package toolbox

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

var startTime = time.Now()
var pid int

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

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 "start cpuprof":
		StartCPUProfile()
	case "stop cpuprof":
		StopCPUProfile()
	case "get memprof":
		MemProf()
	case "gc summary":
		PrintGCSummary(w)
	}
}

func MemProf() {
	if f, err := os.Create("mem-" + strconv.Itoa(pid) + ".memprof"); err != nil {
		log.Fatal("record memory profile failed: %v", err)
	} else {
		runtime.GC()
		pprof.WriteHeapProfile(f)
		f.Close()
	}
}

func StartCPUProfile() {
	f, err := os.Create("cpu-" + strconv.Itoa(pid) + ".pprof")
	if err != nil {
		log.Fatal(err)
	}
	pprof.StartCPUProfile(f)
}

func StopCPUProfile() {
	pprof.StopCPUProfile()
}

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.Now().Sub(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,
			toS(lastPause),
			toS(avg(gcstats.Pause)),
			overhead,
			toH(memStats.Alloc),
			toH(memStats.Sys),
			toH(uint64(allocatedRate)),
			toS(gcstats.PauseQuantiles[94]),
			toS(gcstats.PauseQuantiles[98]),
			toS(gcstats.PauseQuantiles[99]))
	} else {
		// while GC has disabled
		elapsed := time.Now().Sub(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)))
}

// human readable format
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)
	}
}

// short string format
func toS(d time.Duration) string {

	u := uint64(d)
	if u < uint64(time.Second) {
		switch {
		case u == 0:
			return "0"
		case u < uint64(time.Microsecond):
			return fmt.Sprintf("%.2fns", float64(u))
		case u < uint64(time.Millisecond):
			return fmt.Sprintf("%.2fus", float64(u)/1000)
		default:
			return fmt.Sprintf("%.2fms", float64(u)/1000/1000)
		}
	} else {
		switch {
		case u < uint64(time.Minute):
			return fmt.Sprintf("%.2fs", float64(u)/1000/1000/1000)
		case u < uint64(time.Hour):
			return fmt.Sprintf("%.2fm", float64(u)/1000/1000/1000/60)
		default:
			return fmt.Sprintf("%.2fh", float64(u)/1000/1000/1000/60/60)
		}
	}

}