<?php

declare(strict_types=1);

namespace Sarcio\WordPress;

/**
 * The declarative response transform, shared by the REST and generic
 * interceptors. Data only: each op sets a named top-level field to a constant
 * (including null). There is deliberately no expression language here — a patch
 * is constrained ops, never arbitrary code, and the server is the enforcement
 * line.
 */
final class Transform
{
    /**
     * @param array<string,mixed> $data
     * @param array<int,array{field:string,value:mixed}> $ops
     * @return array<string,mixed>
     */
    public static function apply(array $data, array $ops): array
    {
        foreach ($ops as $op) {
            if (!is_array($op) || !isset($op['field']) || !is_string($op['field'])) {
                continue;
            }
            $data[$op['field']] = $op['value'] ?? null;
        }
        return $data;
    }

    /**
     * Apply ops to a buffered response body. Anything that is not a JSON object
     * comes back byte-identical — an HTML page must never be rewritten by a
     * field transform meant for an API response.
     *
     * @param array<int,array{field:string,value:mixed}> $ops
     */
    public static function applyToJsonBuffer(string $buffer, array $ops): string
    {
        if ($ops === [] || $buffer === '') {
            return $buffer;
        }
        $decoded = json_decode($buffer, true);
        // A JSON list has nothing to reshape (only objects carry the keys ops name).
        if (!is_array($decoded) || array_keys($decoded) === range(0, count($decoded) - 1)) {
            return $buffer;
        }
        $encoded = wp_json_encode(self::apply($decoded, $ops));
        return is_string($encoded) ? $encoded : $buffer;
    }
}