import asyncio
import json
import os
import time
from pathlib import Path

from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import Flow

from app.config import Settings


GOOGLE_SCOPES = [
    "https://www.googleapis.com/auth/gmail.readonly",
    "https://www.googleapis.com/auth/drive.metadata.readonly",
    "https://www.googleapis.com/auth/drive.file",
]


class GoogleAuthError(RuntimeError):
    pass


_OAUTH_STATES: dict[str, float] = {}
_OAUTH_STATE_TTL_SECONDS = 900


class GoogleAuthManager:
    def __init__(self, settings: Settings, workspace_root: Path) -> None:
        self.settings = settings
        self.workspace_root = workspace_root.resolve()

    async def get_credentials(self) -> Credentials:
        return await asyncio.to_thread(self._load_credentials)

    def _load_credentials(self) -> Credentials:
        token_path = self.token_path
        client_path = self.client_path

        if not client_path.exists():
            raise GoogleAuthError(
                f"Google client secrets file is missing: {client_path}. "
                "Create a Google OAuth Web Application and place its JSON here."
            )
        if not token_path.exists():
            raise GoogleAuthError(
                f"Google token file is missing: {token_path}. "
                "Run the Google OAuth bootstrap step first."
            )

        credentials = Credentials.from_authorized_user_file(str(token_path), GOOGLE_SCOPES)
        if credentials.expired and credentials.refresh_token:
            credentials.refresh(Request())
            token_path.write_text(credentials.to_json(), encoding="utf-8")

        if not credentials.valid:
            raise GoogleAuthError(
                "Google credentials are invalid. Re-run the Google OAuth bootstrap step."
            )
        return credentials

    @property
    def client_path(self) -> Path:
        return self._resolve_path(self.settings.google_client_secrets_file)

    @property
    def token_path(self) -> Path:
        return self._resolve_path(self.settings.google_token_file)

    def write_client_secrets_file(self, client_id: str, client_secret: str) -> Path:
        client_id = client_id.strip()
        client_secret = client_secret.strip()
        if not client_id or not client_secret:
            raise GoogleAuthError("Google client ID and client secret are required.")

        redirect_uris = [
            f"http://127.0.0.1:{self.settings.admin_port}/admin/integrations/google/callback",
            f"http://localhost:{self.settings.admin_port}/admin/integrations/google/callback",
        ]
        payload = {
            "web": {
                "client_id": client_id,
                "project_id": "wiseclaw-local",
                "auth_uri": "https://accounts.google.com/o/oauth2/auth",
                "token_uri": "https://oauth2.googleapis.com/token",
                "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
                "client_secret": client_secret,
                "redirect_uris": redirect_uris,
            }
        }
        self.client_path.parent.mkdir(parents=True, exist_ok=True)
        self.client_path.write_text(json.dumps(payload, indent=2), encoding="utf-8")
        return self.client_path

    def begin_web_oauth(self, redirect_uri: str) -> str:
        if not self.client_path.exists():
            raise GoogleAuthError(
                f"Google client secrets file is missing: {self.client_path}. "
                "Place your Google OAuth client JSON there first."
            )

        self._configure_local_oauth_transport(redirect_uri)
        flow = Flow.from_client_secrets_file(str(self.client_path), GOOGLE_SCOPES)
        flow.redirect_uri = redirect_uri
        authorization_url, state = flow.authorization_url(
            access_type="offline",
            include_granted_scopes="true",
            prompt="consent",
        )
        self._store_state(state)
        return authorization_url

    def complete_web_oauth(self, redirect_uri: str, state: str, authorization_response: str) -> Credentials:
        if not self._consume_state(state):
            raise GoogleAuthError("Google OAuth state is missing or expired. Start the connect flow again.")

        self._configure_local_oauth_transport(redirect_uri)
        flow = Flow.from_client_secrets_file(str(self.client_path), GOOGLE_SCOPES, state=state)
        flow.redirect_uri = redirect_uri
        flow.fetch_token(authorization_response=authorization_response)
        credentials = flow.credentials
        self.token_path.parent.mkdir(parents=True, exist_ok=True)
        self.token_path.write_text(credentials.to_json(), encoding="utf-8")
        return credentials

    def oauth_status(self) -> tuple[bool, bool, str]:
        if not self.client_path.exists():
            return False, False, (
                f"Missing Google OAuth client file at {self.client_path}. "
                "Add client_secret.json first."
            )
        if not self.token_path.exists():
            return False, False, "Google account is not connected yet."
        try:
            self._load_credentials()
        except GoogleAuthError as exc:
            return True, False, str(exc)
        return True, True, "Google account is connected."

    def _resolve_path(self, raw_path: str) -> Path:
        path = Path(raw_path).expanduser()
        if not path.is_absolute():
            path = (self.workspace_root / path).resolve()
        else:
            path = path.resolve()
        return path

    def _store_state(self, state: str) -> None:
        now = time.time()
        expired = [item for item, created_at in _OAUTH_STATES.items() if now - created_at > _OAUTH_STATE_TTL_SECONDS]
        for item in expired:
            _OAUTH_STATES.pop(item, None)
        _OAUTH_STATES[state] = now

    def _consume_state(self, state: str) -> bool:
        created_at = _OAUTH_STATES.pop(state, None)
        if created_at is None:
            return False
        return time.time() - created_at <= _OAUTH_STATE_TTL_SECONDS

    def _configure_local_oauth_transport(self, redirect_uri: str) -> None:
        if redirect_uri.startswith("http://127.0.0.1") or redirect_uri.startswith("http://localhost"):
            os.environ["OAUTHLIB_INSECURE_TRANSPORT"] = "1"