// veza-backend-api/internal/api/user/service.go
package user

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"veza-backend-api/internal/database"
	"veza-backend-api/internal/utils"

	"github.com/google/uuid"
)

// Service handles user business logic
type Service struct {
	db *database.DB
}

// NewService creates a new user service
func NewService(db *database.DB) *Service {
	return &Service{
		db: db,
	}
}

// GetUsers retrieves users with pagination and optional search
func (s *Service) GetUsers(page, limit int, search string) ([]UserResponse, int, error) {
	offset := (page - 1) * limit

	// Build the query with optional search
	baseQuery := `
		SELECT id, email, first_name, last_name, username, avatar, bio, 
			   role, is_active, is_verified, last_login_at, created_at, updated_at
		FROM users
	`
	countQuery := "SELECT COUNT(*) FROM users"

	var whereClause string
	var args []interface{}
	argIndex := 1

	if search != "" {
		whereClause = ` WHERE (
			email ILIKE $` + fmt.Sprintf("%d", argIndex) + ` OR 
			first_name ILIKE $` + fmt.Sprintf("%d", argIndex) + ` OR 
			last_name ILIKE $` + fmt.Sprintf("%d", argIndex) + ` OR 
			username ILIKE $` + fmt.Sprintf("%d", argIndex) + `
		)`
		args = append(args, "%"+search+"%")
		argIndex++
	}

	// Get total count
	var total int
	err := s.db.QueryRow(countQuery+whereClause, args...).Scan(&total)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to count users: %w", err)
	}

	// Get users
	orderClause := " ORDER BY created_at DESC"
	limitClause := fmt.Sprintf(" LIMIT $%d OFFSET $%d", argIndex, argIndex+1)
	args = append(args, limit, offset)

	query := baseQuery + whereClause + orderClause + limitClause
	rows, err := s.db.Query(query, args...)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to query users: %w", err)
	}
	defer rows.Close()

	var users []UserResponse
	for rows.Next() {
		var user UserResponse
		err := rows.Scan(
			&user.ID, &user.Email, &user.FirstName, &user.LastName,
			&user.Username, &user.Avatar, &user.Bio, &user.Role,
			&user.IsActive, &user.IsVerified, &user.LastLoginAt,
			&user.CreatedAt, &user.UpdatedAt,
		)
		if err != nil {
			return nil, 0, fmt.Errorf("failed to scan user: %w", err)
		}
		users = append(users, user)
	}

	return users, total, nil
}

// GetUserByID retrieves a user by ID
func (s *Service) GetUserByID(userID uuid.UUID) (*UserResponse, error) {
	query := `
		SELECT id, email, first_name, last_name, username, avatar, bio,
			   role, is_active, is_verified, last_login_at, created_at, updated_at
		FROM users 
		WHERE id = $1 AND is_active = true
	`

	var user UserResponse
	err := s.db.QueryRow(query, userID).Scan(
		&user.ID, &user.Email, &user.FirstName, &user.LastName,
		&user.Username, &user.Avatar, &user.Bio, &user.Role,
		&user.IsActive, &user.IsVerified, &user.LastLoginAt,
		&user.CreatedAt, &user.UpdatedAt,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("user not found")
		}
		return nil, fmt.Errorf("failed to get user: %w", err)
	}

	return &user, nil
}

// GetUserByEmail retrieves a user by email (includes password hash for auth)
func (s *Service) GetUserByEmail(email string) (*User, error) {
	query := `
		SELECT id, email, password_hash, first_name, last_name, username, 
			   avatar, bio, role, is_active, is_verified, last_login_at, 
			   created_at, updated_at
		FROM users 
		WHERE email = $1
	`

	var user User
	err := s.db.QueryRow(query, email).Scan(
		&user.ID, &user.Email, &user.Password, &user.FirstName,
		&user.LastName, &user.Username, &user.Avatar, &user.Bio,
		&user.Role, &user.IsActive, &user.IsVerified, &user.LastLoginAt,
		&user.CreatedAt, &user.UpdatedAt,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("user not found")
		}
		return nil, fmt.Errorf("failed to get user: %w", err)
	}

	return &user, nil
}

// CreateUser creates a new user
func (s *Service) CreateUser(req CreateUserRequest) (*UserResponse, error) {
	// Hash the password
	passwordHash, err := utils.HashPassword(req.Password)
	if err != nil {
		return nil, fmt.Errorf("failed to hash password: %w", err)
	}

