"""
Phone / SIP Integration  (Twilio + Bandwidth stubs)
=====================================================
Handles inbound calls → streams audio → runs pipeline → streams TTS back.

For a real deployment, use:
  - Twilio Media Streams (WebSocket) + <Stream> TwiML verb
  - Bandwidth BXML + WebSocket audio streaming
  - Vonage Voice API + WebSocket

Environment variables:
  TWILIO_ACCOUNT_SID  = ACxxxx
  TWILIO_AUTH_TOKEN   = xxxx
  TWILIO_PHONE_NUMBER = +1234567890
  SIP_PROVIDER        = twilio | bandwidth | demo
"""

import os
import logging
from typing import Callable, Optional

logger = logging.getLogger(__name__)


class TwilioAdapter:
    """
    Twilio Media Streams WebSocket adapter.
    
    Flow:
      1.  Inbound call → Twilio webhook → /voice endpoint
      2.  Return TwiML with <Connect><Stream> → Twilio opens WS
      3.  WebSocket handler receives mulaw 8kHz chunks
      4.  Chunks accumulated → ASR → NLU → TTS → send back over WS
    """

    def __init__(self):
        self.sid   = os.getenv("TWILIO_ACCOUNT_SID",  "DEMO")
        self.token = os.getenv("TWILIO_AUTH_TOKEN",   "DEMO")
        self.phone = os.getenv("TWILIO_PHONE_NUMBER", "+0000000000")
        self._demo = self.sid == "DEMO"

    def incoming_call_twiml(self, websocket_url: str) -> str:
        """
        Returns TwiML that Twilio will execute when a call arrives.
        websocket_url: wss://yourserver.com/ws/audio
        """
        return f"""<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Say language="ha-NG">Sannu, barka da zuwa PlotWeaver. Muna jira…</Say>
  <Connect>
    <Stream url="{websocket_url}">
      <Parameter name="language" value="hausa"/>
    </Stream>
  </Connect>
</Response>"""

    def handle_ws_message(self, message: dict,
                           on_audio_chunk: Callable[[bytes], None]) -> None:
        """
        Called for each WebSocket message from Twilio.
        Twilio sends: start, media (base64 mulaw), stop events.
        """
        import base64
        event = message.get("event")
        if event == "media":
            chunk = base64.b64decode(message["media"]["payload"])
            on_audio_chunk(chunk)
        elif event == "stop":
            logger.info(f"Call ended: {message.get('stop', {}).get('callSid')}")

    def send_audio_twiml(self, call_sid: str, audio_url: str) -> dict:
        """
        Interrupt the current call and play synthesised audio.
        Production: POST to Twilio API to update call.
        """
        if self._demo:
            logger.info(f"[DEMO] Would play {audio_url} on call {call_sid}")
            return {"status": "demo"}
        from twilio.rest import Client
        client = Client(self.sid, self.token)
        call = client.calls(call_sid).update(
            twiml=f'<Response><Play>{audio_url}</Play></Response>'
        )
        return {"status": call.status}

    def make_outbound_call(self, to: str, message_en: str,
                            message_ha: str = "") -> dict:
        """Outbound IVR call with TTS message."""
        twiml = f"""<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Say language="ha-NG">{message_ha or message_en}</Say>
</Response>"""
        if self._demo:
            logger.info(f"[DEMO] Outbound to {to}: {message_en[:60]}…")
            return {"status": "demo_queued", "to": to}
        from twilio.rest import Client
        client = Client(self.sid, self.token)
        call = client.calls.create(
            to=to, from_=self.phone, twiml=twiml
        )
        return {"sid": call.sid, "status": call.status}

    @staticmethod
    def mulaw_to_pcm(mulaw_bytes: bytes) -> bytes:
        """
        Convert 8kHz G.711 mu-law to 16-bit PCM at 16kHz for Whisper.

        Implemented in numpy rather than the stdlib `audioop` module, which
        was removed in Python 3.13. Keeping this dependency-free means the
        telephony path works on any modern image.
        """
        import numpy as np

        u = np.frombuffer(mulaw_bytes, dtype=np.uint8).astype(np.int32)
        u = ~u & 0xFF                                  # mu-law is stored inverted
        sign     = u & 0x80
        exponent = (u >> 4) & 0x07
        mantissa = u & 0x0F
        # ITU-T G.711: t = ((mantissa << 3) + BIAS) << exponent, BIAS = 0x84
        t = ((mantissa << 3) + 0x84) << exponent
        pcm8k = np.where(sign != 0, 0x84 - t, t - 0x84).astype(np.int16)

        # 8kHz → 16kHz (linear interpolation; the band-limited content of a
        # phone call makes a higher-order filter unnecessary here)
        if len(pcm8k) == 0:
            return b""
        x  = np.arange(len(pcm8k))
        xi = np.arange(len(pcm8k) * 2) / 2.0      # exact 2x: 0, 0.5, 1, 1.5, …
        pcm16k = np.interp(xi, x, pcm8k).astype(np.int16)
        return pcm16k.tobytes()


class BandwidthAdapter:
    """Bandwidth BXML + WebSocket audio streaming (stub)."""

    def __init__(self):
        self.account_id   = os.getenv("BANDWIDTH_ACCOUNT_ID",   "DEMO")
        self.api_token    = os.getenv("BANDWIDTH_API_TOKEN",     "DEMO")
        self._demo        = self.account_id == "DEMO"

    def incoming_call_bxml(self, websocket_url: str) -> str:
        return f"""<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <SpeakSentence locale="ha-NG">Sannu da zuwa PlotWeaver.</SpeakSentence>
  <StartStream url="{websocket_url}" streamEventUrl="{websocket_url}/events"/>
</Response>"""

    def send_tts(self, call_id: str, text: str, locale: str = "ha-NG") -> dict:
        if self._demo:
            logger.info(f"[DEMO] Bandwidth TTS on call {call_id}: {text[:60]}…")
            return {"status": "demo"}
        # Production: PATCH /calls/{callId} with BXML
        raise NotImplementedError


class SIPRouter:
    """
    Routes a call to the correct adapter based on SIP_PROVIDER env var.
    Also manages human-agent transfer via SIP REFER.
    """

    PROVIDERS = {"twilio": TwilioAdapter, "bandwidth": BandwidthAdapter}

    def __init__(self):
        provider = os.getenv("SIP_PROVIDER", "demo").lower()
        if provider in self.PROVIDERS:
            self.adapter = self.PROVIDERS[provider]()
        else:
            self.adapter = TwilioAdapter()   # demo mode
        logger.info(f"SIP provider: {provider}")

    def transfer_to_human(self, call_sid: str,
                           agent_extension: str = "+0000000001") -> dict:
        """
        REFER / warm transfer to human agent queue.
        In demo mode just logs.
        """
        logger.info(f"[SIP] Transferring {call_sid} → agent {agent_extension}")
        if isinstance(self.adapter, TwilioAdapter) and not self.adapter._demo:
            from twilio.rest import Client
            client = Client(self.adapter.sid, self.adapter.token)
            call = client.calls(call_sid).update(
                url=f"http://twimlets.com/forward?PhoneNumber={agent_extension}"
            )
            return {"status": call.status, "agent": agent_extension}
        return {"status": "demo_transfer", "agent": agent_extension}