<?php
declare(strict_types=1);

/**
 * Per-user Azure AI Search index management.
 *
 * Each user gets their own private index: case-{user_id}
 * - Hybrid search (BM25 + vector + Norwegian Bokmål analyzer nb.microsoft)
 * - Vector dim 1536 (text-embedding-3-small)
 * - Schema: id, doc_id, user_id, filename, page, chunk_text, vector, doc_type, detected_date
 *
 * Isolation enforced at INDEX level — no shared index. Cross-user data leak is structurally impossible.
 */
final class AzureSearchAdmin
{
    private const API_VERSION = '2024-07-01';
    private string $endpoint;
    private string $adminKey;

    public function __construct(?string $endpoint = null, ?string $adminKey = null)
    {
        $cfg = self::loadConfig();
        $this->endpoint = rtrim($endpoint ?? ($cfg['endpoint'] ?? ''), '/');
        $this->adminKey = $adminKey ?? ($cfg['admin_key'] ?? '');
        if ($this->endpoint === '' || $this->adminKey === '') {
            throw new RuntimeException('AzureSearchAdmin: endpoint or admin key not configured.');
        }
    }

    private static function loadConfig(): array
    {
        $path = '/etc/bnl/azure.php';
        if (is_readable($path)) {
            $cfg = require $path;
            return [
                'endpoint' => (string)($cfg['SEARCH_ENDPOINT'] ?? 'https://bnl-legal-search.search.windows.net'),
                'admin_key' => (string)($cfg['SEARCH_ADMIN_KEY'] ?? ''),
            ];
        }
        return [
            'endpoint' => (string)(getenv('AZURE_SEARCH_ENDPOINT') ?: 'https://bnl-legal-search.search.windows.net'),
            'admin_key' => (string)(getenv('AZURE_SEARCH_ADMIN_KEY') ?: ''),
        ];
    }

    public static function indexName(int $userId): string
    {
        return 'case-' . $userId;
    }

    /** Create the per-user index if it does not exist. Idempotent. */
    public function ensureUserIndex(int $userId): string
    {
        $name = self::indexName($userId);
        if ($this->indexExists($name)) {
            return $name;
        }
        $body = [
            'name' => $name,
            'fields' => [
                ['name' => 'id', 'type' => 'Edm.String', 'key' => true, 'filterable' => true],
                ['name' => 'doc_id', 'type' => 'Edm.Int32', 'filterable' => true, 'facetable' => true],
                ['name' => 'user_id', 'type' => 'Edm.Int32', 'filterable' => true],
                ['name' => 'filename', 'type' => 'Edm.String', 'filterable' => true, 'sortable' => true, 'searchable' => true, 'analyzer' => 'standard.lucene'],
                ['name' => 'page', 'type' => 'Edm.Int32', 'filterable' => true, 'sortable' => true],
                ['name' => 'chunk_text', 'type' => 'Edm.String', 'searchable' => true, 'analyzer' => 'nb.microsoft'],
                ['name' => 'doc_type', 'type' => 'Edm.String', 'filterable' => true, 'facetable' => true],
                ['name' => 'detected_date', 'type' => 'Edm.DateTimeOffset', 'filterable' => true, 'sortable' => true],
                [
                    'name' => 'vector',
                    'type' => 'Collection(Edm.Single)',
                    'searchable' => true,
                    'dimensions' => 1536,
                    'vectorSearchProfile' => 'caseVectorProfile',
                ],
            ],
            'vectorSearch' => [
                'algorithms' => [[
                    'name' => 'caseHnsw',
                    'kind' => 'hnsw',
                    'hnswParameters' => ['m' => 4, 'efConstruction' => 400, 'efSearch' => 500, 'metric' => 'cosine'],
                ]],
                'profiles' => [['name' => 'caseVectorProfile', 'algorithm' => 'caseHnsw']],
            ],
            'semantic' => [
                'configurations' => [[
                    'name' => 'caseSemantic',
                    'prioritizedFields' => [
                        'contentFields' => [['fieldName' => 'chunk_text']],
                        'titleField' => ['fieldName' => 'filename'],
                    ],
                ]],
            ],
        ];
        $this->request('PUT', '/indexes/' . rawurlencode($name) . '?api-version=' . self::API_VERSION, $body);
        return $name;
    }

    public function indexExists(string $name): bool
    {
        $code = $this->request('GET', '/indexes/' . rawurlencode($name) . '?api-version=' . self::API_VERSION, null, true);
        return $code === 200;
    }

