<?php

declare(strict_types=1);

namespace Laminas\Diactoros;

use function array_key_exists;
use function is_string;
use function strpos;
use function strtolower;
use function strtr;
use function substr;

/**
 * @param array $server Values obtained from the SAPI (generally `$_SERVER`).
 * @return array Header/value pairs
 */
function marshalHeadersFromSapi(array $server) : array
{
    $contentHeaderLookup = isset($server['LAMINAS_DIACTOROS_STRICT_CONTENT_HEADER_LOOKUP'])
        ? static function (string $key) : bool {
            static $contentHeaders = [
                'CONTENT_TYPE'   => true,
                'CONTENT_LENGTH' => true,
                'CONTENT_MD5'    => true,
            ];
            return isset($contentHeaders[$key]);
        }
        : static function (string $key): bool {
            return strpos($key, 'CONTENT_') === 0;
        };

    $headers = [];
    foreach ($server as $key => $value) {
        if (! is_string($key)) {
            continue;
        }

        if ($value === '') {
            continue;
        }

        // Apache prefixes environment variables with REDIRECT_
        // if they are added by rewrite rules
        if (strpos($key, 'REDIRECT_') === 0) {
            $key = substr($key, 9);

            // We will not overwrite existing variables with the
            // prefixed versions, though
            if (array_key_exists($key, $server)) {
                continue;
            }
        }

        if (strpos($key, 'HTTP_') === 0) {
            $name = strtr(strtolower(substr($key, 5)), '_', '-');
            $headers[$name] = $value;
            continue;
        }

        if ($contentHeaderLookup($key)) {
            $name = strtr(strtolower($key), '_', '-');
            $headers[$name] = $value;
            continue;
        }
    }

    return $headers;
}
