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|
package opts
import (
"fmt"
"reflect"
"strconv"
"strings"
)
type Kind = reflect.Kind
const (
Bool = reflect.Bool
Int = reflect.Int
String = reflect.String
)
type Param struct {
Name string
Kind Kind
Default string
Required bool
Positive bool
index []int
}
type Opts map[string]string
func Parse(s string) (string, Opts) {
v := strings.Split(s, ",")
m := map[string]string{}
for _, t := range v[1:] {
kv := strings.SplitN(t, "=", 2)
if len(kv) < 2 {
m[kv[0]] = ""
} else {
m[kv[0]] = kv[1]
}
}
return v[0], m
}
func (opts Opts) Bool(key string) bool {
_, ok := opts[key]
return ok
}
func extract(i interface{}) (reflect.Value, error) {
v := reflect.ValueOf(i)
var err error
switch {
case v.Kind() != reflect.Ptr:
err = fmt.Errorf("non-pointer %s", v.Type().String())
case v.IsNil():
err = fmt.Errorf("nil %s", v.Type().String())
case v.Elem().Kind() != reflect.Struct:
err = fmt.Errorf("non-struct %s", v.Elem().Type().String())
}
if err != nil {
return reflect.Value{}, err
}
return v.Elem(), nil
}
func (opts Opts) Configure(i interface{}) error {
v, err := extract(i)
if err != nil {
return fmt.Errorf("opts: configure failed: %w", err)
}
return opts.configure(v)
}
func (p *Param) parseTags(tags string) {
for _, s := range strings.Split(tags, ",") {
switch {
case s == "required":
p.Required = true
case s == "positive":
p.Positive = true
case strings.HasPrefix(s, "default:"):
p.Default = s[8:]
}
}
}
func (opts Opts) setValue(v reflect.Value, p Param) error {
s, ok := opts[p.Name]
if p.Kind == Bool {
if s != "" {
return fmt.Errorf("%s: boolean option does not need a value", p.Name)
}
if ok {
v.SetBool(true)
}
return nil
}
if s == "" {
if p.Required {
return fmt.Errorf("%s: expect value", p.Name)
}
s = p.Default
}
if s == "" {
return nil
}
switch p.Kind {
case String:
v.SetString(s)
case Int:
n, err := strconv.Atoi(s)
if err != nil {
return fmt.Errorf("%s: %w", p.Name, err)
}
if n <= 0 {
return fmt.Errorf("%s: expect positive", p.Name)
}
v.SetInt(int64(n))
default:
return fmt.Errorf("%s: unsupported type '%s'", p.Name, v.Type().String())
}
return nil
}
func Parametrize(t reflect.Type) []Param {
if t.Kind() != reflect.Struct {
return nil
}
return parametrize(reflect.New(t).Elem())
}
func parametrize(v reflect.Value) (param []Param) {
var visit func(index []int, v reflect.Value)
visit = func(index []int, v reflect.Value) {
for n := 0; n < v.NumField(); n++ {
f := v.Type().Field(n)
x := append(append([]int{}, index...), f.Index...)
if f.Anonymous {
visit(x, v.Field(n))
continue
}
if !v.Field(n).CanSet() {
continue
}
p := Param{
Name: strings.ToLower(f.Name),
Kind: f.Type.Kind(),
index: x,
}
p.parseTags(f.Tag.Get("opts"))
param = append(param, p)
}
}
visit(nil, v)
return
}
func (opts Opts) configure(v reflect.Value) error {
param := parametrize(v)
m := map[string]bool{}
for s := range opts {
m[s] = true
}
for _, p := range param {
f := v.FieldByIndex(p.index)
if err := opts.setValue(f, p); err != nil {
return err
}
delete(m, p.Name)
}
if len(m) > 0 {
var ss []string
for s := range m {
ss = append(ss, s)
}
return fmt.Errorf("unknown options: %s", strings.Join(ss, ","))
}
return nil
}
|
