/**
 *  Retry Controller - ระบบควบคุมการทำซ้ำ
 *  Chahua Development Thailand
 *  CEO: Saharath C.
 * 
 *  Purpose: จัดการการ retry operations ที่ล้มเหลว
 */

class RetryController {
    constructor(options = {}) {
        this.config = {
            maxRetries: options.maxRetries || 3,
            baseDelay: options.baseDelay || 1000, // 1 second
            maxDelay: options.maxDelay || 30000, // 30 seconds
            backoffMultiplier: options.backoffMultiplier || 2,
            jitter: options.jitter || true
        };
        
        this.retryHistory = new Map();
        console.log(' Retry Controller initialized');
    }

    async executeWithRetry(operation, context = {}, customConfig = {}) {
        const config = { ...this.config, ...customConfig };
        const operationId = context.id || this.generateOperationId();
        
        console.log(` Starting operation with retry: ${operationId}`);
        
        let lastError;
        let attempt = 0;
        
        while (attempt <= config.maxRetries) {
            try {
                console.log(`   Attempt ${attempt + 1}/${config.maxRetries + 1}`);
                
                const result = await operation(context, attempt);
                
                if (attempt > 0) {
                    console.log(` Operation succeeded on attempt ${attempt + 1}`);
                }
                
                this.logSuccess(operationId, attempt);
                return result;
                
            } catch (error) {
                lastError = error;
                attempt++;
                
                console.log(` Attempt ${attempt} failed: ${error.message}`);
                
                if (attempt <= config.maxRetries) {
                    const delay = this.calculateDelay(attempt, config);
                    console.log(` Retrying in ${delay}ms...`);
                    
                    await this.sleep(delay);
                } else {
                    console.log(` All retry attempts exhausted for ${operationId}`);
                }
            }
        }
        
        this.logFailure(operationId, config.maxRetries + 1, lastError);
        throw new Error(`Operation failed after ${config.maxRetries + 1} attempts: ${lastError.message}`);
    }

    calculateDelay(attempt, config) {
        let delay = config.baseDelay * Math.pow(config.backoffMultiplier, attempt - 1);
        
        // Cap at max delay
        delay = Math.min(delay, config.maxDelay);
        
        // Add jitter to prevent thundering herd
        if (config.jitter) {
            delay = delay * (0.5 + Math.random() * 0.5);
        }
        
        return Math.round(delay);
    }

    async sleep(ms) {
        return new Promise(resolve => setTimeout(resolve, ms));
    }

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

    logSuccess(operationId, attempts) {
        this.retryHistory.set(operationId, {
            operationId,
            success: true,
            attempts: attempts + 1,
            timestamp: new Date().toISOString()
        });
    }

    logFailure(operationId, attempts, error) {
        this.retryHistory.set(operationId, {
            operationId,
            success: false,
            attempts,
            error: error.message,
            timestamp: new Date().toISOString()
        });
    }

    getRetryStats() {
        const history = Array.from(this.retryHistory.values());
        const successful = history.filter(h => h.success).length;
        const failed = history.length - successful;
        
        const avgAttempts = history.length > 0 
            ? Math.round(history.reduce((sum, h) => sum + h.attempts, 0) / history.length)
            : 0;
        
        return {
            totalOperations: history.length,
            successful,
            failed,
            successRate: history.length > 0 ? Math.round((successful / history.length) * 100) : 0,
            averageAttempts: avgAttempts
        };
    }

    clearHistory() {
        this.retryHistory.clear();
        console.log(' Retry history cleared');
    }
}

module.exports = RetryController;