	// Set default role if not provided
	role := req.Role
	if role == "" {
		role = "user"
	}

	query := `
		INSERT INTO users (email, password_hash, first_name, last_name, username, role, is_active, is_verified, created_at, updated_at)
		VALUES ($1, $2, $3, $4, $5, $6, true, false, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
		RETURNING id, email, first_name, last_name, username, role, is_active, is_verified, created_at, updated_at
	`

	var user UserResponse
	err = s.db.QueryRow(
		query, req.Email, passwordHash, req.FirstName, req.LastName,
		req.Username, role,
	).Scan(
		&user.ID, &user.Email, &user.FirstName, &user.LastName,
		&user.Username, &user.Role, &user.IsActive, &user.IsVerified,
		&user.CreatedAt, &user.UpdatedAt,
	)

	if err != nil {
		if strings.Contains(err.Error(), "unique") {
			return nil, fmt.Errorf("email already exists")
		}
		return nil, fmt.Errorf("failed to create user: %w", err)
	}

	return &user, nil
}

// UpdateUser updates an existing user.
// SECURITY(REM-008): Privileged fields (role, is_active, is_verified) are ignored —
// they can only be modified via admin endpoints.
func (s *Service) UpdateUser(userID uuid.UUID, req UpdateUserRequest) (*UserResponse, error) {
	// Build dynamic update query
	setParts := []string{"updated_at = CURRENT_TIMESTAMP"}
	args := []interface{}{}
	argIndex := 1

	if req.FirstName != nil {
		setParts = append(setParts, fmt.Sprintf("first_name = $%d", argIndex))
		args = append(args, req.FirstName)
		argIndex++
	}

	if req.LastName != nil {
		setParts = append(setParts, fmt.Sprintf("last_name = $%d", argIndex))
		args = append(args, req.LastName)
		argIndex++
	}

	if req.Username != nil {
		setParts = append(setParts, fmt.Sprintf("username = $%d", argIndex))
		args = append(args, req.Username)
		argIndex++
	}

	if req.Avatar != nil {
		setParts = append(setParts, fmt.Sprintf("avatar = $%d", argIndex))
		args = append(args, req.Avatar)
		argIndex++
	}

	if req.Bio != nil {
		setParts = append(setParts, fmt.Sprintf("bio = $%d", argIndex))
		args = append(args, req.Bio)
		argIndex++
	}

	// SECURITY(REM-008): Privileged fields blocked for non-admin callers.
	// IsActive, IsVerified, and Role are intentionally excluded from user self-update.
	// These fields can only be modified through admin endpoints with RequireRole("admin") middleware.

	// Add user ID as the last argument
	args = append(args, userID)

	query := fmt.Sprintf(`
		UPDATE users 
		SET %s
		WHERE id = $%d
		RETURNING id, email, first_name, last_name, username, avatar, bio,
				  role, is_active, is_verified, last_login_at, created_at, updated_at
	`, strings.Join(setParts, ", "), argIndex)

	var user UserResponse
	err := s.db.QueryRow(query, args...).Scan(
		&user.ID, &user.Email, &user.FirstName, &user.LastName,
		&user.Username, &user.Avatar, &user.Bio, &user.Role,
		&user.IsActive, &user.IsVerified, &user.LastLoginAt,
		&user.CreatedAt, &user.UpdatedAt,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("user not found")
		}
		return nil, fmt.Errorf("failed to update user: %w", err)
	}

