package runner

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

const runIdLength = 20

type Limits struct {
    Processes int32
    Core      int32
    Memory    int32
    Time      int32
}

const Mib = 1024*1024;
const BuildMemory = 1024*Mib;
const BuildTime = 5000;

type RunnerService struct {
    CoresIsolated []int32
    CoreFreed chan int32
}

func genRunId() (runId string) {
    for i := 0; i < runIdLength; i++ {
        runId += string('a' + byte(rand.Int31n(26)))
    }
    return
}

func int32ToString(n int32) string {
    return fmt.Sprintf("%d", n)
}

func copyFile(src string,dst string) error {
    log.Println(src,dst)
    srcFile,err := os.Open(src)
    if(err!=nil) {return err}
    defer srcFile.Close()
    dstFile,err := os.Create(dst)
    if(err!=nil) {return err}
    defer dstFile.Close()
    _,err = io.Copy(dstFile,srcFile)
    if(err!=nil) {return err}
    err = dstFile.Sync()
    if(err!=nil) {return err}
    return nil
}

func extractNumbers(s string) (result []int32) {
    lastNumber, isNumber := false,false
    var curNumber int32 = 0
    for _, char := range s {
        isNumber = (char >= '0' && char <= '9')
        if(isNumber) {
            curNumber *= 10
            curNumber += int32(char - '0')
        }
        if(!isNumber && lastNumber) {
            result = append(result, curNumber)
            curNumber = 0
        }
        lastNumber = isNumber
    }
    if(lastNumber) {
        result = append(result, curNumber)
    }
    return
}

func NewRunnerService() (*RunnerService, error) {
    runnerService := RunnerService{make([]int32,0),make(chan int32)} 
    rand.Seed(time.Now().UnixNano())
    //croup initialisation:
    if cgroups.Mode() == cgroups.Unified {
        log.Println("cgroups v2 usage approved")
    } else {
        return nil,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=") {
            runnerService.CoresIsolated = append(runnerService.CoresIsolated, extractNumbers(param[9:])...)
        }
    }
    if(len(runnerService.CoresIsolated) == 0) {
        return nil,fmt.Errorf("no free cores available")//TODO: trouble description
    }
    go func() {
        for _,core := range runnerService.CoresIsolated {
            runnerService.CoreFreed <- core
        }
    }()
    log.Println("running on cores:", runnerService.CoresIsolated)
    //runs directory
    os.Mkdir("runs",0777)
    os.Chmod("runs",0777)
    //complete
    log.Println("Runner initialisation successful!")
    return &runnerService,nil
}

func (runnerService RunnerService) Build(buildCmd []string, filename string) {
    core := <-runnerService.CoreFreed
    runId := genRunId()
    err := os.Mkdir("runs/" + runId, 0777)
    if(err!=nil) { log.Fatal(err) }
    os.Chmod("runs/" + runId, 0777)
    copyFile("starter/shared/main.c","runs/"+runId+"/main.c")//FIXME add source and file extension
    runnerService.IsolatedRun([]string{"/usr/bin/gcc","/shared/main.c","-o","/shared/executable","-save-temps=obj"},"../runs/"+runId,Limits{Processes: 10,Core:core,Memory:BuildMemory,Time:BuildTime});
    copyFile("runs/"+runId+"/executable","destination")//FIXME add destination
    os.RemoveAll("runs/" + runId)
    go func() {
        runnerService.CoreFreed <- core
    }()
}

func (runnerService RunnerService) IsolatedRun(command []string, sharedFolder string, limits Limits) {
    args := []string{int32ToString(limits.Processes),int32ToString(limits.Core), int32ToString(limits.Memory), int32ToString(limits.Time), sharedFolder}
    args = append(args, command...)
    log.Println(limits.Processes)
    log.Println(string(limits.Processes))
    log.Println(args)
    cmd := exec.Command("starter/starter", args...)
    var stdBuffer bytes.Buffer
    mw := io.MultiWriter(os.Stdout, &stdBuffer)
    cmd.Stdout = mw
    err := cmd.Run();
    if err != nil {
        log.Println(123)
        log.Println(err)
    }
    //cmd.Wait()
}