# app/api/routes/oauth_provider.py
"""
OAuth Provider routes (Authorization Server mode).

This is a skeleton implementation for MCP (Model Context Protocol) client authentication.
Provides basic OAuth 2.0 endpoints that can be expanded for full functionality.

Endpoints:
- GET /.well-known/oauth-authorization-server - Server metadata (RFC 8414)
- GET /oauth/provider/authorize - Authorization endpoint (skeleton)
- POST /oauth/provider/token - Token endpoint (skeleton)
- POST /oauth/provider/revoke - Token revocation endpoint (skeleton)

NOTE: This is intentionally minimal. Full implementation should include:
- Complete authorization code flow
- Refresh token handling
- Scope validation
- Client authentication
- PKCE support
"""

import logging
from typing import Any

from fastapi import APIRouter, Depends, Form, HTTPException, Query, status
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import settings
from app.core.database import get_db
from app.crud import oauth_client
from app.schemas.oauth import OAuthServerMetadata

router = APIRouter()
logger = logging.getLogger(__name__)


@router.get(
    "/.well-known/oauth-authorization-server",
    response_model=OAuthServerMetadata,
    summary="OAuth Server Metadata",
    description="""
    OAuth 2.0 Authorization Server Metadata (RFC 8414).

    Returns server metadata including supported endpoints, scopes,
    and capabilities for MCP clients.
    """,
    operation_id="get_oauth_server_metadata",
    tags=["OAuth Provider"],
)
async def get_server_metadata() -> Any:
    """
    Get OAuth 2.0 server metadata.

    This endpoint is used by MCP clients to discover the authorization
    server's capabilities.
    """
    if not settings.OAUTH_PROVIDER_ENABLED:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="OAuth provider mode is not enabled",
        )

    base_url = settings.OAUTH_ISSUER.rstrip("/")

    return OAuthServerMetadata(
        issuer=base_url,
        authorization_endpoint=f"{base_url}/api/v1/oauth/provider/authorize",
        token_endpoint=f"{base_url}/api/v1/oauth/provider/token",
        revocation_endpoint=f"{base_url}/api/v1/oauth/provider/revoke",
        registration_endpoint=None,  # Dynamic registration not implemented
        scopes_supported=[
            "openid",
            "profile",
            "email",
            "read:users",
            "write:users",
            "read:organizations",
            "write:organizations",
        ],
        response_types_supported=["code"],
        grant_types_supported=["authorization_code", "refresh_token"],
        code_challenge_methods_supported=["S256"],
    )


@router.get(
    "/provider/authorize",
    summary="Authorization Endpoint (Skeleton)",
    description="""
    OAuth 2.0 Authorization Endpoint.

    **NOTE**: This is a skeleton implementation. In a full implementation,
    this would:
    1. Validate client_id and redirect_uri
    2. Display consent screen to user
    3. Generate authorization code
    4. Redirect back to client with code

    Currently returns a 501 Not Implemented response.
    """,
    operation_id="oauth_provider_authorize",
    tags=["OAuth Provider"],
)
async def authorize(
    response_type: str = Query(..., description="Must be 'code'"),
    client_id: str = Query(..., description="OAuth client ID"),
    redirect_uri: str = Query(..., description="Redirect URI"),
    scope: str = Query(default="", description="Requested scopes"),
    state: str = Query(default="", description="CSRF state parameter"),
    code_challenge: str | None = Query(default=None, description="PKCE code challenge"),
    code_challenge_method: str | None = Query(
        default=None, description="PKCE method (S256)"
    ),
    db: AsyncSession = Depends(get_db),
) -> Any:
    """
    Authorization endpoint (skeleton).

    In a full implementation, this would:
    1. Validate the client and redirect URI
    2. Authenticate the user (if not already)
    3. Show consent screen
    4. Generate authorization code
    5. Redirect to redirect_uri with code
    """
    if not settings.OAUTH_PROVIDER_ENABLED:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="OAuth provider mode is not enabled",
        )

    # Validate client exists
    client = await oauth_client.get_by_client_id(db, client_id=client_id)
    if not client:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="invalid_client: Unknown client_id",
        )

    # Validate redirect_uri
    if redirect_uri not in (client.redirect_uris or []):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="invalid_request: Invalid redirect_uri",
        )

    # Skeleton: Return not implemented
    # Full implementation would redirect to consent screen
    raise HTTPException(
        status_code=status.HTTP_501_NOT_IMPLEMENTED,
        detail="Authorization endpoint not fully implemented. "
        "This is a skeleton for MCP integration.",
    )


@router.post(
    "/provider/token",
    summary="Token Endpoint (Skeleton)",
    description="""
    OAuth 2.0 Token Endpoint.

