<?php
declare(strict_types=1);

namespace Fendx\Service\LoadBalancer\Strategy;

use Fendx\Service\LoadBalancer\Strategy\Router\TrafficRouter;
use Fendx\Service\LoadBalancer\Strategy\Analyzer\TrafficAnalyzer;
use Fendx\Service\LoadBalancer\Strategy\Balancer\TrafficBalancer;
use Fendx\Service\LoadBalancer\Strategy\Monitor\TrafficMonitor;

class TrafficDistributionStrategy
{
    protected TrafficRouter $router;
    protected TrafficAnalyzer $analyzer;
    protected TrafficBalancer $balancer;
    protected TrafficMonitor $monitor;
    protected array $config = [];
    protected array $rules = [];
    protected array $trafficStats = [];
    protected array $distributionHistory = [];

    public function __construct(array $config = [])
    {
        $this->config = array_merge($this->getDefaultConfig(), $config);
        $this->router = new TrafficRouter($this->config);
        $this->analyzer = new TrafficAnalyzer($this->config);
        $this->balancer = new TrafficBalancer($this->config);
        $this->monitor = new TrafficMonitor($this->config);
        
        $this->initialize();
    }

    /**
     * Distribute traffic to services based on strategy.
     */
    public function distributeTraffic(array $instances, array $request, string $strategy = 'weighted'): ?array
    {
        if (empty($instances)) {
            return null;
        }

        // Analyze request
        $requestAnalysis = $this->analyzer->analyzeRequest($request);
        
        // Apply routing rules
        $filteredInstances = $this->applyRoutingRules($instances, $requestAnalysis);
        
        if (empty($filteredInstances)) {
            return null;
        }
        
        // Select instance based on strategy
        $selectedInstance = $this->selectInstance($filteredInstances, $requestAnalysis, $strategy);
        
        if ($selectedInstance) {
            // Record traffic distribution
            $this->recordTrafficDistribution($selectedInstance['id'], $requestAnalysis, $strategy);
            
            // Update monitoring
            $this->monitor->recordRequest($selectedInstance['id'], $requestAnalysis);
        }
        
        return $selectedInstance;
    }

    /**
     * Add traffic distribution rule.
     */
    public function addRule(string $name, array $rule): void
    {
        $this->validateRule($rule);
        
        $this->rules[$name] = array_merge([
            'name' => $name,
            'enabled' => true,
            'priority' => 100,
            'conditions' => [],
            'actions' => [],
            'weight' => 1,
            'created_at' => time(),
            'updated_at' => time()
        ], $rule);
        
        // Sort rules by priority
        uasort($this->rules, function($a, $b) {
            return $a['priority'] <=> $b['priority'];
        });
        
        $this->logInfo("Traffic distribution rule added: {$name}");
    }

    /**
     * Remove traffic distribution rule.
     */
    public function removeRule(string $name): bool
    {
        if (!isset($this->rules[$name])) {
            return false;
        }
        
        unset($this->rules[$name]);
        
        $this->logInfo("Traffic distribution rule removed: {$name}");
        
        return true;
    }

    /**
     * Update traffic distribution rule.
     */
    public function updateRule(string $name, array $updates): bool
    {
        if (!isset($this->rules[$name])) {
            return false;
        }
        
        $this->rules[$name] = array_merge($this->rules[$name], $updates);
        $this->rules[$name]['updated_at'] = time();
        
        $this->logInfo("Traffic distribution rule updated: {$name}");
        
        return true;
    }

    /**
     * Get all rules.
     */
    public function getRules(): array
    {
        return $this->rules;
    }

    /**
     * Get rule by name.
     */
    public function getRule(string $name): ?array
    {
        return $this->rules[$name] ?? null;
    }

    /**
     * Enable/disable rule.
     */
    public function setRuleEnabled(string $name, bool $enabled): bool
    {
        if (!isset($this->rules[$name])) {
            return false;
        }
        