	return &user, nil
}

// DeleteUser soft deletes a user (sets is_active to false)
func (s *Service) DeleteUser(userID uuid.UUID) error {
	query := `
		UPDATE users 
		SET is_active = false, updated_at = CURRENT_TIMESTAMP
		WHERE id = $1 AND is_active = true
	`

	result, err := s.db.Exec(query, userID)
	if err != nil {
		return fmt.Errorf("failed to delete user: %w", err)
	}

	rowsAffected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rowsAffected == 0 {
		return fmt.Errorf("user not found")
	}

	return nil
}

// UpdateLastLogin updates the user's last login timestamp
func (s *Service) UpdateLastLogin(userID uuid.UUID) error {
	query := `
		UPDATE users 
		SET last_login_at = CURRENT_TIMESTAMP, updated_at = CURRENT_TIMESTAMP
		WHERE id = $1
	`

	_, err := s.db.Exec(query, userID)
	if err != nil {
		return fmt.Errorf("failed to update last login: %w", err)
	}

	return nil
}

// ChangePassword updates a user's password
func (s *Service) ChangePassword(userID uuid.UUID, currentPassword, newPassword string) error {
	// First, get the current password hash
	var currentHash string
	err := s.db.QueryRow("SELECT password_hash FROM users WHERE id = $1", userID).Scan(&currentHash)
	if err != nil {
		if err == sql.ErrNoRows {
			return fmt.Errorf("user not found")
		}
		return fmt.Errorf("failed to get user password: %w", err)
	}

	// Verify current password
	if err := utils.CheckPasswordHash(currentPassword, currentHash); err != nil {
		return fmt.Errorf("current password is incorrect")
	}

	// Hash new password
	newHash, err := utils.HashPassword(newPassword)
	if err != nil {
		return fmt.Errorf("failed to hash new password: %w", err)
	}

	// Update password
	query := `
		UPDATE users 
		SET password_hash = $1, updated_at = CURRENT_TIMESTAMP
		WHERE id = $2
	`

	_, err = s.db.Exec(query, newHash, userID)
	if err != nil {
		return fmt.Errorf("failed to update password: %w", err)
	}

	return nil
}

// GetUserStats returns basic user statistics
func (s *Service) GetUserStats() (map[string]interface{}, error) {
	stats := make(map[string]interface{})

	// Total users
	var totalUsers int
	err := s.db.QueryRow("SELECT COUNT(*) FROM users WHERE is_active = true").Scan(&totalUsers)
	if err != nil {
		return nil, fmt.Errorf("failed to get total users: %w", err)
	}
	stats["total_users"] = totalUsers

	// Verified users
	var verifiedUsers int
	err = s.db.QueryRow("SELECT COUNT(*) FROM users WHERE is_active = true AND is_verified = true").Scan(&verifiedUsers)
	if err != nil {
		return nil, fmt.Errorf("failed to get verified users: %w", err)
	}
	stats["verified_users"] = verifiedUsers

	// Active users (logged in within last 30 days)
	var activeUsers int
	err = s.db.QueryRow(`
		SELECT COUNT(*) FROM users 
		WHERE is_active = true AND last_login_at > CURRENT_TIMESTAMP - INTERVAL '30 days'
	`).Scan(&activeUsers)
	if err != nil {
		return nil, fmt.Errorf("failed to get active users: %w", err)
	}
	stats["active_users"] = activeUsers

	// New users this month
	var newUsersThisMonth int
	err = s.db.QueryRow(`
		SELECT COUNT(*) FROM users 
		WHERE is_active = true AND created_at >= date_trunc('month', CURRENT_TIMESTAMP)
	`).Scan(&newUsersThisMonth)
	if err != nil {
		return nil, fmt.Errorf("failed to get new users this month: %w", err)
	}
	stats["new_users_this_month"] = newUsersThisMonth

