"""FlowDeck — CSRF protection middleware."""
from __future__ import annotations

import secrets

from starlette.middleware.base import BaseHTTPMiddleware
from starlette.requests import Request
from starlette.responses import JSONResponse


class CSRFMiddleware(BaseHTTPMiddleware):
    """Lightweight CSRF protection for state-changing requests.

    All POST/PUT/PATCH/DELETE requests must include X-CSRF-Token
    header matching the csrf_token cookie.
    """

    SAFE_METHODS = {"GET", "HEAD", "OPTIONS"}
    # NOTE: ``/scim/v2`` is Bearer-token only (no cookie auth), so CSRF does not
    # apply — IdP SCIM clients (Okta, Entra) cannot send an X-CSRF-Token.
    # A19 : le CSRF ne s'exempte plus que pour ce qui ne dépend PAS d'un cookie de
    # session (Bearer, webhooks entrants, callbacks OAuth/SSO, pages publiques,
    # probe d'infra, remontée d'erreur client).
    # Retirés après scan du front (tous les appels non-GET envoient déjà
    # `X-CSRF-Token`) : /db/, /workspace, /workspace/automations,
    # /board/api/favorites, /api/pages, /api/recents, /api/notifications,
    # /api/comments, /api/automations, /api/github, /api/admin, /api/onboarding.
    # Reste A19 (front à équiper d'abord) : /api/workspace (couvre aussi
    # /api/workspaces), /api/local-workspace, /api/settings, /api/gitea, /api/agent.
    EXCLUDED_PATHS = {
        "/api/webhook", "/api/v1", "/api/v2", "/scim/v2",
        "/auth/callback", "/auth/register", "/auth/local-login", "/auth/local-verify",
        "/auth/2fa", "/auth/saml", "/auth/oidc", "/auth/webauthn",
        "/s/", "/f/", "/api/frontend-error", "/api/csrf-token",
        "/api/workspace", "/api/local-workspace", "/api/settings", "/api/gitea", "/api/agent",
    }

    async def dispatch(self, request: Request, call_next):
        # Webhook receiver, OAuth callback, and internal API are exempt
        if any(request.url.path.startswith(p) for p in self.EXCLUDED_PATHS):
            return await call_next(request)

        if request.method in self.SAFE_METHODS:
            response = await call_next(request)
            # Set CSRF cookie if not present
            if "csrf_token" not in request.cookies:
                response.set_cookie(
                    "csrf_token",
                    secrets.token_hex(32),
                    httponly=False,  # Must be readable by JS
                    samesite="lax",
                    max_age=86400,
                    path="/",
                )
            return response

        # Validate CSRF for state-changing methods
        csrf_cookie = request.cookies.get("csrf_token", "")
        csrf_header = request.headers.get("X-CSRF-Token", "")

        if not csrf_cookie or not csrf_header or not secrets.compare_digest(csrf_cookie, csrf_header):
            return JSONResponse(
                {"detail": "CSRF validation failed"},
                status_code=403,
            )

        return await call_next(request)