        $this->rules[$name]['enabled'] = $enabled;
        $this->rules[$name]['updated_at'] = time();
        
        $this->logInfo("Rule " . ($enabled ? 'enabled' : 'disabled') . ": {$name}");
        
        return true;
    }

    /**
     * Set traffic weights for services.
     */
    public function setTrafficWeights(array $weights): void
    {
        $this->balancer->setWeights($weights);
        
        $this->logInfo("Traffic weights updated for " . count($weights) . " services");
    }

    /**
     * Get traffic weights.
     */
    public function getTrafficWeights(): array
    {
        return $this->balancer->getWeights();
    }

    /**
     * Distribute traffic by percentage.
     */
    public function distributeByPercentage(array $instances, array $percentages): ?array
    {
        if (empty($instances) || empty($percentages)) {
            return null;
        }
        
        // Validate percentages sum to 100
        $totalPercentage = array_sum($percentages);
        if (abs($totalPercentage - 100) > 0.01) {
            throw new \InvalidArgumentException("Percentages must sum to 100, got: {$totalPercentage}");
        }
        
        // Select instance based on percentage distribution
        return $this->balancer->selectByPercentage($instances, $percentages);
    }

    /**
     * Distribute traffic by geographic location.
     */
    public function distributeByGeography(array $instances, string $clientLocation): ?array
    {
        if (empty($instances)) {
            return null;
        }
        
        // Find closest instances
        $closestInstances = $this->findClosestInstances($instances, $clientLocation);
        
        if (empty($closestInstances)) {
            // Fallback to any instance
            return $instances[0];
        }
        
        // Select from closest instances using weighted random
        return $this->balancer->selectWeightedRandom($closestInstances);
    }

    /**
     * Distribute traffic by user segment.
     */
    public function distributeBySegment(array $instances, string $userSegment): ?array
    {
        if (empty($instances)) {
            return null;
        }
        
        // Filter instances by segment
        $segmentInstances = array_filter($instances, function($instance) use ($userSegment) {
            $segments = $instance['segments'] ?? [];
            return in_array($userSegment, $segments) || in_array('all', $segments);
        });
        
        if (empty($segmentInstances)) {
            // Fallback to instances without segment restriction
            $segmentInstances = array_filter($instances, function($instance) {
                $segments = $instance['segments'] ?? [];
                return empty($segments) || in_array('all', $segments);
            });
        }
        
        if (empty($segmentInstances)) {
            return $instances[0]; // Ultimate fallback
        }
        
        return $this->balancer->selectRoundRobin(array_values($segmentInstances));
    }

    /**
     * Distribute traffic by time of day.
     */
    public function distributeByTime(array $instances, \DateTime $dateTime = null): ?array
    {
        $dateTime = $dateTime ?? new \DateTime();
        $hour = (int) $dateTime->format('H');
        
        if (empty($instances)) {
            return null;
        }
        
        // Filter instances by time availability
        $availableInstances = array_filter($instances, function($instance) use ($hour) {
            $availability = $instance['availability'] ?? [];
            
            if (empty($availability)) {
                return true; // Always available
            }
            
            foreach ($availability as $period) {
                if ($hour >= $period['start'] && $hour < $period['end']) {
                    return true;
                }
            }
            
            return false;
        });
        
        if (empty($availableInstances)) {
            return $instances[0]; // Fallback
        }
        
        return $this->balancer->selectWeightedRandom(array_values($availableInstances));
    }

    /**
     * Distribute traffic by load capacity.
     */
    public function distributeByCapacity(array $instances): ?array
    {
        if (empty($instances)) {
            return null;
        }
        
        // Calculate available capacity for each instance
        $capacityScores = [];
        
        foreach ($instances as $instance) {
            $maxCapacity = $instance['max_capacity'] ?? 100;
            $currentLoad = $instance['current_load'] ?? 0;
            $availableCapacity = max(0, $maxCapacity - $currentLoad);
            
