<?php

declare(strict_types=1);

namespace KTXM\ProviderImap\Client\Protocol\Parser;

use KTXM\ProviderImap\Client\ImapException;
use KTXM\ProviderImap\Client\Mailbox;

/**
 * Decodes an individual LIST response payload into a mailbox.
 */
final class ListResponseParser
{
    public function parse(string $payload): Mailbox
    {
        $payload = trim($payload);
        $offset = 0;

        $attributesToken = $this->readToken($payload, $offset);
        $delimiterToken = $this->readToken($payload, $offset);
        $nameToken = $this->readToken($payload, $offset);

        if ($attributesToken === null || $delimiterToken === null || $nameToken === null) {
            throw new ImapException('Unable to parse LIST response payload: ' . $payload);
        }

        $attributeString = trim($attributesToken, '() ');
        $attributes = $attributeString === '' || strtoupper($attributeString) === 'NIL'
            ? []
            : array_map('strtoupper', preg_split('/\s+/', $attributeString) ?: []);

        $delimiter = $this->decodeAtom($delimiterToken);
        $name = $this->decodeMailboxName($nameToken);

        return new Mailbox($name, $delimiter, $attributes);
    }

    private function readToken(string $payload, int &$offset): ?string
    {
        $length = strlen($payload);

        while ($offset < $length && ctype_space($payload[$offset])) {
            $offset++;
        }

        if ($offset >= $length) {
            return null;
        }

        if ($payload[$offset] === '(') {
            $end = strpos($payload, ')', $offset);

            if ($end === false) {
                throw new ImapException('Unterminated LIST attribute block: ' . $payload);
            }

            $token = substr($payload, $offset, $end - $offset + 1);
            $offset = $end + 1;

            return $token;
        }

        if ($payload[$offset] === '"') {
            $start = $offset;
            $offset++;

            while ($offset < $length) {
                if ($payload[$offset] === '\\') {
                    $offset += 2;
                    continue;
                }

                if ($payload[$offset] === '"') {
                    $offset++;
                    return substr($payload, $start, $offset - $start);
                }

                $offset++;
            }

            throw new ImapException('Unterminated quoted LIST token: ' . $payload);
        }

        $start = $offset;
        while ($offset < $length && !ctype_space($payload[$offset])) {
            $offset++;
        }

        return substr($payload, $start, $offset - $start);
    }

    private function decodeAtom(string $value): ?string
    {
        $value = trim($value);

        if (strtoupper($value) === 'NIL') {
            return null;
        }

        if (str_starts_with($value, '"') && str_ends_with($value, '"')) {
            return stripcslashes(substr($value, 1, -1));
        }

        return $value;
    }

    private function decodeMailboxName(string $value): string
    {
        $name = $this->decodeAtom($value);

        // LIST may advertise the root mailbox as an empty quoted string.
        return $name ?? '';
    }

}