/**
 * Notification Scheduler Service
 * Manages scheduled AI notifications with predictive timing
 */

require('dotenv').config();
const { PrismaClient: CMSClient } = require("../../prisma/clients/cms");
const prisma = new CMSClient();
const logger = require('./logger.services');
const { localTime } = require('./time.services');
const { predictOptimalDeliveryTime } = require('./ai.services');

/**
 * Create a scheduled notification with AI-predicted optimal delivery time
 * @param {Object} params - Notification parameters
 * @param {string} params.userID - User ID
 * @param {Array} params.recentActivities - Recent user activities for pattern analysis
 * @param {Object} params.notificationContent - The generated notification {title, description}
 * @param {number} params.analyzedActivityCount - Number of activities analyzed
 * @param {string} params.activityTypes - Comma-separated activity types
 * @param {number} params.activityTimeRange - Time range in minutes
 * @param {string} params.aiModel - AI model used
 * @param {number} params.processingTime - Time taken to process (ms)
 * @returns {Promise<Object>} Created scheduled notification record
 */
exports.createScheduledNotification = async (params) => {
    try {
        const {
            userID,
            recentActivities,
            notificationContent,
            analyzedActivityCount,
            activityTypes,
            activityTimeRange,
            aiModel,
            processingTime
        } = params;

        const userToken = await prisma.usersToken.findFirst({
            where: { UserID_UT: userID }
        });

        if (!userToken) {
            throw new Error(`User token not found for userID: ${userID}`);
        }

        const historicalActivities = await prisma.usersActivity.findMany({
            where: {
                UUID_UT: userToken.UUID_UT,
                CreatedAt_UA: {
                    gte: new Date(Date.now() - 7 * 24 * 60 * 60 * 1000)
                }
            },
            orderBy: {
                CreatedAt_UA: 'desc'
            },
            take: 50
        });

        const activityPattern = {
            userId: userID,
            currentTime: new Date().toISOString(),
            recentActivities: recentActivities.map(a => ({
                type: a.ActivityType_UA || a.type,
                createdAt: a.CreatedAt_UA || a.timestamp,
                params: a.Params_UA || a.params
            })),
            historicalPattern: historicalActivities.map(a => ({
                type: a.ActivityType_UA,
                hour: new Date(a.CreatedAt_UA).getHours(),
                dayOfWeek: new Date(a.CreatedAt_UA).getDay(),
                createdAt: a.CreatedAt_UA
            })),
            stats: {
                totalActivities: historicalActivities.length,
                uniqueDays: [...new Set(historicalActivities.map(a => 
                    new Date(a.CreatedAt_UA).toISOString().split('T')[0]
                ))].length,
                avgActivitiesPerDay: historicalActivities.length / 7
            }
        };

        logger.info(`Requesting AI predictive timing for user ${userID}...`);
        let timingPrediction = await predictOptimalDeliveryTime(activityPattern);

        if (timingPrediction.error || !timingPrediction.optimalDeliveryTime) {
            logger.error(`AI timing prediction failed, using fallback`, timingPrediction);
            const now = new Date();
            const fallbackTime = new Date(now.getTime() + 2 * 60 * 60 * 1000); // 2 hours from now
            timingPrediction = {
                optimalDeliveryTime: fallbackTime.toISOString(),
                confidenceScore: 50,
                reasoning: "AI prediction failed, using default 2-hour delay",
                userEngagementPattern: "unknown",
                delayMinutes: 120
            };
        }

        const scheduledTime = new Date(timingPrediction.optimalDeliveryTime);
        const now = new Date();

        if (isNaN(scheduledTime.getTime())) {
            logger.error(`Invalid scheduled time from AI prediction: ${timingPrediction.optimalDeliveryTime}`);
            const fallbackTime = new Date(now.getTime() + 2 * 60 * 60 * 1000);
            timingPrediction.optimalDeliveryTime = fallbackTime.toISOString();
            timingPrediction.reasoning = "Invalid time corrected to 2-hour delay";
            scheduledTime.setTime(fallbackTime.getTime());
        }

        const scheduledNotification = await prisma.aINotification.create({
            data: {
                UserID_AIN: userID,
                AnalyzedActivities_AIN: analyzedActivityCount,
                ActivityTypes_AIN: activityTypes,
                GeneratedTitle_AIN: notificationContent.title,
                GeneratedDesc_AIN: notificationContent.description,
                SentStatus_AIN: 'scheduled',
                ScheduledAt_AIN: localTime(scheduledTime),
                PredictedConfidence_AIN: timingPrediction.confidenceScore,
                PredictionReasoning_AIN: timingPrediction.reasoning,
                UserEngagementPattern_AIN: timingPrediction.userEngagementPattern,
                DelayMinutes_AIN: timingPrediction.delayMinutes,
                ActivityTimeRange_AIN: activityTimeRange,
                AIModel_AIN: aiModel,
                ProcessingTime_AIN: processingTime,
                CreatedAt_AIN: localTime(now),
                UpdatedAt_AIN: localTime(now)
            }
        });

