converter/cmd/time.go

package cmd

import (
	"fmt"
	"os"
	"strings"
	"time"
	"unicode"

	"github.com/spf13/cobra"
)

var timeCmd = &cobra.Command{
	Use:   "time",
	Short: "gets current time in given city",
	Long:  `gets current time in given city`,
	Args:  cobra.MatchAll(cobra.RangeArgs(1, 2), cobra.OnlyValidArgs),
	ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
		if len(args) == 1 {
			return nil, cobra.ShellCompDirectiveNoFileComp
		}
		return getOsTimeZones(toComplete), cobra.ShellCompDirectiveNoFileComp
	},
	RunE: func(cmd *cobra.Command, args []string) error {
		loc, _ := time.LoadLocation(args[0])
		if len(args) == 2 {
			t, err := time.Parse("03:04PM", args[1])
			if err != nil {
				return err
			}
			fmt.Println(t.In(loc).Format("03:04PM"))
			return nil
		}
		fmt.Println(time.Now().In(loc).Format("03:04PM"))
		return nil
	},
}

func getOsTimeZones(toComplete string) []string {
	var zones []string
	zoneDirs := []string{
		"/usr/share/zoneinfo/",
		"/usr/share/lib/zoneinfo/",
		"/usr/lib/locale/TZ/",
	}

	for _, zd := range zoneDirs {
		zones = walkTzDir(zd, zones)

		for idx, zone := range zones {
			zones[idx] = strings.ReplaceAll(zone, zd+"/", "")
		}
	}

	return zones
}

func isAlpha(s string) bool {
	for _, r := range s {
		if !unicode.IsLetter(r) {
			return false
		}
	}
	return true
}

func walkTzDir(path string, zones []string) []string {
	fileInfos, err := os.ReadDir(path)
	if err != nil {
		return zones
	}

	for _, info := range fileInfos {
		if info.Name() != strings.ToUpper(info.Name()[:1])+info.Name()[1:] {
			continue
		}

		if !isAlpha(info.Name()[:1]) {
			continue
		}

		newPath := path + "/" + info.Name()

		if info.IsDir() {
			zones = walkTzDir(newPath, zones)
		} else {
			zones = append(zones, newPath)
		}
	}
	return zones
}

func init() {
	rootCmd.AddCommand(timeCmd)
}