// Copyright 2014 beego Author. All Rights Reserved.
//
// 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 admin

import (
	"fmt"
	"io"
	"log"
	"os"
	"path"
	"runtime"
	"runtime/debug"
	"runtime/pprof"
	"strconv"
	"time"

	"github.com/beego/beego/v2/core/utils"
)

var (
	startTime = time.Now()
	pid       int
)

func init() {
	pid = os.Getpid()
}

// ProcessInput parse input command string
func ProcessInput(input string, w io.Writer) {
	switch input {
	case "lookup goroutine":
		p := pprof.Lookup("goroutine")
		p.WriteTo(w, 2)
	case "lookup heap":
		p := pprof.Lookup("heap")
		p.WriteTo(w, 2)
	case "lookup threadcreate":
		p := pprof.Lookup("threadcreate")
		p.WriteTo(w, 2)
	case "lookup block":
		p := pprof.Lookup("block")
		p.WriteTo(w, 2)
	case "get cpuprof":
		GetCPUProfile(w)
	case "get memprof":
		MemProf(w)
	case "gc summary":
		PrintGCSummary(w)
	}
}

// MemProf record memory profile in pprof
func MemProf(w io.Writer) {
	filename := "mem-" + strconv.Itoa(pid) + ".memprof"
	f, err := utils.OpenFileSecure(filename, os.O_RDWR|os.O_CREATE, 0600)
	if err != nil {
		fmt.Fprintf(w, "create file %s error %s\n", filename, err.Error())
		log.Fatal("record heap profile failed: ", err)
	} else {
		runtime.GC()
		pprof.WriteHeapProfile(f)
		f.Close()
		fmt.Fprintf(w, "create heap profile %s \n", filename)
		_, fl := path.Split(os.Args[0])
		fmt.Fprintf(w, "Now you can use this to check it: go tool pprof %s %s\n", fl, filename)
	}
}

// GetCPUProfile start cpu profile monitor
func GetCPUProfile(w io.Writer) {
	sec := 30
	filename := "cpu-" + strconv.Itoa(pid) + ".pprof"
	f, err := utils.OpenFileSecure(filename, os.O_RDWR|os.O_CREATE, 0600)
	if err != nil {
		fmt.Fprintf(w, "Could not enable CPU profiling: %s\n", err)
		log.Fatal("record cpu profile failed: ", err)
	}
	pprof.StartCPUProfile(f)
	time.Sleep(time.Duration(sec) * time.Second)
	pprof.StopCPUProfile()

	fmt.Fprintf(w, "create cpu profile %s \n", filename)
	_, fl := path.Split(os.Args[0])
	fmt.Fprintf(w, "Now you can use this to check it: go tool pprof %s %s\n", fl, filename)
}

// PrintGCSummary print gc information to io.Writer
func PrintGCSummary(w io.Writer) {
	memStats := &runtime.MemStats{}
	runtime.ReadMemStats(memStats)
	gcstats := &debug.GCStats{PauseQuantiles: make([]time.Duration, 100)}
	debug.ReadGCStats(gcstats)

	printGC(memStats, gcstats, w)
}

func printGC(memStats *runtime.MemStats, gcstats *debug.GCStats, w io.Writer) {
	if gcstats.NumGC > 0 {
		lastPause := gcstats.Pause[0]
		elapsed := time.Since(startTime)
		overhead := float64(gcstats.PauseTotal) / float64(elapsed) * 100
		allocatedRate := float64(memStats.TotalAlloc) / elapsed.Seconds()

		fmt.Fprintf(w, "NumGC:%d Pause:%s Pause(Avg):%s Overhead:%3.2f%% Alloc:%s Sys:%s Alloc(Rate):%s/s Histogram:%s %s %s \n",
			gcstats.NumGC,
			utils.ToShortTimeFormat(lastPause),
			utils.ToShortTimeFormat(avg(gcstats.Pause)),
			overhead,
			toH(memStats.Alloc),
			toH(memStats.Sys),
			toH(uint64(allocatedRate)),
			utils.ToShortTimeFormat(gcstats.PauseQuantiles[94]),
			utils.ToShortTimeFormat(gcstats.PauseQuantiles[98]),
			utils.ToShortTimeFormat(gcstats.PauseQuantiles[99]))
	} else {
		// while GC has disabled
		elapsed := time.Since(startTime)
		allocatedRate := float64(memStats.TotalAlloc) / elapsed.Seconds()

		fmt.Fprintf(w, "Alloc:%s Sys:%s Alloc(Rate):%s/s\n",
			toH(memStats.Alloc),
			toH(memStats.Sys),
			toH(uint64(allocatedRate)))
	}
}

func avg(items []time.Duration) time.Duration {
	var sum time.Duration
	for _, item := range items {
		sum += item
	}
	return time.Duration(int64(sum) / int64(len(items)))
}

// toH format bytes number friendly
func toH(bytes uint64) string {
	switch {
	case bytes < 1024:
		return fmt.Sprintf("%dB", bytes)
	case bytes < 1024*1024:
		return fmt.Sprintf("%.2fK", float64(bytes)/1024)
	case bytes < 1024*1024*1024:
		return fmt.Sprintf("%.2fM", float64(bytes)/1024/1024)
	default:
		return fmt.Sprintf("%.2fG", float64(bytes)/1024/1024/1024)
	}
}
