from flask import Flask, request, jsonify
from prometheus_flask_exporter import PrometheusMetrics
import smtplib
from email.utils import formatdate, make_msgid, parseaddr
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.application import MIMEApplication
import os
import time
import html
import re
import logging


class FilterRemoveDate(logging.Filter):
	# '192.168.0.102 - - [30/Jun/2024 01:14:03] "%s" %s %s' -> '192.168.0.102 - "%s" %s %s'
	pattern: re.Pattern = re.compile(r' - \[.+?]')

	def filter(self, record: logging.LogRecord) -> bool:
		record.msg = self.pattern.sub('', record.msg)
		return True

class FilterReplaceWerkzeug(logging.Filter):
	# 'werkzeug:' -> 'app:flask:'
	pattern: re.Pattern = re.compile(r'werkzeug:')

	def filter(self, record: logging.LogRecord) -> bool:
		record.msg = self.pattern.sub('app:flask:', record.msg)
		return True

class FilterReplaceLowercaseI(logging.Filter):
	# 'I:' -> 'i:'
	pattern: re.Pattern = re.compile(r'I:')

	def filter(self, record: logging.LogRecord) -> bool:
		record.msg = self.pattern.sub('i:', record.msg)
		return True

# Setup logger
logging.basicConfig(
	level=logging.DEBUG,
	format='%(asctime)s.%(msecs)03dZ %(name)s:%(levelname).1s: %(message)s',
	datefmt='%Y-%m-%d %H:%M:%S'
)

logger = logging.getLogger('app')
logger_werkzeug = logging.getLogger('werkzeug')
logger_werkzeug.addFilter(FilterRemoveDate())
logger_werkzeug.addFilter(FilterReplaceWerkzeug())
logger_werkzeug.addFilter(FilterReplaceLowercaseI())

app = Flask(__name__, static_folder=None)

# Wrap the Flask app with PrometheusMetrics
metrics = PrometheusMetrics(app, defaults_prefix="mail")

email_sent_counter = metrics.counter(
	'mail_text_sent_total',
	'Total number of text messages sent',
	labels={'endpoint': lambda: request.endpoint}
)

pdf_sent_counter = metrics.counter(
	'mail_pdf_sent_total',
	'Total number of pdfs sent',
	labels={'endpoint': lambda: request.endpoint}
)


# --- SMTP --------------------------------------------------------------------
# One connection path for every endpoint. SMTP_RELAY_SECURITY is "ssl" (TLS from the first byte, port 465), "starttls"
# (port 587 or 25) or "none" (a relay on a private network, e.g. Mailu's smtp container trusting its own subnet).
# Without it, port 465 means ssl and any other port starttls. The service logs in only when both SMTP_RELAY_USERNAME
# and SMTP_RELAY_PASSWORD are set. SMTP_FROM is the sender (default: SMTP_RELAY_USERNAME); SMTP_REPLY_TO, if set,
# is where replies go.
SECURITIES = ("ssl", "starttls", "none")


class SmtpConfigError(Exception):
	pass


def smtp_settings():
	host = os.environ.get('SMTP_RELAY_HOST', '')
	port_text = os.environ.get('SMTP_RELAY_PORT', '')
	if not host or not port_text.isdigit():
		raise SmtpConfigError("SMTP_RELAY_HOST and a numeric SMTP_RELAY_PORT are required")
	port = int(port_text)
	security = os.environ.get('SMTP_RELAY_SECURITY') or ("ssl" if port == 465 else "starttls")
	if security not in SECURITIES:
		raise SmtpConfigError(f"SMTP_RELAY_SECURITY must be one of {', '.join(SECURITIES)}")
	username = os.environ.get('SMTP_RELAY_USERNAME', '')
	password = os.environ.get('SMTP_RELAY_PASSWORD', '')
	sender = os.environ.get('SMTP_FROM') or username
	if not parseaddr(sender)[1]:
		raise SmtpConfigError("SMTP_FROM (or SMTP_RELAY_USERNAME) must be a mail address")
	return {
		'host': host, 'port': port, 'security': security, 'username': username, 'password': password,
		'sender': sender, 'reply_to': os.environ.get('SMTP_REPLY_TO', '')
	}


def open_smtp(settings, timeout=30):
	"""Connects, secures the connection as configured and logs in if credentials are set. A failed STARTTLS is an error:
	the credentials and the mail must not travel in the clear."""
	if settings['security'] == "ssl":
		smtp = smtplib.SMTP_SSL(settings['host'], settings['port'], timeout=timeout)
	else:
		smtp = smtplib.SMTP(settings['host'], settings['port'], timeout=timeout)
	try:
		smtp.ehlo()
		if settings['security'] == "starttls":
			smtp.starttls()
			smtp.ehlo()
		if settings['username'] and settings['password']:
			smtp.login(settings['username'], settings['password'])
	except Exception:
		smtp.close()
		raise
	return smtp


def new_message(settings, to_email, subject):
	msg = MIMEMultipart('mixed')
	msg['From'] = settings['sender']
	msg['To'] = to_email
	msg['Subject'] = subject
	msg['Date'] = formatdate(localtime=False)
	msg['Message-ID'] = make_msgid(domain=parseaddr(settings['sender'])[1].rpartition('@')[2] or None)
	if settings['reply_to']:
		msg['Reply-To'] = settings['reply_to']
	return msg


def deliver(settings, to_email, msg):
	smtp = open_smtp(settings)
	try:
		smtp.sendmail(parseaddr(settings['sender'])[1], [to_email], msg.as_string())
	finally:
		try:
			smtp.quit()
		except smtplib.SMTPException:
			smtp.close()


