<?php
declare(strict_types=1);

namespace Fendx\Service\Performance;

use Fendx\Service\Performance\Database\QueryProfiler;
use Fendx\Service\Performance\Database\IndexAnalyzer;
use Fendx\Service\Performance\Database\QueryOptimizer;
use Fendx\Service\Performance\Database\ConnectionPool;
use Fendx\Service\Performance\Reporter\DatabaseReporter;

class DatabaseOptimizer
{
    protected array $config = [];
    protected QueryProfiler $queryProfiler;
    protected IndexAnalyzer $indexAnalyzer;
    protected QueryOptimizer $queryOptimizer;
    protected ConnectionPool $connectionPool;
    protected DatabaseReporter $reporter;
    protected array $queryResults = [];
    protected array $optimizationHistory = [];

    public function __construct(array $config = [])
    {
        $this->config = array_merge($this->getDefaultConfig(), $config);
        $this->queryProfiler = new QueryProfiler($this->config['query_profiler'] ?? []);
        $this->indexAnalyzer = new IndexAnalyzer($this->config['index_analyzer'] ?? []);
        $this->queryOptimizer = new QueryOptimizer($this->config['query_optimizer'] ?? []);
        $this->connectionPool = new ConnectionPool($this->config['connection_pool'] ?? []);
        $this->reporter = new DatabaseReporter($this->config['reporter'] ?? []);
    }

    /**
     * Profile database query performance.
     */
    public function profileQuery(string $query, array $params = [], array $options = []): array
    {
        $testConfig = array_merge($this->config['query_profiling'] ?? [], $options);
        
        $result = [
            'query' => $query,
            'params' => $params,
            'executions' => $testConfig['executions'] ?? 100,
            'warmup_executions' => $testConfig['warmup_executions'] ?? 10,
            'execution_times' => [],
            'statistics' => [],
            'query_plan' => [],
            'performance_issues' => [],
            'optimization_suggestions' => [],
            'timestamp' => microtime(true)
        ];

        // Start query profiling
        $this->queryProfiler->startProfiling();
        
        // Warmup executions
        for ($i = 0; $i < $result['warmup_executions']; $i++) {
            $this->executeQuery($query, $params);
        }
        
        $executionTimes = [];
        $queryPlans = [];
        
        // Actual profiling
        for ($i = 0; $i < $result['executions']; $i++) {
            $executionStart = microtime(true);
            
            $resultSet = $this->executeQuery($query, $params);
            $queryPlan = $this->getQueryPlan($query, $params);
            
            $executionEnd = microtime(true);
            $executionTime = ($executionEnd - $executionStart) * 1000; // milliseconds
            
            $executionTimes[] = $executionTime;
            $queryPlans[] = $queryPlan;
        }
        
        // Stop profiling
        $profileData = $this->queryProfiler->stopProfiling();
        
        $result['execution_times'] = $executionTimes;
        $result['query_plan'] = $this->analyzeQueryPlans($queryPlans);
        $result['profile_data'] = $profileData;
        
        // Calculate statistics
        $result['statistics'] = $this->calculateQueryStatistics($executionTimes);
        
        // Detect performance issues
        $result['performance_issues'] = $this->detectPerformanceIssues($result);
        
        // Generate optimization suggestions
        $result['optimization_suggestions'] = $this->generateQueryOptimizationSuggestions($result);
        
        // Store result
        $this->queryResults[] = $result;

        return $result;
    }

    /**
     * Analyze database indexes.
     */
    public function analyzeIndexes(string $tableName, array $options = []): array
    {
        $testConfig = array_merge($this->config['index_analysis'] ?? [], $options);
        
        $result = [
            'table' => $tableName,
            'current_indexes' => [],
            'unused_indexes' => [],
            'missing_indexes' => [],
            'duplicate_indexes' => [],
            'index_usage_stats' => [],
            'optimization_recommendations' => [],
            'timestamp' => microtime(true)
        ];

        // Get current indexes
        $result['current_indexes'] = $this->getTableIndexes($tableName);
        
        // Analyze index usage
        $result['index_usage_stats'] = $this->getIndexUsageStats($tableName);
        
        // Find unused indexes
        $result['unused_indexes'] = $this->findUnusedIndexes($result['current_indexes'], $result['index_usage_stats']);
        
        // Find missing indexes by analyzing queries
        if ($testConfig['analyze_queries'] ?? true) {
            $result['missing_indexes'] = $this->findMissingIndexes($tableName);
        }
        
        // Find duplicate indexes
        $result['duplicate_indexes'] = $this->findDuplicateIndexes($result['current_indexes']);
        
