package services

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/google/uuid"

	"veza-backend-api/internal/database"

	"go.uber.org/zap"
)

// NotificationService handles notification operations
type NotificationService struct {
	db          *database.Database
	logger      *zap.Logger
	pushService *PushService // optional, for N1.2 Web Push
}

// Notification represents a notification
type Notification struct {
	ID        uuid.UUID `json:"id" db:"id"`
	UserID    uuid.UUID `json:"user_id" db:"user_id"`
	Type      string    `json:"type" db:"type"`
	Title     string    `json:"title" db:"title"`
	Content   string    `json:"content" db:"content"`
	Link      string    `json:"link" db:"link"`
	Read      bool      `json:"read" db:"read"`
	CreatedAt string    `json:"created_at" db:"created_at"`
}

// NewNotificationService creates a new notification service
func NewNotificationService(db *database.Database, logger *zap.Logger) *NotificationService {
	return &NotificationService{
		db:     db,
		logger: logger,
	}
}

// SetPushService injects the push service for Web Push (N1.2)
func (ns *NotificationService) SetPushService(ps *PushService) {
	ns.pushService = ps
}

// CreateNotification creates a new notification and optionally sends Web Push (N1.2)
func (ns *NotificationService) CreateNotification(userID uuid.UUID, notificationType, title, content, link string) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		INSERT INTO notifications (user_id, type, title, content, link)
		VALUES ($1, $2, $3, $4, $5)
	`, userID, notificationType, title, content, link)

	if err != nil {
		return fmt.Errorf("failed to create notification: %w", err)
	}

	// N1.2: Send Web Push if enabled and user has subscriptions
	if ns.pushService != nil {
		prefs, err := ns.GetPreferences(userID)
		if err != nil {
			ns.logger.Warn("failed to get push preferences", zap.Error(err))
			return nil
		}
		var shouldPush bool
		switch notificationType {
		case "follow":
			shouldPush = prefs.PushFollow
		case "like":
			shouldPush = prefs.PushLike
		case "comment":
			shouldPush = prefs.PushComment
		case "new_message", "message":
			shouldPush = prefs.PushMessage
		case "user_mentioned", "mention":
			shouldPush = prefs.PushMention
		default:
			shouldPush = false
		}
		if shouldPush {
			if err := ns.pushService.SendPushToUser(ctx, userID, title, content, link); err != nil {
				ns.logger.Warn("failed to send push notification", zap.Error(err), zap.String("user_id", userID.String()))
			}
		}
	}

	return nil
}

// GetNotifications retrieves notifications for a user
func (ns *NotificationService) GetNotifications(userID uuid.UUID, unreadOnly bool) ([]Notification, error) {
	ctx := context.Background()

	query := `
		SELECT id, user_id, type, title, content, link, read, created_at
		FROM notifications
		WHERE user_id = $1
	`
	args := []interface{}{userID}

	if unreadOnly {
		query += " AND read = FALSE"
	}

	query += " ORDER BY created_at DESC LIMIT 50"

	rows, err := ns.db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("failed to get notifications: %w", err)
	}
	defer rows.Close()

	var notifications []Notification
	for rows.Next() {
		var notification Notification
		if err := rows.Scan(
			&notification.ID,
			&notification.UserID,
			&notification.Type,
			&notification.Title,
			&notification.Content,
			&notification.Link,
			&notification.Read,
			&notification.CreatedAt,
		); err != nil {
			continue
		}
		notifications = append(notifications, notification)
	}

	return notifications, nil
}

// MarkAsRead marks a notification as read
func (ns *NotificationService) MarkAsRead(userID uuid.UUID, notificationID uuid.UUID) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		UPDATE notifications
		SET read = TRUE
		WHERE id = $1 AND user_id = $2
	`, notificationID, userID)

	if err != nil {
		return fmt.Errorf("failed to mark notification as read: %w", err)
	}

