package runner

import (
    //"errors"
    "bytes"
    "io"
    "fmt"
    "log"
    "os"
    "strings"
    exec "os/exec"
    cgroups "github.com/containerd/cgroups"
    rand "math/rand"
    "time"
)

const runIdLength = 20
var coresIsolated []int

type Limits struct {
    Core    int
    Memory  int
    Time    int
}

func extractNumbers(s string) (result []int) {
    lastNumber,isNumber := false,false
    var curNumber=0
    for _,char :=range s {
        isNumber=(char>='0' && char<='9')
        if(isNumber) {
            curNumber*=10
            curNumber+=int(char-'0')
        }
        if(!isNumber && lastNumber) {
            result=append(result,curNumber)
            curNumber=0
        }
        lastNumber=isNumber
    }
    if(lastNumber) {
        result=append(result,curNumber)
    }
    return
}

func Init() error {
    rand.Seed(time.Now().UnixNano())
    //croup initialisation:
    if cgroups.Mode() == cgroups.Unified {
        log.Println("cgroups v2 usage approved")
    } else {
        return fmt.Errorf("cgroups v2 are not enabled")//TODO: trouble description
    }
    //isolated cores initialisation:
    cmdlineBytes := make([]byte, 400)
    cmdlineFile,_:=os.Open("/proc/cmdline");
    countCmdlineBytes,_:=cmdlineFile.Read(cmdlineBytes);
    cmdline:=string(cmdlineBytes[:countCmdlineBytes])
    kernelParams:=strings.Split(cmdline," ")
    for _,param := range kernelParams{
        if(len(param)>=9 && param[:9]=="isolcpus=") {
            coresIsolated=append(coresIsolated, extractNumbers(param[9:])...)
        }
    }
    if(len(coresIsolated)==0) {
        return fmt.Errorf("no free cores available")//TODO: trouble description
    }
    log.Println("running on cores:",coresIsolated)
    log.Println("Runner initialisation successful!")
    return nil
}

func IsolatedRun(command []string,limits Limits) {
    var runId string
    for i:=0;i<runIdLength;i++{runId+=string('a'+byte(rand.Int31n(26)))}
    os.Mkdir("starter/"+runId,0777)
    //log.Printf("%d",limits.Core)
    //exec.Command("starter/starter", string(limits.Core),string(limits.Memory),string(limits.Time),runId,command...);
    args:=[]string{string(limits.Core),string(limits.Memory),string(limits.Time),runId}
    args=append(args,command...)
    cmd:=exec.Command("/root/runner/starter/starter",args...)
    //cmd:=exec.Command("/usr/bin/echo","123")
    var stdBuffer bytes.Buffer
    mw := io.MultiWriter(os.Stdout, &stdBuffer)
    cmd.Stdout = mw
    err := cmd.Run();
    if err != nil { log.Fatal(err) }
    //log.Println(stdBuffer.String())
    os.RemoveAll("starter/"+runId)
    cmd.Wait()
}