import os
from typing import Optional

from fastapi import HTTPException, Request
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.responses import JSONResponse


class PasswordAuthMiddleware(BaseHTTPMiddleware):
    """
    Middleware to check password authentication for all API requests.
    Only active when OPEN_NOTEBOOK_PASSWORD environment variable is set.
    """
    
    def __init__(self, app, excluded_paths: Optional[list] = None):
        super().__init__(app)
        self.password = os.environ.get("OPEN_NOTEBOOK_PASSWORD")
        self.excluded_paths = excluded_paths or ["/", "/health", "/docs", "/openapi.json", "/redoc"]
    
    async def dispatch(self, request: Request, call_next):
        # Skip authentication if no password is set
        if not self.password:
            return await call_next(request)
        
        # Skip authentication for excluded paths
        if request.url.path in self.excluded_paths:
            return await call_next(request)
        
        # Skip authentication for CORS preflight requests (OPTIONS)
        if request.method == "OPTIONS":
            return await call_next(request)
        
        # Check authorization header
        auth_header = request.headers.get("Authorization")
        
        if not auth_header:
            return JSONResponse(
                status_code=401,
                content={"detail": "Missing authorization header"},
                headers={"WWW-Authenticate": "Bearer"}
            )
        
        # Expected format: "Bearer {password}"
        try:
            scheme, credentials = auth_header.split(" ", 1)
            if scheme.lower() != "bearer":
                raise ValueError("Invalid authentication scheme")
        except ValueError:
            return JSONResponse(
                status_code=401,
                content={"detail": "Invalid authorization header format"},
                headers={"WWW-Authenticate": "Bearer"}
            )
        
        # Check password
        if credentials != self.password:
            return JSONResponse(
                status_code=401,
                content={"detail": "Invalid password"},
                headers={"WWW-Authenticate": "Bearer"}
            )
        
        # Password is correct, proceed with the request
        response = await call_next(request)
        return response


# Optional: HTTPBearer security scheme for OpenAPI documentation
security = HTTPBearer(auto_error=False)


def check_api_password(credentials: Optional[HTTPAuthorizationCredentials] = None) -> bool:
    """
    Utility function to check API password.
    Can be used as a dependency in individual routes if needed.
    """
    password = os.environ.get("OPEN_NOTEBOOK_PASSWORD")
    
    # No password set, allow access
    if not password:
        return True
    
    # No credentials provided
    if not credentials:
        raise HTTPException(
            status_code=401,
            detail="Missing authorization",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    # Check password
    if credentials.credentials != password:
        raise HTTPException(
            status_code=401,
            detail="Invalid password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    return True