import os
import boto3
import smtplib
import time
import requests
from email.parser import BytesParser
from email.policy import default
from email.utils import getaddresses

s3 = boto3.client('s3')

MAILCOW_HOST = os.environ['MAILCOW_SMTP_HOST']
MAILCOW_PORT = int(os.environ.get('MAILCOW_SMTP_PORT', 587))
SMTP_USER    = os.environ.get('MAILCOW_SMTP_USER')
SMTP_PASS    = os.environ.get('MAILCOW_SMTP_PASS')
MAILCOW_API_KEY = os.environ.get('MAILCOW_API_KEY')

def domain_to_bucket(domain):
    return domain.replace('.', '-') + '-emails'

def get_valid_inboxes():
    url = 'https://mail.email-srvr.com/api/v1/get/mailbox/all'
    headers = {'X-API-Key': MAILCOW_API_KEY}
    try:
        response = requests.get(url, headers=headers, timeout=10)
        response.raise_for_status()
        mailboxes = response.json()
        return {mb['username'].lower() for mb in mailboxes if mb['active_int'] == 1}
    except requests.RequestException as e:
        print(f"Fehler beim Abrufen der Postfächer: {e}")
        raise Exception("Konnte gültige Postfächer nicht abrufen")

def lambda_handler(event, context):
    rec = event['Records'][0]
    
    if 'ses' in rec:
        ses = rec['ses']
        msg_id = ses['mail']['messageId']
        recipients = ses['receipt']['recipients']
        first_recipient = recipients[0]
        domain = first_recipient.split('@')[1]
        bucket = domain_to_bucket(domain)
        prefix = f"emails/{msg_id}"
        print(f"SES-Receipt erkannt, domain={domain}, bucket={bucket}, prefix={prefix}")
        
        resp_list = s3.list_objects_v2(Bucket=bucket, Prefix=prefix)
        if 'Contents' not in resp_list or not resp_list['Contents']:
            raise Exception(f"Kein Objekt unter Prefix {prefix} in Bucket {bucket} gefunden")
        key = resp_list['Contents'][0]['Key']
        
    elif 's3' in rec:
        s3info = rec['s3']
        bucket = s3info['bucket']['name']
        key = s3info['object']['key']
        print("S3-Put erkannt, bucket =", bucket, "key =", key)
        recipients = []
        
    else:
        raise Exception("Unbekannter Event-Typ")

    # Prüfen, ob das Objekt bereits verarbeitet wurde
    try:
        resp = s3.head_object(Bucket=bucket, Key=key)
        if resp.get('Metadata', {}).get('processed') == 'true':
            print(f"Objekt {key} bereits verarbeitet (processed=true), überspringe Verarbeitung")
            return {
                'statusCode': 200,
                'body': f"Objekt {key} bereits verarbeitet, keine erneute Weiterleitung"
            }
    except Exception as e:
        print(f"Fehler beim Prüfen der Metadaten: {e}")
        # Fortfahren, falls Metadaten nicht lesbar sind

    # Raw-Mail aus S3 holen
    resp = s3.get_object(Bucket=bucket, Key=key)
    raw_bytes = resp['Body'].read()
    print(f"E-Mail geladen: {len(raw_bytes)} Bytes")

    # Parsen für Logging
    parsed = BytesParser(policy=default).parsebytes(raw_bytes)
    subj = parsed.get('subject', '(kein Subject)')
    frm_addr = getaddresses(parsed.get_all('from', []))[0][1]
    print(f"Parsed: From={frm_addr} Subject={subj}")

    # Empfänger aus Headern ziehen, falls nicht aus SES
    if not recipients:
        to_addrs = [addr for _name, addr in getaddresses(parsed.get_all('to', []))]
        cc_addrs = [addr for _name, addr in getaddresses(parsed.get_all('cc', []))]
        bcc_addrs = [addr for _name, addr in getaddresses(parsed.get_all('bcc', []))]
        recipients = to_addrs + cc_addrs + bcc_addrs
        print("Empfänger aus Headern:", recipients)

    if not recipients:
        raise Exception("Keine Empfänger gefunden, Abbruch")

    # Gültige Postfächer abrufen und Empfänger filtern
    valid_inboxes = get_valid_inboxes()
    valid_recipients = [rcpt for rcpt in recipients if rcpt.lower() in valid_inboxes]
    print(f"Gültige Empfänger: {valid_recipients}")
    
    if not valid_recipients:
        raise Exception("Keine gültigen Postfächer für die Empfänger gefunden, Abbruch")

    # SMTP-Verbindung und Envelope
    start = time.time()
    print("=== SMTP: Verbinde zu", MAILCOW_HOST, "Port", MAILCOW_PORT)
    with smtplib.SMTP(MAILCOW_HOST, MAILCOW_PORT, timeout=30) as smtp:
        smtp.ehlo()
        smtp.starttls()
        smtp.ehlo()
        if SMTP_USER and SMTP_PASS:
            smtp.login(SMTP_USER, SMTP_PASS)
        
        print("=== SMTP: MAIL FROM", frm_addr)
        smtp.mail(frm_addr)
        
        for rcpt in valid_recipients:
            print("=== SMTP: RCPT TO", rcpt)
            smtp.rcpt(rcpt)

        smtp.data(raw_bytes)
    print(f"SMTP-Transfer in {time.time()-start:.2f}s abgeschlossen ...")
    
    # Metadatum "processed": "true" hinzufügen
    try:
        resp = s3.head_object(Bucket=bucket, Key=key)
        current_metadata = resp.get('Metadata', {})
        new_metadata = current_metadata.copy()
        new_metadata['processed'] = 'true'
        s3.copy_object(
            Bucket=bucket,
            Key=key,
            CopySource={'Bucket': bucket, 'Key': key},
            Metadata=new_metadata,
            MetadataDirective='REPLACE'
        )
        print("Metadatum 'processed:true' hinzugefügt.")
    except Exception as e:
        print(f"Fehler beim Schreiben des Metadatums: {e}")
        raise  # Fehler weiterleiten, um in CloudWatch sichtbar zu bleiben

    return {
        'statusCode': 200,
        'body': f"E-Mail erfolgreich an {MAILCOW_HOST}:{MAILCOW_PORT} weitergeleitet ..."
    }