            $capacityScores[$instance['id']] = $availableCapacity;
        }
        
        // Select instance with most available capacity
        $maxCapacity = max($capacityScores);
        $bestInstanceIds = array_keys($capacityScores, $maxCapacity);
        
        if (count($bestInstanceIds) === 1) {
            $bestInstanceId = $bestInstanceIds[0];
        } else {
            // Multiple instances with same capacity, use round-robin
            $bestInstanceId = $bestInstanceIds[array_rand($bestInstanceIds)];
        }
        
        foreach ($instances as $instance) {
            if ($instance['id'] === $bestInstanceId) {
                return $instance;
            }
        }
        
        return null;
    }

    /**
     * Get traffic distribution statistics.
     */
    public function getStatistics(): array
    {
        $totalRequests = 0;
        $serviceStats = [];
        $ruleStats = [];
        
        // Calculate service statistics
        foreach ($this->trafficStats as $serviceId => $stats) {
            $requests = $stats['total_requests'] ?? 0;
            $totalRequests += $requests;
            
            $serviceStats[$serviceId] = [
                'total_requests' => $requests,
                'percentage' => 0, // Will be calculated below
                'average_response_time' => $this->calculateAverageResponseTime($serviceId),
                'error_rate' => $this->calculateErrorRate($serviceId),
                'last_request' => $stats['last_request'] ?? null
            ];
        }
        
        // Calculate percentages
        if ($totalRequests > 0) {
            foreach ($serviceStats as $serviceId => &$stats) {
                $stats['percentage'] = ($stats['total_requests'] / $totalRequests) * 100;
            }
        }
        
        // Calculate rule statistics
        foreach ($this->rules as $ruleName => $rule) {
            $ruleStats[$ruleName] = [
                'enabled' => $rule['enabled'],
                'priority' => $rule['priority'],
                'match_count' => $rule['match_count'] ?? 0,
                'last_matched' => $rule['last_matched'] ?? null
            ];
        }
        
        return [
            'total_requests' => $totalRequests,
            'service_statistics' => $serviceStats,
            'rule_statistics' => $ruleStats,
            'active_rules' => count(array_filter($this->rules, fn($r) => $r['enabled'])),
            'distribution_history' => array_slice($this->distributionHistory, -10)
        ];
    }

    /**
     * Get traffic distribution history.
     */
    public function getDistributionHistory(int $limit = 100): array
    {
        return array_slice($this->distributionHistory, -$limit);
    }

    /**
     * Get real-time traffic metrics.
     */
    public function getRealTimeMetrics(): array
    {
        return [
            'current_rps' => $this->monitor->getCurrentRPS(),
            'active_connections' => $this->monitor->getActiveConnections(),
            'average_response_time' => $this->monitor->getAverageResponseTime(),
            'error_rate' => $this->monitor->getErrorRate(),
            'top_services' => $this->monitor->getTopServices(10),
            'geographic_distribution' => $this->monitor->getGeographicDistribution(),
            'user_segment_distribution' => $this->monitor->getSegmentDistribution()
        ];
    }

    /**
     * Optimize traffic distribution.
     */
    public function optimizeDistribution(): array
    {
        $recommendations = [];
        $currentStats = $this->getStatistics();
        
        // Analyze service performance
        foreach ($currentStats['service_statistics'] as $serviceId => $stats) {
            if ($stats['error_rate'] > 5) {
                $recommendations[] = [
                    'type' => 'high_error_rate',
                    'service_id' => $serviceId,
                    'message' => "Service {$serviceId} has high error rate: {$stats['error_rate']}%",
                    'action' => 'consider_reducing_weight_or_failing_over'
                ];
            }
            
            if ($stats['average_response_time'] > 1000) { // 1 second
                $recommendations[] = [
                    'type' => 'slow_response',
                    'service_id' => $serviceId,
                    'message' => "Service {$serviceId} has slow response time: {$stats['average_response_time']}ms",
                    'action' => 'consider_reducing_weight'
                ];
            }
        }
        
