<?php

namespace App\Services\Payment\Support;

use Illuminate\Support\Str;

/**
 * ابزار امضای HMAC مطابق EXTERNAL_PAYMENT_PARTNER.md (Montify).
 * فقط سمت سرور استفاده شود.
 */
class MontifyHmacSigner
{
    public function __construct(private string $clientId, private string $clientSecret)
    {
    }

    /**
     * @param  array<string, mixed>|null  $body
     * @return array<string, string>
     */
    public function signRequest(string $method, string $path, ?array $body): array
    {
        $timestamp = (string) time();
        $nonce = (string) Str::uuid();
        $bodyString = $body !== null ? $this->stableStringify($body) : '';
        $bodyHash = hash('sha256', $bodyString);
        $canonical = implode("\n", [
            strtoupper($method),
            $path,
            $bodyHash,
            $timestamp,
            $nonce,
        ]);
        $signature = hash_hmac('sha256', $canonical, $this->clientSecret);

        return [
            'Content-Type' => 'application/json',
            'Accept' => 'application/json',
            'X-Client-Id' => $this->clientId,
            'X-Timestamp' => $timestamp,
            'X-Nonce' => $nonce,
            'X-Signature' => $signature,
        ];
    }

    /**
     * @param  array<string, mixed>  $query
     */
    public function verifyReturnSignature(array $query): bool
    {
        return $this->matchReturnSignatureVariant($query) !== null;
    }

    /**
     * نام قالبی که امضا با آن خواند، یا null اگر هیچ‌کدام نخواند.
     *
     * پارتنر ممکن است مقادیر عددی را به‌صورت number امضا کند یا پارامتر خالی
     * (مثل track_number) را اصلاً در payload نگذارد؛ همه حالت‌ها بررسی می‌شود.
     *
     * @param  array<string, mixed>  $query
     */
    public function matchReturnSignatureVariant(array $query): ?string
    {
        $signature = (string) ($query['signature'] ?? '');
        if ($signature === '' || !ctype_xdigit($signature)) {
            return null;
        }

        unset($query['signature']);

        foreach ($this->payloadVariants($query) as $name => $payload) {
            $expected = hash_hmac('sha256', $this->stableStringify($payload), $this->clientSecret);
            if ($this->hashEqualsHex($signature, $expected)) {
                return $name;
            }
        }

        return null;
    }

    /**
     * @param  array<string, mixed>  $body
     */
    public function verifyWebhookSignature(array $body, ?string $signatureHeader): bool
    {
        $signature = (string) ($signatureHeader ?? '');
        if ($signature === '' || !ctype_xdigit($signature)) {
            return false;
        }

        // بدنه همان‌طور که آمده (نوع‌ها از JSON) اولویت دارد، بعد حالت‌های نرمال‌شده
        $candidates = array_merge(
            ['raw' => $body],
            $this->payloadVariants($body)
        );

        foreach ($candidates as $payload) {
            $expected = hash_hmac('sha256', $this->stableStringify($payload), $this->clientSecret);
            if ($this->hashEqualsHex($signature, $expected)) {
                return true;
            }
        }

        return false;
    }

    /**
     * حالت‌های ممکن payload برای مقایسه امضا (بدون تکرار).
     *
     * @param  array<string, mixed>  $payload
     * @return array<string, array<string, mixed>>
     */
    private function payloadVariants(array $payload): array
    {
        $strings = [];
        foreach ($payload as $key => $value) {
            if (!is_string($key) || $key === '' || is_array($value) || $value === null) {
                continue;
            }
            $strings[$key] = is_bool($value) ? ($value ? 'true' : 'false') : (string) $value;
        }

        $withoutEmpty = array_filter($strings, static fn ($value) => $value !== '');

        $variants = [
            'strings' => $strings,
            'strings_without_empty' => $withoutEmpty,
            'numeric' => $this->castNumericValues($strings),
            'numeric_without_empty' => $this->castNumericValues($withoutEmpty),
        ];

        $unique = [];
        $seen = [];
        foreach ($variants as $name => $variant) {
            $fingerprint = $this->stableStringify($variant);
            if (isset($seen[$fingerprint])) {
                continue;
            }
            $seen[$fingerprint] = true;
            $unique[$name] = $variant;
        }

        return $unique;
    }

    /**
     * @param  array<string, string>  $payload
     * @return array<string, mixed>
     */
    private function castNumericValues(array $payload): array
    {
        foreach (['amount', 'timestamp'] as $key) {
            if (isset($payload[$key]) && is_string($payload[$key]) && ctype_digit($payload[$key])) {
                $payload[$key] = (int) $payload[$key];
            }
        }

        return $payload;
    }

    public function isTimestampFresh(int|string|null $timestamp, int $skewSeconds = 300): bool
    {
        if ($timestamp === null || $timestamp === '') {
            return false;
        }

        return abs(time() - (int) $timestamp) <= $skewSeconds;
    }

    /**
     * @param  mixed  $value
     */
    public function stableStringify($value): string
    {
        if ($value === null || !is_array($value)) {
            return json_encode($value, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
        }

        if (array_is_list($value)) {
            $parts = array_map(fn ($item) => $this->stableStringify($item), $value);

            return '[' . implode(',', $parts) . ']';
        }

        ksort($value);
        $parts = [];
        foreach ($value as $key => $item) {
            $parts[] = '"' . $key . '":' . $this->stableStringify($item);
        }

        return '{' . implode(',', $parts) . '}';
    }

    private function hashEqualsHex(string $a, string $b): bool
    {
        if (!ctype_xdigit($a) || !ctype_xdigit($b) || strlen($a) !== strlen($b)) {
            return false;
        }

        return hash_equals(strtolower($a), strtolower($b));
    }
}