        // Generate recommendations
        $result['optimization_recommendations'] = $this->generateIndexRecommendations($result);
        
        return $result;
    }

    /**
     * Optimize database query.
     */
    public function optimizeQuery(string $query, array $params = [], array $options = []): array
    {
        $testConfig = array_merge($this->config['query_optimization'] ?? [], $options);
        
        $result = [
            'original_query' => $query,
            'original_params' => $params,
            'optimized_queries' => [],
            'performance_comparison' => [],
            'best_optimization' => [],
            'improvement_percentage' => 0,
            'timestamp' => microtime(true)
        ];

        // Profile original query
        $originalProfile = $this->profileQuery($query, $params, ['executions' => 50]);
        $result['original_performance'] = $originalProfile;
        
        // Generate optimization strategies
        $optimizationStrategies = $this->generateOptimizationStrategies($query, $testConfig);
        
        $optimizedResults = [];
        
        foreach ($optimizationStrategies as $strategy => $optimizedQuery) {
            try {
                $optimizedProfile = $this->profileQuery($optimizedQuery['query'], $optimizedQuery['params'], ['executions' => 50]);
                
                $optimizedResults[$strategy] = [
                    'query' => $optimizedQuery['query'],
                    'params' => $optimizedQuery['params'],
                    'strategy' => $strategy,
                    'performance' => $optimizedProfile,
                    'improvement' => $this->calculateQueryImprovement($originalProfile, $optimizedProfile)
                ];
                
            } catch (\Exception $e) {
                $optimizedResults[$strategy] = [
                    'query' => $optimizedQuery['query'],
                    'strategy' => $strategy,
                    'error' => $e->getMessage()
                ];
            }
        }
        
        $result['optimized_queries'] = $optimizedResults;
        
        // Find best optimization
        $bestImprovement = 0;
        $bestStrategy = '';
        
        foreach ($optimizedResults as $strategy => $optimized) {
            if (isset($optimized['improvement']['performance_improvement'])) {
                $improvement = $optimized['improvement']['performance_improvement'];
                if ($improvement > $bestImprovement) {
                    $bestImprovement = $improvement;
                    $bestStrategy = $strategy;
                }
            }
        }
        
        if ($bestStrategy !== '') {
            $result['best_optimization'] = $optimizedResults[$bestStrategy];
            $result['improvement_percentage'] = $bestImprovement;
        }
        
        // Store optimization history
        $this->optimizationHistory[] = $result;
        
        return $result;
    }

    /**
     * Test connection pool performance.
     */
    public function testConnectionPoolPerformance(array $options = []): array
    {
        $testConfig = array_merge($this->config['connection_pool_testing'] ?? [], $options);
        
        $result = [
            'pool_size' => $testConfig['pool_size'] ?? 10,
            'concurrent_connections' => $testConfig['concurrent_connections'] ?? 50,
            'operations_per_connection' => $testConfig['operations_per_connection'] ?? 20,
            'with_pool' => [],
            'without_pool' => [],
            'performance_gain' => [],
            'timestamp' => microtime(true)
        ];

        // Test without connection pool
        $withoutPoolResult = $this->testConnectionsDirectly($testConfig);
        $result['without_pool'] = $withoutPoolResult;
        
        // Test with connection pool
        $withPoolResult = $this->testConnectionsWithPool($testConfig);
        $result['with_pool'] = $withPoolResult;
        
        // Calculate performance gain
        $result['performance_gain'] = $this->calculateConnectionPoolGain($withoutPoolResult, $withPoolResult);
        
        return $result;
    }

    /**
     * Analyze query patterns.
     */
    public function analyzeQueryPatterns(array $queries, array $options = []): array
    {
        $testConfig = array_merge($this->config['pattern_analysis'] ?? [], $options);
        
        $result = [
            'total_queries' => count($queries),
            'query_types' => [],
            'table_access_patterns' => [],
            'frequent_queries' => [],
            'slow_queries' => [],
            'optimization_opportunities' => [],
            'recommendations' => [],
            'timestamp' => microtime(true)
        ];

        $queryTypes = [];
        $tableAccess = [];
        $queryProfiles = [];
        
        foreach ($queries as $index => $query) {
            $profile = $this->profileQuery($query['sql'], $query['params'] ?? [], ['executions' => 10]);
            $queryProfiles[] = $profile;
            
            // Analyze query type
            $queryType = $this->getQueryType($query['sql']);
            $queryTypes[$queryType] = ($queryTypes[$queryType] ?? 0) + 1;
            
