
<?php
/**
 * A/B TESTING ENGINE
 * Multi-variant testing with auto-winner
 */
header('Content-Type: application/json');
$pdo = new PDO("pgsql:host=localhost;dbname=adx_system", "admin", "admin123", [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);

$pdo->exec("
CREATE TABLE IF NOT EXISTS admin.ab_tests (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255),
    campaign_id INTEGER,
    test_type VARCHAR(50) DEFAULT 'subject',
    variants TEXT,
    test_size_percent INTEGER DEFAULT 20,
    winning_metric VARCHAR(50) DEFAULT 'open_rate',
    min_sample_size INTEGER DEFAULT 1000,
    confidence_level FLOAT DEFAULT 0.95,
    status VARCHAR(50) DEFAULT 'draft',
    winner_variant VARCHAR(10),
    results TEXT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    started_at TIMESTAMP,
    completed_at TIMESTAMP
);

CREATE TABLE IF NOT EXISTS admin.ab_variant_stats (
    id SERIAL PRIMARY KEY,
    test_id INTEGER,
    variant VARCHAR(10),
    sent INTEGER DEFAULT 0,
    delivered INTEGER DEFAULT 0,
    opened INTEGER DEFAULT 0,
    clicked INTEGER DEFAULT 0,
    converted INTEGER DEFAULT 0,
    revenue FLOAT DEFAULT 0,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
");

class ABTestEngine {
    private $pdo;
    
    public function __construct($pdo) { $this->pdo = $pdo; }
    
    public function createTest($data) {
        $variants = [];
        foreach (['A', 'B', 'C', 'D', 'E'] as $v) {
            if (!empty($data["variant_$v"])) {
                $variants[$v] = $data["variant_$v"];
            }
        }
        
        $this->pdo->prepare("INSERT INTO admin.ab_tests (name, campaign_id, test_type, variants, test_size_percent, winning_metric, min_sample_size) VALUES (?, ?, ?, ?, ?, ?, ?)")
            ->execute([
                $data['name'], $data['campaign_id'] ?? null, $data['test_type'] ?? 'subject',
                json_encode($variants), $data['test_size_percent'] ?? 20,
                $data['winning_metric'] ?? 'open_rate', $data['min_sample_size'] ?? 1000
            ]);
        
        $testId = $this->pdo->lastInsertId();
        
        // Create variant stats
        foreach (array_keys($variants) as $v) {
            $this->pdo->exec("INSERT INTO admin.ab_variant_stats (test_id, variant) VALUES ($testId, '$v')");
        }
        
        return ['success' => true, 'test_id' => $testId, 'variants' => count($variants)];
    }
    
    public function recordEvent($testId, $variant, $eventType) {
        $column = ['send' => 'sent', 'deliver' => 'delivered', 'open' => 'opened', 'click' => 'clicked', 'convert' => 'converted'][$eventType] ?? null;
        if ($column) {
            $this->pdo->exec("UPDATE admin.ab_variant_stats SET $column = $column + 1, updated_at = NOW() WHERE test_id = $testId AND variant = '$variant'");
        }
        return ['success' => true];
    }
    
    public function getResults($testId) {
        $test = $this->pdo->query("SELECT * FROM admin.ab_tests WHERE id = $testId")->fetch(PDO::FETCH_ASSOC);
        $stats = $this->pdo->query("SELECT * FROM admin.ab_variant_stats WHERE test_id = $testId")->fetchAll(PDO::FETCH_ASSOC);
        
        $results = [];
        foreach ($stats as $s) {
            $sent = max(1, $s['sent']);
            $results[$s['variant']] = [
                'sent' => $s['sent'],
                'open_rate' => round($s['opened'] / $sent * 100, 2),
                'click_rate' => round($s['clicked'] / $sent * 100, 2),
                'conversion_rate' => round($s['converted'] / $sent * 100, 2)
            ];
        }
        
        // Determine winner
        $metric = $test['winning_metric'];
        $winner = null;
        $bestValue = 0;
        foreach ($results as $v => $r) {
            if ($r[$metric] > $bestValue) {
                $bestValue = $r[$metric];
                $winner = $v;
            }
        }
        
        // Statistical significance
        $isSignificant = $this->calculateSignificance($stats, $metric, $test['confidence_level']);
        
        return [
            'test' => $test,
            'results' => $results,
            'winner' => $winner,
            'is_significant' => $isSignificant,
            'recommendation' => $isSignificant ? "Use variant $winner" : "Need more data"
        ];
    }
    
    private function calculateSignificance($stats, $metric, $confidence) {
        // Simplified significance check
        $totalSent = array_sum(array_column($stats, 'sent'));
        return $totalSent >= 2000;
    }
    
    public function autoSelectWinner($testId) {
        $results = $this->getResults($testId);
        if ($results['is_significant'] && $results['winner']) {
            $this->pdo->prepare("UPDATE admin.ab_tests SET status = 'completed', winner_variant = ?, completed_at = NOW(), results = ? WHERE id = ?")
                ->execute([$results['winner'], json_encode($results['results']), $testId]);
            return ['success' => true, 'winner' => $results['winner']];
        }
        return ['success' => false, 'message' => 'Not enough data yet'];
    }
}

$engine = new ABTestEngine($pdo);
$action = $_POST['action'] ?? $_GET['action'] ?? '';

switch ($action) {
    case 'create':
        echo json_encode($engine->createTest($_POST));
        break;
    case 'event':
        echo json_encode($engine->recordEvent($_POST['test_id'], $_POST['variant'], $_POST['event_type']));
        break;
    case 'results':
        echo json_encode($engine->getResults($_GET['test_id']));
        break;
    case 'auto_winner':
        echo json_encode($engine->autoSelectWinner($_POST['test_id']));
        break;
    case 'list':
        echo json_encode(['tests' => $pdo->query("SELECT * FROM admin.ab_tests ORDER BY created_at DESC")->fetchAll(PDO::FETCH_ASSOC)]);
        break;
    default:
        echo json_encode(['name' => 'A/B Testing Engine', 'actions' => ['create','event','results','auto_winner','list']]);
}