	return nil
}

// MarkAllAsRead marks all notifications as read for a user
func (ns *NotificationService) MarkAllAsRead(userID uuid.UUID) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		UPDATE notifications
		SET read = TRUE
		WHERE user_id = $1 AND read = FALSE
	`, userID)

	if err != nil {
		return fmt.Errorf("failed to mark all notifications as read: %w", err)
	}

	return nil
}

// GetUnreadCount returns the count of unread notifications
func (ns *NotificationService) GetUnreadCount(userID uuid.UUID) (int, error) {
	ctx := context.Background()

	var count int
	err := ns.db.QueryRowContext(ctx, `
		SELECT COUNT(*)
		FROM notifications
		WHERE user_id = $1 AND read = FALSE
	`, userID).Scan(&count)

	if err != nil {
		return 0, fmt.Errorf("failed to get unread count: %w", err)
	}

	return count, nil
}

// DeleteNotification deletes a notification
func (ns *NotificationService) DeleteNotification(userID uuid.UUID, notificationID uuid.UUID) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		DELETE FROM notifications
		WHERE id = $1 AND user_id = $2
	`, notificationID, userID)

	if err != nil {
		return fmt.Errorf("failed to delete notification: %w", err)
	}

	return nil
}

// DeleteAllNotifications deletes all notifications for a user
func (ns *NotificationService) DeleteAllNotifications(userID uuid.UUID) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		DELETE FROM notifications
		WHERE user_id = $1
	`, userID)

	if err != nil {
		return fmt.Errorf("failed to delete all notifications: %w", err)
	}

	return nil
}

// NotificationPrefs represents notification preferences (N1.3)
type NotificationPrefs struct {
	PushFollow   bool `json:"push_follow"`
	PushLike     bool `json:"push_like"`
	PushComment  bool `json:"push_comment"`
	PushMessage  bool `json:"push_message"`
	PushMention  bool `json:"push_mention"`
}

// GetPreferences returns notification preferences for a user
func (ns *NotificationService) GetPreferences(userID uuid.UUID) (*NotificationPrefs, error) {
	ctx := context.Background()

	prefs := &NotificationPrefs{PushFollow: true, PushLike: true, PushComment: true, PushMessage: true, PushMention: true}

	err := ns.db.QueryRowContext(ctx, `
		SELECT push_follow, push_like, push_comment, push_message, push_mention
		FROM notification_preferences
		WHERE user_id = $1
	`, userID).Scan(&prefs.PushFollow, &prefs.PushLike, &prefs.PushComment, &prefs.PushMessage, &prefs.PushMention)

	if err == nil {
		return prefs, nil
	}
	if err != sql.ErrNoRows {
		return nil, fmt.Errorf("failed to get preferences: %w", err)
	}

	return prefs, nil
}

// UpdatePreferences updates notification preferences
func (ns *NotificationService) UpdatePreferences(userID uuid.UUID, pushFollow, pushLike, pushComment, pushMessage, pushMention *bool) error {
	ctx := context.Background()

	_, err := ns.db.ExecContext(ctx, `
		INSERT INTO notification_preferences (user_id, push_follow, push_like, push_comment, push_message, push_mention, updated_at)
		VALUES ($1, COALESCE($2, true), COALESCE($3, true), COALESCE($4, true), COALESCE($5, true), COALESCE($6, true), NOW())
		ON CONFLICT (user_id) DO UPDATE SET
			push_follow = CASE WHEN $2 IS NOT NULL THEN $2 ELSE notification_preferences.push_follow END,
			push_like = CASE WHEN $3 IS NOT NULL THEN $3 ELSE notification_preferences.push_like END,
			push_comment = CASE WHEN $4 IS NOT NULL THEN $4 ELSE notification_preferences.push_comment END,
			push_message = CASE WHEN $5 IS NOT NULL THEN $5 ELSE notification_preferences.push_message END,
			push_mention = CASE WHEN $6 IS NOT NULL THEN $6 ELSE notification_preferences.push_mention END,
			updated_at = NOW()
	`, userID, pushFollow, pushLike, pushComment, pushMessage, pushMention)

	return err
}