            // Analyze table access
            $tables = $this->extractTables($query['sql']);
            foreach ($tables as $table) {
                if (!isset($tableAccess[$table])) {
                    $tableAccess[$table] = ['access_count' => 0, 'total_time' => 0, 'queries' => []];
                }
                $tableAccess[$table]['access_count']++;
                $tableAccess[$table]['total_time'] += $profile['statistics']['average'];
                $tableAccess[$table]['queries'][] = $index;
            }
        }
        
        $result['query_types'] = $queryTypes;
        $result['table_access_patterns'] = $tableAccess;
        
        // Identify frequent and slow queries
        $result['frequent_queries'] = $this->identifyFrequentQueries($queries, $tableAccess);
        $result['slow_queries'] = $this->identifySlowQueries($queries, $queryProfiles);
        
        // Find optimization opportunities
        $result['optimization_opportunities'] = $this->findOptimizationOpportunities($queries, $queryProfiles, $tableAccess);
        
        // Generate recommendations
        $result['recommendations'] = $this->generatePatternRecommendations($result);
        
        return $result;
    }

    /**
     * Test database performance under load.
     */
    public function testDatabaseLoad(array $queries, array $options = []): array
    {
        $testConfig = array_merge($this->config['load_testing'] ?? [], $options);
        
        $result = [
            'queries' => $queries,
            'concurrent_users' => $testConfig['concurrent_users'] ?? 20,
            'duration' => $testConfig['duration'] ?? 60, // seconds
            'ramp_up_time' => $testConfig['ramp_up_time'] ?? 10,
            'performance_metrics' => [],
            'resource_usage' => [],
            'bottlenecks' => [],
            'recommendations' => [],
            'timestamp' => microtime(true)
        ];

        // Start load test
        $startTime = microtime(true);
        $endTime = $startTime + $result['duration'];
        
        $performanceData = [];
        $resourceData = [];
        
        $currentTime = $startTime;
        
        while ($currentTime < $endTime) {
            $batchStart = microtime(true);
            
            // Calculate current concurrent users based on ramp-up
            if ($currentTime - $startTime < $result['ramp_up_time']) {
                $currentUsers = (int) (($currentTime - $startTime) / $result['ramp_up_time'] * $result['concurrent_users']);
            } else {
                $currentUsers = $result['concurrent_users'];
            }
            
            // Execute queries concurrently
            $batchResults = $this->executeConcurrentQueries($queries, $currentUsers);
            
            $batchEnd = microtime(true);
            $batchDuration = $batchEnd - $batchStart;
            
            $performanceData[] = [
                'timestamp' => $currentTime,
                'concurrent_users' => $currentUsers,
                'queries_executed' => count($batchResults),
                'average_response_time' => $this->calculateAverageResponseTime($batchResults),
                'throughput' => count($batchResults) / $batchDuration,
                'error_rate' => $this->calculateErrorRate($batchResults)
            ];
            
            // Collect resource usage
            $resourceData[] = [
                'timestamp' => $currentTime,
                'cpu_usage' => $this->getCpuUsage(),
                'memory_usage' => memory_get_usage(true),
                'database_connections' => $this->getActiveConnections()
            ];
            
            $currentTime = microtime(true);
            
            // Small delay between batches
            usleep(100000); // 100ms
        }
        
        $result['performance_metrics'] = $performanceData;
        $result['resource_usage'] = $resourceData;
        
        // Analyze bottlenecks
        $result['bottlenecks'] = $this->analyzeDatabaseBottlenecks($performanceData, $resourceData);
        
        // Generate recommendations
        $result['recommendations'] = $this->generateLoadTestRecommendations($result);
        
        return $result;
    }

    /**
     * Generate database optimization report.
     */
    public function getOptimizationReport(array $results, string $format = 'html'): string
    {
        return $this->reporter->generate($results, $format);
    }

    /**
     * Get database performance statistics.
     */
    public function getDatabaseStatistics(): array
    {
        return [
            'queries_profiled' => count($this->queryResults),
            'optimizations_performed' => count($this->optimizationHistory),
            'average_query_time' => $this->calculateAverageQueryTime(),
            'slow_queries_count' => $this->countSlowQueries(),
            'connection_pool_stats' => $this->connectionPool->getStatistics()
        ];
    }

    /**
     * Clear optimization results.
     */
    public function clearResults(): void
    {
        $this->queryResults = [];
        $this->optimizationHistory = [];
    }

    /**
     * Execute database query.
     */
    protected function executeQuery(string $query, array $params = []): array
    {
        // This would be implemented based on your database layer
        // For now, simulate query execution
        usleep(rand(1000, 5000)); // Simulate 1-5ms execution time
        
        return [
            'id' => rand(1, 1000),
            'data' => 'sample_data',
            'execution_time' => rand(1000, 5000) / 1000 // milliseconds
        ];
    }

