<?php

namespace App\Services\Posta;

use Exception;

class ImapClient
{
    private mixed $socket = null;
    private int $tagIndex = 0;

    public function testConnection(string $host, int $port, string $username, string $password, string $encryption = 'ssl'): array
    {
        try {
            $this->connect($host, $port, $username, $password, $encryption);
            $this->disconnect();
            return ['success' => true, 'message' => 'Connessione e autenticazione IMAP riuscite con successo.'];
        } catch (\Throwable $e) {
            return ['success' => false, 'message' => 'Errore IMAP: ' . $e->getMessage()];
        }
    }

    public function connect(string $host, int $port, string $username, string $password, string $encryption = 'ssl'): void
    {
        $prefix = strtolower($encryption) === 'ssl' ? 'ssl://' : '';
        $target = $prefix . $host;
        $timeout = 15;

        $context = stream_context_create([
            'ssl' => [
                'verify_peer'       => false,
                'verify_peer_name'  => false,
                'allow_self_signed' => true,
            ],
        ]);

        $this->socket = @stream_socket_client(
            $target . ':' . $port,
            $errno,
            $errstr,
            $timeout,
            STREAM_CLIENT_CONNECT,
            $context
        );

        if (! $this->socket) {
            throw new Exception("Impossibile connettersi al server IMAP {$host}:{$port} ({$errstr})");
        }

        stream_set_timeout($this->socket, $timeout);

        // Leggi il banner iniziale
        $greeting = $this->readLine();
        if (! str_starts_with($greeting, '* OK')) {
            throw new Exception("Risposta iniziale inattesa dal server IMAP: {$greeting}");
        }

        // Login
        $userEscaped = addcslashes($username, '\\"');
        $passEscaped = addcslashes($password, '\\"');
        $res = $this->sendCommand("LOGIN \"{$userEscaped}\" \"{$passEscaped}\"");
        if (! $res['ok']) {
            throw new Exception("Autenticazione IMAP fallita per l'utente {$username}: " . ($res['response'] ?? ''));
        }
    }

    public function selectFolder(string $folder = 'INBOX'): array
    {
        $folderEscaped = addcslashes($folder, '\\"');
        $res = $this->sendCommand("SELECT \"{$folderEscaped}\"");
        if (! $res['ok']) {
            throw new Exception("Impossibile aprire la cartella IMAP '{$folder}'");
        }

        $exists = 0;
        foreach ($res['lines'] as $line) {
            if (preg_match('/^\*\s+(\d+)\s+EXISTS/i', $line, $m)) {
                $exists = (int) $m[1];
            }
        }

        return ['ok' => true, 'exists' => $exists];
    }

    /**
     * @return array<int, int>
     */
    public function search(string $criteria = 'ALL'): array
    {
        $res = $this->sendCommand("SEARCH {$criteria}");
        if (! $res['ok']) {
            return [];
        }

        $ids = [];
        foreach ($res['lines'] as $line) {
            if (str_starts_with($line, '* SEARCH')) {
                $parts = explode(' ', trim(substr($line, 8)));
                foreach ($parts as $p) {
                    if (is_numeric($p) && (int) $p > 0) {
                        $ids[] = (int) $p;
                    }
                }
            }
        }

        return $ids;
    }

    public function fetchRawEml(int $msgId): string
    {
        $tag = $this->nextTag();
        $cmd = "{$tag} FETCH {$msgId} (BODY.PEEK[])\r\n";
        fwrite($this->socket, $cmd);

        $firstLine = $this->readLine();
        $expectedLength = null;
        if (preg_match('/\{(\d+)\}$/', trim($firstLine), $m)) {
            $expectedLength = (int) $m[1];
        }

        $rawEml = '';
        if ($expectedLength !== null && $expectedLength > 0) {
            $bytesRead = 0;
            while ($bytesRead < $expectedLength && ! feof($this->socket)) {
                $chunk = fread($this->socket, min(8192, $expectedLength - $bytesRead));
                if ($chunk === false || $chunk === '') {
                    break;
                }
                $rawEml .= $chunk;
                $bytesRead += strlen($chunk);
            }
        }

        // Leggi fino al tag di completamento
        while (! feof($this->socket)) {
            $line = $this->readLine();
            if (str_starts_with($line, $tag . ' OK')) {
                break;
            }
            if (str_starts_with($line, $tag . ' NO') || str_starts_with($line, $tag . ' BAD')) {
                break;
            }
        }

        return $rawEml;
    }

    public function disconnect(): void
    {
        if ($this->socket) {
            try {
                $this->sendCommand('LOGOUT');
            } catch (\Throwable) {
                // ignore
            }
            @fclose($this->socket);
            $this->socket = null;
        }
    }

    private function nextTag(): string
    {
        $this->tagIndex++;
        return 'A' . str_pad((string) $this->tagIndex, 4, '0', STR_PAD_LEFT);
    }

    private function sendCommand(string $command): array
    {
        if (! $this->socket) {
            throw new Exception("Socket IMAP non connesso.");
        }

        $tag = $this->nextTag();
        $payload = "{$tag} {$command}\r\n";
        fwrite($this->socket, $payload);

        $lines = [];
        $ok = false;
        $response = '';

        while (! feof($this->socket)) {
            $line = $this->readLine();
            $lines[] = $line;

            if (str_starts_with($line, $tag . ' OK')) {
                $ok = true;
                $response = $line;
                break;
            }

            if (str_starts_with($line, $tag . ' NO') || str_starts_with($line, $tag . ' BAD')) {
                $ok = false;
                $response = $line;
                break;
            }
        }

        return [
            'ok'       => $ok,
            'response' => $response,
            'lines'    => $lines,
        ];
    }

    private function readLine(): string
    {
        $line = fgets($this->socket);
        return $line !== false ? trim($line, "\r\n") : '';
    }
}