Getting started

arg.go

@@ -0,0 +1,50 @@
+package args
+
+import "time"
+
+type Arg struct {
+	Env     string
+	Flag    string
+	Help    string
+	Default interface{}
+	Value   interface{}
+	ArgType Type
+}
+
+func NewArg(argType Type, key, help string, def interface{}) *Arg {
+	return &Arg{
+		Env:     key,
+		Flag:    key,
+		Help:    help,
+		Default: def,
+		ArgType: argType,
+	}
+}
+
+func (a *Arg) GetInt(key string) int {
+	if a.ArgType != INT {
+		return -1
+	}
+	return a.Value.(int)
+}
+
+func (a *Arg) GetString(key string) string {
+	if a.ArgType != STRING {
+		return ""
+	}
+	return a.Value.(string)
+}
+
+func (a *Arg) GetBool(key string) bool {
+	if a.ArgType != BOOL {
+		return false
+	}
+	return a.Value.(bool)
+}
+
+func (a *Arg) GetDuration(key string) time.Duration {
+	if a.ArgType != DURATION {
+		return time.Duration(0)
+	}
+	return a.Value.(time.Duration)
+}

argset.go

@@ -0,0 +1,78 @@
+package args
+
+import (
+	"errors"
+	"os"
+)
+
+type ArgSet struct {
+	parsed bool
+	args   []*Arg
+}
+
+func NewArgSet() *ArgSet {
+	return &ArgSet{
+		args: []*Arg{},
+	}
+}
+
+func (as *ArgSet) Append(argType Type, key, help string, def interface{}) {
+	as.args = append(as.args, NewArg(argType, key, help, def))
+}
+
+func (as *ArgSet) Get(key string) *Arg {
+	if !as.parsed {
+		return nil
+	}
+	for i := range as.args {
+		if as.args[i].Key == key {
+			return as[i]
+		}
+	}
+	return nil
+}
+
+func (as *ArgSet) Parse() error {
+	if as.parsed {
+		return nil
+	}
+	defer func() {
+		as.parsed = true
+	}()
+
+	if err := as.setValueFromDefaults(); err != nil {
+		return err
+	}
+	if err := as.setValueFromEnv(); err != nil {
+		return err
+	}
+	if err := as.setValueFromFlag(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (as *ArgSet) setValueFromDefaults() error {
+	// TODO if not casted type, return err
+	for i := range as.args {
+		args[i].Value = args[i].Default
+	}
+	return nil
+}
+
+func (as *ArgSet) setValueFromEnv() error {
+	// TODO if not casted type, return err
+	for i := range as.args {
+		key := args[i].Key
+		if v, ok := os.LookupEnv(key); ok {
+			args[i].Value = v
+		}
+	}
+	return nil
+}
+
+func (as *ArgSet) setValueFromFlags() error {
+	// TODO if not casted type, return err
+	return errors.New("not impl")
+}

type.go

@@ -0,0 +1,10 @@
+package args
+
+type Type int
+
+const (
+	INT      = Type(iota)
+	STRING   = Type(iota)
+	BOOL     = Type(iota)
+	DURATION = Type(iota)
+)