"""Bounded synthetic SMTP/mailbox fixture, available only inside a network-none peer."""

import email
import email.policy
import json
import re
import socketserver
import threading
import urllib.parse
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from pathlib import Path

MESSAGES = []
LOCK = threading.Lock()


class SMTP(socketserver.StreamRequestHandler):
    def handle(self):
        self.connection.settimeout(15)
        recipient = None
        sender = False

        def reply(line):
            self.wfile.write((line + '\r\n').encode())
            self.wfile.flush()

        reply('220 synthetic fixture')
        while True:
            raw = self.rfile.readline(8193)
            if not raw or len(raw) > 8192:
                return
            command = raw.decode(errors='replace').strip()
            upper = command.upper()
            if upper.startswith(('EHLO ', 'HELO ')):
                reply('250 synthetic fixture')
            elif upper.startswith('MAIL FROM:'):
                sender = upper == 'MAIL FROM:<NO-REPLY@EXAMPLE.TEST>'
                reply('250 OK' if sender else '550 fixture sender only')
            elif upper.startswith('RCPT TO:'):
                recipient = ('alice@example.test'
                             if upper == 'RCPT TO:<ALICE@EXAMPLE.TEST>' else None)
                reply('250 OK' if recipient else '550 fixture recipient only')
            elif upper == 'DATA' and sender and recipient:
                reply('354 End with dot')
                lines, size = [], 0
                while True:
                    line = self.rfile.readline(65537)
                    if not line or len(line) > 65536:
                        return
                    if line == b'.\r\n':
                        break
                    size += len(line)
                    if size > 65536:
                        reply('552 fixture message too large')
                        return
                    lines.append(line[1:] if line.startswith(b'..') else line)
                message = email.message_from_bytes(b''.join(lines), policy=email.policy.default)
                body = message.get_body(preferencelist=('plain', 'html'))
                text = body.get_content() if body else message.get_content()
                links = re.findall(r'https://auth\.recovery\.test:9091/'
                                   r'reset-password/step2\?token=[A-Za-z0-9_.-]+', str(text))
                with LOCK:
                    if len(MESSAGES) >= 20:
                        reply('452 fixture mailbox full')
                        return
                    MESSAGES.append({'number': len(MESSAGES) + 1, 'recipient': recipient,
                                     'reset_links': list(dict.fromkeys(links))})
                recipient, sender = None, False
                reply('250 fixture accepted')
            elif upper in {'RSET', 'NOOP'}:
                recipient, sender = None, False
                reply('250 OK')
            elif upper == 'QUIT':
                reply('221 bye')
                return
            else:
                reply('502 fixture command refused')


class SMTPServer(socketserver.ThreadingTCPServer):
    daemon_threads = True
    allow_reuse_address = True


class Mailbox(BaseHTTPRequestHandler):
    def log_message(self, *args):
        pass

    def do_GET(self):  # noqa: N802
        if urllib.parse.urlsplit(self.path).path == '/client-callback':
            body = b'{"status":"synthetic_callback_receiver"}'
            self.send_response(200)
            self.send_header('Content-Type', 'application/json')
            self.send_header('Content-Length', str(len(body)))
            self.send_header('Cache-Control', 'no-store')
            self.end_headers()
            self.wfile.write(body)
            return
        if self.path not in {'/health', '/messages'}:
            self.send_error(404)
            return
        with LOCK:
            body = json.dumps({'messages': MESSAGES} if self.path == '/messages'
                              else {'status': 'fixture-ready'}).encode()
        self.send_response(200)
        self.send_header('Content-Type', 'application/json')
        self.send_header('Content-Length', str(len(body)))
        self.send_header('Cache-Control', 'no-store')
        self.end_headers()
        self.wfile.write(body)


if __name__ == '__main__':
    if not __debug__ or {p.name for p in Path('/sys/class/net').iterdir()} != {'lo'}:
        raise SystemExit('Fixture loopback boundary required')
    with SMTPServer(('127.0.0.1', 2525), SMTP) as smtp:
        thread = threading.Thread(target=smtp.serve_forever, daemon=True)
        thread.start()
        ThreadingHTTPServer(('127.0.0.1', 8088), Mailbox).serve_forever()