import os
import boto3
import json
import time
from email.parser import BytesParser
from email.policy import SMTP as SMTPPolicy

s3 = boto3.client('s3')
sqs = boto3.client('sqs', region_name='us-east-2')

# AWS Region
AWS_REGION = 'us-east-2'

# Dynamo Table
dynamo = boto3.resource('dynamodb', region_name=AWS_REGION)
msg_table = dynamo.Table('ses-outbound-messages')

# Metadata Keys
PROCESSED_KEY = 'processed'
PROCESSED_VALUE = 'true'

def is_ses_bounce_or_autoreply(parsed):
    """Erkennt SES Bounces und Auto-Replies"""
    from_h = (parsed.get('From') or '').lower()
    auto_sub = (parsed.get('Auto-Submitted') or '').lower()
    
    # SES MAILER-DAEMON oder Auto-Submitted Header
    is_mailer_daemon = 'mailer-daemon@' in from_h and 'amazonses.com' in from_h
    is_auto_replied = 'auto-replied' in auto_sub or 'auto-generated' in auto_sub
    
    return is_mailer_daemon or is_auto_replied


def extract_original_message_id(parsed):
    """Extrahiert die ursprüngliche Message-ID aus In-Reply-To oder References"""
    # Versuche In-Reply-To
    in_reply_to = (parsed.get('In-Reply-To') or '').strip()
    if in_reply_to:
        msg_id = in_reply_to
        if msg_id.startswith('<') and '>' in msg_id:
            msg_id = msg_id[1:msg_id.find('>')]
        
        # ✅ WICHTIG: Entferne @amazonses.com Suffix falls vorhanden
        if '@' in msg_id:
            msg_id = msg_id.split('@')[0]
        
        return msg_id
    
    # Fallback: References Header (nimm die ERSTE ID)
    refs = (parsed.get('References') or '').strip()
    if refs:
        first_ref = refs.split()[0]
        if first_ref.startswith('<') and '>' in first_ref:
            first_ref = first_ref[1:first_ref.find('>')]
        
        # ✅ WICHTIG: Entferne @amazonses.com Suffix falls vorhanden
        if '@' in first_ref:
            first_ref = first_ref.split('@')[0]
        
        return first_ref
    
    return None


def domain_to_bucket(domain: str) -> str:
    """Konvertiert Domain zu S3 Bucket Namen"""
    domain = domain.lower()
    return domain.replace('.', '-') + '-emails'


def domain_to_queue_name(domain: str) -> str:
    """Konvertiert Domain zu SQS Queue Namen"""
    domain = domain.lower()
    return domain.replace('.', '-') + '-queue'


def get_queue_url_for_domain(domain: str) -> str:
    """Ermittelt SQS Queue URL für Domain"""
    queue_name = domain_to_queue_name(domain)
    
    try:
        response = sqs.get_queue_url(QueueName=queue_name)
        queue_url = response['QueueUrl']
        print(f"✓ Found queue: {queue_name}")
        return queue_url
        
    except sqs.exceptions.QueueDoesNotExist:
        raise Exception(
            f"Queue does not exist: {queue_name} "
            f"(for domain: {domain.lower()})"
        )
    except Exception as e:
        raise Exception(f"Error getting queue URL for {domain.lower()}: {e}")


def is_already_processed(bucket: str, key: str) -> bool:
    """Prüft ob E-Mail bereits verarbeitet wurde"""
    try:
        head = s3.head_object(Bucket=bucket, Key=key)
        metadata = head.get('Metadata', {}) or {}
        
        if metadata.get(PROCESSED_KEY) == PROCESSED_VALUE:
            processed_at = metadata.get('processed_at', 'unknown')
            print(f"✓ Already processed at {processed_at}")
            return True
        
        return False
        
    except s3.exceptions.NoSuchKey:
        print(f"⚠ Object {key} not found in {bucket}")
        return True
    
    except Exception as e:
        print(f"⚠ Error checking processed status: {e}")
        return False


def set_processing_lock(bucket: str, key: str) -> bool:
    """
    Setzt Processing Lock um Duplicate Processing zu verhindern
    Returns: True wenn Lock erfolgreich gesetzt, False wenn bereits locked
    """
    try:
        head = s3.head_object(Bucket=bucket, Key=key)
        metadata = head.get('Metadata', {}) or {}
        
        # Prüfe auf existierenden Lock
        processing_started = metadata.get('processing_started')
        if processing_started:
            lock_age = time.time() - float(processing_started)
            
            if lock_age < 300:  # 5 Minuten Lock
                print(f"⚠ Processing lock active (age: {lock_age:.0f}s)")
                return False
            else:
                print(f"⚠ Stale lock detected ({lock_age:.0f}s old), overriding")
        
