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'

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


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


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


def get_queue_url_for_domain(domain: str) -> str:
    """
    Ermittelt SQS Queue URL für Domain
    Queue Name: domain-mit-bindestrichen-queue
    """
    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})"
        )
    except Exception as e:
        raise Exception(f"Error getting queue URL for {domain}: {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  # Wenn nicht existiert, als verarbeitet betrachten
    
    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  # Bei Fehler trotzdem verarbeiten (besser als Mail verlieren)


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)  # Lock entfernen
        
        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, recipient: str, domain: str, 
                  subject: str, message_id: str):
    """
    Sendet E-Mail-Job in domain-spezifische SQS Queue
    """
    
    # Queue Name aus URL extrahieren (für Logging)
    queue_name = queue_url.split('/')[-1]
    
    message = {
        'bucket': bucket,
        'key': key,
        'from': from_addr,
        'recipient': recipient,  # Nur 1 Empfänger
        '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': {
                    'StringValue': recipient,
                    'DataType': 'String'
                },
                'message_id': {
                    'StringValue': message_id,
                    'DataType': 'String'
                }
            }
        )
        
        sqs_message_id = response['MessageId']
        print(f"✓ Queued to {queue_name}: SQS MessageId={sqs_message_id}")
        
        # Als queued markieren
        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 Events
    WICHTIG: SES ruft Lambda einmal PRO Empfänger auf!
    Jedes Event hat genau 1 Empfänger in receipt.recipients
    """
    
    print(f"{'='*70}")
    print(f"Lambda invoked: {context.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', '')
    
    # ✨ WICHTIG: receipt.recipients enthält NUR den Empfänger für DIESES Event
    # (NICHT mail.destination verwenden - das hat alle Original-Empfänger)
    recipients = receipt.get('recipients', [])
    
    if not recipients or len(recipients) != 1:
        print(f"✗ Unexpected recipients count: {len(recipients)}")
        return {
            'statusCode': 400,
            'body': json.dumps({
                'error': 'Expected exactly 1 recipient',
                'found': len(recipients)
            })
        }
    
    # SES garantiert: genau 1 Empfänger pro Event
    recipient = recipients[0]
    domain = recipient.split('@')[1]
    bucket = domain_to_bucket(domain)
    
    print(f"\n📧 Email Event:")
    print(f"  MessageId: {message_id}")
    print(f"  From: {source}")
    print(f"  To: {recipient}")
    print(f"  Domain: {domain}")
    print(f"  Bucket: {bucket}")
    print(f"  Timestamp: {timestamp}")
    
    # Queue für Domain ermitteln
    try:
        queue_url = get_queue_url_for_domain(domain)
        queue_name = queue_url.split('/')[-1]
        print(f"  Queue: {queue_name}")
    except Exception as e:
        print(f"\n✗ ERROR: {e}")
        return {
            'statusCode': 500,
            'body': json.dumps({
                'error': 'queue_not_configured',
                'domain': domain,
                'recipient': recipient,
                'message': str(e)
            })
        }
    
    # S3 Object finden
    try:
        print(f"\n📦 Searching S3...")
        response = s3.list_objects_v2(
            Bucket=bucket,
            Prefix=message_id,
            MaxKeys=1
        )
        
        if 'Contents' not in response or not response['Contents']:
            raise Exception(f"No S3 object found for message {message_id}")
        
        key = response['Contents'][0]['Key']
        size = response['Contents'][0]['Size']
        print(f"  Found: s3://{bucket}/{key}")
        print(f"  Size: {size:,} bytes ({size/1024:.1f} KB)")
        
    except Exception as e:
        print(f"\n✗ S3 ERROR: {e}")
        return {
            'statusCode': 404,
            'body': json.dumps({
                'error': 's3_object_not_found',
                'message_id': message_id,
                'bucket': bucket,
                'details': str(e)
            })
        }
    
    # Duplicate Check
    print(f"\n🔍 Checking for duplicates...")
    if is_already_processed(bucket, key):
        print(f"  Already processed, skipping")
        return {
            'statusCode': 200,
            'body': json.dumps({
                'status': 'already_processed',
                'message_id': message_id,
                'recipient': recipient
            })
        }
    
    # Processing Lock setzen
    print(f"\n🔒 Setting processing lock...")
    if not set_processing_lock(bucket, key):
        print(f"  Already being processed by another instance")
        return {
            'statusCode': 200,
            'body': json.dumps({
                'status': 'already_processing',
                'message_id': message_id,
                'recipient': recipient
            })
        }
    
    # E-Mail laden um Subject zu extrahieren (optional, für besseres Logging)
    subject = '(unknown)'
    try:
        print(f"\n📖 Reading email for metadata...")
        obj = s3.get_object(Bucket=bucket, Key=key)
        raw_bytes = obj['Body'].read()
        
        # Nur Headers parsen (schneller)
        parsed = BytesParser(policy=SMTPPolicy).parsebytes(raw_bytes)
        subject = parsed.get('subject', '(no subject)')
        
        print(f"  Subject: {subject}")
        
    except Exception as e:
        print(f"  ⚠ Could not parse email (continuing): {e}")
    
    # In domain-spezifische Queue einreihen
    try:
        print(f"\n📤 Queuing to {queue_name}...")
        
        sqs_message_id = send_to_queue(
            queue_url=queue_url,
            bucket=bucket,
            key=key,
            from_addr=source,
            recipient=recipient,  # Nur 1 Empfänger
            domain=domain,
            subject=subject,
            message_id=message_id
        )
        
        print(f"\n{'='*70}")
        print(f"✅ SUCCESS - Email queued for delivery")
        print(f"{'='*70}\n")
        
        return {
            'statusCode': 200,
            'body': json.dumps({
                'status': 'queued',
                'message_id': message_id,
                'sqs_message_id': sqs_message_id,
                'queue': queue_name,
                'domain': domain,
                'recipient': recipient,
                'subject': subject
            })
        }
        
    except Exception as e:
        print(f"\n{'='*70}")
        print(f"✗ FAILED TO QUEUE")
        print(f"{'='*70}")
        print(f"Error: {e}")
        
        return {
            'statusCode': 500,
            'body': json.dumps({
                'error': 'failed_to_queue',
                'message': str(e),
                'message_id': message_id,
                'recipient': recipient
            })
        }