cmd/opts/parser.go

package opts

import (
	"errors"
	"fmt"
	"strings"
)

var (
	ErrInvalidShortOption = errors.New("invalid short option")
	ErrCannotChainOption  = errors.New("cannot chain option as it takes an argument")
)

func (s Set) Parse(args []string) (restArgs []string, err error) {
	for i := 0; i < len(args); i++ {
		arg := args[i]

		// Handle regular argument
		if !strings.HasPrefix(arg, "-") {
			restArgs = append(restArgs, arg)
			continue
		}

		// Handle options terminator
		if arg == "--" {
			restArgs = append(restArgs, args[i+1:]...)
			return
		}

		// Handle long option
		if strings.HasPrefix(arg, "--") {
			longName := arg[2:]
			value := ""

			equals := strings.Index(longName, "=")
			if equals > 0 {
				longName = longName[:equals]
				value = longName[equals+1:]
			} else if i < len(args)-1 && !strings.HasPrefix(args[i+1], "-") {
				value = args[i+1]
				i++
			}

			parsed := false
			for _, opt := range s {
				if opt.Name() != longName {
					continue
				}

				if err = opt.Parse(value); err != nil {
					return
				}

				parsed = true
				break
			}

			if !parsed {
				restArgs = append(restArgs, arg)
			}

			continue
		}

		// Handle short option
		shortNames := arg[1:]
		if len(shortNames) == 0 {
			err = ErrInvalidShortOption
		} else if len(shortNames) == 1 {
			parsed := false
			value := ""
			if i < len(args)-1 && !strings.HasPrefix(args[i+1], "-") {
				value = args[i+1]
				i++
			}

			for _, opt := range s {
				if opt.ShortName() != shortNames {
					continue
				}

				if err = opt.Parse(value); err != nil {
					return
				}

				parsed = true
				break
			}

			if !parsed {
				restArgs = append(restArgs, arg)
			}
		} else {
			for j := 0; j < len(shortNames); j++ {
				shortName := shortNames[j]
				value := ""
				takesValue := false
				parsed := false

				for _, opt := range s {
					if opt.ShortName() != string(shortName) {
						continue
					}

					if opt.TakesArg() {
						if j > 0 {
							err = ErrCannotChainOption
							return
						}

						takesValue = true
						value = shortNames[j+1:]
						value = strings.TrimPrefix(value, "=")
						if len(value) == 0 && i < len(args)-1 && !strings.HasPrefix(args[i+1], "-") {
							value = args[i+1]
							i++
						}
						j = len(shortNames)
					}

					parsed = true

					if err = opt.Parse(value); err != nil {
						return
					}

					break
				}

				if !parsed {
					if takesValue {
						restArgs = append(restArgs, arg)
						break
					} else {
						restArgs = append(restArgs, fmt.Sprintf("-%c", shortName))
					}
				}
			}
		}
	}

	return
}