package z

import (
  "os/user"
  "os/exec"
  "bytes"
  "regexp"
  "strconv"
  "strings"
  "time"
  "math"
  "errors"
)


const (
  TFAbsTwelveHour int = 0
  TFAbsTwentyfourHour int = 1
  TFRelHourMinute int = 2
  TFRelHourFraction int = 3
)

func TimeFormats() []string {
  return []string{
    `^\d{1,2}:\d{1,2}(am|pm)$`, // Absolute twelve hour format
    `^\d{1,2}:\d{1,2}$`, // Absolute twenty four hour format
    `^([+-])(\d{1,2}):(\d{1,2})$`, // Relative hour:minute format
    `^([+-])(\d{1,2})\.(\d{1,2})$`, // Relative hour.fraction format
  }
}

func GetCurrentUser() (string) {
  user, err := user.Current()
  if err != nil {
    return "unknown"
  }

  return user.Username
}

func GetTimeFormat(timeStr string) (int) {
  var matched bool
  var regerr error

  for timeFormatId, timeFormat := range TimeFormats() {
    matched, regerr = regexp.MatchString(timeFormat, timeStr)
    if regerr != nil {
      return -1
    }

    if matched == true {
      return timeFormatId
    }
  }

  return -1
}

// TODO: Use https://golang.org/pkg/time/#ParseDuration
func RelToTime(timeStr string, ftId int) (time.Time, error) {
    var re = regexp.MustCompile(TimeFormats()[ftId])
    gm := re.FindStringSubmatch(timeStr)

    if len(gm) < 4 {
      return time.Now(), errors.New("No match")
    }

    var hours int = 0
    var minutes int = 0

    if ftId == TFRelHourFraction {
      f, _ := strconv.ParseFloat(gm[2] + "." + gm[3], 32)
      minutes = int(f * 60.0)
    } else {
      hours, _ = strconv.Atoi(gm[2])
      minutes, _ = strconv.Atoi(gm[3])
    }

    var t time.Time

    switch gm[1] {
    case "+":
      t = time.Now().Local().Add(time.Hour * time.Duration(hours) + time.Minute * time.Duration(minutes))
    case "-":
      t = time.Now().Local().Add((time.Hour * time.Duration(hours) + time.Minute * time.Duration(minutes)) * -1)
    }

    return t, nil
}

func ParseTime(timeStr string) (time.Time, error) {
  tfId := GetTimeFormat(timeStr)

  t:= time.Now()

  switch tfId {
  case TFAbsTwelveHour:
    tadj, err := time.Parse("3:04pm", timeStr)
    tnew := time.Date(t.Year(), t.Month(), t.Day(), tadj.Hour(), tadj.Minute(), t.Second(), t.Nanosecond(), t.Location())
    return tnew, err
  case TFAbsTwentyfourHour:
    tadj, err := time.Parse("15:04", timeStr)
    tnew := time.Date(t.Year(), t.Month(), t.Day(), tadj.Hour(), tadj.Minute(), t.Second(), t.Nanosecond(), t.Location())
    return tnew, err
  case TFRelHourMinute, TFRelHourFraction:
    return RelToTime(timeStr, tfId)
  default:
    return time.Now(), errors.New("could not match passed time")
  }
}

func GetIdFromName(name string) string {
  reg, regerr := regexp.Compile("[^a-zA-Z0-9]+")
  if regerr != nil {
      return ""
  }

  id := strings.ToLower(reg.ReplaceAllString(name, ""))

  return id
}

func GetISOCalendarWeek(date time.Time) (int) {
  var _, cw = date.ISOWeek()
  return cw
}

func GetISOWeekInMonth(date time.Time) (month int, weeknumber int) {
  if date.IsZero() {
    return -1, -1
  }

  newDay := (date.Day() - int(date.Weekday()) + 1)
  addDay := (date.Day() - newDay) * -1
  changedDate := date.AddDate(0, 0, addDay)

  return int(changedDate.Month()), int(math.Ceil(float64(changedDate.Day()) / 7.0));
}

func GetGitLog(repo string, since time.Time, until time.Time) (string, string, error) {
  var stdout, stderr bytes.Buffer
  cmd := exec.Command("git", "-C", repo, "config", "user.name")
  cmd.Stdout = &stdout
  cmd.Stderr = &stderr
  err := cmd.Run()
  if err != nil {
      return "", "", err
  }
  gitUserStr, gitUserErrStr := string(stdout.Bytes()), string(stderr.Bytes())
  if gitUserStr == "" && gitUserErrStr != "" {
    return gitUserStr, gitUserErrStr, errors.New(gitUserErrStr)
  }

  stdout.Reset()
  stderr.Reset()

  cmd = exec.Command("git", "-C", repo, "log", "--author", gitUserStr, "--since", since.Format("2006-01-02T15:04:05-0700"), "--until", until.Format("2006-01-02T15:04:05-0700"), "--pretty=oneline")
  cmd.Stdout = &stdout
  cmd.Stderr = &stderr
  err = cmd.Run()
  if err != nil {
      return "", "", err
  }

  stdoutStr, stderrStr := string(stdout.Bytes()), string(stderr.Bytes())
  return stdoutStr, stderrStr, nil
}