	return stats, nil
}

// GetUserPreferences récupère les préférences d'un utilisateur
func (s *Service) GetUserPreferences(userID uuid.UUID) (*UserPreferencesResponse, error) {
	query := `
		SELECT user_id, theme, language, timezone, 
		       COALESCE(notifications, '{}') as notifications,
		       COALESCE(privacy, '{}') as privacy,
		       COALESCE(audio, '{}') as audio,
		       COALESCE(contrast, 'normal') as contrast,
		       COALESCE(density, 'comfortable') as density,
		       COALESCE(accent_hue, 220) as accent_hue,
		       COALESCE(font_size, 16) as font_size,
		       updated_at
		FROM user_preferences 
		WHERE user_id = $1
	`

	var preferences UserPreferencesResponse
	var notificationsJSON, privacyJSON, audioJSON string

	err := s.db.QueryRow(query, userID).Scan(
		&preferences.UserID, &preferences.Theme, &preferences.Language,
		&preferences.Timezone, &notificationsJSON, &privacyJSON,
		&audioJSON, &preferences.Contrast, &preferences.Density,
		&preferences.AccentHue, &preferences.FontSize, &preferences.UpdatedAt,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			// Retourner les préférences par défaut
			return &UserPreferencesResponse{
				UserID:   userID,
				Theme:    "light",
				Language: "en",
				Timezone: "UTC",
				Notifications: NotificationSettings{
					Email: true, Push: true, Desktop: true,
					NewFollowers: true, TrackComments: true,
					DirectMessages: true, Mentions: true, Likes: false,
				},
				Privacy: PrivacySettings{
					ShowEmail: false, ShowActivity: true, AllowDM: true,
					TrackVisibility: "public", ProfileVisibility: "public",
				},
				Audio: AudioSettings{
					AutoPlay: true, Quality: "high", Volume: 0.8, Crossfade: 5,
				},
				Contrast:  "normal",
				Density:   "comfortable",
				AccentHue: 220,
				FontSize:  16,
				UpdatedAt: time.Now(),
			}, nil
		}
		return nil, fmt.Errorf("failed to get user preferences: %w", err)
	}

	// Parse JSON strings to structs
	if err := json.Unmarshal([]byte(notificationsJSON), &preferences.Notifications); err != nil {
		preferences.Notifications = NotificationSettings{
			Email: true, Push: true, Desktop: true,
			NewFollowers: true, TrackComments: true,
			DirectMessages: true, Mentions: true, Likes: false,
		}
	}
	if err := json.Unmarshal([]byte(privacyJSON), &preferences.Privacy); err != nil {
		preferences.Privacy = PrivacySettings{
			ShowEmail: false, ShowActivity: true, AllowDM: true,
			TrackVisibility: "public", ProfileVisibility: "public",
		}
	}
	if err := json.Unmarshal([]byte(audioJSON), &preferences.Audio); err != nil {
		preferences.Audio = AudioSettings{
			AutoPlay: true, Quality: "high", Volume: 0.8, Crossfade: 5,
		}
	}

	return &preferences, nil
}

// UpdateUserPreferences met à jour les préférences d'un utilisateur
func (s *Service) UpdateUserPreferences(userID uuid.UUID, req UserPreferencesRequest) (*UserPreferencesResponse, error) {
	// Récupérer les préférences actuelles
	current, err := s.GetUserPreferences(userID)
	if err != nil {
		return nil, err
	}

	// Appliquer les mises à jour
	if req.Theme != nil {
		current.Theme = *req.Theme
	}
	if req.Language != nil {
		current.Language = *req.Language
	}
	if req.Timezone != nil {
		current.Timezone = *req.Timezone
	}
	if req.Notifications != nil {
		current.Notifications = *req.Notifications
	}
	if req.Privacy != nil {
		current.Privacy = *req.Privacy
	}
	if req.Audio != nil {
		current.Audio = *req.Audio
	}
	if req.Contrast != nil {
		current.Contrast = *req.Contrast
	}
	if req.Density != nil {
		current.Density = *req.Density
	}
	if req.AccentHue != nil {
		current.AccentHue = *req.AccentHue
	}
	if req.FontSize != nil {
		current.FontSize = *req.FontSize
	}

	current.UpdatedAt = time.Now()

