<?php

declare(strict_types=1);

namespace KTXM\ProviderImap\Client\Command;

use KTXM\ProviderImap\Client\ImapException;

final class StatusResponseParser
{
    /**
     * @return array{0: string, 1: array<string, int>}
     */
    public function parse(string $payload): array
    {
        $payload = trim($payload);
        $offset = 0;

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

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

        $mailbox = $this->decodeAtom($nameToken);
        if ($mailbox === null || $mailbox === '') {
            throw new ImapException('STATUS response is missing a mailbox name: ' . $payload);
        }

        return [$mailbox, $this->parseItems($statusToken, $payload)];
    }

    /**
     * @return array<string, int>
     */
    private function parseItems(string $statusToken, string $payload): array
    {
        $statusToken = trim($statusToken);

        if (!str_starts_with($statusToken, '(') || !str_ends_with($statusToken, ')')) {
            throw new ImapException('Invalid STATUS data payload: ' . $payload);
        }

        $items = trim(substr($statusToken, 1, -1));
        if ($items === '') {
            return [];
        }

        $tokens = preg_split('/\s+/', $items) ?: [];
        if (count($tokens) % 2 !== 0) {
            throw new ImapException('Malformed STATUS item list: ' . $payload);
        }

        $status = [];

        for ($index = 0; $index < count($tokens); $index += 2) {
            $item = strtoupper($tokens[$index]);
            $value = $tokens[$index + 1];

            if (!preg_match('/^\d+$/', $value)) {
                throw new ImapException('STATUS item value must be numeric: ' . $payload);
            }

            $status[$item] = (int) $value;
        }

        return $status;
    }

    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 STATUS item 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 STATUS 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;
    }
}