<?php
/**
 * ╔══════════════════════════════════════════════════════════╗
 * ║  WEVIA OPUS — RAG Engine (Retrieval-Augmented Gen)     ║
 * ║  pgvector + Ollama Embeddings + Semantic Search        ║
 * ╚══════════════════════════════════════════════════════════╝
 */

class RAGEngine {
    private $pdo;
    private $embeddingModel = 'nomic-embed-text';
    private $ollamaUrl;
    private $topK = 5;
    private $minSimilarity = 0.3;
    
    public function __construct(?PDO $pdo = null, string $ollamaUrl = 'http://127.0.0.1:11434') {
        $this->ollamaUrl = $ollamaUrl;
        if ($pdo) {
            $this->pdo = $pdo;
        } else {
            $this->pdo = new PDO("pgsql:host=127.0.0.1;dbname=wevia_db", "postgres", "");
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        }
        $this->ensureSchema();
    }
    
    private function ensureSchema(): void {
        $this->pdo->exec("CREATE EXTENSION IF NOT EXISTS vector");
        $this->pdo->exec("
            CREATE TABLE IF NOT EXISTS kb_embeddings (
                id SERIAL PRIMARY KEY,
                source VARCHAR(255),
                category VARCHAR(100),
                chunk_text TEXT NOT NULL,
                embedding vector(768),
                metadata JSONB DEFAULT '{}',
                created_at TIMESTAMP DEFAULT NOW(),
                access_count INT DEFAULT 0
            )
        ");
        $this->pdo->exec("
            CREATE INDEX IF NOT EXISTS idx_kb_embedding ON kb_embeddings 
            USING ivfflat (embedding vector_cosine_ops) WITH (lists = 100)
        ");
    }
    
    /**
     * Ingère un document en le découpant en chunks avec overlap
     */
    public function ingest(string $text, string $source, string $category = 'general', array $meta = []): int {
        $chunks = $this->chunkText($text, 512, 64);
        $count = 0;
        
        foreach ($chunks as $chunk) {
            $embedding = $this->getEmbedding($chunk);
            if (!$embedding) continue;
            
            $stmt = $this->pdo->prepare("
                INSERT INTO kb_embeddings (source, category, chunk_text, embedding, metadata)
                VALUES (?, ?, ?, ?::vector, ?::jsonb)
            ");
            $stmt->execute([
                $source, $category, $chunk,
                '[' . implode(',', $embedding) . ']',
                json_encode($meta)
            ]);
            $count++;
        }
        
        return $count;
    }
    
    /**
     * Recherche sémantique — trouve les chunks les plus pertinents
     */
    public function search(string $query, int $topK = null, string $category = null): array {
        $k = $topK ?? $this->topK;
        $embedding = $this->getEmbedding($query);
        if (!$embedding) return [];
        
        $vecStr = '[' . implode(',', $embedding) . ']';
        
        $sql = "SELECT id, source, category, chunk_text, metadata,
                1 - (embedding <=> ?::vector) as similarity
                FROM kb_embeddings
                WHERE 1=1";
        $params = [$vecStr];
        
        if ($category) {
            $sql .= " AND category = ?";
            $params[] = $category;
        }
        
        $sql .= " ORDER BY embedding <=> ?::vector LIMIT ?";
        $params[] = $vecStr;
        $params[] = $k;
        
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($params);
        $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
        
        // Update access count
        foreach ($results as $r) {
            $this->pdo->exec("UPDATE kb_embeddings SET access_count = access_count + 1 WHERE id = " . intval($r['id']));
        }
        
        return array_filter($results, fn($r) => $r['similarity'] >= $this->minSimilarity);
    }
    
    /**
     * Génère le contexte RAG pour une requête
     */
    public function getContext(string $query, string $category = null): string {
        $results = $this->search($query, $this->topK, $category);
        
        if (empty($results)) return '';
        
        $context = "--- CONTEXTE KNOWLEDGE BASE ---\n";
        foreach ($results as $i => $r) {
            $sim = round($r['similarity'] * 100);
            $context .= "[{$r['source']}] (pertinence: {$sim}%)\n{$r['chunk_text']}\n\n";
        }
        $context .= "--- FIN CONTEXTE ---\n";
        
        return $context;
    }
    
    /**
     * Obtient l'embedding d'un texte via Ollama
     */
    private function getEmbedding(string $text): ?array {
        $ch = curl_init("{$this->ollamaUrl}/api/embed");
        curl_setopt_array($ch, [
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => json_encode([
                'model' => $this->embeddingModel,
                'input' => $text
            ]),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT => 30,
            CURLOPT_HTTPHEADER => ['Content-Type: application/json']
        ]);
        $raw = curl_exec($ch);
        curl_close($ch);
        
        $data = json_decode($raw, true);
        return $data['embeddings'][0] ?? null;
    }
    
    /**
     * Découpe un texte en chunks avec overlap
     */
    private function chunkText(string $text, int $chunkSize = 512, int $overlap = 64): array {
        $words = preg_split('/\s+/', $text);
        $chunks = [];
        $total = count($words);
        
        for ($i = 0; $i < $total; $i += ($chunkSize - $overlap)) {
            $chunk = implode(' ', array_slice($words, $i, $chunkSize));
            if (mb_strlen($chunk) > 20) {
                $chunks[] = $chunk;
            }
        }
        
        return $chunks;
    }
    
    /**
     * Stats du KB
     */
    public function getStats(): array {
        $stats = $this->pdo->query("
            SELECT category, COUNT(*) as chunks, 
                   SUM(access_count) as total_access,
                   COUNT(DISTINCT source) as sources
            FROM kb_embeddings 
            GROUP BY category ORDER BY chunks DESC
        ")->fetchAll(PDO::FETCH_ASSOC);
        
        $total = $this->pdo->query("SELECT COUNT(*) FROM kb_embeddings")->fetchColumn();
        
        return ['total_chunks' => $total, 'categories' => $stats];
    }
}