    **NOTE**: This is a skeleton implementation. In a full implementation,
    this would exchange authorization codes for access tokens.

    Currently returns a 501 Not Implemented response.
    """,
    operation_id="oauth_provider_token",
    tags=["OAuth Provider"],
)
async def token(
    grant_type: str = Form(..., description="Grant type (authorization_code)"),
    code: str | None = Form(default=None, description="Authorization code"),
    redirect_uri: str | None = Form(default=None, description="Redirect URI"),
    client_id: str | None = Form(default=None, description="Client ID"),
    client_secret: str | None = Form(default=None, description="Client secret"),
    code_verifier: str | None = Form(default=None, description="PKCE code verifier"),
    refresh_token: str | None = Form(default=None, description="Refresh token"),
    db: AsyncSession = Depends(get_db),
) -> Any:
    """
    Token endpoint (skeleton).

    Supported grant types (when fully implemented):
    - authorization_code: Exchange code for tokens
    - refresh_token: Refresh access token
    """
    if not settings.OAUTH_PROVIDER_ENABLED:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="OAuth provider mode is not enabled",
        )

    if grant_type not in ["authorization_code", "refresh_token"]:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="unsupported_grant_type",
        )

    # Skeleton: Return not implemented
    raise HTTPException(
        status_code=status.HTTP_501_NOT_IMPLEMENTED,
        detail="Token endpoint not fully implemented. "
        "This is a skeleton for MCP integration.",
    )


@router.post(
    "/provider/revoke",
    summary="Token Revocation Endpoint (Skeleton)",
    description="""
    OAuth 2.0 Token Revocation Endpoint (RFC 7009).

    **NOTE**: This is a skeleton implementation.

    Currently returns a 501 Not Implemented response.
    """,
    operation_id="oauth_provider_revoke",
    tags=["OAuth Provider"],
)
async def revoke(
    token: str = Form(..., description="Token to revoke"),
    token_type_hint: str | None = Form(
        default=None, description="Token type hint (access_token, refresh_token)"
    ),
    client_id: str | None = Form(default=None, description="Client ID"),
    client_secret: str | None = Form(default=None, description="Client secret"),
    db: AsyncSession = Depends(get_db),
) -> Any:
    """
    Token revocation endpoint (skeleton).

    In a full implementation, this would invalidate the specified token.
    """
    if not settings.OAUTH_PROVIDER_ENABLED:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="OAuth provider mode is not enabled",
        )

    # Skeleton: Return not implemented
    raise HTTPException(
        status_code=status.HTTP_501_NOT_IMPLEMENTED,
        detail="Revocation endpoint not fully implemented. "
        "This is a skeleton for MCP integration.",
    )


# ============================================================================
# Client Management (Admin only)
# ============================================================================


@router.post(
    "/provider/clients",
    summary="Register OAuth Client (Admin)",
    description="""
    Register a new OAuth client (admin only).

    This endpoint allows creating MCP clients that can authenticate
    against this API.

    **NOTE**: This is a minimal implementation.
    """,
    operation_id="register_oauth_client",
    tags=["OAuth Provider"],
)
async def register_client(
    client_name: str = Form(..., description="Client application name"),
    redirect_uris: str = Form(..., description="Comma-separated list of redirect URIs"),
    client_type: str = Form(default="public", description="public or confidential"),
    db: AsyncSession = Depends(get_db),
) -> Any:
    """
    Register a new OAuth client (skeleton).

    In a full implementation, this would require admin authentication.
    """
    if not settings.OAUTH_PROVIDER_ENABLED:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="OAuth provider mode is not enabled",
        )

    # NOTE: In production, this should require admin authentication
    # For now, this is a skeleton that shows the structure

    from app.schemas.oauth import OAuthClientCreate

    client_data = OAuthClientCreate(
        client_name=client_name,
        client_description=None,
        redirect_uris=[uri.strip() for uri in redirect_uris.split(",")],
        allowed_scopes=["openid", "profile", "email"],
        client_type=client_type,
    )

    client, secret = await oauth_client.create_client(db, obj_in=client_data)

    result = {
        "client_id": client.client_id,
        "client_name": client.client_name,
        "client_type": client.client_type,
        "redirect_uris": client.redirect_uris,
    }

    if secret:
        result["client_secret"] = secret
        result["warning"] = (
            "Store the client_secret securely. It will not be shown again."
        )

    return result