    /** Upsert a batch of documents (chunks) into the user's index. */
    public function upsertChunks(int $userId, array $chunks): void
    {
        if (empty($chunks)) return;
        $name = self::indexName($userId);
        $body = [
            'value' => array_map(fn($c) => array_merge(['@search.action' => 'mergeOrUpload'], $c), $chunks),
        ];
        $this->request('POST', '/indexes/' . rawurlencode($name) . '/docs/index?api-version=' . self::API_VERSION, $body);
    }

    /** Delete all chunks for a given doc_id (used on document deletion). */
    public function deleteDoc(int $userId, int $docId): void
    {
        $name = self::indexName($userId);
        // First search to get all chunk ids for this doc
        $resp = $this->request('POST', '/indexes/' . rawurlencode($name) . '/docs/search?api-version=' . self::API_VERSION, [
            'search' => '*',
            'filter' => 'doc_id eq ' . $docId,
            'select' => 'id',
            'top' => 1000,
        ]);
        $ids = array_map(fn($v) => $v['id'] ?? null, $resp['value'] ?? []);
        $ids = array_filter($ids);
        if (empty($ids)) return;

        $body = [
            'value' => array_map(fn($id) => ['@search.action' => 'delete', 'id' => $id], array_values($ids)),
        ];
        $this->request('POST', '/indexes/' . rawurlencode($name) . '/docs/index?api-version=' . self::API_VERSION, $body);
    }

    /** Delete the entire index (account deletion / GDPR). */
    public function deleteIndex(int $userId): void
    {
        $name = self::indexName($userId);
        $this->request('DELETE', '/indexes/' . rawurlencode($name) . '?api-version=' . self::API_VERSION, null, true);
    }

    /**
     * Hybrid search: BM25 (Norwegian analyzer) + vector + semantic ranker.
     * Returns ['value' => [{id, doc_id, filename, page, chunk_text, @search.score, @search.rerankerScore}, ...]]
     */
    public function hybridSearch(int $userId, string $query, array $queryVector, int $k = 5): array
    {
        $name = self::indexName($userId);
        $body = [
            'search' => $query,
            'queryType' => 'semantic',
            'semanticConfiguration' => 'caseSemantic',
            'searchFields' => 'chunk_text,filename',
            'select' => 'id,doc_id,filename,page,chunk_text,doc_type,detected_date',
            'top' => $k,
            'vectorQueries' => [[
                'kind' => 'vector',
                'vector' => $queryVector,
                'k' => $k,
                'fields' => 'vector',
            ]],
        ];
        return $this->request('POST', '/indexes/' . rawurlencode($name) . '/docs/search?api-version=' . self::API_VERSION, $body);
    }

    /** Low-level HTTP. If $returnStatusOnly, returns http code instead of decoded body. */
    private function request(string $method, string $path, ?array $body = null, bool $returnStatusOnly = false)
    {
        $url = $this->endpoint . $path;
        $headers = [
            'api-key: ' . $this->adminKey,
            'Content-Type: application/json',
        ];
        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL => $url,
            CURLOPT_CUSTOMREQUEST => strtoupper($method),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_HTTPHEADER => $headers,
            CURLOPT_TIMEOUT => 30,
        ]);
        if ($body !== null) {
            curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($body, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES));
        }
        $raw = curl_exec($ch);
        $status = (int)curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
        $errno = curl_errno($ch);
        curl_close($ch);

        if ($returnStatusOnly) {
            return $status;
        }
        if ($errno !== 0) {
            throw new RuntimeException('AzureSearch curl error: ' . curl_strerror($errno));
        }
        if ($status >= 400) {
            throw new RuntimeException("AzureSearch HTTP {$status}: " . substr((string)$raw, 0, 300));
        }
        $decoded = json_decode((string)$raw, true);
        return is_array($decoded) ? $decoded : [];
    }
}