"""GitHub OAuth provider for FastMCP.

This module provides a complete GitHub OAuth integration that's ready to use
with just a client ID and client secret. It handles all the complexity of
GitHub's OAuth flow, token validation, and user management.

Example:
    ```python
    from fastmcp import FastMCP
    from fastmcp.server.auth.providers.github import GitHubProvider

    # Simple GitHub OAuth protection
    auth = GitHubProvider(
        client_id="your-github-client-id",
        client_secret="your-github-client-secret"
    )

    mcp = FastMCP("My Protected Server", auth=auth)
    ```
"""

from __future__ import annotations

import contextlib
from typing import Literal

import httpx
from key_value.aio.protocols import AsyncKeyValue
from pydantic import AnyHttpUrl

from fastmcp.server.auth import TokenVerifier
from fastmcp.server.auth.auth import AccessToken
from fastmcp.server.auth.oauth_proxy import OAuthProxy
from fastmcp.utilities.auth import parse_scopes
from fastmcp.utilities.logging import get_logger
from fastmcp.utilities.token_cache import TokenCache

logger = get_logger(__name__)


class GitHubTokenVerifier(TokenVerifier):
    """Token verifier for GitHub OAuth tokens.

    GitHub OAuth tokens are opaque (not JWTs), so we verify them
    by calling GitHub's API to check if they're valid and get user info.

    Caching is disabled by default.  Set ``cache_ttl_seconds`` to a positive
    integer to cache successful verification results and avoid repeated
    GitHub API calls for the same token.
    """

    def __init__(
        self,
        *,
        required_scopes: list[str] | None = None,
        timeout_seconds: int = 10,
        cache_ttl_seconds: int | None = None,
        max_cache_size: int | None = None,
        http_client: httpx.AsyncClient | None = None,
    ):
        """Initialize the GitHub token verifier.

        Args:
            required_scopes: Required OAuth scopes (e.g., ['user:email'])
            timeout_seconds: HTTP request timeout
            cache_ttl_seconds: How long to cache verification results in seconds.
                Caching is disabled by default (None).  Set to a positive integer
                to enable (e.g., 300 for 5 minutes).
            max_cache_size: Maximum number of tokens to cache.  Default: 10 000.
            http_client: Optional httpx.AsyncClient for connection pooling. When provided,
                the client is reused across calls and the caller is responsible for its
                lifecycle. When None (default), a fresh client is created per call.
        """
        super().__init__(required_scopes=required_scopes)
        self.timeout_seconds = timeout_seconds
        self._http_client = http_client
        self._cache = TokenCache(
            ttl_seconds=cache_ttl_seconds,
            max_size=max_cache_size,
        )

    async def verify_token(self, token: str) -> AccessToken | None:
        """Verify GitHub OAuth token by calling GitHub API."""
        is_cached, cached_result = self._cache.get(token)
        if is_cached:
            logger.debug("GitHub token cache hit")
            return cached_result

        try:
            async with (
                contextlib.nullcontext(self._http_client)
                if self._http_client is not None
                else httpx.AsyncClient(timeout=self.timeout_seconds)
            ) as client:
                # Get token info from GitHub API
                response = await client.get(
                    "https://api.github.com/user",
                    headers={
                        "Authorization": f"Bearer {token}",
                        "Accept": "application/vnd.github.v3+json",
                        "User-Agent": "FastMCP-GitHub-OAuth",
                    },
                )

                if response.status_code != 200:
                    logger.debug(
                        "GitHub token verification failed: %d - %s",
                        response.status_code,
                        response.text[:200],
                    )
                    return None

                user_data = response.json()

                # Get token scopes from GitHub API
                # GitHub includes scopes in the X-OAuth-Scopes header
                scopes_response = await client.get(
                    "https://api.github.com/user/repos",  # Any authenticated endpoint
                    headers={
                        "Authorization": f"Bearer {token}",
                        "Accept": "application/vnd.github.v3+json",
                        "User-Agent": "FastMCP-GitHub-OAuth",
                    },
                )

                # Extract scopes from X-OAuth-Scopes header if available
                scopes_verified = scopes_response.status_code == 200
                oauth_scopes_header = scopes_response.headers.get("x-oauth-scopes", "")
                token_scopes = [
                    scope.strip()
                    for scope in oauth_scopes_header.split(",")
                    if scope.strip()
                ]

                # If no scopes in header, assume basic scopes based on successful user API call
                if not token_scopes:
                    token_scopes = ["user"]  # Basic scope if we can access user info

                # Check required scopes
                if self.required_scopes:
                    token_scopes_set = set(token_scopes)
                    required_scopes_set = set(self.required_scopes)
                    if not required_scopes_set.issubset(token_scopes_set):
                        logger.debug(
                            "GitHub token missing required scopes. Has %d, needs %d",
                            len(token_scopes_set),
                            len(required_scopes_set),
                        )
                        return None

                # Create AccessToken with GitHub user info
                result = AccessToken(
                    token=token,
                    client_id=str(user_data.get("id", "unknown")),  # Use GitHub user ID
                    scopes=token_scopes,
                    expires_at=None,  # GitHub tokens don't typically expire
                    claims={
                        "sub": str(user_data["id"]),
                        "login": user_data.get("login"),
                        "name": user_data.get("name"),
                        "email": user_data.get("email"),
                        "avatar_url": user_data.get("avatar_url"),
                        "github_user_data": user_data,
                    },
                )
                if scopes_verified:
                    self._cache.set(token, result)
                return result

        except httpx.RequestError as e:
            logger.debug("Failed to verify GitHub token: %s", e)
            return None
        except Exception as e:
            logger.debug("GitHub token verification error: %s", e)
            return None


class GitHubProvider(OAuthProxy):
    """Complete GitHub OAuth provider for FastMCP.

