package process

import (
	"encoding/json"
	"runtime"
	"time"

	"github.com/shirou/gopsutil/cpu"
	"github.com/shirou/gopsutil/internal/common"
	"github.com/shirou/gopsutil/mem"
)

var invoke common.Invoker

func init() {
	invoke = common.Invoke{}
}

type Process struct {
	Pid            int32 `json:"pid"`
	name           string
	status         string
	parent         int32
	numCtxSwitches *NumCtxSwitchesStat
	uids           []int32
	gids           []int32
	numThreads     int32
	memInfo        *MemoryInfoStat

	lastCPUTimes *cpu.TimesStat
	lastCPUTime  time.Time
}

type OpenFilesStat struct {
	Path string `json:"path"`
	Fd   uint64 `json:"fd"`
}

type MemoryInfoStat struct {
	RSS  uint64 `json:"rss"`  // bytes
	VMS  uint64 `json:"vms"`  // bytes
	Swap uint64 `json:"swap"` // bytes
}

type RlimitStat struct {
	Resource int32 `json:"resource"`
	Soft     int32 `json:"soft"`
	Hard     int32 `json:"hard"`
}

type IOCountersStat struct {
	ReadCount  uint64 `json:"readCount"`
	WriteCount uint64 `json:"writeCount"`
	ReadBytes  uint64 `json:"readBytes"`
	WriteBytes uint64 `json:"writeBytes"`
}

type NumCtxSwitchesStat struct {
	Voluntary   int64 `json:"voluntary"`
	Involuntary int64 `json:"involuntary"`
}

// Resource limit constants are from /usr/include/x86_64-linux-gnu/bits/resource.h
// from libc6-dev package in Ubuntu 16.10
const (
	RLIMIT_CPU        int32 = 0
	RLIMIT_FSIZE      int32 = 1
	RLIMIT_DATA       int32 = 2
	RLIMIT_STACK      int32 = 3
	RLIMIT_CORE       int32 = 4
	RLIMIT_RSS        int32 = 5
	RLIMIT_NPROC      int32 = 6
	RLIMIT_NOFILE     int32 = 7
	RLIMIT_MEMLOCK    int32 = 8
	RLIMIT_AS         int32 = 9
	RLIMIT_LOCKS      int32 = 10
	RLIMIT_SIGPENDING int32 = 11
	RLIMIT_MSGQUEUE   int32 = 12
	RLIMIT_NICE       int32 = 13
	RLIMIT_RTPRIO     int32 = 14
	RLIMIT_RTTIME     int32 = 15
)

func (p Process) String() string {
	s, _ := json.Marshal(p)
	return string(s)
}

func (o OpenFilesStat) String() string {
	s, _ := json.Marshal(o)
	return string(s)
}

func (m MemoryInfoStat) String() string {
	s, _ := json.Marshal(m)
	return string(s)
}

func (r RlimitStat) String() string {
	s, _ := json.Marshal(r)
	return string(s)
}

func (i IOCountersStat) String() string {
	s, _ := json.Marshal(i)
	return string(s)
}

func (p NumCtxSwitchesStat) String() string {
	s, _ := json.Marshal(p)
	return string(s)
}

func PidExists(pid int32) (bool, error) {
	pids, err := Pids()
	if err != nil {
		return false, err
	}

	for _, i := range pids {
		if i == pid {
			return true, err
		}
	}

	return false, err
}

// If interval is 0, return difference from last call(non-blocking).
// If interval > 0, wait interval sec and return diffrence between start and end.
func (p *Process) Percent(interval time.Duration) (float64, error) {
	cpuTimes, err := p.Times()
	if err != nil {
		return 0, err
	}
	now := time.Now()

	if interval > 0 {
		p.lastCPUTimes = cpuTimes
		p.lastCPUTime = now
		time.Sleep(interval)
		cpuTimes, err = p.Times()
		now = time.Now()
		if err != nil {
			return 0, err
		}
	} else {
		if p.lastCPUTimes == nil {
			// invoked first time
			p.lastCPUTimes = cpuTimes
			p.lastCPUTime = now
			return 0, nil
		}
	}

	numcpu := runtime.NumCPU()
	delta := (now.Sub(p.lastCPUTime).Seconds()) * float64(numcpu)
	ret := calculatePercent(p.lastCPUTimes, cpuTimes, delta, numcpu)
	p.lastCPUTimes = cpuTimes
	p.lastCPUTime = now
	return ret, nil
}

func calculatePercent(t1, t2 *cpu.TimesStat, delta float64, numcpu int) float64 {
	if delta == 0 {
		return 0
	}
	delta_proc := t2.Total() - t1.Total()
	overall_percent := ((delta_proc / delta) * 100) * float64(numcpu)
	return overall_percent
}

// MemoryPercent returns how many percent of the total RAM this process uses
func (p *Process) MemoryPercent() (float32, error) {
	machineMemory, err := mem.VirtualMemory()
	if err != nil {
		return 0, err
	}
	total := machineMemory.Total

	processMemory, err := p.MemoryInfo()
	if err != nil {
		return 0, err
	}
	used := processMemory.RSS

	return (100 * float32(used) / float32(total)), nil
}