@app.route('/v1')
@metrics.do_not_track()
def info():
	today = time.strftime("%Y-%m-%d")
	url_map = app.url_map
	return f"<h1>mail v1.0.0 - {today}</h1><pre>" + html.escape(str(url_map), False) + "</pre>"


@app.route('/v1/send/message', methods=['POST'])
@email_sent_counter
def send_message():
	logger = logging.getLogger('app:send-message')
	data = request.json
	subject = data.get('subject')
	text_content = data.get('message')
	to_email = data.get('to_email')
	html_content = data.get('html')

	logger.info(f"Sending text email to {to_email}")
	logger.debug(f"Subject: {subject}")

	try:
		settings = smtp_settings()
		msg = new_message(settings, to_email, subject)

		# Create the multipart/alternative part
		msgAlternative = MIMEMultipart('alternative')
		msg.attach(msgAlternative)

		# Attach plain text message first (lower priority)
		msgAlternative.attach(MIMEText(text_content, 'plain', 'utf-8'))

		# Attach HTML version if provided (higher priority)
		if html_content:
			logger.debug("HTML content included in email")
			msgAlternative.attach(MIMEText(html_content, 'html', 'utf-8'))

		logger.debug(f"Connecting to SMTP server {settings['host']}:{settings['port']} ({settings['security']})")
		deliver(settings, to_email, msg)

		logger.info("Email sent successfully")
		return jsonify({"message": "Email sent successfully"}), 200
	except Exception as e:
		logger.error(f"Error sending email: {str(e)}")
		return jsonify({"error": str(e)}), 500


@app.route('/v1/send/pdf', methods=['POST'])
@pdf_sent_counter
def send_pdf():
	logger = logging.getLogger('app:send-pdf')
	data = request.form
	subject = data.get('subject')
	text_content = data.get('message')
	html_content = data.get('html')
	to_email = data.get('to_email')
	pdf_blob = request.files.get('pdf_blob')

	logger.info(f"Sending PDF email to {to_email}")
	logger.debug(f"Subject: {subject}")

	try:
		settings = smtp_settings()
		msg = new_message(settings, to_email, subject)

		# Create the multipart/alternative part for text and HTML
		msgAlternative = MIMEMultipart('alternative')
		msg.attach(msgAlternative)

		# Attach plain text message first (lower priority)
		msgAlternative.attach(MIMEText(text_content, 'plain', 'utf-8'))

		# Attach HTML version if provided (higher priority)
		if html_content:
			logger.debug("HTML content included in email")
			msgAlternative.attach(MIMEText(html_content, 'html', 'utf-8'))

		# Attach PDF if provided
		if pdf_blob:
			logger.debug("Attaching PDF to email")
			pdf_attachment = MIMEApplication(pdf_blob.read(), _subtype="pdf")
			pdf_attachment.add_header('Content-Disposition', 'attachment', filename='document.pdf')
			msg.attach(pdf_attachment)
		else:
			logger.warning("No PDF attachment provided")

		logger.debug(f"Connecting to SMTP server {settings['host']}:{settings['port']} ({settings['security']})")
		deliver(settings, to_email, msg)

		logger.info("PDF email sent successfully")
		return jsonify({"message": "Email sent successfully"}), 200
	except Exception as e:
		logger.error(f"Error sending PDF email: {str(e)}")
		return jsonify({"error": str(e)}), 500


@app.route('/health', methods=['GET'])
def health_check():
	"""503 unless the configured SMTP server answers and accepts the connection's security and login, so Docker's
	healthcheck marks the container unhealthy when no mail can leave."""
	logger = logging.getLogger('app:health-check')
	health_status = {'status': 'ok', 'smtp_config': True, 'smtp_responding': False}

	try:
		settings = smtp_settings()
	except SmtpConfigError as e:
		logger.error(f"SMTP configuration incomplete: {e}")
		health_status.update(status='error', smtp_config=False)
		return jsonify(health_status), 503

	try:
		smtp = open_smtp(settings, timeout=5)
		try:
			smtp.noop()
			health_status['smtp_responding'] = True
		finally:
			try:
				smtp.quit()
			except smtplib.SMTPException:
				smtp.close()
	except Exception as e:
		logger.error(f"SMTP connection test failed: {str(e)}")
		health_status['status'] = 'error'

	logger.debug(f"Health check performed: {health_status}")
	return jsonify(health_status), (200 if health_status['status'] == 'ok' else 503)

if __name__ == '__main__':
	app.run(host='0.0.0.0', port=2222, debug=False)