package gupta

import (
	"fmt"
	"strconv"
	"strings"
)

// collect all CPU stat from /proc/cpustat
type CPUStat struct {
	totalTime    float64
	idleTime     float64
	totalTimeNew float64
	idleTimeNew  float64
}

func (c *CPUStat) ReadInfoNew(statline string) {
	rawInfo := strings.Fields(statline)
	idleNew, _ := strconv.ParseFloat(rawInfo[4], 10)
	iowaitNew, _ := strconv.ParseFloat(rawInfo[5], 10)
	c.idleTimeNew = idleNew + iowaitNew
	for _, s := range rawInfo {
		u, _ := strconv.ParseFloat(s, 10)
		c.totalTimeNew += u
	}
}

func (c *CPUStat) ReadInfo(statline string) {
	rawInfo := strings.Fields(statline)
	for _, s := range rawInfo[1:] {
		u, _ := strconv.ParseFloat(s, 10)
		c.totalTime += u
	}
	idle, _ := strconv.ParseFloat(rawInfo[4], 10)
	iowait, _ := strconv.ParseFloat(rawInfo[5], 10)
	c.idleTime = idle + iowait
}

func (c *CPUStat) CPUUsage() float64 {
	deltaIdleTime := c.idleTimeNew - c.idleTime
	deltaTotalTime := c.totalTimeNew - c.totalTime
	cpuUsage := (1.0 - float64(deltaIdleTime)/float64(deltaTotalTime)) * 100
	return cpuUsage
}

func NewCPUStat(procstatline, procstatlineNew string) CPUStat {
	cpustat := CPUStat{}

	cpustat.ReadInfo(procstatline)
	cpustat.ReadInfoNew(procstatlineNew)
	return cpustat
}

func (c CPUStat) MarshalJSON() ([]byte, error) {
	jsonData := []byte(
		fmt.Sprintf("{\"cpu usage\": \"%.2f%%\"}", c.CPUUsage()))
	return jsonData, nil
}