	// Serialize structs to JSON
	notificationsJSON, _ := json.Marshal(current.Notifications)
	privacyJSON, _ := json.Marshal(current.Privacy)
	audioJSON, _ := json.Marshal(current.Audio)

	// Sauvegarder en base (upsert)
	query := `
		INSERT INTO user_preferences (user_id, theme, language, timezone, notifications, privacy, audio, contrast, density, accent_hue, font_size, updated_at)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12)
		ON CONFLICT (user_id) DO UPDATE SET
			theme = EXCLUDED.theme,
			language = EXCLUDED.language,
			timezone = EXCLUDED.timezone,
			notifications = EXCLUDED.notifications,
			privacy = EXCLUDED.privacy,
			audio = EXCLUDED.audio,
			contrast = EXCLUDED.contrast,
			density = EXCLUDED.density,
			accent_hue = EXCLUDED.accent_hue,
			font_size = EXCLUDED.font_size,
			updated_at = EXCLUDED.updated_at
	`

	_, err = s.db.Exec(query, userID, current.Theme, current.Language, current.Timezone,
		string(notificationsJSON), string(privacyJSON), string(audioJSON),
		current.Contrast, current.Density, current.AccentHue, current.FontSize,
		current.UpdatedAt)
	if err != nil {
		return nil, fmt.Errorf("failed to update user preferences: %w", err)
	}

	return current, nil
}

// DeleteAccount supprime le compte d'un utilisateur (soft delete)
func (s *Service) DeleteAccount(userID uuid.UUID, password, reason string) error {
	// Vérifier le mot de passe
	var currentHash string
	err := s.db.QueryRow("SELECT password_hash FROM users WHERE id = $1", userID).Scan(&currentHash)
	if err != nil {
		if err == sql.ErrNoRows {
			return fmt.Errorf("user not found")
		}
		return fmt.Errorf("failed to get user password: %w", err)
	}

	if err := utils.CheckPasswordHash(password, currentHash); err != nil {
		return fmt.Errorf("invalid password")
	}

	// Marquer le compte comme supprimé avec période de grâce de 30 jours
	recoveryDeadline := time.Now().Add(30 * 24 * time.Hour)
	query := `
		UPDATE users 
		SET is_active = false, deleted_at = CURRENT_TIMESTAMP, 
		    deletion_reason = $2, recovery_deadline = $3, updated_at = CURRENT_TIMESTAMP
		WHERE id = $1
	`

	_, err = s.db.Exec(query, userID, reason, recoveryDeadline)
	if err != nil {
		return fmt.Errorf("failed to delete account: %w", err)
	}

	return nil
}

// RecoverAccount récupère un compte supprimé
func (s *Service) RecoverAccount(email, password string) error {
	// Vérifier l'utilisateur et son statut
	var userID uuid.UUID
	var currentHash string
	var deletedAt sql.NullTime
	var recoveryDeadline sql.NullTime

	query := `
		SELECT id, password_hash, deleted_at, recovery_deadline
		FROM users 
		WHERE email = $1 AND deleted_at IS NOT NULL
	`

	err := s.db.QueryRow(query, email).Scan(&userID, &currentHash, &deletedAt, &recoveryDeadline)
	if err != nil {
		if err == sql.ErrNoRows {
			return fmt.Errorf("no deleted account found for this email")
		}
		return fmt.Errorf("failed to find account: %w", err)
	}

	// Vérifier que la période de récupération n'est pas expirée
	if recoveryDeadline.Valid && time.Now().After(recoveryDeadline.Time) {
		return fmt.Errorf("recovery period has expired")
	}

	// Vérifier le mot de passe
	if err := utils.CheckPasswordHash(password, currentHash); err != nil {
		return fmt.Errorf("invalid password")
	}

	// Réactiver le compte
	updateQuery := `
		UPDATE users 
		SET is_active = true, deleted_at = NULL, deletion_reason = NULL, 
		    recovery_deadline = NULL, updated_at = CURRENT_TIMESTAMP
		WHERE id = $1
	`

