// Licensed to the LF AI & Data foundation 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 grpcproxy

import (
	"context"
	"strconv"
	"strings"
	"time"

	"google.golang.org/grpc"

	"github.com/milvus-io/milvus/pkg/v3/metrics"
	"github.com/milvus-io/milvus/pkg/v3/mlog"
	"github.com/milvus-io/milvus/pkg/v3/util/conc"
	"github.com/milvus-io/milvus/pkg/v3/util/merr"
	"github.com/milvus-io/milvus/pkg/v3/util/paramtable"
	"github.com/milvus-io/milvus/pkg/v3/util/requestutil"
	"github.com/milvus-io/milvus/pkg/v3/util/typeutil"
)

var (
	fullMethodName2Tag *typeutil.ConcurrentMap[string, string]
	sf                 conc.Singleflight[string]
)

func init() {
	fullMethodName2Tag = typeutil.NewConcurrentMap[string, string]()
}

// UnaryRequestStatsInterceptor implements `grpc.UnaryServerInterceptor`
// it records incoming grpc request metrics in unified interceptor
//
// when some retirable error occurs, it will record it as `RetryLabel` instead of failure one
// when other interceptor rejects the request, it will record it as `RejectedLabel`
func UnaryRequestStatsInterceptor(ctx context.Context, req any, rpcInfo *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
	methodTag := FullMethodName2Tag(rpcInfo.FullMethod)
	db, _ := requestutil.GetDbNameFromRequest(req)
	collection, _ := requestutil.GetCollectionNameFromRequest(req)

	dbName := db.(string)
	collectionName := collection.(string)

	metrics.ProxyFunctionCall.WithLabelValues(
		strconv.FormatInt(paramtable.GetNodeID(), 10),
		methodTag,
		metrics.TotalLabel,
		metrics.CauseNA,
		dbName,
		collectionName,
	).Inc()

	start := time.Now()
	resp, err := handler(ctx, req)
	label, cause := requestutil.ParseMetricLabel(resp, err)

	// set metrics for state code
	metrics.ProxyFunctionCall.WithLabelValues(
		strconv.FormatInt(paramtable.GetNodeID(), 10),
		methodTag,
		label,
		cause,
		dbName,
		collectionName,
	).Inc()

	// Mirror the metric's cause into the logs so a failed request can be
	// filtered by error_type the same way the metric is. System failures are
	// logged at Warn (actionable for SRE); input failures at Info (expected user
	// mistakes — keeping them at Warn would spam the logs).
	if label == metrics.FailLabel && (cause == metrics.CauseSystem || cause == metrics.CauseUser) {
		status, _ := requestutil.GetStatusFromResponse(resp)
		errType := merr.SystemError
		if cause == metrics.CauseUser {
			errType = merr.InputError
		}
		logger := mlog.With(
			mlog.String("method", methodTag),
			mlog.String("error_type", errType.String()),
			mlog.Int32("code", status.GetCode()),
			mlog.String("reason", status.GetReason()),
		)
		if errType == merr.InputError {
			logger.Info(ctx, "rpc returned an input error")
		} else {
			logger.Warn(ctx, "rpc returned a system error")
		}
	}

	// set metrics for latency
	metrics.ProxyGRPCLatency.WithLabelValues(
		strconv.FormatInt(paramtable.GetNodeID(), 10),
		methodTag,
		label,
		cause,
	).Observe(float64(time.Since(start).Milliseconds()))

	return resp, err
}

// FullMethodName2Tag returns method tag for grpc full method name
// it utilizes `fullMethodName2Tag` as cache result
// if cache miss, it will call `ParseShortMethodName` to parse method tag
// SingleFlight `sf` will make sure there is only one call.
func FullMethodName2Tag(fullMethodName string) string {
	tag, ok := fullMethodName2Tag.Get(fullMethodName)
	if ok {
		return tag
	}

	tag, _, _ = sf.Do(fullMethodName, func() (string, error) {
		tag = ParseShortMethodName(fullMethodName)
		fullMethodName2Tag.Insert(fullMethodName, tag)
		return tag, nil
	})
	return tag
}

// ParseShortMethodName parse short method name from full method name
// input like: "/milvus.proto.milvus.MilvusService/Search"
// returns "Search"
func ParseShortMethodName(fullMethodName string) string {
	parts := strings.Split(fullMethodName, "/")
	return parts[len(parts)-1]
}
