this seeks to work

arg.go

@@ -1,6 +1,10 @@
 package args
 
-import "time"
+import (
+	"fmt"
+	"strconv"
+	"time"
+)
 
 type Arg struct {
 	Env     string
@@ -17,34 +21,90 @@ func NewArg(argType Type, key, help string, def interface{}) *Arg {
 		Flag:    key,
 		Help:    help,
 		Default: def,
+		Value:   def,
 		ArgType: argType,
 	}
 }
 
-func (a *Arg) GetInt(key string) int {
+func (a *Arg) GetInt() int {
 	if a.ArgType != INT {
 		return -1
 	}
+	if _, ok := a.Value.(int); !ok {
+		return -1
+	}
 	return a.Value.(int)
 }
 
-func (a *Arg) GetString(key string) string {
+func (a *Arg) GetString() string {
 	if a.ArgType != STRING {
 		return ""
 	}
+	if _, ok := a.Value.(string); !ok {
+		return ""
+	}
 	return a.Value.(string)
 }
 
-func (a *Arg) GetBool(key string) bool {
+func (a *Arg) GetBool() bool {
 	if a.ArgType != BOOL {
 		return false
 	}
+	if _, ok := a.Value.(bool); !ok {
+		return false
+	}
 	return a.Value.(bool)
 }
 
-func (a *Arg) GetDuration(key string) time.Duration {
+func (a *Arg) GetDuration() time.Duration {
 	if a.ArgType != DURATION {
-		return time.Duration(0)
+		return time.Duration(-1)
+	}
+	if _, ok := a.Value.(time.Duration); !ok {
+		return time.Duration(-1)
 	}
 	return a.Value.(time.Duration)
 }
+
+func (a *Arg) Set(value interface{}) error {
+	err := fmt.Errorf("incompatible set of type %T for arg $%v/-%v type %v", value, a.Env, a.Flag, a.ArgType)
+	switch a.ArgType {
+	case INT:
+		i, ok := value.(int)
+		if ok {
+			a.Value = i
+			err = nil
+		} else if s, ok := value.(string); !ok {
+		} else if i, err = strconv.Atoi(s); err == nil {
+			a.Value = i
+			err = nil
+		}
+	case STRING:
+		i, ok := value.(string)
+		if ok {
+			a.Value = i
+			err = nil
+		}
+	case BOOL:
+		i, ok := value.(bool)
+		if ok {
+			a.Value = i
+			err = nil
+		} else if s, ok := value.(string); !ok {
+		} else if i, err = strconv.ParseBool(s); err == nil {
+			a.Value = i
+			err = nil
+		}
+	case DURATION:
+		i, ok := value.(time.Duration)
+		if ok {
+			a.Value = i
+			err = nil
+		} else if s, ok := value.(string); !ok {
+		} else if i, err = time.ParseDuration(s); err == nil {
+			a.Value = i
+			err = nil
+		}
+	}
+	return err
+}

arg_test.go

@@ -0,0 +1,137 @@
+package args
+
+import (
+	"testing"
+	"time"
+)
+
+func TestNewArg(t *testing.T) {
+	NewArg(INT, "key", "help", 5)
+}
+
+func TestGets(t *testing.T) {
+	cases := []struct {
+		t  Type
+		v  interface{}
+		ok bool
+	}{
+		{
+			t:  STRING,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  DURATION,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  BOOL,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  INT,
+			v:  "5",
+			ok: false,
+		},
+		{
+			t:  STRING,
+			v:  "5",
+			ok: true,
+		},
+		{
+			t:  DURATION,
+			v:  time.Duration(5),
+			ok: true,
+		},
+		{
+			t:  BOOL,
+			v:  true,
+			ok: true,
+		},
+		{
+			t:  INT,
+			v:  5,
+			ok: true,
+		},
+	}
+
+	for _, c := range cases {
+		a := NewArg(c.t, "key", "help", c.v)
+		switch c.t {
+		case INT:
+			if (a.GetInt() == c.v) != c.ok {
+				t.Errorf("failed to get int: want %v, got %v", c.v, a.GetInt())
+			}
+		case STRING:
+			if (a.GetString() == c.v) != c.ok {
+				t.Errorf("failed to get string: want %v, got %v", c.v, a.GetString())
+			}
+		case BOOL:
+			if (a.GetBool() == c.v) != c.ok {
+				t.Errorf("failed to get bool: want %v, got %v", c.v, a.GetBool())
+			}
+		case DURATION:
+			if (a.GetDuration() == c.v) != c.ok {
+				t.Errorf("failed to get duration: want %v, got %v", c.v, a.GetDuration())
+			}
+		}
+	}
+}
+
+func TestSets(t *testing.T) {
+	cases := []struct {
+		t  Type
+		v  interface{}
+		ok bool
+	}{
+		{
+			t:  STRING,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  DURATION,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  BOOL,
+			v:  5,
+			ok: false,
+		},
+		{
+			t:  INT,
+			v:  "a",
+			ok: false,
+		},
+		{
+			t:  STRING,
+			v:  "5",
+			ok: true,
+		},
+		{
+			t:  DURATION,
+			v:  time.Duration(5),
+			ok: true,
+		},
+		{
+			t:  BOOL,
+			v:  true,
+			ok: true,
+		},
+		{
+			t:  INT,
+			v:  5,
+			ok: true,
+		},
+	}
+
+	for i, c := range cases {
+		a := NewArg(c.t, "key", "help", nil)
+		if err := a.Set(c.v); (err == nil) != c.ok {
+			t.Errorf("[%d] failed to set %v: want ok=%v, got %v", i, c.t, c.ok, err)
+		}
+	}
+}

