package io.delphiplatform.api.v3.view.interceptor;

import org.springframework.core.MethodParameter;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class UnknownParamsHandlerInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            if (handlerMethod.hasMethodAnnotation(OnlyDeclaredParams.class)) {
                checkParams(request, getDeclaredRequestParams(handlerMethod));
            }
        }
        return true;
    }

    private void checkParams(HttpServletRequest request, Set<String> allowedParams) {
        List<String> unknownParams = new ArrayList<>();
        request.getParameterMap().forEach((param, value) -> {
            if (!allowedParams.contains(param) && allowedParams.size() > 0) {
                unknownParams.add(param);
            }
        });
        if (!CollectionUtils.isEmpty(unknownParams)) {
            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "Unknown params: " + unknownParams);
        }
    }

    private Set<String> getDeclaredRequestParams(HandlerMethod handlerMethod) {
        Set<String> declaredRequestParams = new HashSet<>();
        MethodParameter[] methodParameters = handlerMethod.getMethodParameters();

        for (MethodParameter methodParameter : methodParameters) {
            if (methodParameter.hasParameterAnnotation(RequestParam.class)) {
                RequestParam requestParam = methodParameter.getParameterAnnotation(RequestParam.class);
                if (requestParam != null) {
                    if (StringUtils.hasText(requestParam.value())) {
                        declaredRequestParams.add(requestParam.value());
                    }
                }
            }
        }
        return declaredRequestParams;
    }

}