library_excerpt.php

<?php
declare(strict_types=1);

require_once __DIR__ . '/bootstrap.php';

header('Content-Type: application/json');

if (empty($_SESSION['user_data']['userid']) || empty($_SESSION['authorized'])) {
    http_response_code(401);
    echo json_encode([
        'ok' => false,
        'error' => 'unauthorized',
        'message' => 'Session expired. Please refresh the page.',
    ]);
    exit;
}

$libraryId = filter_input(INPUT_GET, 'library_id', FILTER_VALIDATE_INT);
$chatId = filter_input(INPUT_GET, 'chat_id', FILTER_SANITIZE_STRING);

if (!$libraryId || $libraryId < 1) {
    http_response_code(400);
    echo json_encode([
        'ok' => false,
        'error' => 'invalid_library_id',
        'message' => 'A valid library id is required.',
    ]);
    exit;
}

$userId = $_SESSION['user_data']['userid'];

try {
    global $pdo;

    $sql = "
        SELECT
            l.id,
            l.name,
            l.prompt,
            l.content,
            l.source,
            l.library_token_length,
            l.full_text_available,
            l.ready,
            l.deleted,
            lc.chat_id
        FROM library l
        LEFT JOIN library_chat lc
               ON lc.library_id = l.id
              AND lc.chat_id = :chat_id
        LEFT JOIN chat c
               ON c.id = lc.chat_id
              AND c.user = :user
        WHERE l.id = :library_id
        LIMIT 1
    ";

    $stmt = $pdo->prepare($sql);
    $stmt->execute([
        'library_id' => $libraryId,
        'chat_id' => (string)$chatId,
        'user' => $userId,
    ]);
    $row = $stmt->fetch(PDO::FETCH_ASSOC);

    if (!$row || (int)$row['deleted'] === 1) {
        http_response_code(404);
        echo json_encode([
            'ok' => false,
            'error' => 'not_found',
            'message' => 'Library not found.',
        ]);
        exit;
    }

    if (!empty($chatId) && (string)($row['chat_id'] ?? '') !== (string)$chatId) {
        http_response_code(403);
        echo json_encode([
            'ok' => false,
            'error' => 'forbidden',
            'message' => 'You do not have access to this library in this chat.',
        ]);
        exit;
    }

    $rawContent = (string)($row['content'] ?? '');
    $maxPreviewChars = 8000;
    $excerpt = $rawContent;
    $truncated = false;

    if (function_exists('mb_strlen')) {
        if (mb_strlen($excerpt, 'UTF-8') > $maxPreviewChars) {
            $excerpt = mb_substr($excerpt, 0, $maxPreviewChars, 'UTF-8');
            $truncated = true;
        }
    } else {
        if (strlen($excerpt) > $maxPreviewChars) {
            $excerpt = substr($excerpt, 0, $maxPreviewChars);
            $truncated = true;
        }
    }

    if ($excerpt === '') {
        $excerpt = 'No preview text is available for this library yet.';
    }

    echo json_encode([
        'ok' => true,
        'document' => [
            'id' => (int)$row['id'],
            'chat_id' => (string)$chatId,
            'name' => (string)$row['name'],
            'type' => 'library',
            'source' => 'library',
            'prompt' => (string)($row['prompt'] ?? ''),
            'token_length' => (int)($row['library_token_length'] ?? 0),
            'full_text_available' => (bool)($row['full_text_available'] ?? 0),
            'ready' => ((int)($row['ready'] ?? 0) === 1),
            'has_preview' => $rawContent !== '',
            'excerpt_truncated' => $truncated,
            'generated_at' => date('c'),
            'excerpt' => $excerpt,
        ],
    ]);
} catch (Throwable $e) {
    error_log('library_excerpt error: ' . $e->getMessage());
    http_response_code(500);
    echo json_encode([
        'ok' => false,
        'error' => 'server_error',
        'message' => 'Unable to load the requested library excerpt.',
    ]);
}