        # Setze neuen Lock
        new_meta = metadata.copy()
        new_meta['processing_started'] = str(int(time.time()))
        
        s3.copy_object(
            Bucket=bucket,
            Key=key,
            CopySource={'Bucket': bucket, 'Key': key},
            Metadata=new_meta,
            MetadataDirective='REPLACE'
        )
        
        print(f"✓ Processing lock set")
        return True
        
    except Exception as e:
        print(f"⚠ Error setting processing lock: {e}")
        return True


def mark_as_queued(bucket: str, key: str, queue_name: str):
    """Markiert E-Mail als in Queue eingereiht"""
    try:
        head = s3.head_object(Bucket=bucket, Key=key)
        metadata = head.get('Metadata', {}) or {}
        
        metadata['queued_at'] = str(int(time.time()))
        metadata['queued_to'] = queue_name
        metadata['status'] = 'queued'
        metadata.pop('processing_started', None)
        
        s3.copy_object(
            Bucket=bucket,
            Key=key,
            CopySource={'Bucket': bucket, 'Key': key},
            Metadata=metadata,
            MetadataDirective='REPLACE'
        )
        
        print(f"✓ Marked as queued to {queue_name}")
        
    except Exception as e:
        print(f"⚠ Failed to mark as queued: {e}")


def send_to_queue(queue_url: str, bucket: str, key: str, 
                  from_addr: str, recipients: list, domain: str, 
                  subject: str, message_id: str):
    """
    Sendet E-Mail-Job in domain-spezifische SQS Queue
    EINE Message mit ALLEN Recipients für diese Domain
    """
    
    queue_name = queue_url.split('/')[-1]
    
    message = {
        'bucket': bucket,
        'key': key,
        'from': from_addr,
        'recipients': recipients,
        'domain': domain,
        'subject': subject,
        'message_id': message_id,
        'timestamp': int(time.time())
    }
    
    try:
        response = sqs.send_message(
            QueueUrl=queue_url,
            MessageBody=json.dumps(message, ensure_ascii=False),
            MessageAttributes={
                'domain': {
                    'StringValue': domain,
                    'DataType': 'String'
                },
                'bucket': {
                    'StringValue': bucket,
                    'DataType': 'String'
                },
                'recipient_count': {
                    'StringValue': str(len(recipients)),
                    'DataType': 'Number'
                },
                'message_id': {
                    'StringValue': message_id,
                    'DataType': 'String'
                }
            }
        )
        
        sqs_message_id = response['MessageId']
        print(f"✓ Queued to {queue_name}: SQS MessageId={sqs_message_id}")
        print(f"  Recipients: {len(recipients)} - {', '.join(recipients)}")
        
        mark_as_queued(bucket, key, queue_name)
        
        return sqs_message_id
        
    except Exception as e:
        print(f"✗ Failed to queue message: {e}")
        raise


def lambda_handler(event, context):
    """
    Lambda Handler für SES Inbound Events
    """
    
    print(f"{'='*70}")
    print(f"Lambda invoked: {context.aws_request_id}")
    print(f"Region: {AWS_REGION}")
    print(f"{'='*70}")
    
    # SES Event parsen
    try:
        record = event['Records'][0]
        ses = record['ses']
    except (KeyError, IndexError) as e:
        print(f"✗ Invalid event structure: {e}")
        return {'statusCode': 400, 'body': json.dumps({'error': 'Invalid SES event'})}
    
    mail = ses['mail']
    receipt = ses['receipt']
    
    message_id = mail['messageId']
    source = mail['source']
    timestamp = mail.get('timestamp', '')
    recipients = receipt.get('recipients', [])
    
    print(f"\n🔑 S3 Key: {message_id}")
    print(f"👥 Recipients ({len(recipients)}): {', '.join(recipients)}")
    
    if not recipients:
        print(f"✗ No recipients found in event")
        return {'statusCode': 400, 'body': json.dumps({'error': 'No recipients'})}
    
    # Domain extrahieren
    domain = recipients[0].split('@')[1].lower()
    bucket = domain_to_bucket(domain)
    
    print(f"\n📧 Email Event:")
    print(f"  MessageId: {message_id}")
    print(f"  From: {source}")
    print(f"  Domain: {domain}")
    print(f"  Bucket: {bucket}")
    
    # Queue ermitteln
    try:
        queue_url = get_queue_url_for_domain(domain)
        queue_name = queue_url.split('/')[-1]
    except Exception as e:
        print(f"\n✗ Queue ERROR: {e}")
        return {'statusCode': 500, 'body': json.dumps({'error': str(e)})}
    