    /**
     * Get query execution plan.
     */
    protected function getQueryPlan(string $query, array $params = []): array
    {
        // This would execute EXPLAIN or similar command
        // For now, return mock plan
        return [
            'type' => 'ALL',
            'table' => 'users',
            'rows' => 1000,
            'filtered' => 100,
            'key' => null,
            'possible_keys' => ['PRIMARY', 'email_index']
        ];
    }

    /**
     * Get table indexes.
     */
    protected function getTableIndexes(string $tableName): array
    {
        // This would query the database for index information
        // For now, return mock indexes
        return [
            [
                'name' => 'PRIMARY',
                'columns' => ['id'],
                'type' => 'BTREE',
                'unique' => true,
                'cardinality' => 1000
            ],
            [
                'name' => 'email_index',
                'columns' => ['email'],
                'type' => 'BTREE',
                'unique' => true,
                'cardinality' => 1000
            ]
        ];
    }

    /**
     * Get index usage statistics.
     */
    protected function getIndexUsageStats(string $tableName): array
    {
        // This would query index usage statistics
        // For now, return mock stats
        return [
            'PRIMARY' => [
                'usage_count' => 5000,
                'last_used' => date('Y-m-d H:i:s'),
                'efficiency' => 0.95
            ],
            'email_index' => [
                'usage_count' => 100,
                'last_used' => date('Y-m-d H:i:s', strtotime('-1 day')),
                'efficiency' => 0.80
            ]
        ];
    }

    /**
     * Find unused indexes.
     */
    protected function findUnusedIndexes(array $indexes, array $usageStats): array
    {
        $unused = [];
        
        foreach ($indexes as $index) {
            $indexName = $index['name'];
            
            if (!isset($usageStats[$indexName]) || 
                $usageStats[$indexName]['usage_count'] < 10) {
                $unused[] = $index;
            }
        }
        
        return $unused;
    }

    /**
     * Find missing indexes.
     */
    protected function findMissingIndexes(string $tableName): array
    {
        // This would analyze query patterns and suggest missing indexes
        // For now, return mock suggestions
        return [
            [
                'columns' => ['created_at', 'status'],
                'reason' => 'Frequent filtering on these columns',
                'estimated_improvement' => '50%'
            ]
        ];
    }

    /**
     * Find duplicate indexes.
     */
    protected function findDuplicateIndexes(array $indexes): array
    {
        $duplicates = [];
        
        for ($i = 0; $i < count($indexes); $i++) {
            for ($j = $i + 1; $j < count($indexes); $j++) {
                if ($this->areIndexesDuplicate($indexes[$i], $indexes[$j])) {
                    $duplicates[] = [
                        'index1' => $indexes[$i]['name'],
                        'index2' => $indexes[$j]['name'],
                        'columns' => $indexes[$i]['columns']
                    ];
                }
            }
        }
        
        return $duplicates;
    }

    /**
     * Check if indexes are duplicate.
     */
    protected function areIndexesDuplicate(array $index1, array $index2): bool
    {
        // Simple check - if one index is a prefix of another
        $cols1 = $index1['columns'];
        $cols2 = $index2['columns'];
        
        if (count($cols1) <= count($cols2)) {
            for ($i = 0; $i < count($cols1); $i++) {
                if ($cols1[$i] !== $cols2[$i]) {
                    return false;
                }
            }
            return true;
        }
        
        return false;
    }

    /**
     * Analyze query plans.
     */
    protected function analyzeQueryPlans(array $plans): array
    {
        if (empty($plans)) {
            return [];
        }
        
        $analysis = [
            'most_common_type' => '',
            'average_rows_examined' => 0,
            'index_usage_rate' => 0,
            'full_table_scans' => 0
        ];
        
        $types = [];
        $totalRows = 0;
        $indexUsed = 0;
        $fullScans = 0;
        
        foreach ($plans as $plan) {
            $types[$plan['type']] = ($types[$plan['type']] ?? 0) + 1;
            $totalRows += $plan['rows'] ?? 0;
            
            if ($plan['key'] !== null) {
                $indexUsed++;
            }
            
            if ($plan['type'] === 'ALL') {
                $fullScans++;
            }
        }
        
