<?php

declare(strict_types=1);

// Shared request handling for the token-authenticated api/v1 endpoints.
//
// Protocol v1: every request carries the instance id and its secret token in
// two headers. There is no session, no cookie and no shared password.
//
//   X-Manage-Instance: example-prod
//   X-Manage-Token:    <64 hex chars>

require_once __DIR__ . "/bootstrap.php";
require_once __DIR__ . "/instances.php";

function manageApiSendJson(int $status, array $payload): void
{
    http_response_code($status);
    header("Content-Type: application/json; charset=utf-8");
    header("Cache-Control: no-store");
    header("X-Content-Type-Options: nosniff");

    echo json_encode(
        $payload,
        JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE,
    );
    exit;
}

function manageApiFail(int $status, string $error, array $extra = []): void
{
    manageApiSendJson($status, array_merge([
        "success" => false,
        "error" => $error,
    ], $extra));
}

function manageApiRequireMethod(string $method): void
{
    if (($_SERVER["REQUEST_METHOD"] ?? "") !== $method) {
        header("Allow: " . $method);
        manageApiFail(405, $method . " erforderlich.");
    }
}

// Reads a request header regardless of SAPI. Apache with mod_php exposes
// X-Manage-Token as HTTP_X_MANAGE_TOKEN; some setups only fill getallheaders().
function manageApiHeader(string $name): string
{
    $key = "HTTP_" . strtoupper(str_replace("-", "_", $name));
    if (isset($_SERVER[$key])) {
        return trim((string) $_SERVER[$key]);
    }

    if (function_exists("getallheaders")) {
        foreach (getallheaders() ?: [] as $headerName => $value) {
            if (strcasecmp((string) $headerName, $name) === 0) {
                return trim((string) $value);
            }
        }
    }

    return "";
}

/**
 * Authenticates the calling instance or terminates the request.
 *
 * Failures are rate-limited per IP and answered with the same generic message,
 * so the endpoint cannot be used to enumerate valid instance ids.
 *
 * @return array the instance record
 */
function manageApiAuthenticate(): array
{
    if (!manageRateLimitTryConsume(
        "api-auth",
        (int) MANAGE_API_RATE_LIMIT_MAX,
        (int) MANAGE_API_RATE_LIMIT_WINDOW,
    )) {
        manageApiFail(429, "Zu viele Anfragen. Bitte später erneut versuchen.");
    }

    $id = manageApiHeader("X-Manage-Instance");
    $token = manageApiHeader("X-Manage-Token");

    if ($id === "" || $token === "") {
        manageApiFail(401, "Authentifizierung erforderlich.");
    }

    try {
        $id = manageInstanceValidateId($id);
    } catch (Throwable $exception) {
        manageApiFail(401, "Authentifizierung fehlgeschlagen.");
    }

    $instance = manageInstanceAuthenticate($id, $token);
    if ($instance === null) {
        manageLogError("API authentication failed", ["instance" => $id]);
        manageApiFail(401, "Authentifizierung fehlgeschlagen.");
    }

    if (!$instance["enabled"]) {
        manageApiFail(403, "Diese Instanz ist deaktiviert.");
    }

    // A valid token clears the failure budget for this IP.
    manageRateLimitClearIp("api-auth");

    return $instance;
}

// Decodes a JSON request body. Returns an empty array for an empty body so
// optional payloads do not need a special case at every call site.
function manageApiReadJsonBody(): array
{
    $raw = file_get_contents("php://input");
    if (!is_string($raw) || trim($raw) === "") {
        return [];
    }

    $decoded = json_decode($raw, true);
    if (!is_array($decoded)) {
        manageApiFail(400, "Anfrage-Body ist kein gültiges JSON.");
    }

    return $decoded;
}