    # S3 Object finden
    try:
        response = s3.list_objects_v2(Bucket=bucket, Prefix=message_id, MaxKeys=1)
        
        if 'Contents' not in response:
            raise Exception(f"No S3 object found for {message_id}")
        
        key = response['Contents'][0]['Key']
        size = response['Contents'][0]['Size']
        print(f"  Found: s3://{bucket}/{key} ({size/1024:.1f} KB)")
        
    except Exception as e:
        print(f"\n✗ S3 ERROR: {e}")
        return {'statusCode': 404, 'body': json.dumps({'error': str(e)})}
    
    # Duplicate Check
    if is_already_processed(bucket, key):
        return {'statusCode': 200, 'body': json.dumps({'status': 'already_processed'})}
    
    # Processing Lock
    if not set_processing_lock(bucket, key):
        return {'statusCode': 200, 'body': json.dumps({'status': 'already_processing'})}
    
    # E-Mail laden und ggf. umschreiben
    subject = '(unknown)'
    modified = False
    
    try:
        print(f"\n📖 Reading email...")
        obj = s3.get_object(Bucket=bucket, Key=key)
        raw_bytes = obj['Body'].read()
        metadata = obj.get('Metadata', {}) or {}
        
        parsed = BytesParser(policy=SMTPPolicy).parsebytes(raw_bytes)
        subject = parsed.get('Subject', '(no subject)')
        print(f"  Subject: {subject}")
        
        # 🔁 Auto-Response / Bounce Detection
        if is_ses_bounce_or_autoreply(parsed):
            print(f"  🔍 Detected auto-response/bounce from SES")
            
            # Extrahiere ursprüngliche Message-ID
            original_msg_id = extract_original_message_id(parsed)
            
            if original_msg_id:
                print(f"  📋 Original MessageId: {original_msg_id}")
                
                try:
                    # Hole Original-Send aus DynamoDB
                    result = msg_table.get_item(Key={'MessageId': original_msg_id})
                    original_send = result.get('Item')
                    
                    if original_send:
                        orig_source = original_send.get('source', '')
                        orig_destinations = original_send.get('destinations', [])
                        
                        print(f"  ✓ Found original send:")
                        print(f"    Original From: {orig_source}")
                        print(f"    Original To: {orig_destinations}")
                        
                        # **WICHTIG**: Der erste Empfänger war der eigentliche Empfänger
                        original_recipient = orig_destinations[0] if orig_destinations else ''
                        
                        if original_recipient:
                            # Absender umschreiben auf ursprünglichen Empfänger
                            original_from = parsed.get('From', '')
                            parsed['X-Original-SES-From'] = original_from
                            parsed['X-Original-MessageId'] = original_msg_id
                            
                            # **From auf den ursprünglichen Empfänger setzen**
                            parsed.replace_header('From', original_recipient)
                            
                            # Reply-To optional beibehalten
                            if not parsed.get('Reply-To'):
                                parsed['Reply-To'] = original_recipient
                            
                            # Subject anpassen falls nötig
                            if 'delivery status notification' in subject.lower():
                                parsed.replace_header('Subject', f"Delivery Status: {orig_destinations[0]}")
                            
                            raw_bytes = parsed.as_bytes()
                            modified = True
                            
                            print(f"  ✅ Rewritten: From={original_recipient}")
                    else:
                        print(f"  ⚠ No DynamoDB record found for {original_msg_id}")
                        
                except Exception as e:
                    print(f"  ⚠ DynamoDB lookup failed: {e}")
            else:
                print(f"  ⚠ Could not extract original Message-ID")
        
        # S3 aktualisieren falls modified
        if modified:
            s3.put_object(Bucket=bucket, Key=key, Body=raw_bytes, Metadata=metadata)
            print(f"  💾 Updated S3 object with rewritten email")
            
    except Exception as e:
        print(f"  ⚠ Email parsing error: {e}")
    
    # In Queue einreihen
    try:
        sqs_message_id = send_to_queue(
            queue_url=queue_url,
            bucket=bucket,
            key=key,
            from_addr=source,
            recipients=recipients,
            domain=domain,
            subject=subject,
            message_id=message_id
        )
        
        print(f"\n✅ SUCCESS - Queued for delivery\n")
        
        return {
            'statusCode': 200,
            'body': json.dumps({
                'status': 'queued',
                'message_id': message_id,
                'sqs_message_id': sqs_message_id,
                'modified': modified
            })
        }
        
    except Exception as e:
        print(f"\n✗ QUEUE FAILED: {e}")
        return {'statusCode': 500, 'body': json.dumps({'error': str(e)})}