        $analysis['most_common_type'] = array_keys($types, max($values))[0] ?? 'UNKNOWN';
        $analysis['average_rows_examined'] = $totalRows / count($plans);
        $analysis['index_usage_rate'] = ($indexUsed / count($plans)) * 100;
        $analysis['full_table_scans'] = $fullScans;
        
        return $analysis;
    }

    /**
     * Calculate query statistics.
     */
    protected function calculateQueryStatistics(array $executionTimes): array
    {
        if (empty($executionTimes)) {
            return [
                'count' => 0,
                'min' => 0,
                'max' => 0,
                'average' => 0,
                'median' => 0,
                'std_dev' => 0
            ];
        }

        sort($executionTimes);
        $count = count($executionTimes);
        $sum = array_sum($executionTimes);
        
        $mean = $sum / $count;
        $median = $count % 2 === 0 ? 
            ($executionTimes[$count / 2 - 1] + $executionTimes[$count / 2]) / 2 : 
            $executionTimes[floor($count / 2)];
        
        // Calculate standard deviation
        $variance = 0;
        foreach ($executionTimes as $time) {
            $variance += pow($time - $mean, 2);
        }
        $stdDev = sqrt($variance / $count);
        
        return [
            'count' => $count,
            'min' => min($executionTimes),
            'max' => max($executionTimes),
            'average' => $mean,
            'median' => $median,
            'std_dev' => $stdDev
        ];
    }

    /**
     * Detect performance issues.
     */
    protected function detectPerformanceIssues(array $result): array
    {
        $issues = [];
        
        $stats = $result['statistics'];
        $planAnalysis = $result['query_plan'];
        
        // Slow query
        if ($stats['average'] > 1000) { // > 1 second
            $issues[] = [
                'type' => 'slow_query',
                'severity' => 'high',
                'description' => "Average execution time is {$stats['average']}ms",
                'recommendation' => 'Optimize query or add appropriate indexes'
            ];
        }
        
        // High variance
        if ($stats['std_dev'] > $stats['average'] * 0.5) {
            $issues[] = [
                'type' => 'inconsistent_performance',
                'severity' => 'medium',
                'description' => 'Query execution time is inconsistent',
                'recommendation' => 'Investigate parameter sniffing or caching issues'
            ];
        }
        
        // Full table scans
        if (isset($planAnalysis['full_table_scans']) && $planAnalysis['full_table_scans'] > 0) {
            $issues[] = [
                'type' => 'full_table_scan',
                'severity' => 'high',
                'description' => 'Query performs full table scans',
                'recommendation' => 'Add appropriate indexes to avoid full scans'
            ];
        }
        
        // Low index usage
        if (isset($planAnalysis['index_usage_rate']) && $planAnalysis['index_usage_rate'] < 50) {
            $issues[] = [
                'type' => 'low_index_usage',
                'severity' => 'medium',
                'description' => 'Low index usage rate',
                'recommendation' => 'Review query structure and available indexes'
            ];
        }
        
        return $issues;
    }

    /**
     * Generate query optimization suggestions.
     */
    protected function generateQueryOptimizationSuggestions(array $result): array
    {
        $suggestions = [];
        
        $issues = $result['performance_issues'];
        
        foreach ($issues as $issue) {
            $suggestions[] = $issue['recommendation'];
        }
        
        // Additional suggestions based on query analysis
        if (strpos(strtolower($result['query']), 'select *') !== false) {
            $suggestions[] = 'Avoid SELECT *, specify only needed columns';
        }
        
        if (strpos(strtolower($result['query']), 'order by') !== false && 
            !isset($result['query_plan']['key'])) {
            $suggestions[] = 'Consider adding index for ORDER BY clause';
        }
        
        return array_unique($suggestions);
    }

    /**
     * Generate optimization strategies.
     */
    protected function generateOptimizationStrategies(string $query, array $config): array
    {
        $strategies = [];
        
        // Strategy 1: Add LIMIT clause
        if (stripos($query, 'LIMIT') === false && stripos($query, 'SELECT') === 0) {
            $strategies['add_limit'] = [
                'query' => $query . ' LIMIT 100',
                'params' => []
            ];
        }
        
        // Strategy 2: Optimize SELECT columns
        if (stripos($query, 'SELECT *') !== false) {
            $optimizedQuery = str_replace('SELECT *', 'SELECT id, name, email', $query);
            $strategies['specific_columns'] = [
                'query' => $optimizedQuery,
                'params' => []
            ];
        }
        
        // Strategy 3: Add index hints (MySQL specific)
        if (stripos($query, 'SELECT') === 0) {
            $strategies['index_hint'] = [
                'query' => preg_replace('/SELECT/i', 'SELECT /*+ INDEX(users email_index) */', $query, 1),
                'params' => []
            ];
        }
        
        return $strategies;
    }

    /**
     * Calculate query improvement.
     */
    protected function calculateQueryImprovement(array $original, array $optimized): array
    {
        $originalTime = $original['statistics']['average'];
        $optimizedTime = $optimized['statistics']['average'];
        
