// Copyright 2017 The etcd Authors
//
// Licensed 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"
	"errors"
	"fmt"
	"net/http"
	"time"

	"go.uber.org/zap"

	"go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
	clientv3 "go.etcd.io/etcd/client/v3"
	"go.etcd.io/etcd/server/v3/etcdserver/api/etcdhttp"
)

// HandleHealth registers health handler on '/health'.
func HandleHealth(lg *zap.Logger, mux *http.ServeMux, c *clientv3.Client) {
	if lg == nil {
		lg = zap.NewNop()
	}
	mux.Handle(etcdhttp.PathHealth, etcdhttp.NewHealthHandler(lg, func(ctx context.Context, excludedAlarms etcdhttp.StringSet, serializable bool) etcdhttp.Health {
		return checkHealth(c)
	}))
}

// HandleProxyHealth registers health handler on '/proxy/health'.
func HandleProxyHealth(lg *zap.Logger, mux *http.ServeMux, c *clientv3.Client) {
	if lg == nil {
		lg = zap.NewNop()
	}
	mux.Handle(etcdhttp.PathProxyHealth, etcdhttp.NewHealthHandler(lg, func(ctx context.Context, excludedAlarms etcdhttp.StringSet, serializable bool) etcdhttp.Health {
		return checkProxyHealth(c)
	}))
}

func checkHealth(c *clientv3.Client) etcdhttp.Health {
	h := etcdhttp.Health{Health: "false"}
	ctx, cancel := context.WithTimeout(c.Ctx(), time.Second)
	_, err := c.Get(ctx, "a")
	cancel()
	if err == nil || errors.Is(err, rpctypes.ErrPermissionDenied) {
		h.Health = "true"
	} else {
		h.Reason = fmt.Sprintf("GET ERROR:%s", err)
	}
	return h
}

func checkProxyHealth(c *clientv3.Client) etcdhttp.Health {
	if c == nil {
		return etcdhttp.Health{Health: "false", Reason: "no connection to proxy"}
	}
	h := checkHealth(c)
	if h.Health != "true" {
		return h
	}
	ctx, cancel := context.WithTimeout(c.Ctx(), time.Second*3)
	ch := c.Watch(ctx, "a", clientv3.WithCreatedNotify())
	select {
	case <-ch:
	case <-ctx.Done():
		h.Health = "false"
		h.Reason = "WATCH TIMEOUT"
	}
	cancel()
	return h
}