<?php

declare(strict_types=1);

namespace KTXM\ProviderImap\Client\Protocol;

use KTXM\ProviderImap\Client\ImapException;
use KTXM\ProviderImap\Client\Protocol\Response\ContinuationResponse;
use KTXM\ProviderImap\Client\Protocol\Response\GreetingResponse;
use KTXM\ProviderImap\Client\Protocol\Response\ResponseInterface;
use KTXM\ProviderImap\Client\Protocol\Response\TaggedResponse;
use KTXM\ProviderImap\Client\Protocol\Response\UntaggedResponse;
use KTXM\ProviderImap\Client\Transport\ConnectionInterface;
use Psr\Log\LoggerInterface;

final class ProtocolReader
{
    public function __construct(
        private readonly ConnectionInterface $connection,
        private readonly ?LoggerInterface $logger = null,
    ) {}

    public function readGreeting(): GreetingResponse
    {
        $raw = $this->trimTrailingLineEnding($this->connection->readLine());

        if (!str_starts_with($raw, '* ')) {
            throw new ImapException(sprintf('Expected IMAP greeting, got: %s', $raw));
        }

        $parts = preg_split('/\s+/', substr($raw, 2), 2) ?: [];
        $status = strtoupper($parts[0] ?? '');
        $text = $parts[1] ?? '';

        $this->logger?->debug('IMAP greeting received: {raw}', [
            'status' => $status,
            'raw' => $raw,
        ]);

        return new GreetingResponse($status, $text, $raw);
    }

    public function readResponse(): ResponseInterface
    {
        $raw = $this->readRawResponse();

        if ($raw === '') {
            throw new ImapException('Received empty IMAP response line.');
        }

        if (str_starts_with($raw, '* ')) {
            $parts = preg_split('/\s+/', substr($raw, 2), 2) ?: [];
            $label = strtoupper($parts[0] ?? '');
            $this->logger?->debug('IMAP untagged response received: {raw}', [
                'label' => $label,
                'raw' => $raw,
            ]);
            return new UntaggedResponse(
                $label,
                $parts[1] ?? '',
                $raw,
            );
        }

        if (str_starts_with($raw, '+')) {
            $this->logger?->debug('IMAP continuation response received: {raw}', [
                'raw' => $raw,
            ]);
            return new ContinuationResponse(ltrim(substr($raw, 1)), $raw);
        }

        $parts = preg_split('/\s+/', $raw, 3) ?: [];

        if (count($parts) < 2) {
            throw new ImapException(sprintf('Malformed tagged IMAP response: %s', $raw));
        }

        $status = strtoupper($parts[1]);
        $this->logger?->debug('IMAP tagged response received: {raw}', [
            'tag' => $parts[0],
            'status' => $status,
            'raw' => $raw,
        ]);

        return new TaggedResponse($parts[0], $status, $parts[2] ?? '', $raw);
    }

    private function readRawResponse(): string
    {
        $raw = $this->connection->readLine();

        while (($literalLength = $this->trailingLiteralLength($raw)) !== null) {
            $raw .= $this->connection->readBytes($literalLength);
            $raw .= $this->connection->readLine();
        }

        return $this->trimTrailingLineEnding($raw);
    }

    private function trailingLiteralLength(string $raw): ?int
    {
        if (preg_match('/\{(\d+)\}\r?\n$/', $raw, $matches) !== 1) {
            return null;
        }

        return (int) $matches[1];
    }

    private function trimTrailingLineEnding(string $raw): string
    {
        if (str_ends_with($raw, "\r\n")) {
            return substr($raw, 0, -2);
        }

        if (str_ends_with($raw, "\n")) {
            return substr($raw, 0, -1);
        }

        return $raw;
    }
}