        $improvement = 0;
        if ($originalTime > 0) {
            $improvement = (($originalTime - $optimizedTime) / $originalTime) * 100;
        }
        
        return [
            'performance_improvement' => $improvement,
            'original_time' => $originalTime,
            'optimized_time' => $optimizedTime,
            'time_saved' => $originalTime - $optimizedTime
        ];
    }

    /**
     * Test connections directly.
     */
    protected function testConnectionsDirectly(array $config): array
    {
        $startTime = microtime(true);
        $startMemory = memory_get_usage(true);
        
        $connectionTimes = [];
        $totalOperations = 0;
        
        for ($i = 0; $i < $config['concurrent_connections']; $i++) {
            $connStart = microtime(true);
            
            // Simulate direct connection
            $connection = $this->createDirectConnection();
            
            for ($j = 0; $j < $config['operations_per_connection']; $j++) {
                $this->executeQuery('SELECT 1');
                $totalOperations++;
            }
            
            $this->closeConnection($connection);
            
            $connEnd = microtime(true);
            $connectionTimes[] = ($connEnd - $connStart) * 1000;
        }
        
        $endTime = microtime(true);
        $endMemory = memory_get_usage(true);
        
        return [
            'duration' => $endTime - $startTime,
            'memory_used' => $endMemory - $startMemory,
            'total_operations' => $totalOperations,
            'average_connection_time' => array_sum($connectionTimes) / count($connectionTimes),
            'throughput' => $totalOperations / ($endTime - $startTime)
        ];
    }

    /**
     * Test connections with pool.
     */
    protected function testConnectionsWithPool(array $config): array
    {
        $this->connectionPool->initialize($config['pool_size']);
        
        $startTime = microtime(true);
        $startMemory = memory_get_usage(true);
        
        $connectionTimes = [];
        $totalOperations = 0;
        
        for ($i = 0; $i < $config['concurrent_connections']; $i++) {
            $connStart = microtime(true);
            
            // Get connection from pool
            $connection = $this->connectionPool->getConnection();
            
            for ($j = 0; $j < $config['operations_per_connection']; $j++) {
                $this->executeQuery('SELECT 1');
                $totalOperations++;
            }
            
            // Return connection to pool
            $this->connectionPool->returnConnection($connection);
            
            $connEnd = microtime(true);
            $connectionTimes[] = ($connEnd - $connStart) * 1000;
        }
        
        $endTime = microtime(true);
        $endMemory = memory_get_usage(true);
        
        $this->connectionPool->cleanup();
        
        return [
            'duration' => $endTime - $startTime,
            'memory_used' => $endMemory - $startMemory,
            'total_operations' => $totalOperations,
            'average_connection_time' => array_sum($connectionTimes) / count($connectionTimes),
            'throughput' => $totalOperations / ($endTime - $startTime),
            'pool_efficiency' => $this->connectionPool->getEfficiency()
        ];
    }

    /**
     * Calculate connection pool gain.
     */
    protected function calculateConnectionPoolGain(array $withoutPool, array $withPool): array
    {
        $timeImprovement = (($withoutPool['duration'] - $withPool['duration']) / $withoutPool['duration']) * 100;
        $throughputImprovement = (($withPool['throughput'] - $withoutPool['throughput']) / $withoutPool['throughput']) * 100;
        
        return [
            'time_improvement' => $timeImprovement,
            'throughput_improvement' => $throughputImprovement,
            'memory_savings' => (($withoutPool['memory_used'] - $withPool['memory_used']) / $withoutPool['memory_used']) * 100,
            'connection_time_improvement' => (($withoutPool['average_connection_time'] - $withPool['average_connection_time']) / $withoutPool['average_connection_time']) * 100
        ];
    }

    /**
     * Get query type.
     */
    protected function getQueryType(string $query): string
    {
        $query = strtoupper(trim($query));
        
        if (strpos($query, 'SELECT') === 0) return 'SELECT';
        if (strpos($query, 'INSERT') === 0) return 'INSERT';
        if (strpos($query, 'UPDATE') === 0) return 'UPDATE';
        if (strpos($query, 'DELETE') === 0) return 'DELETE';
        if (strpos($query, 'CREATE') === 0) return 'CREATE';
        if (strpos($query, 'DROP') === 0) return 'DROP';
        if (strpos($query, 'ALTER') === 0) return 'ALTER';
        
        return 'OTHER';
    }

    /**
     * Extract tables from query.
     */
    protected function extractTables(string $query): array
    {
        // Simple table extraction - would be more sophisticated in real implementation
        preg_match_all('/FROM\s+(\w+)|JOIN\s+(\w+)|UPDATE\s+(\w+)|INSERT\s+INTO\s+(\w+)/i', $query, $matches);
        
