package services

import (
	"testing"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"veza-backend-api/internal/models"
)

func TestNewTrackRecommendationService(t *testing.T) {
	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
	if err != nil {
		t.Fatalf("Failed to open database: %v", err)
	}

	logger := zap.NewNop()
	service := NewTrackRecommendationService(db, logger)

	if service == nil {
		t.Error("NewTrackRecommendationService() returned nil")
	}
	if service.db == nil {
		t.Error("NewTrackRecommendationService() returned service with nil db")
	}
	if service.logger == nil {
		t.Error("NewTrackRecommendationService() returned service with nil logger")
	}
}

func TestTrackRecommendationService_calculatePopularityScore(t *testing.T) {
	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
	if err != nil {
		t.Fatalf("Failed to open database: %v", err)
	}

	service := NewTrackRecommendationService(db, zap.NewNop())

	tests := []struct {
		name    string
		track   *models.Track
		wantMin float64
		wantMax float64
	}{
		{
			name: "high popularity track",
			track: &models.Track{
				PlayCount: 10000,
				LikeCount: 1000,
			},
			wantMin: 0.8,
			wantMax: 1.0,
		},
		{
			name: "medium popularity track",
			track: &models.Track{
				PlayCount: 1000,
				LikeCount: 100,
			},
			wantMin: 0.3,
			wantMax: 0.8,
		},
		{
			name: "low popularity track",
			track: &models.Track{
				PlayCount: 10,
				LikeCount: 1,
			},
			wantMin: 0.0,
			wantMax: 0.3,
		},
		{
			name: "zero popularity track",
			track: &models.Track{
				PlayCount: 0,
				LikeCount: 0,
			},
			wantMin: 0.0,
			wantMax: 0.1,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			score := service.calculatePopularityScore(tt.track)
			if score < tt.wantMin || score > tt.wantMax {
				t.Errorf("calculatePopularityScore() = %v, want between %v and %v", score, tt.wantMin, tt.wantMax)
			}
			if score < 0 || score > 1 {
				t.Errorf("calculatePopularityScore() = %v, want score between 0 and 1", score)
			}
		})
	}
}

func TestTrackRecommendationService_calculateRecencyScore(t *testing.T) {
	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
	if err != nil {
		t.Fatalf("Failed to open database: %v", err)
	}

	service := NewTrackRecommendationService(db, zap.NewNop())

	now := time.Now()

	tests := []struct {
		name    string
		track   *models.Track
		wantMin float64
		wantMax float64
	}{
		{
			name: "very recent track",
			track: &models.Track{
				CreatedAt: now.Add(-1 * time.Hour),
			},
			wantMin: 0.9,
			wantMax: 1.0,
		},
		{
			name: "recent track (15 days old)",
			track: &models.Track{
				CreatedAt: now.Add(-15 * 24 * time.Hour),
			},
			wantMin: 0.4,
			wantMax: 0.6,
		},
		{
			name: "old track (30+ days)",
			track: &models.Track{
				CreatedAt: now.Add(-35 * 24 * time.Hour),
			},
			wantMin: 0.0,
			wantMax: 0.2,
		},
		{
			name: "zero time track",
			track: &models.Track{
				CreatedAt: time.Time{},
			},
			wantMin: 0.0,
			wantMax: 0.0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			score := service.calculateRecencyScore(tt.track)
			if score < tt.wantMin || score > tt.wantMax {
				t.Errorf("calculateRecencyScore() = %v, want between %v and %v", score, tt.wantMin, tt.wantMax)
			}
			if score < 0 || score > 1 {
				t.Errorf("calculateRecencyScore() = %v, want score between 0 and 1", score)
			}
		})
	}
}

func TestGetKeys(t *testing.T) {
	tests := []struct {
		name string
		m    map[uuid.UUID]bool
		want int
	}{
		{
			name: "empty map",
			m:    map[uuid.UUID]bool{},
			want: 0,
		},
		{
			name: "map with one key",
			m: map[uuid.UUID]bool{
				uuid.New(): true,
			},
			want: 1,
		},
		{
			name: "map with multiple keys",
			m: map[uuid.UUID]bool{
				uuid.New(): true,
				uuid.New(): true,
				uuid.New(): true,
			},
			want: 3,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := getKeys(tt.m)
			if len(got) != tt.want {
				t.Errorf("getKeys() returned %d keys, want %d", len(got), tt.want)
			}
		})
	}
}

func TestTrackRecommendationParams_Defaults(t *testing.T) {
	params := TrackRecommendationParams{}

	// Test that defaults are applied in GetRecommendations method
	if params.Limit <= 0 {
		params.Limit = 20
	}
	if params.Limit > 100 {
		params.Limit = 100
	}
	if params.MinScore <= 0 {
		params.MinScore = 0.1
	}

	if params.Limit != 20 {
		t.Errorf("Expected default limit 20, got %d", params.Limit)
	}
	if params.MinScore != 0.1 {
		t.Errorf("Expected default min score 0.1, got %f", params.MinScore)
	}
}

// Note: Full integration tests would require:
// 1. A real database with test data (tracks, users, likes, plays)
// 2. Verification of collaborative filtering algorithm
// 3. Verification of content-based filtering
// 4. Performance testing with large datasets
//
// Example integration test structure:
// func TestTrackRecommendationService_GetRecommendations_Integration(t *testing.T) {
//     // Setup test database
//     db := setupTestDB(t)
//     defer cleanupTestDB(t, db)
//
//     // Create test data
//     userID := createTestUser(t, db)
//     tracks := createTestTracks(t, db, 50)
//     createTestLikes(t, db, userID, tracks[:10])
//     createTestPlays(t, db, userID, tracks[10:20])
//
//     service := NewTrackRecommendationService(db, zap.NewNop())
//
//     ctx := context.Background()
//     params := TrackRecommendationParams{
//         UserID: userID,
//         Limit:  10,
//     }
//
//     recommendations, err := service.GetRecommendations(ctx, params)
//     if err != nil {
//         t.Fatalf("GetRecommendations() error = %v", err)
//     }
//
//     if len(recommendations) == 0 {
//         t.Error("GetRecommendations() returned no recommendations")
//     }
//
//     // Verify recommendations are sorted by score
//     for i := 1; i < len(recommendations); i++ {
//         if recommendations[i].Score > recommendations[i-1].Score {
//             t.Error("Recommendations are not sorted by score")
//         }
//     }
// }