<?php
// POST api/advisor.php -> ask the AI course advisor
//      JSON body: {messages: [{role: 'user'|'assistant', content: string}, ...]}
//                 (the whole conversation so far; the last entry is the question)
//      Response: {answer, recommended: [{folder_id, order, reason, course}],
//                 courses: {"412": {folder_id, name}, ...}  (the "#412" mentions
//                          in `answer`, resolved so the browser can link them),
//                 from_ine: [{catalog_id, name, difficulty, vendor, url, reason}],
//                 missing_prerequisites: [...], degraded,
//                 usage: {prompt_tokens, cache_hit_tokens, completion_tokens,
//                         reasoning_tokens, remaining_today}}
//      503 when the advisor is switched off, 429 past the daily cap,
//      502 when the AI service could not answer.
require_once __DIR__ . '/../includes/auth.php';
require_once __DIR__ . '/../includes/advisor.php';

header('Content-Type: application/json');
$userId = requireLoginApi();

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit;
}

$data = json_decode(file_get_contents('php://input'), true) ?: [];
verifyCsrfApi($data);

if (!aiEnabled()) {
    http_response_code(503);
    echo json_encode(['error' => 'The course advisor is switched off on this install.', 'advisor' => false]);
    exit;
}

try {
    $messages = advisorNormalizeMessages($data['messages'] ?? null);
} catch (InvalidArgumentException $e) {
    http_response_code(400);
    echo json_encode(['error' => $e->getMessage()]);
    exit;
}

$limit = advisorLimit();
$used  = advisorUsedToday($userId);
if ($used >= $limit) {
    http_response_code(429);
    echo json_encode([
        'error'           => "You have used today's $limit advisor question" . ($limit === 1 ? '' : 's')
                             . ' — the count resets over the next 24 hours.',
        'remaining_today' => 0,
    ]);
    exit;
}

$requestId = advisorRecordUse($userId);
set_time_limit(120);

try {
    $result = advisorAsk($userId, $messages);
} catch (AiRejected | AiUnavailable | AiBadReply $e) {
    http_response_code(502);
    echo json_encode(['error' => $e->getMessage()]);
    exit;
}

advisorMarkOk($requestId, $result['usage'], $result['model']);
$result['usage']['remaining_today'] = max(0, $limit - $used - 1);
unset($result['model']);
echo json_encode($result);