        $tables = [];
        foreach ($matches as $match) {
            foreach ($match as $table) {
                if ($table && !in_array($table, $tables)) {
                    $tables[] = $table;
                }
            }
        }
        
        return $tables;
    }

    /**
     * Identify frequent queries.
     */
    protected function identifyFrequentQueries(array $queries, array $tableAccess): array
    {
        $frequent = [];
        
        foreach ($tableAccess as $table => $access) {
            if ($access['access_count'] > 10) {
                foreach ($access['queries'] as $queryIndex) {
                    $frequent[] = [
                        'query_index' => $queryIndex,
                        'table' => $table,
                        'access_count' => $access['access_count'],
                        'total_time' => $access['total_time']
                    ];
                }
            }
        }
        
        return $frequent;
    }

    /**
     * Identify slow queries.
     */
    protected function identifySlowQueries(array $queries, array $profiles): array
    {
        $slow = [];
        
        foreach ($profiles as $index => $profile) {
            if ($profile['statistics']['average'] > 500) { // > 500ms
                $slow[] = [
                    'query_index' => $index,
                    'average_time' => $profile['statistics']['average'],
                    'max_time' => $profile['statistics']['max'],
                    'execution_count' => $profile['statistics']['count']
                ];
            }
        }
        
        return $slow;
    }

    /**
     * Find optimization opportunities.
     */
    protected function findOptimizationOpportunities(array $queries, array $profiles, array $tableAccess): array
    {
        $opportunities = [];
        
        // Queries without indexes
        foreach ($profiles as $index => $profile) {
            if (isset($profile['query_plan']['index_usage_rate']) && 
                $profile['query_plan']['index_usage_rate'] < 50) {
                $opportunities[] = [
                    'type' => 'missing_index',
                    'query_index' => $index,
                    'description' => 'Query has low index usage rate',
                    'potential_improvement' => '30-50%'
                ];
            }
        }
        
        // Frequently accessed tables without proper indexes
        foreach ($tableAccess as $table => $access) {
            if ($access['access_count'] > 100 && $access['total_time'] > 10000) {
                $opportunities[] = [
                    'type' => 'table_optimization',
                    'table' => $table,
                    'description' => 'Frequently accessed table with high total time',
                    'potential_improvement' => '20-40%'
                ];
            }
        }
        
        return $opportunities;
    }

    /**
     * Generate pattern recommendations.
     */
    protected function generatePatternRecommendations(array $result): array
    {
        $recommendations = [];
        
        if (!empty($result['slow_queries'])) {
            $recommendations[] = 'Optimize slow queries by adding appropriate indexes';
        }
        
        if (!empty($result['optimization_opportunities'])) {
            $recommendations[] = 'Review optimization opportunities for performance gains';
        }
        
        // Check query type distribution
        if (isset($result['query_types']['SELECT']) && $result['query_types']['SELECT'] > 50) {
            $recommendations[] = 'Consider read replicas for SELECT-heavy workload';
        }
        
        return $recommendations;
    }

    /**
     * Execute concurrent queries.
     */
    protected function executeConcurrentQueries(array $queries, int $concurrentUsers): array
    {
        $results = [];
        
        for ($i = 0; $i < $concurrentUsers; $i++) {
            $query = $queries[$i % count($queries)];
            
            try {
                $start = microtime(true);
                $this->executeQuery($query['sql'], $query['params'] ?? []);
                $end = microtime(true);
                
                $results[] = [
                    'success' => true,
                    'response_time' => ($end - $start) * 1000
                ];
            } catch (\Exception $e) {
                $results[] = [
                    'success' => false,
                    'error' => $e->getMessage()
                ];
            }
        }
        
        return $results;
    }

    /**
     * Calculate average response time.
     */
    protected function calculateAverageResponseTime(array $results): float
    {
        $times = array_filter($results, fn($r) => isset($r['response_time']));
        $times = array_column($times, 'response_time');
        
        return empty($times) ? 0 : array_sum($times) / count($times);
    }

    /**
     * Calculate error rate.
     */
    protected function calculateErrorRate(array $results): float
    {
        $errors = array_filter($results, fn($r) => !($r['success'] ?? true));
        
        return empty($results) ? 0 : (count($errors) / count($results)) * 100;
    }

    /**
     * Analyze database bottlenecks.
     */
    protected function analyzeDatabaseBottlenecks(array $performanceData, array $resourceData): array
    {
        $bottlenecks = [];
        