    This provider makes it trivial to add GitHub OAuth protection to any
    FastMCP server. Just provide your GitHub OAuth app credentials and
    a base URL, and you're ready to go.

    Features:
    - Transparent OAuth proxy to GitHub
    - Automatic token validation via GitHub API
    - User information extraction
    - Minimal configuration required

    Example:
        ```python
        from fastmcp import FastMCP
        from fastmcp.server.auth.providers.github import GitHubProvider

        auth = GitHubProvider(
            client_id="Ov23li...",
            client_secret="abc123...",
            base_url="https://my-server.com"
        )

        mcp = FastMCP("My App", auth=auth)
        ```
    """

    def __init__(
        self,
        *,
        client_id: str,
        client_secret: str,
        base_url: AnyHttpUrl | str,
        resource_base_url: AnyHttpUrl | str | None = None,
        issuer_url: AnyHttpUrl | str | None = None,
        redirect_path: str | None = None,
        required_scopes: list[str] | None = None,
        timeout_seconds: int = 10,
        cache_ttl_seconds: int | None = None,
        max_cache_size: int | None = None,
        allowed_client_redirect_uris: list[str] | None = None,
        client_storage: AsyncKeyValue | None = None,
        jwt_signing_key: str | bytes | None = None,
        require_authorization_consent: bool | Literal["remember", "external"] = True,
        consent_csp_policy: str | None = None,
        forward_resource: bool = True,
        fallback_refresh_token_expiry_seconds: int | None = None,
        http_client: httpx.AsyncClient | None = None,
        enable_cimd: bool = True,
    ):
        """Initialize GitHub OAuth provider.

        Args:
            client_id: GitHub OAuth app client ID (e.g., "Ov23li...")
            client_secret: GitHub OAuth app client secret
            base_url: Public URL where OAuth endpoints will be accessible (includes any mount path)
            resource_base_url: Optional public base URL for the protected resource metadata
                and token audience. Defaults to ``base_url``.
            issuer_url: Issuer URL for OAuth metadata (defaults to base_url). Use root-level URL
                to avoid 404s during discovery when mounting under a path.
            redirect_path: Redirect path configured in GitHub OAuth app (defaults to "/auth/callback")
            required_scopes: Required GitHub scopes (defaults to ["user"])
            timeout_seconds: HTTP request timeout for GitHub API calls (defaults to 10)
            cache_ttl_seconds: How long to cache token verification results in seconds.
                Caching is disabled by default (None).  Set to a positive integer to
                enable (e.g., 300 for 5 minutes).
            max_cache_size: Maximum number of tokens to cache.  Default: 10 000.
            allowed_client_redirect_uris: List of allowed redirect URI patterns for MCP clients.
                If None (default), all URIs are allowed. If empty list, no URIs are allowed.
            client_storage: Storage backend for OAuth state (client registrations, encrypted tokens).
                If None, an encrypted file store will be created in the data directory
                (derived from `platformdirs`).
            jwt_signing_key: Secret for signing FastMCP JWT tokens (any string or bytes). If bytes are provided,
                they will be used as is. If a string is provided, it will be derived into a 32-byte key. If not
                provided, the upstream client secret will be used to derive a 32-byte key using PBKDF2.
            require_authorization_consent: Whether to require user consent before authorizing clients (default True).
                When True, users see a consent screen before being redirected to GitHub.
                When False, authorization proceeds directly without user confirmation.
                When "external", the built-in consent screen is skipped but no warning is
                logged, indicating that consent is handled externally (e.g. by the upstream IdP).
                SECURITY WARNING: Only set to False for local development or testing environments.
            http_client: Optional httpx.AsyncClient for connection pooling in token verification.
                When provided, the client is reused across verify_token calls and the caller
                is responsible for its lifecycle. When None (default), a fresh client is created per call.
            enable_cimd: Enable CIMD (Client ID Metadata Document) support for URL-based
                client IDs (default True). Set to False to disable.
        """
        # Parse scopes if provided as string
        required_scopes_final = (
            parse_scopes(required_scopes) if required_scopes is not None else ["user"]
        )

        # Create GitHub token verifier
        token_verifier = GitHubTokenVerifier(
            required_scopes=required_scopes_final,
            timeout_seconds=timeout_seconds,
            cache_ttl_seconds=cache_ttl_seconds,
            max_cache_size=max_cache_size,
            http_client=http_client,
        )

        # Initialize OAuth proxy with GitHub endpoints
        super().__init__(
            upstream_authorization_endpoint="https://github.com/login/oauth/authorize",
            upstream_token_endpoint="https://github.com/login/oauth/access_token",
            upstream_client_id=client_id,
            upstream_client_secret=client_secret,
            token_verifier=token_verifier,
            base_url=base_url,
            resource_base_url=resource_base_url,
            redirect_path=redirect_path,
            issuer_url=issuer_url or base_url,  # Default to base_url if not specified
            allowed_client_redirect_uris=allowed_client_redirect_uris,
            client_storage=client_storage,
            jwt_signing_key=jwt_signing_key,
            require_authorization_consent=require_authorization_consent,
            consent_csp_policy=consent_csp_policy,
            forward_resource=forward_resource,
            fallback_refresh_token_expiry_seconds=fallback_refresh_token_expiry_seconds,
            enable_cimd=enable_cimd,
        )

        logger.debug(
            "Initialized GitHub OAuth provider for client %s with scopes: %s",
            client_id,
            required_scopes_final,
        )
