/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
Package tps provides a filter for limiting the requests by TPS.

	if you wish to use the TpsLimiter, please add the configuration into your service provider configuration:
	for example:
	"UserProvider":
	  registry: "hangzhouzk"
	  protocol : "dubbo"
	  interface : "com.ikurento.user.UserProvider"
	  ... # other configuration
	  tps.limiter: "method-service", # it should be the name of limiter. if the value is 'default',
	                                 # the MethodServiceTpsLimiter will be used.
	  tps.limit.rejected.handler: "default", # optional, or the name of the implementation
	  if the value of 'tps.limiter' is nil or empty string, the tps filter will do nothing
*/
package tps

import (
	"context"
	"sync"
)

import (
	"github.com/dubbogo/gost/log/logger"
)

import (
	"dubbo.apache.org/dubbo-go/v3/common/constant"
	"dubbo.apache.org/dubbo-go/v3/common/extension"
	"dubbo.apache.org/dubbo-go/v3/filter"
	_ "dubbo.apache.org/dubbo-go/v3/filter/handler"
	_ "dubbo.apache.org/dubbo-go/v3/filter/tps/limiter"
	"dubbo.apache.org/dubbo-go/v3/protocol"
)

var (
	once     sync.Once
	tpsLimit *tpsLimitFilter
)

func init() {
	extension.SetFilter(constant.TpsLimitFilterKey, newTpsLimitFilter)
}

type tpsLimitFilter struct{}

func newTpsLimitFilter() filter.Filter {
	if tpsLimit == nil {
		once.Do(func() {
			tpsLimit = &tpsLimitFilter{}
		})
	}
	return tpsLimit
}

// Invoke gets the configured limter to impose TPS limiting
func (t *tpsLimitFilter) Invoke(ctx context.Context, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
	url := invoker.GetURL()
	tpsLimiter := url.GetParam(constant.TPSLimiterKey, "")
	rejectedExeHandler := url.GetParam(constant.TPSRejectedExecutionHandlerKey, constant.DefaultKey)
	if len(tpsLimiter) > 0 {
		limiter, err := extension.GetTpsLimiter(tpsLimiter)
		if err != nil {
			logger.Warn(err)
			return invoker.Invoke(ctx, invocation)
		}
		allow := limiter.IsAllowable(invoker.GetURL(), invocation)
		if allow {
			return invoker.Invoke(ctx, invocation)
		}
		logger.Errorf("The invocation was rejected due to over the limiter limitation, url: %s ", url.String())
		rejectedExecutionHandler, err := extension.GetRejectedExecutionHandler(rejectedExeHandler)
		if err != nil {
			logger.Warn(err)
		} else {
			return rejectedExecutionHandler.RejectedExecution(url, invocation)
		}
	}
	return invoker.Invoke(ctx, invocation)
}

// OnResponse dummy process, returns the result directly
func (t *tpsLimitFilter) OnResponse(_ context.Context, result protocol.Result, _ protocol.Invoker,
	_ protocol.Invocation) protocol.Result {
	return result
}