<?php

namespace App\Services\Esign;

use InvalidArgumentException;

final class EsignRequestSigner
{
    public const ACCEPT = '*/*';
    public const CONTENT_TYPE = 'application/json; charset=UTF-8';

    public function __construct(
        private readonly string $appId,
        private readonly string $appSecret,
    ) {
        if ($this->appId === '' || $this->appSecret === '') {
            throw new InvalidArgumentException('E 签宝 App ID 和 AppSecret 不能为空。');
        }
    }

    public function headers(string $method, string $pathAndParameters, string $body = ''): array
    {
        $method = strtoupper($method);
        $pathAndParameters = $this->canonicalPath($pathAndParameters);
        $contentMd5 = $body === '' ? '' : base64_encode(md5($body, true));
        $stringToSign = implode("\n", [
            $method,
            self::ACCEPT,
            $contentMd5,
            self::CONTENT_TYPE,
            '',
        ]) . "\n" . $pathAndParameters;

        return [
            'X-Tsign-Open-App-Id' => $this->appId,
            'X-Tsign-Open-Auth-Mode' => 'Signature',
            'X-Tsign-Open-Ca-Timestamp' => (string) floor(microtime(true) * 1000),
            'X-Tsign-Open-Ca-Signature' => base64_encode(hash_hmac('sha256', $stringToSign, $this->appSecret, true)),
            'Accept' => self::ACCEPT,
            'Content-Type' => self::CONTENT_TYPE,
            'Content-MD5' => $contentMd5,
        ];
    }

    public function canonicalPath(string $pathAndParameters): string
    {
        $parts = parse_url($pathAndParameters);
        $path = (string) ($parts['path'] ?? '');

        if ($path === '' || ! str_starts_with($path, '/')) {
            throw new InvalidArgumentException('E 签宝 API 路径必须以 / 开头。');
        }

        if (! isset($parts['query']) || $parts['query'] === '') {
            return $path;
        }

        $parameters = [];

        foreach (explode('&', $parts['query']) as $pair) {
            [$key, $value] = array_pad(explode('=', $pair, 2), 2, null);

            if (! array_key_exists($key, $parameters)) {
                $parameters[$key] = $value;
            }
        }

        ksort($parameters, SORT_STRING);
        $query = collect($parameters)->map(function (?string $value, string $key): string {
            return $value === null || $value === '' ? $key : $key . '=' . $value;
        })->implode('&');

        return $path . '?' . $query;
    }
}