<?php
/**
 * Glossar API
 * GET  /api/glossar                  → alle Einträge (nur Kernfelder)
 * GET  /api/glossar?key=co2          → einzelner Eintrag (volles Detail für Tooltip/Seite)
 * GET  /api/glossar?module=klima     → alle Einträge eines Moduls
 * GET  /api/glossar?search=treibhaus → Volltextsuche
 *
 * POST /api/glossar (nur Admin)      → neuer Eintrag  (TODO)
 * PUT  /api/glossar?id=42 (Admin)    → bearbeiten     (TODO)
 */

require_once __DIR__ . '/../config/app.php';
require_once __DIR__ . '/../config/db.php';

header('Content-Type: application/json; charset=utf-8');

$db = getDB();

// === Leichte Sprache ===
// Priorität: ?easy=1|0 (explizit)  >  Schüler-Session mit students.easy_language=1  >  normal
if (session_status() === PHP_SESSION_NONE) session_start();
$easy = false;
if (isset($_GET['easy'])) {
    $easy = $_GET['easy'] === '1';
} elseif (!empty($_SESSION['student_id'])) {
    if (!isset($_SESSION['_easy_cache']) || ($_SESSION['_easy_cache']['id'] ?? null) !== $_SESSION['student_id']) {
        $stmt = $db->prepare('SELECT easy_language FROM students WHERE id = ?');
        $stmt->execute([$_SESSION['student_id']]);
        $r = $stmt->fetch(PDO::FETCH_ASSOC);
        $_SESSION['_easy_cache'] = ['id' => $_SESSION['student_id'], 'val' => !empty($r['easy_language'])];
    }
    $easy = $_SESSION['_easy_cache']['val'];
}
// Cache pro Variante
header($easy ? 'Cache-Control: private, max-age=60' : 'Cache-Control: public, max-age=600');

/** Liefert Easy-Variante, sonst Fallback auf normal */
function pickText(array $row, string $normalKey, string $easyKey, bool $easy) {
    if ($easy && !empty($row[$easyKey])) return $row[$easyKey];
    return $row[$normalKey] ?? null;
}

try {
    $method = $_SERVER['REQUEST_METHOD'];

    if ($method === 'GET') {
        // Graph-Endpoint: alle Nodes + Edges für die Mindmap
        if (!empty($_GET['graph'])) {
            // Nodes inkl. Module-Zuordnung
            $nodes = $db->query('
                SELECT g.id, g.key_slug, g.title, g.short, g.category, g.image_path,
                       GROUP_CONCAT(m.module_id) AS modules
                FROM glossar g
                LEFT JOIN glossar_modules m ON m.glossar_id = g.id
                GROUP BY g.id
                ORDER BY g.title
            ')->fetchAll(PDO::FETCH_ASSOC);
            foreach ($nodes as &$n) {
                $n['modules'] = $n['modules'] ? explode(',', $n['modules']) : [];
                $n['id'] = (int) $n['id'];
            }
            unset($n);

            // Edges: related-Tabelle — jede Kante einmal (kleinere id → grössere id)
            $edges = $db->query('
                SELECT LEAST(glossar_id, related_id) AS a, GREATEST(glossar_id, related_id) AS b
                FROM glossar_related
                GROUP BY a, b
            ')->fetchAll(PDO::FETCH_ASSOC);
            foreach ($edges as &$e) {
                $e['a'] = (int) $e['a'];
                $e['b'] = (int) $e['b'];
            }
            unset($e);

            echo json_encode(['nodes' => $nodes, 'edges' => $edges], JSON_UNESCAPED_UNICODE);
            exit;
        }

        // Einzelner Eintrag per key_slug
        if (!empty($_GET['key'])) {
            $key = $_GET['key'];
            $entry = $db->prepare('SELECT * FROM glossar WHERE key_slug = ?');
            $entry->execute([$key]);
            $row = $entry->fetch(PDO::FETCH_ASSOC);
            if (!$row) {
                http_response_code(404);
                echo json_encode(['error' => 'not found']);
                exit;
            }

            // Leichte Sprache: falls aktiv, short/text durch easy-Varianten ersetzen (Fallback auf normal)
            $row['short'] = pickText($row, 'short', 'short_easy', $easy);
            $row['text']  = pickText($row, 'text',  'text_easy',  $easy);
            $row['_easy'] = $easy;  // Meta-Info fürs Frontend
            // Roh-Easy-Felder entfernen, damit JSON schlank bleibt
            unset($row['short_easy'], $row['text_easy']);

