import requests
import logging
from .models import Fanpage, Flow, Node, Edge, ChatSession, MessageLog

logger = logging.getLogger(__name__)

def send_fb_message(psid, access_token, message_content):
    """
    Sends a message to a Facebook user via the Graph API.
    message_content: dict matching Facebook's message object (e.g., {"text": "..."})
    """
    url = f"https://graph.facebook.com/v12.0/me/messages?access_token={access_token}"
    payload = {
        "recipient": {"id": psid},
        "message": message_content
    }
    try:
        response = requests.post(url, json=payload)
        response.raise_for_status()
        return response.json()
    except Exception as e:
        logger.error(f"Error sending message to Facebook: {e}")
        return None

def get_next_node(session, message_text):
    """
    Determines the next node in the flow based on user input.
    """
    fanpage = session.fanpage
    
    if not session.current_node:
        # Start of conversation: find the default flow and its start node
        flow = Flow.objects.filter(fanpage=fanpage, is_default=True).first()
        if not flow:
            flow = Flow.objects.filter(fanpage=fanpage).first()
        
        if flow:
            return Node.objects.filter(flow=flow, is_start_node=True).first()
        return None
    
    # We are in an active session, look for a matching edge
    edges = Edge.objects.filter(source_node=session.current_node)
    message_text_clean = message_text.strip().lower()
    
    for edge in edges:
        if edge.condition.lower() == message_text_clean:
            return edge.target_node
            
    # If no matching edge, we might want to stay at the current node or find a global start
    # For now, let's just return the current node (re-prompting) if it was a text node,
    # or None if we don't know what to do.
    return session.current_node

def handle_webhook_event(data):
    """
    Main entry point for processing Facebook webhook POST data.
    """
    if data.get('object') != 'page':
        return
        
    for entry in data.get('entry', []):
        for messaging_event in entry.get('messaging', []):
            sender_id = messaging_event.get('sender', {}).get('id')
            recipient_id = messaging_event.get('recipient', {}).get('id')
            
            if not sender_id or not recipient_id:
                continue
                
            # 1. Identify Fanpage
            try:
                fanpage = Fanpage.objects.get(page_id=recipient_id, is_active=True)
            except Fanpage.DoesNotExist:
                logger.warning(f"Received event for unknown or inactive Page ID: {recipient_id}")
                continue
                
            # 2. Extract Message
            message_text = ""
            if 'message' in messaging_event:
                message_text = messaging_event['message'].get('text', "")
            elif 'postback' in messaging_event:
                # Handle button clicks
                message_text = messaging_event['postback'].get('payload', "")
                
            if not message_text:
                continue
                
            # 3. Get or Create Session
            session, created = ChatSession.objects.get_or_create(
                psid=sender_id,
                fanpage=fanpage
            )
            
            # 4. Log User Message
            MessageLog.objects.create(
                session=session,
                sender_type='user',
                message_text=message_text
            )
            
            # 5. Determine Next Node
            next_node = get_next_node(session, message_text)
            
            if next_node:
                # 6. Send Reply
                # next_node.content is a JSONField, expected to be {"text": "..."} or similar
                result = send_fb_message(sender_id, fanpage.access_token, next_node.content)
                
                if result:
                    # 7. Update Session
                    session.current_node = next_node
                    session.save()
                    
                    # 8. Log Bot Response
                    bot_text = next_node.content.get('text', '[Non-text message]')
                    MessageLog.objects.create(
                        session=session,
                        sender_type='bot',
                        message_text=bot_text
                    )