<?php
/**
 * User Avatar API
 *
 * Serves profile pictures fetched from lldap via LDAP.
 * Caches images locally to avoid repeated LDAP queries.
 *
 * GET /api/user_avatar.php?user_id=123
 *   Returns the user's JPEG avatar (from cache or LDAP).
 *   Returns 404 if the user has no avatar set in lldap.
 */

ini_set('display_errors', 0);
error_reporting(E_ALL);

require_once dirname(__DIR__) . '/middleware/RateLimitMiddleware.php';
RateLimitMiddleware::apply('api');

if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

require_once dirname(__DIR__) . '/config/config.php';
require_once dirname(__DIR__) . '/helpers/Database.php';

// Must be authenticated
if (!isset($_SESSION['user']['user_id'])) {
    http_response_code(401);
    exit;
}

if ($_SERVER['REQUEST_METHOD'] !== 'GET') {
    http_response_code(405);
    exit;
}

$cfg = $GLOBALS['config'];

// Validate user_id parameter
$userId = isset($_GET['user_id']) ? (int)$_GET['user_id'] : 0;
if ($userId <= 0) {
    http_response_code(400);
    exit;
}

// Ensure LDAP is enabled and extension is loaded
if (!$cfg['LDAP_ENABLED'] || !extension_loaded('ldap')) {
    http_response_code(404);
    exit;
}

// Ensure avatar cache directory exists
$cacheDir = rtrim($cfg['AVATAR_CACHE_DIR'], '/');
if (!is_dir($cacheDir)) {
    mkdir($cacheDir, 0755, true);
}

$cacheFile = $cacheDir . '/user_' . $userId . '.jpg';
$cacheTtl  = (int)($cfg['AVATAR_CACHE_TTL'] ?? 3600);

// Serve from cache if fresh
if (file_exists($cacheFile) && (time() - filemtime($cacheFile)) < $cacheTtl) {
    header('Content-Type: image/jpeg');
    header('Cache-Control: private, max-age=' . $cacheTtl);
    header('X-Avatar-Source: cache');
    readfile($cacheFile);
    exit;
}

// A sentinel empty file means "no avatar" — don't re-query LDAP until TTL expires
$noAvatarSentinel = $cacheDir . '/user_' . $userId . '.none';
if (file_exists($noAvatarSentinel) && (time() - filemtime($noAvatarSentinel)) < $cacheTtl) {
    http_response_code(404);
    exit;
}

// Look up username from DB
try {
    $conn = Database::getConnection();
    $stmt = $conn->prepare("SELECT username FROM users WHERE user_id = ? LIMIT 1");
    $stmt->bind_param('i', $userId);
    $stmt->execute();
    $result = $stmt->get_result();
    $row = $result->fetch_assoc();
    $stmt->close();

    if (!$row || empty($row['username'])) {
        http_response_code(404);
        exit;
    }
    $username = $row['username'];
} catch (Exception $e) {
    error_log("user_avatar: DB error for user_id=$userId: " . $e->getMessage());
    http_response_code(500);
    exit;
}

// Query lldap via LDAP
$ldapHost = $cfg['LDAP_HOST'];
$ldapPort = $cfg['LDAP_PORT'];
$bindDn   = $cfg['LDAP_BIND_DN'];
$bindPw   = $cfg['LDAP_BIND_PW'];
$userBase = $cfg['LDAP_USER_BASE'];

// Escape username for LDAP filter (RFC 4515)
$safeUsername = ldap_escape($username, '', LDAP_ESCAPE_FILTER);
$filter       = "(uid=$safeUsername)";

$avatarData = null;

try {
    $ldap = @ldap_connect("ldap://$ldapHost:$ldapPort");
    if (!$ldap) {
        throw new RuntimeException("ldap_connect failed");
    }

    ldap_set_option($ldap, LDAP_OPT_PROTOCOL_VERSION, 3);
    ldap_set_option($ldap, LDAP_OPT_REFERRALS, 0);
    ldap_set_option($ldap, LDAP_OPT_NETWORK_TIMEOUT, 3);
    ldap_set_option($ldap, LDAP_OPT_TIMELIMIT, 3);

    if (!@ldap_bind($ldap, $bindDn, $bindPw)) {
        throw new RuntimeException("LDAP bind failed: " . ldap_error($ldap));
    }

    $search = @ldap_search($ldap, $userBase, $filter, ['avatar'], 0, 1, 3);
    if (!$search) {
        throw new RuntimeException("LDAP search failed: " . ldap_error($ldap));
    }

    $entries = ldap_get_entries($ldap, $search);
    if ($entries['count'] > 0 && !empty($entries[0]['avatar'][0])) {
        // ldap_get_entries() returns the attribute value as raw binary.
        $avatarData = $entries[0]['avatar'][0];
    }

    ldap_unbind($ldap);
} catch (Exception $e) {
    error_log("user_avatar: LDAP error for username=$username: " . $e->getMessage());
    // Fall through to 404
}

if ($avatarData === null || strlen($avatarData) < 100) {
    // Write sentinel so we don't hammer LDAP for users without avatars
    file_put_contents($noAvatarSentinel, '');
    http_response_code(404);
    exit;
}

// Validate it's actually a JPEG (magic bytes FF D8 FF)
if (substr($avatarData, 0, 3) !== "\xFF\xD8\xFF") {
    error_log("user_avatar: non-JPEG data for username=$username");
    file_put_contents($noAvatarSentinel, '');
    http_response_code(404);
    exit;
}

// Cache to disk
file_put_contents($cacheFile, $avatarData);
// Remove stale sentinel if present
if (file_exists($noAvatarSentinel)) {
    unlink($noAvatarSentinel);
}

header('Content-Type: image/jpeg');
header('Cache-Control: private, max-age=' . $cacheTtl);
header('X-Avatar-Source: ldap');
echo $avatarData;