            // Module
            $mods = $db->prepare('SELECT module_id FROM glossar_modules WHERE glossar_id = ?');
            $mods->execute([$row['id']]);
            $row['modules'] = $mods->fetchAll(PDO::FETCH_COLUMN);

            // Beispiele (inkl. optionaler Quellen-Referenz + Easy-Variante)
            $ex = $db->prepare('SELECT text, text_easy, source_ref FROM glossar_examples WHERE glossar_id = ? ORDER BY sort_order');
            $ex->execute([$row['id']]);
            $examples = $ex->fetchAll(PDO::FETCH_ASSOC);
            foreach ($examples as &$e) {
                $e['text'] = pickText($e, 'text', 'text_easy', $easy);
                unset($e['text_easy']);
            }
            unset($e);
            $row['examples'] = $examples;

            // Quellen
            $sr = $db->prepare('SELECT ref_num, label, url, access_date FROM glossar_sources WHERE glossar_id = ? ORDER BY ref_num');
            $sr->execute([$row['id']]);
            $row['sources'] = $sr->fetchAll(PDO::FETCH_ASSOC);

            // Links
            $lk = $db->prepare('SELECT label, url FROM glossar_links WHERE glossar_id = ? ORDER BY sort_order');
            $lk->execute([$row['id']]);
            $row['links'] = $lk->fetchAll(PDO::FETCH_ASSOC);

            // Related (mit title + key)
            $rel = $db->prepare('
                SELECT g.key_slug, g.title
                FROM glossar_related r
                JOIN glossar g ON g.id = r.related_id
                WHERE r.glossar_id = ?
            ');
            $rel->execute([$row['id']]);
            $row['related'] = $rel->fetchAll(PDO::FETCH_ASSOC);

            echo json_encode($row, JSON_UNESCAPED_UNICODE);
            exit;
        }

        // Alle Einträge eines Moduls
        if (!empty($_GET['module'])) {
            $mod = $_GET['module'];
            $stmt = $db->prepare('
                SELECT g.id, g.key_slug, g.title, g.short, g.short_easy, g.text, g.text_easy,
                       g.unit, g.category, g.image_path, g.animation_path
                FROM glossar g
                JOIN glossar_modules m ON m.glossar_id = g.id
                WHERE m.module_id = ?
                ORDER BY g.title
            ');
            $stmt->execute([$mod]);
            $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
            foreach ($rows as &$r) {
                $r['short'] = pickText($r, 'short', 'short_easy', $easy);
                $r['text']  = pickText($r, 'text',  'text_easy',  $easy);
                unset($r['short_easy'], $r['text_easy']);
            }
            unset($r);
            echo json_encode($rows, JSON_UNESCAPED_UNICODE);
            exit;
        }

        // Volltextsuche
        if (!empty($_GET['search'])) {
            $q = '%' . $_GET['search'] . '%';
            $stmt = $db->prepare('
                SELECT id, key_slug, title, short, category
                FROM glossar
                WHERE title LIKE ? OR short LIKE ? OR text LIKE ?
                ORDER BY title
                LIMIT 50
            ');
            $stmt->execute([$q, $q, $q]);
            echo json_encode($stmt->fetchAll(PDO::FETCH_ASSOC), JSON_UNESCAPED_UNICODE);
            exit;
        }

        // Alle Einträge (Übersicht) mit Modul-Zuordnungen
        $stmt = $db->query('
            SELECT g.id, g.key_slug, g.title, g.short, g.category, g.image_path,
                   GROUP_CONCAT(m.module_id) AS modules
            FROM glossar g
            LEFT JOIN glossar_modules m ON m.glossar_id = g.id
            GROUP BY g.id
            ORDER BY g.title
        ');
        $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
        foreach ($rows as &$r) {
            $r['modules'] = $r['modules'] ? explode(',', $r['modules']) : [];
        }
        echo json_encode($rows, JSON_UNESCAPED_UNICODE);
        exit;
    }

    http_response_code(405);
    echo json_encode(['error' => 'method not allowed']);
} catch (Throwable $e) {
    http_response_code(500);
    echo json_encode(['error' => $e->getMessage()]);
}