<?php

namespace App\Services;

use App\Models\SandboxMail;

class SandboxMailParser
{
    public function parseAndStore(string $raw, array $recipients = []): SandboxMail
    {
        [$headerBlock, $body] = $this->splitHeadersBody($raw);
        $headers = $this->parseHeaders($headerBlock);

        [$textBody, $htmlBody] = $this->extractBodies($headers, $body);

        $from       = $this->parseAddress($headers['from'] ?? '');
        $toHeader   = $this->parseAddressList($headers['to'] ?? '');
        $toAddresses = !empty($recipients) ? $recipients : $toHeader;

        return SandboxMail::create([
            'message_id'   => trim($headers['message-id'] ?? '', '<>') ?: null,
            'from_address' => $from['address'],
            'from_name'    => $from['name'] ?: null,
            'to_addresses' => $toAddresses,
            'subject'      => $this->decodeMimeHeader($headers['subject'] ?? '(kein Betreff)'),
            'body_text'    => $textBody,
            'body_html'    => $htmlBody,
            'raw_headers'  => $headerBlock,
            'received_at'  => now(),
        ]);
    }

    private function splitHeadersBody(string $raw): array
    {
        $raw = str_replace("\r\n", "\n", $raw);
        $pos = strpos($raw, "\n\n");
        if ($pos === false) {
            return [$raw, ''];
        }
        return [substr($raw, 0, $pos), substr($raw, $pos + 2)];
    }

    private function parseHeaders(string $block): array
    {
        $headers = [];
        // Unfold multi-line headers
        $block = preg_replace("/\n[ \t]+/", ' ', $block);
        foreach (explode("\n", $block) as $line) {
            if (str_contains($line, ':')) {
                [$name, $value] = explode(':', $line, 2);
                $headers[strtolower(trim($name))] = trim($value);
            }
        }
        return $headers;
    }

    private function extractBodies(array $headers, string $body): array
    {
        $contentType = $headers['content-type'] ?? 'text/plain';

        if (str_starts_with($contentType, 'multipart/')) {
            preg_match('/boundary="?([^";\s]+)"?/i', $contentType, $m);
            $boundary = $m[1] ?? null;
            if ($boundary) {
                return $this->parseMultipart($body, $boundary);
            }
        }

        if (str_contains($contentType, 'text/html')) {
            return [null, $this->decodeBody($body, $headers['content-transfer-encoding'] ?? '')];
        }

        return [$this->decodeBody($body, $headers['content-transfer-encoding'] ?? ''), null];
    }

    private function parseMultipart(string $body, string $boundary): array
    {
        $text = null;
        $html = null;
        $parts = preg_split('/--' . preg_quote($boundary, '/') . '(--)?\r?\n?/', $body);

        foreach ($parts as $part) {
            $part = ltrim($part);
            if (empty($part) || $part === '--') continue;
            [$ph, $pb] = $this->splitHeadersBody($part);
            $ph = $this->parseHeaders($ph);
            $ct = $ph['content-type'] ?? '';
            $enc = $ph['content-transfer-encoding'] ?? '';

            if (str_contains($ct, 'multipart/')) {
                preg_match('/boundary="?([^";\s]+)"?/i', $ct, $m);
                if (!empty($m[1])) {
                    [$t, $h] = $this->parseMultipart($pb, $m[1]);
                    $text ??= $t;
                    $html ??= $h;
                }
            } elseif (str_contains($ct, 'text/html')) {
                $html ??= $this->decodeBody($pb, $enc);
            } elseif (str_contains($ct, 'text/plain')) {
                $text ??= $this->decodeBody($pb, $enc);
            }
        }

        return [$text, $html];
    }

    private function decodeBody(string $body, string $encoding): string
    {
        $enc = strtolower(trim($encoding));
        if ($enc === 'base64') {
            return base64_decode(str_replace(["\r", "\n"], '', $body));
        }
        if ($enc === 'quoted-printable') {
            return quoted_printable_decode($body);
        }
        return $body;
    }

    private function parseAddress(string $addr): array
    {
        $addr = $this->decodeMimeHeader($addr);
        if (preg_match('/^(.+?)\s*<([^>]+)>$/', trim($addr), $m)) {
            return ['name' => trim($m[1], '"'), 'address' => strtolower(trim($m[2]))];
        }
        return ['name' => '', 'address' => strtolower(trim($addr, '<>'))];
    }

    private function parseAddressList(string $list): array
    {
        $addresses = [];
        foreach (preg_split('/,(?![^<>]*>)/', $list) as $addr) {
            $parsed = $this->parseAddress(trim($addr));
            if ($parsed['address']) {
                $addresses[] = $parsed['address'];
            }
        }
        return $addresses;
    }

    private function decodeMimeHeader(string $value): string
    {
        if (!str_contains($value, '=?')) return $value;
        return mb_decode_mimeheader($value);
    }
}