        // Analyze rule effectiveness
        foreach ($currentStats['rule_statistics'] as $ruleName => $stats) {
            if ($stats['enabled'] && $stats['match_count'] === 0) {
                $recommendations[] = [
                    'type' => 'unused_rule',
                    'rule_name' => $ruleName,
                    'message' => "Rule {$ruleName} is enabled but never matches",
                    'action' => 'review_or_disable_rule'
                ];
            }
        }
        
        // Suggest weight adjustments
        $weightSuggestions = $this->suggestWeightAdjustments();
        $recommendations = array_merge($recommendations, $weightSuggestions);
        
        return $recommendations;
    }

    /**
     * Reset traffic statistics.
     */
    public function resetStatistics(): void
    {
        $this->trafficStats = [];
        $this->distributionHistory = [];
        
        foreach ($this->rules as &$rule) {
            $rule['match_count'] = 0;
            $rule['last_matched'] = null;
        }
        
        $this->logInfo("Traffic statistics reset");
    }

    /**
     * Export traffic configuration.
     */
    public function exportConfiguration(string $format = 'json'): string
    {
        $data = [
            'rules' => $this->rules,
            'traffic_weights' => $this->getTrafficWeights(),
            'statistics' => $this->getStatistics(),
            'distribution_history' => $this->distributionHistory,
            'exported_at' => date('Y-m-d H:i:s'),
            'version' => $this->config['version'] ?? '1.0'
        ];

        switch ($format) {
            case 'json':
                return json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
            case 'php':
                return '<?php return ' . var_export($data, true) . ';';
            default:
                throw new \InvalidArgumentException("Unsupported export format: {$format}");
        }
    }

    /**
     * Apply routing rules to instances.
     */
    protected function applyRoutingRules(array $instances, array $requestAnalysis): array
    {
        $filteredInstances = $instances;
        
        foreach ($this->rules as $rule) {
            if (!$rule['enabled']) {
                continue;
            }
            
            if ($this->matchesRuleConditions($rule['conditions'], $requestAnalysis)) {
                $rule['match_count'] = ($rule['match_count'] ?? 0) + 1;
                $rule['last_matched'] = time();
                
                // Apply rule actions
                $filteredInstances = $this->applyRuleActions($filteredInstances, $rule['actions']);
                
                // If rule has stop_processing flag, break
                if ($rule['stop_processing'] ?? false) {
                    break;
                }
            }
        }
        
        return $filteredInstances;
    }

    /**
     * Check if request matches rule conditions.
     */
    protected function matchesRuleConditions(array $conditions, array $requestAnalysis): bool
    {
        foreach ($conditions as $condition) {
            if (!$this->matchesCondition($condition, $requestAnalysis)) {
                return false;
            }
        }
        
        return true;
    }

    /**
     * Check if single condition matches.
     */
    protected function matchesCondition(array $condition, array $requestAnalysis): bool
    {
        $field = $condition['field'];
        $operator = $condition['operator'];
        $value = $condition['value'];
        $requestValue = $this->getRequestValue($requestAnalysis, $field);
        
        switch ($operator) {
            case 'equals':
                return $requestValue === $value;
            case 'not_equals':
                return $requestValue !== $value;
            case 'in':
                return in_array($requestValue, (array) $value);
            case 'not_in':
                return !in_array($requestValue, (array) $value);
            case 'contains':
                return is_string($requestValue) && strpos($requestValue, $value) !== false;
            case 'starts_with':
                return is_string($requestValue) && strpos($requestValue, $value) === 0;
            case 'ends_with':
                return is_string($requestValue) && substr($requestValue, -strlen($value)) === $value;
            case 'greater_than':
                return $requestValue > $value;
            case 'less_than':
                return $requestValue < $value;
            case 'between':
                return $requestValue >= $value[0] && $requestValue <= $value[1];
            case 'regex':
                return preg_match($value, (string) $requestValue) === 1;
            default:
                return false;
        }
    }

