package metric

import (
	"crypto/md5"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"path"
	"runtime"
	"sort"
	"strings"
	"sync/atomic"

	"repositories.action2quare.com/ayo/gocommon/logger"
)

type MetricDescription struct {
	Key         string
	Type        MetricType
	Name        string            `json:",omitempty"`
	Help        string            `json:",omitempty"`
	ConstLabels map[string]string `json:",omitempty"`
}

type Exporter interface {
	RegisterMetric(*MetricDescription)
	UpdateMetric(string, float64)
}

type MetricPipe struct {
	pipe *os.File
}

func (mp MetricPipe) Close() {
	if mp.pipe != nil {
		mp.pipe.Close()
		mp.pipe = nil
	}
}

func (mp MetricPipe) writeLine(line string) {
	mp.pipe.WriteString(line + "\n")
}

func NewMetricPipe(pipeName string) MetricPipe {
	switch runtime.GOOS {
	case "linux":
		pipeName = "/tmp/" + pipeName
	case "windows":
		pipeName = `\\.\pipe\` + pipeName
	}

	f, _ := os.Open(pipeName)
	return MetricPipe{
		pipe: f,
	}
}

type MetricWriter interface {
	Add(int64)
	Set(int64)
}

type metric_empty struct{}

func (mw *metric_empty) Set(int64) {}
func (mw *metric_empty) Add(int64) {}

var MetricWriterNil = MetricWriter(&metric_empty{})

type metric_int64 struct {
	key    string
	valptr *int64
	pipe   MetricPipe
}

func (mw *metric_int64) printOut() {
	loaded := atomic.LoadInt64(mw.valptr)
	mw.pipe.writeLine(fmt.Sprintf("%s:%d", mw.key, loaded))
}

func (mw *metric_int64) Set(newval int64) {
	atomic.StoreInt64(mw.valptr, newval)
	mw.printOut()
}

func (mw *metric_int64) Add(inc int64) {
	atomic.AddInt64(mw.valptr, inc)
	mw.printOut()
}

func NewMetric(pipe MetricPipe, mt MetricType, name string, help string, constLabels map[string]string) (writer MetricWriter) {
	if !metricEnabled {
		return MetricWriterNil
	}

	if constLabels == nil {
		constLabels = map[string]string{}
	}

	constLabels["pid"] = fmt.Sprintf("%d", os.Getpid())
	var disorder []struct {
		k string
		v string
	}
	for k, v := range constLabels {
		disorder = append(disorder, struct {
			k string
			v string
		}{k: strings.ToLower(k), v: strings.ToLower(v)})
	}

	sort.Slice(disorder, func(i, j int) bool {
		return disorder[i].k < disorder[j].k
	})

	hash := md5.New()
	hash.Write([]byte(strings.ToLower(name)))
	for _, d := range disorder {
		hash.Write([]byte(d.k))
		hash.Write([]byte(d.v))
	}

	key := hex.EncodeToString(hash.Sum(nil))[:metric_key_size]
	temp, _ := json.Marshal(MetricDescription{
		Key:         key,
		Type:        mt,
		Name:        name,
		Help:        help,
		ConstLabels: constLabels,
	})

	impl := &metric_int64{
		key:    key,
		valptr: new(int64),
		pipe:   pipe,
	}

	pipe.writeLine(string(temp))
	// writer

	return impl
}

var metricEnabled = false

func init() {
	if path.Base(os.Args[0]) == "houston" {
		logger.Println("metrics are going to be generated for myself(houston)")
		metricEnabled = true
		return
	}

	ppid := os.Getppid()
	if parent, _ := os.FindProcess(ppid); parent != nil {
		filename := fmt.Sprintf(`/proc/%d/stat`, os.Getppid())
		if fn, err := os.ReadFile(filename); err == nil {
			stats := strings.SplitN(string(fn), " ", 3)
			parentname := strings.Trim(stats[1], "()")

			if path.Base(parentname) == "houston" {
				logger.Println("metrics are going to be generated for houston")
				metricEnabled = true
			} else {
				logger.Println("metrics are NOT going to be generated. parent is not houston :", filename, string(fn))
			}
		} else {
			logger.Println("metrics are NOT going to be generated. ppid proc is missing :", filename)
		}
	} else {
		logger.Println("metrics are NOT going to be generated. parent process is missing. ppid :", ppid)
	}
}