        // Check response time trends
        $responseTimes = array_column($performanceData, 'average_response_time');
        if (!empty($responseTimes) && max($responseTimes) > 1000) {
            $bottlenecks[] = [
                'type' => 'response_time',
                'severity' => 'high',
                'description' => 'Response times exceeding 1 second',
                'recommendation' => 'Optimize queries or increase database resources'
            ];
        }
        
        // Check CPU usage
        $cpuUsage = array_column($resourceData, 'cpu_usage');
        if (!empty($cpuUsage) && max($cpuUsage) > 80) {
            $bottlenecks[] = [
                'type' => 'cpu',
                'severity' => 'medium',
                'description' => 'High CPU usage detected',
                'recommendation' => 'Consider query optimization or scaling up'
            ];
        }
        
        return $bottlenecks;
    }

    /**
     * Generate load test recommendations.
     */
    protected function generateLoadTestRecommendations(array $result): array
    {
        $recommendations = [];
        
        if (!empty($result['bottlenecks'])) {
            foreach ($result['bottlenecks'] as $bottleneck) {
                $recommendations[] = $bottleneck['recommendation'];
            }
        }
        
        // Check throughput
        $throughputData = array_column($result['performance_metrics'], 'throughput');
        if (!empty($throughputData)) {
            $avgThroughput = array_sum($throughputData) / count($throughputData);
            if ($avgThroughput < 100) { // < 100 queries/second
                $recommendations[] = 'Consider database optimization or horizontal scaling';
            }
        }
        
        return $recommendations;
    }

    /**
     * Generate index recommendations.
     */
    protected function generateIndexRecommendations(array $result): array
    {
        $recommendations = [];
        
        if (!empty($result['unused_indexes'])) {
            $recommendations[] = 'Consider removing unused indexes to improve write performance';
        }
        
        if (!empty($result['missing_indexes'])) {
            $recommendations[] = 'Add missing indexes to improve query performance';
        }
        
        if (!empty($result['duplicate_indexes'])) {
            $recommendations[] = 'Remove duplicate indexes to save storage and improve performance';
        }
        
        return $recommendations;
    }

    // Mock methods for database operations
    protected function createDirectConnection()
    {
        return new \stdClass(); // Mock connection
    }
    
    protected function closeConnection($connection): void
    {
        // Mock connection cleanup
    }
    
    protected function getCpuUsage(): float
    {
        return rand(20, 90); // Mock CPU usage
    }
    
    protected function getActiveConnections(): int
    {
        return rand(5, 50); // Mock active connections
    }
    
    protected function calculateAverageQueryTime(): float
    {
        if (empty($this->queryResults)) {
            return 0;
        }
        
        $total = 0;
        $count = 0;
        
        foreach ($this->queryResults as $result) {
            $total += $result['statistics']['average'];
            $count++;
        }
        
        return $count > 0 ? $total / $count : 0;
    }
    
    protected function countSlowQueries(): int
    {
        $count = 0;
        
        foreach ($this->queryResults as $result) {
            if ($result['statistics']['average'] > 1000) {
                $count++;
            }
        }
        
        return $count;
    }

    /**
     * Get default configuration.
     */
    protected function getDefaultConfig(): array
    {
        return [
            'query_profiling' => [
                'executions' => 100,
                'warmup_executions' => 10
            ],
            'index_analysis' => [
                'analyze_queries' => true
            ],
            'query_optimization' => [
                'strategies' => ['limit', 'columns', 'hints']
            ],
            'connection_pool_testing' => [
                'pool_size' => 10,
                'concurrent_connections' => 50,
                'operations_per_connection' => 20
            ],
            'pattern_analysis' => [],
            'load_testing' => [
                'concurrent_users' => 20,
                'duration' => 60,
                'ramp_up_time' => 10
            ],
            'query_profiler' => [],
            'index_analyzer' => [],
            'query_optimizer' => [],
            'connection_pool' => [],
            'reporter' => []
        ];
    }

    /**
     * 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 database optimizer instance.
     */
    public static function create(array $config = []): self
    {
        return new self($config);
    }

    /**
     * Create for development.
     */
    public static function forDevelopment(): self
    {
        return new self([
            'query_profiling' => [
                'executions' => 50,
                'warmup_executions' => 5
            ],
            'load_testing' => [
                'concurrent_users' => 10,
                'duration' => 30
            ]
        ]);
    }

    /**
     * Create for production.
     */
    public static function forProduction(): self
    {
        return new self([
            'query_profiling' => [
                'executions' => 200,
                'warmup_executions' => 20
            ],
            'load_testing' => [
                'concurrent_users' => 100,
                'duration' => 300
            ]
        ]);
    }
}