/**
 * Security Logger - ระบบบันทึกเหตุการณ์ความปลอดภัย
 * Chahua Development Thailand
 * CEO: Saharath C.
 * 
 * Purpose: บันทึกและตรวจสอบเหตุการณ์ด้านความปลอดภัย
 */

const fs = require('fs');
const path = require('path');

class SecurityLogger {
    constructor(options = {}) {
        this.config = {
            logPath: options.logPath || './logs/security',
            maxLogSize: options.maxLogSize || 10 * 1024 * 1024, // 10MB
            maxLogFiles: options.maxLogFiles || 5,
            alertThreshold: options.alertThreshold || 10, // Alert after 10 events
            enableRealTimeAlerts: options.enableRealTimeAlerts || true,
            sensitiveFields: options.sensitiveFields || ['password', 'token', 'secret', 'key']
        };
        
        this.securityEvents = [];
        this.alertCount = 0;
        this.blockedIPs = new Set();
        this.suspiciousActivities = new Map();
        
        this.ensureLogDirectory();
        console.log('Security Logger initialized');
    }

    ensureLogDirectory() {
        try {
            if (!fs.existsSync(this.config.logPath)) {
                fs.mkdirSync(this.config.logPath, { recursive: true });
            }
        } catch (error) {
            console.warn('Warning: Could not create security log directory:', error.message);
        }
    }

    async logSecurityEvent(eventData) {
        const timestamp = new Date().toISOString();
        const eventId = this.generateEventId();
        
        const securityEvent = {
            id: eventId,
            timestamp,
            type: eventData.type || 'UNKNOWN',
            severity: eventData.severity || 'medium',
            details: this.sanitizeDetails(eventData),
            ip: eventData.ip || 'unknown',
            userAgent: eventData.userAgent || 'unknown',
            source: eventData.source || 'system'
        };
        
        // Add to memory
        this.securityEvents.push(securityEvent);
        
        // Maintain max events in memory
        if (this.securityEvents.length > 1000) {
            this.securityEvents.shift();
        }
        
        // Write to file
        this.writeToLogFile(securityEvent);
        
        // Check for alerts
        this.checkForAlerts(securityEvent);
        
        // Update suspicious activity tracking
        this.updateSuspiciousActivity(securityEvent);
        
        console.log(`Security Event [${securityEvent.severity.toUpperCase()}]: ${securityEvent.type} - ${eventId}`);
        
        return eventId;
    }

    logAuthFailure(ip, username, details = {}) {
        return this.logSecurityEvent({
            type: 'AUTH_FAILURE',
            ip,
            username,
            severity: 'high',
            ...details
        });
    }

    logAuthSuccess(ip, username, details = {}) {
        return this.logSecurityEvent({
            type: 'AUTH_SUCCESS',
            ip,
            username,
            severity: 'low',
            ...details
        });
    }

    logSuspiciousAccess(ip, endpoint, details = {}) {
        return this.logSecurityEvent({
            type: 'SUSPICIOUS_ACCESS',
            ip,
            endpoint,
            severity: 'high',
            ...details
        });
    }

    logRateLimitExceeded(ip, endpoint, details = {}) {
        return this.logSecurityEvent({
            type: 'RATE_LIMIT_EXCEEDED',
            ip,
            endpoint,
            severity: 'medium',
            ...details
        });
    }

    logDataBreach(source, details = {}) {
        return this.logSecurityEvent({
            type: 'DATA_BREACH',
            source,
            severity: 'critical',
            ...details
        });
    }

    logUnauthorizedAccess(ip, resource, details = {}) {
        return this.logSecurityEvent({
            type: 'UNAUTHORIZED_ACCESS',
            ip,
            resource,
            severity: 'high',
            ...details
        });
    }

    logSystemAnomaly(anomalyType, details = {}) {
        return this.logSecurityEvent({
            type: 'SYSTEM_ANOMALY',
            anomalyType,
            severity: 'medium',
            ...details
        });
    }

    sanitizeDetails(details) {
        const sanitized = { ...details };
        
        // Remove sensitive fields
        for (const field of this.config.sensitiveFields) {
            if (sanitized[field]) {
                sanitized[field] = '***REDACTED***';
            }
        }
        
        return sanitized;
    }

    writeToLogFile(event) {
        try {
            const logFileName = `security-${new Date().toISOString().split('T')[0]}.log`;
            const logFilePath = path.join(this.config.logPath, logFileName);
            
            const logEntry = JSON.stringify(event) + '\n';
            
            // Check file size and rotate if needed
            if (fs.existsSync(logFilePath)) {
                const stats = fs.statSync(logFilePath);
                if (stats.size > this.config.maxLogSize) {
                    this.rotateLogFile(logFilePath);
                }
            }
            
            fs.appendFileSync(logFilePath, logEntry);
            
        } catch (error) {
            console.error('Error writing security log:', error.message);
        }
    }

    rotateLogFile(logFilePath) {
        try {
            const logDir = path.dirname(logFilePath);
            const baseName = path.basename(logFilePath, '.log');
            