    /**
     * Get value from request analysis.
     */
    protected function getRequestValue(array $requestAnalysis, string $field)
    {
        $fields = explode('.', $field);
        $value = $requestAnalysis;
        
        foreach ($fields as $f) {
            if (!is_array($value) || !array_key_exists($f, $value)) {
                return null;
            }
            $value = $value[$f];
        }
        
        return $value;
    }

    /**
     * Apply rule actions to instances.
     */
    protected function applyRuleActions(array $instances, array $actions): array
    {
        $filteredInstances = $instances;
        
        foreach ($actions as $action) {
            switch ($action['type']) {
                case 'filter':
                    $filteredInstances = $this->filterInstances($filteredInstances, $action['conditions']);
                    break;
                case 'set_weight':
                    $filteredInstances = $this->setInstanceWeights($filteredInstances, $action['weights']);
                    break;
                case 'prioritize':
                    $filteredInstances = $this->prioritizeInstances($filteredInstances, $action['criteria']);
                    break;
                case 'exclude':
                    $filteredInstances = $this->excludeInstances($filteredInstances, $action['instances']);
                    break;
            }
        }
        
        return $filteredInstances;
    }

    /**
     * Select instance based on strategy.
     */
    protected function selectInstance(array $instances, array $requestAnalysis, string $strategy): ?array
    {
        switch ($strategy) {
            case 'weighted':
                return $this->balancer->selectWeightedRandom($instances);
            case 'round_robin':
                return $this->balancer->selectRoundRobin($instances);
            case 'least_connections':
                return $this->balancer->selectLeastConnections($instances);
            case 'response_time':
                return $this->balancer->selectByResponseTime($instances);
            case 'geographic':
                $location = $requestAnalysis['client']['location'] ?? 'unknown';
                return $this->distributeByGeography($instances, $location);
            case 'segment':
                $segment = $requestAnalysis['user']['segment'] ?? 'default';
                return $this->distributeBySegment($instances, $segment);
            case 'capacity':
                return $this->distributeByCapacity($instances);
            default:
                return $instances[0];
        }
    }

    /**
     * Find closest instances by geography.
     */
    protected function findClosestInstances(array $instances, string $clientLocation): array
    {
        // This would use a proper geolocation service in production
        // For now, return instances with location matching
        return array_filter($instances, function($instance) use ($clientLocation) {
            $instanceLocation = $instance['location'] ?? 'unknown';
            return $instanceLocation === $clientLocation || $instanceLocation === 'global';
        });
    }

    /**
     * Record traffic distribution.
     */
    protected function recordTrafficDistribution(string $serviceId, array $requestAnalysis, string $strategy): void
    {
        // Update service stats
        if (!isset($this->trafficStats[$serviceId])) {
            $this->trafficStats[$serviceId] = [
                'total_requests' => 0,
                'requests_by_strategy' => [],
                'response_times' => [],
                'errors' => 0,
                'last_request' => null
            ];
        }
        
        $this->trafficStats[$serviceId]['total_requests']++;
        $this->trafficStats[$serviceId]['requests_by_strategy'][$strategy] = 
            ($this->trafficStats[$serviceId]['requests_by_strategy'][$strategy] ?? 0) + 1;
        $this->trafficStats[$serviceId]['last_request'] = time();
        
        // Add to distribution history
        $this->distributionHistory[] = [
            'timestamp' => time(),
            'service_id' => $serviceId,
            'strategy' => $strategy,
            'request_analysis' => $requestAnalysis
        ];
        
        // Limit history size
        if (count($this->distributionHistory) > 1000) {
            $this->distributionHistory = array_slice($this->distributionHistory, -1000);
        }
    }

