import os
import logging
import asyncio
import functools
import time
from collections import defaultdict
from quart import Blueprint, request, jsonify, abort
from twilio.request_validator import RequestValidator
from twilio.twiml.messaging_response import MessagingResponse

from blueprints.users.models import User
from blueprints.conversation.logic import (
    get_conversation_for_user,
    add_message_to_conversation,
    get_conversation_transcript,
)
from blueprints.conversation.agents import main_agent
from blueprints.conversation.prompts import SIMBA_SYSTEM_PROMPT

whatsapp_blueprint = Blueprint("whatsapp_api", __name__, url_prefix="/api/whatsapp")

# Configure logging
logger = logging.getLogger(__name__)

# Rate limiting: per-number message timestamps
# Format: {phone_number: [timestamp1, timestamp2, ...]}
_rate_limit_store: dict[str, list[float]] = defaultdict(list)

# Configurable via env: max messages per window (default: 10 per 60s)
RATE_LIMIT_MAX = int(os.getenv("WHATSAPP_RATE_LIMIT_MAX", "10"))
RATE_LIMIT_WINDOW = int(os.getenv("WHATSAPP_RATE_LIMIT_WINDOW", "60"))

# Max message length to process (WhatsApp max is 4096, but we cap for LLM sanity)
MAX_MESSAGE_LENGTH = 2000


def _twiml_response(text: str) -> tuple[str, int]:
    """Helper to return a TwiML MessagingResponse."""
    resp = MessagingResponse()
    resp.message(text)
    return str(resp), 200


def _check_rate_limit(phone_number: str) -> bool:
    """Check if a phone number has exceeded the rate limit.

    Returns True if the request is allowed, False if rate-limited.
    Also cleans up expired entries.
    """
    now = time.monotonic()
    cutoff = now - RATE_LIMIT_WINDOW

    # Remove expired timestamps
    timestamps = _rate_limit_store[phone_number]
    _rate_limit_store[phone_number] = [t for t in timestamps if t > cutoff]

    if len(_rate_limit_store[phone_number]) >= RATE_LIMIT_MAX:
        return False

    _rate_limit_store[phone_number].append(now)
    return True


def validate_twilio_request(f):
    """Decorator to validate that the request comes from Twilio.

    Validates the X-Twilio-Signature header using the TWILIO_AUTH_TOKEN.
    Set TWILIO_WEBHOOK_URL if behind a reverse proxy (e.g., ngrok, Caddy)
    so the validated URL matches what Twilio signed against.
    Set TWILIO_SIGNATURE_VALIDATION=false to disable in development.
    """
    @functools.wraps(f)
    async def decorated_function(*args, **kwargs):
        if os.getenv("TWILIO_SIGNATURE_VALIDATION", "true").lower() == "false":
            return await f(*args, **kwargs)

        auth_token = os.getenv("TWILIO_AUTH_TOKEN")
        if not auth_token:
            logger.error("TWILIO_AUTH_TOKEN not set — rejecting request")
            abort(403)

        twilio_signature = request.headers.get("X-Twilio-Signature")
        if not twilio_signature:
            logger.warning("Missing X-Twilio-Signature header")
            abort(403)

        # Use configured webhook URL if behind a proxy, otherwise use request URL
        url = os.getenv("TWILIO_WEBHOOK_URL") or request.url
        form_data = await request.form

        validator = RequestValidator(auth_token)
        if not validator.validate(url, form_data, twilio_signature):
            logger.warning(f"Invalid Twilio signature for URL: {url}")
            abort(403)

        return await f(*args, **kwargs)
    return decorated_function


@whatsapp_blueprint.route("/webhook", methods=["POST"])
@validate_twilio_request
async def webhook():
    """
    Handle incoming WhatsApp messages from Twilio.
    """
    form_data = await request.form
    from_number = form_data.get("From") # e.g., "whatsapp:+1234567890"
    body = form_data.get("Body")

    if not from_number or not body:
        return _twiml_response("Invalid message received.") if from_number else ("Missing From or Body", 400)

    # Strip whitespace and check for empty body
    body = body.strip()
    if not body:
        return _twiml_response("I received an empty message. Please send some text!")

    # Rate limiting
    if not _check_rate_limit(from_number):
        logger.warning(f"Rate limit exceeded for {from_number}")
        return _twiml_response("You're sending messages too quickly. Please wait a moment and try again.")

    # Truncate overly long messages
    if len(body) > MAX_MESSAGE_LENGTH:
        body = body[:MAX_MESSAGE_LENGTH]
        logger.info(f"Truncated long message from {from_number} to {MAX_MESSAGE_LENGTH} chars")

    logger.info(f"Received WhatsApp message from {from_number}: {body[:100]}")

    # Identify or create user
    user = await User.filter(whatsapp_number=from_number).first()

    if not user:
        # Check if number is in allowlist
        allowed_numbers = os.getenv("ALLOWED_WHATSAPP_NUMBERS", "").split(",")
        if from_number not in allowed_numbers and "*" not in allowed_numbers:
            return _twiml_response("Sorry, you are not authorized to use this service.")

        # Create a new user for this WhatsApp number
        username = f"wa_{from_number.split(':')[-1]}"
        try:
            user = await User.create(
                username=username,
                email=f"{username}@whatsapp.simbarag.local",
                whatsapp_number=from_number,
                auth_provider="whatsapp"
            )
            logger.info(f"Created new user for WhatsApp: {username}")
        except Exception as e:
            logger.error(f"Failed to create user for {from_number}: {e}")
            return _twiml_response("Sorry, something went wrong setting up your account. Please try again later.")

    # Get or create a conversation for this user
    try:
        conversation = await get_conversation_for_user(user=user)
        await conversation.fetch_related("messages")
    except Exception as e:
        logger.error(f"Failed to get conversation for user {user.username}: {e}")
        return _twiml_response("Sorry, something went wrong. Please try again later.")

    # Add user message to conversation
    await add_message_to_conversation(
        conversation=conversation,
        message=body,
        speaker="user",
        user=user,
    )

    # Get transcript for context
    transcript = await get_conversation_transcript(user=user, conversation=conversation)

    # Build messages payload for LangChain agent with system prompt and conversation history
    try:
        # Get last 10 messages for conversation history
        messages = await conversation.messages.all()
        recent_messages = list(messages)[-10:]

        # Build messages payload
        messages_payload = [{"role": "system", "content": SIMBA_SYSTEM_PROMPT}]

        # Add recent conversation history (exclude the message we just added)
        for msg in recent_messages[:-1]:
            role = "user" if msg.speaker == "user" else "assistant"
            messages_payload.append({"role": role, "content": msg.text})

        # Add current query
        messages_payload.append({"role": "user", "content": body})

        # Invoke LangChain agent
        logger.info(f"Invoking LangChain agent with {len(messages_payload)} messages")
        response = await main_agent.ainvoke({"messages": messages_payload})
        response_text = response.get("messages", [])[-1].content

        # Log YNAB availability
        if os.getenv("YNAB_ACCESS_TOKEN"):
            logger.info("YNAB integration is available for this conversation")
        else:
            logger.info("YNAB integration is not configured")

    except Exception as e:
        logger.error(f"Error invoking agent: {e}")
        response_text = "Sorry, I'm having trouble thinking right now. 😿"

    # Add Simba's response to conversation
    await add_message_to_conversation(
        conversation=conversation,
        message=response_text,
        speaker="simba",
        user=user,
    )

    return _twiml_response(response_text)