            // Rotate existing files
            for (let i = this.config.maxLogFiles - 1; i > 0; i--) {
                const oldFile = path.join(logDir, `${baseName}.${i}.log`);
                const newFile = path.join(logDir, `${baseName}.${i + 1}.log`);
                
                if (fs.existsSync(oldFile)) {
                    if (i === this.config.maxLogFiles - 1) {
                        fs.unlinkSync(oldFile); // Delete oldest
                    } else {
                        fs.renameSync(oldFile, newFile);
                    }
                }
            }
            
            // Move current file to .1
            const rotatedFile = path.join(logDir, `${baseName}.1.log`);
            fs.renameSync(logFilePath, rotatedFile);
            
            console.log(`Security log rotated: ${logFilePath}`);
            
        } catch (error) {
            console.error('Error rotating security log:', error.message);
        }
    }

    checkForAlerts(event) {
        if (!this.config.enableRealTimeAlerts) return;
        
        // Count events from same IP in last hour
        const oneHourAgo = new Date(Date.now() - 60 * 60 * 1000);
        const recentEvents = this.securityEvents.filter(e => 
            e.ip === event.ip && 
            new Date(e.timestamp) > oneHourAgo
        );
        
        if (recentEvents.length >= this.config.alertThreshold) {
            this.triggerAlert(event.ip, recentEvents);
        }
        
        // Immediate alert for critical events
        if (event.severity === 'critical') {
            this.triggerCriticalAlert(event);
        }
    }

    triggerAlert(ip, events) {
        this.alertCount++;
        console.warn(`SECURITY ALERT: Multiple events from IP ${ip} (${events.length} events)`);
        
        // Block IP after multiple alerts
        if (events.length >= this.config.alertThreshold * 2) {
            this.blockedIPs.add(ip);
            console.warn(`IP ${ip} has been blocked due to suspicious activity`);
        }
        
        // In a real system, you might send email/SMS alerts here
    }

    triggerCriticalAlert(event) {
        console.error(`CRITICAL SECURITY ALERT: ${event.type} - ${event.id}`);
        // In a real system, you might trigger immediate notifications
    }

    updateSuspiciousActivity(event) {
        const key = `${event.ip}_${event.type}`;
        const count = this.suspiciousActivities.get(key) || 0;
        this.suspiciousActivities.set(key, count + 1);
    }

    isIPBlocked(ip) {
        return this.blockedIPs.has(ip);
    }

    unblockIP(ip) {
        if (this.blockedIPs.delete(ip)) {
            console.log(`IP ${ip} has been unblocked`);
            return true;
        }
        return false;
    }

    getSecurityReport(timeRange = '24h') {
        const hours = timeRange === '24h' ? 24 : parseInt(timeRange);
        const startTime = new Date(Date.now() - hours * 60 * 60 * 1000);
        
        const relevantEvents = this.securityEvents.filter(e => 
            new Date(e.timestamp) > startTime
        );
        
        const report = {
            timeRange: `${hours} hours`,
            totalEvents: relevantEvents.length,
            eventTypes: {},
            severityBreakdown: {},
            topIPs: {},
            blockedIPs: Array.from(this.blockedIPs),
            alertsTriggered: this.alertCount
        };
        
        // Analyze events
        relevantEvents.forEach(event => {
            // Event types
            report.eventTypes[event.type] = (report.eventTypes[event.type] || 0) + 1;
            
            // Severity breakdown
            report.severityBreakdown[event.severity] = (report.severityBreakdown[event.severity] || 0) + 1;
            
            // Top IPs
            report.topIPs[event.ip] = (report.topIPs[event.ip] || 0) + 1;
        });
        
        // Sort top IPs
        report.topIPs = Object.entries(report.topIPs)
            .sort(([,a], [,b]) => b - a)
            .slice(0, 10)
            .reduce((obj, [ip, count]) => {
                obj[ip] = count;
                return obj;
            }, {});
        
        return report;
    }

    exportSecurityLogs(startDate, endDate) {
        try {
            const events = this.securityEvents.filter(e => {
                const eventDate = new Date(e.timestamp);
                return eventDate >= startDate && eventDate <= endDate;
            });
            
            const exportData = {
                exportDate: new Date().toISOString(),
                dateRange: { start: startDate, end: endDate },
                totalEvents: events.length,
                events: events
            };
            
            return exportData;
            
        } catch (error) {
            console.error('Error exporting security logs:', error.message);
            return null;
        }
    }

    generateEventId() {
        return `sec_${Date.now()}_${Math.random().toString(36).substring(2, 8)}`;
    }

    getStats() {
        return {
            totalEvents: this.securityEvents.length,
            alertsTriggered: this.alertCount,
            blockedIPs: this.blockedIPs.size,
            suspiciousActivities: this.suspiciousActivities.size
        };
    }
}

module.exports = SecurityLogger;