	_, err = s.db.Exec(updateQuery, userID)
	if err != nil {
		return fmt.Errorf("failed to recover account: %w", err)
	}

	return nil
}

// ExportUserData exporte toutes les données d'un utilisateur (RGPD)
func (s *Service) ExportUserData(userID uuid.UUID) (*UserDataExport, error) {
	// Récupérer le profil
	profile, err := s.GetUserByID(userID)
	if err != nil {
		return nil, fmt.Errorf("failed to get user profile: %w", err)
	}

	// Récupérer les préférences
	preferences, err := s.GetUserPreferences(userID)
	if err != nil {
		return nil, fmt.Errorf("failed to get user preferences: %w", err)
	}

	// Récupérer l'activité (simplifié)
	activity := []UserActivity{
		{ID: uuid.New(), Type: "login", Details: "User login", CreatedAt: time.Now()},
		{ID: uuid.New(), Type: "profile_update", Details: "Profile updated", CreatedAt: time.Now()},
	}

	// Récupérer le contenu (simplifié)
	content := []UserContent{
		{ID: uuid.New(), Type: "track", Title: "Sample Track", URL: "/tracks/1", CreatedAt: time.Now()},
	}

	// Récupérer les interactions (simplifié)
	interactions := []UserInteraction{
		{ID: uuid.New(), Type: "like", TargetID: uuid.New(), CreatedAt: time.Now()},
	}

	export := &UserDataExport{
		UserID:       userID,
		Profile:      *profile,
		Preferences:  *preferences,
		Activity:     activity,
		Content:      content,
		Interactions: interactions,
		ExportedAt:   time.Now(),
	}

	return export, nil
}

// RequestDataDeletion demande la suppression définitive des données
func (s *Service) RequestDataDeletion(userID uuid.UUID, password, reason string) error {
	// Vérifier le mot de passe
	var currentHash string
	err := s.db.QueryRow("SELECT password_hash FROM users WHERE id = $1", userID).Scan(&currentHash)
	if err != nil {
		if err == sql.ErrNoRows {
			return fmt.Errorf("user not found")
		}
		return fmt.Errorf("failed to get user password: %w", err)
	}

	if err := utils.CheckPasswordHash(password, currentHash); err != nil {
		return fmt.Errorf("invalid password")
	}

	// Créer une demande de suppression définitive
	query := `
		INSERT INTO data_deletion_requests (user_id, reason, status, requested_at)
		VALUES ($1, $2, 'pending', CURRENT_TIMESTAMP)
	`

	_, err = s.db.Exec(query, userID, reason)
	if err != nil {
		return fmt.Errorf("failed to create deletion request: %w", err)
	}

	return nil
}

// GetAccountStatus récupère le statut du compte
func (s *Service) GetAccountStatus(userID uuid.UUID) (*AccountStatus, error) {
	query := `
		SELECT id, is_active, is_verified, created_at, deleted_at, 
		       COALESCE(deletion_reason, '') as deletion_reason,
		       recovery_deadline
		FROM users 
		WHERE id = $1
	`

	var status AccountStatus
	var deletedAt sql.NullTime
	var recoveryDeadline sql.NullTime

	err := s.db.QueryRow(query, userID).Scan(
		&status.UserID, &status.IsActive, &status.IsVerified,
		&status.CreatedAt, &deletedAt, &status.DeletionReason, &recoveryDeadline,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("user not found")
		}
		return nil, fmt.Errorf("failed to get account status: %w", err)
	}

	// Déterminer le statut
	if deletedAt.Valid {
		status.Status = "deleted"
		status.DeletedAt = &deletedAt.Time
		if recoveryDeadline.Valid {
			status.RecoveryDeadline = &recoveryDeadline.Time
		}
	} else if !status.IsActive {
		status.Status = "suspended"
	} else {
		status.Status = "active"
	}

	return &status, nil
}