converter/cmd/temp.go

package cmd

import (
	"fmt"
	"strconv"
	"strings"

	u "github.com/bcicen/go-units"
	"github.com/spf13/cobra"
)

var (
	from           string
	to             string
	five_over_nine = float64(5) / float64(9)
	nine_over_five = float64(9) / float64(5)
	kconst         = 273.15
	rconst         = 459.67
	tempCmd        = &cobra.Command{
		Use:   "temp",
		Short: "A brief description of your command",
		Long: `A longer description that spans multiple lines and likely contains examples
and usage of using your command. For example:

Cobra is a CLI library for Go that empowers applications.
This application is a tool to generate the needed files
to quickly create a Cobra application.`,
		Args: cobra.MatchAll(cobra.ExactArgs(1)),
		RunE: func(cmd *cobra.Command, args []string) error {
			err := cmd.ParseFlags(args)
			if err != nil {
				return err
			}
			in, err := strconv.ParseFloat(args[0], 64)
			if err != nil {
				return err
			}
			fromFlag := strings.ToLower(cmd.Flag("from").Value.String())
			toFlag := strings.ToLower(cmd.Flag("to").Value.String())
			var out u.Value
			switch fromFlag {
			case "f", "farenheit":
				out, err = Convert(in, toFlag, u.Fahrenheit)
				if err != nil {
					return err
				}
			case "c", "celsius":
				out, err = Convert(in, toFlag, u.Celsius)
				if err != nil {
					return err
				}
			case "k", "kelvin":
				out, err = Convert(in, toFlag, u.Kelvin)
				if err != nil {
					return err
				}
			}
			fmt.Println(out.String())
			return nil
		},
	}
)

func Convert(in float64, to string, from u.Unit) (u.Value, error) {
	switch to {
	case "f", "farenheit":
		return u.ConvertFloat(in, from, u.Fahrenheit)
	case "c", "celsius":
		return u.ConvertFloat(in, from, u.Celsius)
	case "k", "kelvin":
		return u.ConvertFloat(in, from, u.Kelvin)
	}
	return u.Value{}, fmt.Errorf("Invalid flags provided")
}

func init() {
	rootCmd.AddCommand(tempCmd)
	tempCmd.PersistentFlags().StringVarP(&from, "from", "f", "c", "unit system to convert from, (farenheit, celsius, kelvin)")
	tempCmd.PersistentFlags().StringVarP(&to, "to", "t", "f", "unit system to convert to, (farenheit, celsius, kelvin)")
}