment calls = %d, want 1", calls)
	}
}

func TestIncrementRecommendShareOnceRejectsLongEventID(t *testing.T) {
	err := incrementRecommendShareOnceWith(
		context.Background(),
		&fakeRecommendShareDeduper{},
		123,
		primitive.NewObjectID(),
		string(make([]byte, recommendShareEventIDMaxLength+1)),
		time.Now(),
		func(context.Context, primitive.ObjectID) error { return nil },
	)
	if err == nil {
		t.Fatal("expected long eventId error")
	}
}