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// Package opt implements command-line flag parsing.
package opt // import "modernc.org/opt"
import (
"fmt"
"strings"
)
type opt struct {
handler func(opt, arg string) error
name string
arg bool // Enable argument, e.g. `-I foo` or `-I=foo`
}
// A Set represents a set of defined options.
type Set struct {
cfg map[string]*opt
imm []*opt
}
// NewSet returns a new, empty option set.
func NewSet() *Set { return &Set{cfg: map[string]*opt{}} }
// Opt defines a simple option, e.g. `-f`. When the option is found during
// Parse, the handler is called with the value of the option, e.g. "-f".
func (p *Set) Opt(name string, handler func(opt string) error) {
p.cfg[name] = &opt{
handler: func(opt, arg string) error { return handler(opt) },
}
}
// Arg defines a simple option with an argument, e.g. `-I foo` or `-I=foo`.
// Setting imm argument enables additionally `-Ifoo`. When the option is found
// during Parse, the handler is called with the values of the option and the
// argument, e.g. "-I" and "foo" for all of the variants.
func (p *Set) Arg(name string, imm bool, handler func(opt, arg string) error) {
switch {
case imm:
p.imm = append(p.imm, &opt{
handler: handler,
name: name,
})
default:
p.cfg[name] = &opt{
arg: true,
handler: handler,
name: name,
}
}
}
// Parse parses opts. Must be called after all options are defined. The handler
// is called for all items in opts that were not defined before using Opt or
// Arg.
//
// If any handler returns a non-nil error, Parse will stop. If the error is of
// type Skip, the error returned by Parse will contain all the unprocessed
// items of opts.
//
// The opts slice must not be modified by any handler while Parser is
// executing.
func (p *Set) Parse(opts []string, handler func(string) error) (err error) {
defer func() {
switch err.(type) {
case Skip:
err = Skip(opts)
}
}()
for len(opts) != 0 {
opt := opts[0]
opt0 := opt
opts = opts[1:]
var arg string
out:
switch {
case strings.HasPrefix(opt, "-"):
name := opt[1:]
for _, cfg := range p.imm {
if strings.HasPrefix(name, cfg.name) {
switch {
case name == cfg.name:
if len(opts) == 0 {
return fmt.Errorf("missing argument of %s", opt)
}
if err = cfg.handler(opt, opts[0]); err != nil {
return err
}
opts = opts[1:]
default:
opt = opt[:len(cfg.name)+1]
val := strings.TrimPrefix(name[len(cfg.name):], "=")
if err = cfg.handler(opt, val); err != nil {
return err
}
}
break out
}
}
if n := strings.IndexByte(opt, '='); n > 0 {
arg = opt[n+1:]
name = opt[1:n]
opt = opt[:n]
}
switch cfg := p.cfg[name]; {
case cfg == nil:
if err = handler(opt0); err != nil {
return err
}
default:
switch {
case cfg.arg:
switch {
case arg != "":
if err = cfg.handler(opt, arg); err != nil {
return err
}
default:
if len(opts) == 0 {
return fmt.Errorf("missing argument of %s", opt)
}
if err = cfg.handler(opt, opts[0]); err != nil {
return err
}
opts = opts[1:]
}
default:
if err = cfg.handler(opt, ""); err != nil {
return err
}
}
}
default:
if opt == "" {
break
}
if err = handler(opt); err != nil {
return err
}
}
}
return nil
}
// Skip is an error that contains all unprocessed items passed to Parse.
type Skip []string
func (s Skip) Error() string { return fmt.Sprint([]string(s)) }
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