<?php
require_once __DIR__ . '/sm2.php';
$user_id = require_auth();

// GET /api/cards/deck/{slug}
if (get_method() === 'GET' && ($segments[1] ?? '') === 'deck' && !empty($segments[2])) {
    $slug = $segments[2];
    $stmt = $pdo->prepare("
        SELECT c.id, c.question, c.answer, c.level, c.sort_order,
            cp.next_review, cp.last_rating, cp.last_reviewed_at,
            cp.ease_factor, cp.interval_days, cp.repetitions,
            d.name AS deck_name, d.slug AS deck_slug
        FROM cards c
        JOIN decks d ON d.id = c.deck_id AND d.slug = :slug
        LEFT JOIN card_progress cp ON cp.card_id = c.id AND cp.user_id = :uid
        ORDER BY c.sort_order
    ");
    $stmt->execute([':slug' => $slug, ':uid' => $user_id]);
    json_ok(['cards' => $stmt->fetchAll()]);
}

// GET /api/cards/due?deck={slug}&limit=N
if (get_method() === 'GET' && ($segments[1] ?? '') === 'due') {
    $slug = get_param('deck', '');
    $limit = max(1, min(50, (int) get_param('limit', 20)));

    $query = "
        SELECT c.id, c.question, c.answer, c.level, c.sort_order, c.deck_id,
            d.slug AS deck_slug, d.name AS deck_name,
            cp.next_review, cp.last_rating, cp.last_reviewed_at,
            cp.ease_factor, cp.interval_days, cp.repetitions
        FROM cards c
        JOIN decks d ON d.id = c.deck_id
        LEFT JOIN card_progress cp ON cp.card_id = c.id AND cp.user_id = :uid
        WHERE (cp.next_review IS NULL OR cp.next_review <= CURRENT_DATE)
    ";
    $params = [':uid' => $user_id];

    if ($slug) {
        $query .= " AND d.slug = :slug";
        $params[':slug'] = $slug;
    }

    $query .= " ORDER BY cp.next_review ASC NULLS FIRST, c.sort_order LIMIT " . $limit;

    $stmt = $pdo->prepare($query);
    $stmt->execute($params);
    json_ok(['cards' => $stmt->fetchAll()]);
}

// POST /api/cards/{id}/review
if (get_method() === 'POST' && is_numeric($segments[1] ?? '') && ($segments[2] ?? '') === 'review') {
    $card_id = (int) $segments[1];
    $body = get_json_body();
    $rating = $body['rating'] ?? '';

    if (!in_array($rating, ['easy', 'medium', 'hard', 'wrong'])) {
        json_error('Ungueltige Bewertung. Erlaubt: easy, medium, hard, wrong');
    }

    $stmt = $pdo->prepare("SELECT id FROM cards WHERE id = :id");
    $stmt->execute([':id' => $card_id]);
    if (!$stmt->fetch()) json_error('Karte nicht gefunden', 404);

    $stmt = $pdo->prepare("SELECT * FROM card_progress WHERE user_id = :uid AND card_id = :cid");
    $stmt->execute([':uid' => $user_id, ':cid' => $card_id]);
    $progress = $stmt->fetch();

    $ease = $progress['ease_factor'] ?? 2.5;
    $interval = $progress['interval_days'] ?? 0;
    $reps = $progress['repetitions'] ?? 0;

    $result = sm2_calculate($rating, $ease, $interval, $reps);

    $stmt = $pdo->prepare("
        INSERT INTO card_progress (user_id, card_id, ease_factor, interval_days, repetitions, next_review, last_rating, last_reviewed_at)
        VALUES (:uid, :cid, :ease, :intv, :reps, :next, :rating, NOW())
        ON CONFLICT (user_id, card_id) DO UPDATE SET
            ease_factor = :ease, interval_days = :intv, repetitions = :reps,
            next_review = :next, last_rating = :rating, last_reviewed_at = NOW()
    ");
    $stmt->execute([
        ':uid' => $user_id, ':cid' => $card_id,
        ':ease' => $result['ease_factor'], ':intv' => $result['interval_days'],
        ':reps' => $result['repetitions'], ':next' => $result['next_review'],
        ':rating' => $rating
    ]);

    json_ok(['progress' => $result]);
}

json_error('Unbekannter Cards-Endpunkt', 404);