    /**
     * Calculate average response time for service.
     */
    protected function calculateAverageResponseTime(string $serviceId): float
    {
        $stats = $this->trafficStats[$serviceId] ?? [];
        $responseTimes = $stats['response_times'] ?? [];
        
        if (empty($responseTimes)) {
            return 0.0;
        }
        
        return array_sum($responseTimes) / count($responseTimes);
    }

    /**
     * Calculate error rate for service.
     */
    protected function calculateErrorRate(string $serviceId): float
    {
        $stats = $this->trafficStats[$serviceId] ?? [];
        $totalRequests = $stats['total_requests'] ?? 0;
        $errors = $stats['errors'] ?? 0;
        
        if ($totalRequests === 0) {
            return 0.0;
        }
        
        return ($errors / $totalRequests) * 100;
    }

    /**
     * Suggest weight adjustments.
     */
    protected function suggestWeightAdjustments(): array
    {
        $suggestions = [];
        $stats = $this->getStatistics();
        
        foreach ($stats['service_statistics'] as $serviceId => $serviceStats) {
            if ($serviceStats['error_rate'] > 2) {
                $suggestions[] = [
                    'type' => 'weight_adjustment',
                    'service_id' => $serviceId,
                    'current_weight' => $this->balancer->getWeight($serviceId),
                    'suggested_weight' => max(1, (int) ($this->balancer->getWeight($serviceId) * 0.5)),
                    'reason' => 'High error rate detected'
                ];
            }
        }
        
        return $suggestions;
    }

    /**
     * Validate rule configuration.
     */
    protected function validateRule(array $rule): void
    {
        if (empty($rule['conditions'])) {
            throw new \InvalidArgumentException("Rule must have at least one condition");
        }
        
        if (empty($rule['actions'])) {
            throw new \InvalidArgumentException("Rule must have at least one action");
        }
        
        foreach ($rule['conditions'] as $condition) {
            if (!isset($condition['field']) || !isset($condition['operator']) || !isset($condition['value'])) {
                throw new \InvalidArgumentException("Condition must have field, operator, and value");
            }
        }
    }

    /**
     * Initialize traffic distribution strategy.
     */
    protected function initialize(): void
    {
        // Load configuration from storage
        $this->loadConfiguration();
        
        // Start monitoring
        $this->monitor->start();
        
        $this->logInfo("Traffic distribution strategy initialized");
    }

    /**
     * Load configuration from storage.
     */
    protected function loadConfiguration(): void
    {
        // This would load from persistent storage in production
        $this->logInfo("Configuration loaded");
    }

    /**
     * Log info message.
     */
    protected function logInfo(string $message): void
    {
        if ($this->config['logging_enabled']) {
            error_log("[TrafficDistributionStrategy] {$message}");
        }
    }

    /**
     * Get default configuration.
     */
    protected function getDefaultConfig(): array
    {
        return [
            'default_strategy' => 'weighted',
            'enable_monitoring' => true,
            'monitoring_interval' => 60,
            'history_retention' => 1000,
            'logging_enabled' => true,
            'optimization_enabled' => true,
            'optimization_interval' => 300,
            'version' => '1.0'
        ];
    }

    /**
     * Get configuration.
     */
    public function getConfig(): array
    {
        return $this->config;
    }

    /**
     * Set configuration.
     */
    public function setConfig(array $config): void
    {
        $this->config = array_merge($this->config, $config);
    }

    /**
     * Create traffic distribution strategy instance.
     */
    public static function create(array $config = []): self
    {
        return new self($config);
    }

    /**
     * Create for high traffic.
     */
    public static function forHighTraffic(): self
    {
        return new self([
            'default_strategy' => 'capacity',
            'enable_monitoring' => true,
            'monitoring_interval' => 30,
            'optimization_enabled' => true,
            'optimization_interval' => 120
        ]);
    }

    /**
     * Create for global distribution.
     */
    public static function forGlobalDistribution(): self
    {
        return new self([
            'default_strategy' => 'geographic',
            'enable_monitoring' => true,
            'logging_enabled' => true
        ]);
    }
}