"""
WhatsApp Business API Integration
===================================
Handles inbound webhook messages and outbound replies via the
Meta WhatsApp Cloud API (v18+).

In the POC demo, all send/receive calls are stubbed and logged.
In production, set:
  WHATSAPP_TOKEN        = Bearer token from Meta Business Portal
  WHATSAPP_PHONE_ID     = Phone Number ID
  WHATSAPP_VERIFY_TOKEN = Webhook verification token
"""

import os
import json
import logging
import hashlib
from datetime import datetime
from typing import Optional

logger = logging.getLogger(__name__)

WHATSAPP_API_URL = "https://graph.facebook.com/v18.0/{phone_id}/messages"


class WhatsAppClient:

    def __init__(self):
        self.token    = os.getenv("WHATSAPP_TOKEN", "DEMO_TOKEN")
        self.phone_id = os.getenv("WHATSAPP_PHONE_ID", "DEMO_PHONE_ID")
        self.verify   = os.getenv("WHATSAPP_VERIFY_TOKEN", "plotweaver_verify")
        self._demo    = self.token == "DEMO_TOKEN"

    # ── Outbound ─────────────────────────────────────────────────────────────

    def send_text(self, to: str, body: str) -> dict:
        """Send a plain text message."""
        payload = {
            "messaging_product": "whatsapp",
            "recipient_type": "individual",
            "to": to,
            "type": "text",
            "text": {"preview_url": False, "body": body},
        }
        return self._post(payload)

    def send_audio(self, to: str, audio_url: str) -> dict:
        """Send a voice note (ogg/opus recommended by Meta)."""
        payload = {
            "messaging_product": "whatsapp",
            "recipient_type": "individual",
            "to": to,
            "type": "audio",
            "audio": {"link": audio_url},
        }
        return self._post(payload)

    def send_interactive_buttons(self, to: str, body: str,
                                  buttons: list[dict]) -> dict:
        """
        Quick-reply buttons for disambiguation.
        buttons = [{"id": "yes", "title": "Yes ✓"}, {"id": "no", "title": "No ✗"}]
        """
        payload = {
            "messaging_product": "whatsapp",
            "to": to,
            "type": "interactive",
            "interactive": {
                "type": "button",
                "body": {"text": body},
                "action": {
                    "buttons": [
                        {"type": "reply", "reply": btn} for btn in buttons
                    ]
                },
            },
        }
        return self._post(payload)

    # ── Inbound webhook ──────────────────────────────────────────────────────

    def verify_webhook(self, mode: str, token: str, challenge: str) -> Optional[str]:
        """GET verification handshake from Meta."""
        if mode == "subscribe" and token == self.verify:
            logger.info("WhatsApp webhook verified.")
            return challenge
        return None

    def parse_inbound(self, raw_body: dict) -> Optional[dict]:
        """
        Extract relevant fields from inbound webhook payload.
        Returns normalized event dict or None if not a user message.
        """
        try:
            entry   = raw_body["entry"][0]
            changes = entry["changes"][0]["value"]
            message = changes["messages"][0]
            contact = changes["contacts"][0]

            event = {
                "from":      message["from"],
                "name":      contact["profile"]["name"],
                "timestamp": datetime.fromtimestamp(int(message["timestamp"])).isoformat(),
                "msg_id":    message["id"],
                "type":      message["type"],
            }

            if message["type"] == "text":
                event["text"] = message["text"]["body"]
            elif message["type"] == "audio":
                event["audio_id"] = message["audio"]["id"]
                event["mime"]     = message["audio"].get("mime_type", "audio/ogg")
            elif message["type"] == "interactive":
                event["button_id"] = message["interactive"]["button_reply"]["id"]

            return event
        except (KeyError, IndexError) as e:
            logger.warning(f"Could not parse WhatsApp payload: {e}")
            return None

    def download_media(self, media_id: str) -> Optional[bytes]:
        """Fetch audio bytes for voice messages."""
        if self._demo:
            logger.info(f"[DEMO] Would download media: {media_id}")
            return b""    # Return empty bytes in demo mode
        # Production: GET https://graph.facebook.com/v18.0/{media_id}
        # then fetch the returned URL with Bearer auth
        raise NotImplementedError("Set WHATSAPP_TOKEN in production.")

    # ── Internals ─────────────────────────────────────────────────────────────

    def _post(self, payload: dict) -> dict:
        if self._demo:
            logger.info(f"[DEMO] WhatsApp → {payload['to']}: "
                        f"{json.dumps(payload)[:120]} …")
            return {"status": "demo_ok",
                    "message_id": "demo_" + hashlib.md5(
                        json.dumps(payload).encode()).hexdigest()[:8]}
        import requests
        url = WHATSAPP_API_URL.format(phone_id=self.phone_id)
        headers = {"Authorization": f"Bearer {self.token}",
                   "Content-Type": "application/json"}
        r = requests.post(url, headers=headers, json=payload, timeout=10)
        r.raise_for_status()
        return r.json()