<?php
declare(strict_types=1);

function shopify_api_request_json(string $url, string $method, array $headers, string $body, int $timeoutSeconds = 20): array
{
    $headerLines = [];
    foreach ($headers as $name => $value) {
        if ($name !== '' && $value !== '') {
            $headerLines[] = $name . ': ' . $value;
        }
    }

    $context = stream_context_create([
        'http' => [
            'method' => $method,
            'header' => implode("\r\n", $headerLines),
            'content' => $body,
            'timeout' => $timeoutSeconds,
            'ignore_errors' => true,
        ],
    ]);

    $responseBody = @file_get_contents($url, false, $context);
    $responseHeaders = $http_response_header ?? [];
    $status = 0;
    if (isset($responseHeaders[0]) && preg_match('#HTTP/\S+\s+(\d{3})#', $responseHeaders[0], $matches) === 1) {
        $status = (int) $matches[1];
    }

    if ($responseBody === false || $responseBody === '') {
        throw new RuntimeException('Shopify API returned an empty response');
    }

    try {
        $decoded = json_decode($responseBody, true, 512, JSON_THROW_ON_ERROR);
    } catch (JsonException $exception) {
        throw new RuntimeException('Shopify API returned invalid JSON', 0, $exception);
    }

    if (!is_array($decoded)) {
        throw new RuntimeException('Shopify API returned a non-object JSON response');
    }

    return ['status' => $status, 'body' => $decoded];
}

function shopify_api_credentials(array $env): array
{
    $shop = trim(env_value('SHOPIFY_SHOP', $env));
    $clientId = trim(env_value('SHOPIFY_CLIENT_ID', $env));
    $clientSecret = trim(env_value('SHOPIFY_CLIENT_SECRET', $env));
    $apiVersion = trim(env_value('SHOPIFY_API_VERSION', $env));

    if ($shop === '' || $clientId === '' || $clientSecret === '' || $apiVersion === '') {
        throw new RuntimeException('Incomplete Shopify API configuration');
    }

    if (!preg_match('/^[a-z0-9][a-z0-9-]*\.myshopify\.com$/', $shop)) {
        throw new RuntimeException('Invalid Shopify shop domain');
    }

    if (!preg_match('/^\d{4}-\d{2}$/', $apiVersion)) {
        throw new RuntimeException('Invalid Shopify API version');
    }

    return [
        'shop' => $shop,
        'client_id' => $clientId,
        'client_secret' => $clientSecret,
        'api_version' => $apiVersion,
    ];
}

function shopify_api_access_token(array $env): string
{
    $credentials = shopify_api_credentials($env);
    $body = http_build_query([
        'grant_type' => 'client_credentials',
        'client_id' => $credentials['client_id'],
        'client_secret' => $credentials['client_secret'],
    ], '', '&', PHP_QUERY_RFC3986);

    $response = shopify_api_request_json(
        'https://' . $credentials['shop'] . '/admin/oauth/access_token',
        'POST',
        ['Content-Type' => 'application/x-www-form-urlencoded', 'Accept' => 'application/json'],
        $body
    );

    if ($response['status'] < 200 || $response['status'] >= 300) {
        throw new RuntimeException('Shopify access-token request failed');
    }

    $token = trim((string) ($response['body']['access_token'] ?? ''));
    if ($token === '') {
        throw new RuntimeException('Shopify access-token response did not contain a token');
    }

    return $token;
}

function shopify_graphql_query(array $env, string $query, array $variables = []): array
{
    if (trim($query) === '') {
        throw new InvalidArgumentException('Shopify GraphQL query must not be empty');
    }

    $credentials = shopify_api_credentials($env);
    $token = shopify_api_access_token($env);
    $body = json_encode(['query' => $query, 'variables' => $variables], JSON_THROW_ON_ERROR | JSON_UNESCAPED_SLASHES);
    $response = shopify_api_request_json(
        'https://' . $credentials['shop'] . '/admin/api/' . $credentials['api_version'] . '/graphql.json',
        'POST',
        ['Content-Type' => 'application/json', 'Accept' => 'application/json', 'X-Shopify-Access-Token' => $token],
        $body
    );

    if ($response['status'] < 200 || $response['status'] >= 300) {
        throw new RuntimeException('Shopify GraphQL request failed');
    }

    $errors = $response['body']['errors'] ?? [];
    if (is_array($errors) && $errors !== []) {
        throw new RuntimeException('Shopify GraphQL returned errors');
    }

    return (array) ($response['body']['data'] ?? []);
}