        logger.info(`   Notification scheduled for ${userID} at ${scheduledTime.toISOString()} (${timingPrediction.delayMinutes} min delay, ${timingPrediction.confidenceScore}% confidence)`);
        logger.info(`   Reason: ${timingPrediction.reasoning}`);
        logger.info(`   Pattern: ${timingPrediction.userEngagementPattern}`);

        return {
            success: true,
            notificationID: scheduledNotification.UUID_AIN,
            scheduledFor: scheduledTime.toISOString(),
            delayMinutes: timingPrediction.delayMinutes,
            confidence: timingPrediction.confidenceScore,
            reasoning: timingPrediction.reasoning,
            pattern: timingPrediction.userEngagementPattern,
            notification: {
                title: notificationContent.title,
                description: notificationContent.description
            }
        };

    } catch (error) {
        logger.error(`Error creating scheduled notification: ${error.message}`, error);
        throw error;
    }
};

/**
 * Get all notifications that are due to be sent
 * @returns {Promise<Array>} Array of due notifications
 */
exports.getDueNotifications = async () => {
    try {
        const now = new Date();
        
        const dueNotifications = await prisma.aINotification.findMany({
            where: {
                SentStatus_AIN: 'scheduled',
                ScheduledAt_AIN: {
                    lte: localTime(now)
                }
            },
            orderBy: {
                ScheduledAt_AIN: 'asc'
            }
        });

        logger.info(`Found ${dueNotifications.length} notifications due for delivery`);
        return dueNotifications;

    } catch (error) {
        logger.error(`Error fetching due notifications: ${error.message}`);
        throw error;
    }
};

/**
 * Update notification status after sending
 * @param {string} notificationID - UUID of the notification
 * @param {Object} updateData - Update data
 * @returns {Promise<Object>} Updated notification
 */
exports.updateNotificationStatus = async (notificationID, updateData) => {
    try {
        const updated = await prisma.aINotification.update({
            where: { UUID_AIN: notificationID },
            data: {
                ...updateData,
                UpdatedAt_AIN: localTime(new Date())
            }
        });

        return updated;

    } catch (error) {
        logger.error(`Error updating notification ${notificationID}: ${error.message}`);
        throw error;
    }
};

/**
 * Get scheduled notifications statistics
 * @returns {Promise<Object>} Statistics
 */
exports.getScheduledNotificationsStats = async () => {
    try {
        const [scheduled, pending, upcoming] = await Promise.all([
            prisma.aINotification.count({
                where: { SentStatus_AIN: 'scheduled' }
            }),
            prisma.aINotification.count({
                where: {
                    SentStatus_AIN: 'scheduled',
                    ScheduledAt_AIN: {
                        lte: localTime(new Date())
                    }
                }
            }),
            prisma.aINotification.findMany({
                where: {
                    SentStatus_AIN: 'scheduled',
                    ScheduledAt_AIN: {
                        gte: localTime(new Date()),
                        lte: localTime(new Date(Date.now() + 24 * 60 * 60 * 1000))
                    }
                },
                select: {
                    UUID_AIN: true,
                    UserID_AIN: true,
                    ScheduledAt_AIN: true,
                    GeneratedTitle_AIN: true,
                    PredictedConfidence_AIN: true,
                    UserEngagementPattern_AIN: true
                },
                orderBy: {
                    ScheduledAt_AIN: 'asc'
                },
                take: 10
            })
        ]);

        return {
            totalScheduled: scheduled,
            pendingDelivery: pending,
            upcomingIn24Hours: upcoming.length,
            nextScheduled: upcoming
        };

    } catch (error) {
        logger.error(`Error getting scheduled stats: ${error.message}`);
        throw error;
    }
};

/**
 * Cancel a scheduled notification
 * @param {string} notificationID - UUID of the notification
 * @returns {Promise<Object>} Result
 */
exports.cancelScheduledNotification = async (notificationID) => {
    try {
        const updated = await prisma.aINotification.update({
            where: { UUID_AIN: notificationID },
            data: {
                SentStatus_AIN: 'cancelled',
                UpdatedAt_AIN: localTime(new Date())
            }
        });

        logger.info(`Notification ${notificationID} cancelled`);
        return { success: true, notification: updated };

    } catch (error) {
        logger.error(`Error cancelling notification ${notificationID}: ${error.message}`);
        throw error;
    }
};