"""SpeechEngineResource — client-facing handle for a speech engine instance."""

import base64
import hashlib
import hmac
import json
import logging
import time
import typing

from .server import SpeechEngineServer
from .session import SpeechEngineSession
from .types import WebSocketLike
from ..types.speech_engine_response import SpeechEngineResponse

logger = logging.getLogger("elevenlabs.speech_engine")

_ISSUER = "https://api.elevenlabs.io/convai/speech-engine"
_SUBJECT = "convai_speech_engine_upstream"
_LEEWAY_SECONDS = 60


def _base64url_decode(data: str) -> bytes:
    padded = data.replace("-", "+").replace("_", "/")
    remainder = len(padded) % 4
    if remainder:
        padded += "=" * (4 - remainder)
    return base64.b64decode(padded)


def verify_speech_engine_jwt(value: str, api_key: str) -> typing.Dict[str, typing.Any]:
    """Verify an HS256 JWT from the ElevenLabs Speech Engine API.

    The HMAC secret is the SHA-256 hash of the API key.  Returns the
    decoded payload on success, raises :class:`ValueError` on failure.
    """
    token = value.strip()
    if token.lower().startswith("bearer "):
        token = token[7:].strip()

    parts = token.split(".")
    if len(parts) != 3:
        raise ValueError("Invalid JWT: expected 3 parts")

    header_b64, payload_b64, signature_b64 = parts

    try:
        payload = json.loads(_base64url_decode(payload_b64))
    except Exception:
        raise ValueError("Invalid JWT: failed to decode payload")

    trimmed_key = api_key.strip()
    secret = hashlib.sha256(trimmed_key.encode("utf-8")).digest()

    expected_sig = hmac.new(
        secret, f"{header_b64}.{payload_b64}".encode(), hashlib.sha256
    ).digest()
    actual_sig = _base64url_decode(signature_b64)

    if not hmac.compare_digest(expected_sig, actual_sig):
        raise ValueError(
            "Invalid JWT: signature mismatch — make sure the API key used "
            "by your Speech Engine server matches the one used to create "
            "the engine."
        )

    if payload.get("iss") != _ISSUER:
        raise ValueError(
            f'Invalid JWT: expected issuer "{_ISSUER}", got "{payload.get("iss")}"'
        )
    if payload.get("sub") != _SUBJECT:
        raise ValueError(
            f'Invalid JWT: expected subject "{_SUBJECT}", got "{payload.get("sub")}"'
        )

    now = int(time.time())

    exp = payload.get("exp")
    if not isinstance(exp, (int, float)):
        raise ValueError("Invalid JWT: missing exp claim")
    iat = payload.get("iat")
    if not isinstance(iat, (int, float)):
        raise ValueError("Invalid JWT: missing iat claim")
    if exp + _LEEWAY_SECONDS < now:
        raise ValueError("Invalid JWT: token has expired")
    if iat - _LEEWAY_SECONDS > now:
        raise ValueError("Invalid JWT: iat is in the future")

    return payload


class SpeechEngineResource:
    """Represents a speech engine instance.

    Returned by ``await client.speech_engine.get("seng_123")``.

    Use :meth:`serve` to start a standalone WebSocket server, or
    :meth:`create_session` to wrap an existing WebSocket for custom
    server integration (FastAPI, Starlette, etc.).

    Example::

        engine = await elevenlabs.speech_engine.get("seng_123")

        async def on_transcript(transcript, session):
            stream = await openai.responses.create(...)
            await session.send_response(stream)

        await engine.serve(
            port=3001,
            debug=True,
            on_transcript=on_transcript,
        )
    """

    def __init__(
        self,
        engine_id: str,
        client_wrapper: typing.Any = None,
        response: typing.Optional[SpeechEngineResponse] = None,
    ) -> None:
        self.engine_id = engine_id
        self._client_wrapper = client_wrapper

        # Full API response, accessible as engine.config.asr, engine.config.overrides, etc.
        # None when the resource is constructed directly without an API call.
        self.config: typing.Optional[SpeechEngineResponse] = response

    def _get_api_key(self) -> typing.Optional[str]:
        if self._client_wrapper is None:
            return None
        headers = self._client_wrapper.get_headers()
        return headers.get("xi-api-key")

    def verify_request(
        self, headers: typing.Dict[str, typing.Any]
    ) -> bool:
        """Verify that an incoming request is from the ElevenLabs API.

        Checks the ``X-Elevenlabs-Speech-Engine-Authorization`` header
        for a valid JWT signed with the SHA-256 hash of the API key.

        Only needed when managing the WebSocket upgrade yourself.
        When using :meth:`serve`, verification is handled automatically.
        """
        api_key = self._get_api_key()
        if not api_key:
            return False
        raw = headers.get("x-elevenlabs-speech-engine-authorization")
        if isinstance(raw, list):
            raw = raw[0] if raw else None
        if not raw:
            return False
        try:
            verify_speech_engine_jwt(raw, api_key)
            return True
        except ValueError:
            return False

    async def serve(
        self,
        *,
        port: int = 3001,
        path: typing.Optional[str] = None,
        debug: bool = False,
        **handlers: typing.Any,
    ) -> None:
        """Start a standalone WebSocket server.  Blocks until stopped."""
        api_key = self._get_api_key()
        server = SpeechEngineServer(
            port=port, path=path, debug=debug, api_key=api_key, **handlers
        )
        await server.serve()

    def create_session(
        self,
        ws: WebSocketLike,
        *,
        debug: bool = False,
    ) -> SpeechEngineSession:
        """Wrap *ws* in a :class:`SpeechEngineSession`.

        Use this for custom server integration (e.g. FastAPI, Starlette).
        Wire handlers via :meth:`~SpeechEngineSession.on` then ``await
        session.run()``.
        """
        return SpeechEngineSession(ws, debug=debug)
