<?php

namespace Ulmus\User\Authorize\Bearer;

class JsonWebTokenDecoder
{
    protected array $header;

    protected array $payload;

    public function __construct(
        public string $encoded,
        public string $secretKey,
    ) {}

    protected function parse() : bool
    {
        try {
            list($encodedHeader, $encodedPayload, $signature) = explode('.', $this->encoded);

            foreach([ 'header' => $encodedHeader, 'payload' => $encodedPayload ] as $key => $value) {
                $decoded = static::base64url_decode($value) ;

                if ( $decoded !== false ){
                    $jsonArray = json_decode($decoded, true);

                    if ( is_array($jsonArray) ) {
                        if ($key === 'header') {
                            JsonWebTokenValidate::validateHeaderType($jsonArray);
                            JsonWebTokenValidate::validateHeaderAlgorithm($jsonArray);
                        }
                        elseif ($key === 'payload') {
                            JsonWebTokenValidate::validatePayloadExpiration($jsonArray);
                        }

                        $this->$key = $jsonArray;
                    }
                    else {
                        throw new JsonWebTokenDecodingError(sprintf("Invalid JSON returned while decoding section %s ; an array must be provided", $key));
                    }
                }
                else {
                    throw new JsonWebTokenDecodingError(sprintf("An error occured while decoding a base64 string from section %s", $key));
                }
            }

            JsonWebTokenValidate::validateSignature($this->header['alg'], $this->secretKey, $encodedHeader, $encodedPayload, $signature);
        }
        catch(\Throwable $t) {
            throw new JsonWebTokenDecodingError($t->getMessage(), $t->getCode(), $t);
        }

        return true;
    }

    public static function base64url_decode($data) : string|false
    {
        return base64_decode(strtr($data, '-_', '+/'));
    }

    public function decode() : bool
    {
        return $this->parse();
    }

    /**
     * Basic validation of JWT encoded string
     * @return bool
     */
    public function isJWT() : bool
    {
        try {
            return $this->parse();
        }
        catch(\Throwable $t) {}

        return false;
    }

    public function getPayload() : array
    {
        return $this->payload;
    }
}