argset.go

@@ -2,7 +2,9 @@ package args
 
 import (
 	"errors"
+	"flag"
 	"os"
+	"time"
 )
 
 type ArgSet struct {
@@ -25,8 +27,8 @@ func (as *ArgSet) Get(key string) *Arg {
 		return nil
 	}
 	for i := range as.args {
-		if as.args[i].Key == key {
-			return as[i]
+		if as.args[i].Env == key || as.args[i].Flag == key {
+			return as.args[i]
 		}
 	}
 	return nil
@@ -46,7 +48,7 @@ func (as *ArgSet) Parse() error {
 	if err := as.setValueFromEnv(); err != nil {
 		return err
 	}
-	if err := as.setValueFromFlag(); err != nil {
+	if err := as.setValueFromFlags(); err != nil {
 		return err
 	}
 
@@ -54,25 +56,58 @@ func (as *ArgSet) Parse() error {
 }
 
 func (as *ArgSet) setValueFromDefaults() error {
-	// TODO if not casted type, return err
 	for i := range as.args {
-		args[i].Value = args[i].Default
+		if err := as.args[i].Set(as.args[i].Default); err != nil {
+			return err
+		}
 	}
 	return nil
 }
 
 func (as *ArgSet) setValueFromEnv() error {
-	// TODO if not casted type, return err
 	for i := range as.args {
-		key := args[i].Key
+		key := as.args[i].Env
 		if v, ok := os.LookupEnv(key); ok {
-			args[i].Value = v
+			if err := as.args[i].Set(v); err != nil {
+				return err
+			}
 		}
 	}
 	return nil
 }
 
 func (as *ArgSet) setValueFromFlags() error {
-	// TODO if not casted type, return err
-	return errors.New("not impl")
+	fs := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
+	for i := range as.args {
+		arg := as.args[i]
+		switch arg.ArgType {
+		case INT:
+			arg.Default = fs.Int(arg.Flag, arg.Value.(int), arg.Help)
+		case STRING:
+			arg.Default = fs.String(arg.Flag, arg.Value.(string), arg.Help)
+		case BOOL:
+			arg.Default = fs.Bool(arg.Flag, arg.Value.(bool), arg.Help)
+		case DURATION:
+			arg.Default = fs.Duration(arg.Flag, arg.Value.(time.Duration), arg.Help)
+		default:
+			return errors.New("unknown type, cannot set from flag")
+		}
+	}
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		return err
+	}
+	for i := range as.args {
+		arg := as.args[i]
+		switch arg.ArgType {
+		case INT:
+			arg.Value = *arg.Default.(*int)
+		case STRING:
+			arg.Value = *arg.Default.(*string)
+		case BOOL:
+			arg.Value = *arg.Default.(*bool)
+		case DURATION:
+			arg.Value = *arg.Default.(*time.Duration)
+		}
+	}
+	return nil
 }

argset_test.go

@@ -0,0 +1,60 @@
+package args
+
+import (
+	"os"
+	"testing"
+)
+
+func TestNewArgSet(t *testing.T) {
+	NewArgSet()
+}
+
+func TestAppend(t *testing.T) {
+	as := NewArgSet()
+	as.Append(INT, "key", "help", nil)
+	if len(as.args) != 1 || *as.args[0] != *NewArg(INT, "key", "help", nil) {
+		t.Errorf("argset.Append failed: got %v, want %v", *as.args[0], *NewArg(INT, "key", "help", nil))
+	}
+}
+
+func TestParse(t *testing.T) {
+	osArgs := append([]string{}, os.Args[:]...)
+	defer func() {
+		os.Args = osArgs
+	}()
+	os.Args = []string{"nothing", "-testkeyFlag", "5"}
+	os.Setenv("testkeyEnv", "9")
+	as := NewArgSet()
+	as.Append(INT, "testkeyFlag", "help", 1)
+	as.Append(INT, "testkeyEnv", "help", 2)
+	as.Append(INT, "testkeyDefault", "help", 3)
+	if err := as.Parse(); err != nil {
+		t.Fatalf("cannot parse legal: %v", err)
+	} else if arg := as.Get("testkeyFlag"); arg == nil || arg.Value != 5 {
+		t.Errorf("cannot set from flag: got %v", arg)
+	} else if arg := as.Get("testkeyEnv"); arg == nil || arg.Value != 9 {
+		t.Errorf("cannot set from env: got %v", arg)
+	} else if arg := as.Get("testkeyDefault"); arg == nil || arg.Value != 3 {
+		t.Errorf("cannot set from default: got %v", arg)
+	}
+
+	os.Args = []string{"nothing", "-testkey5", "bad"}
+	as = NewArgSet()
+	as.Append(INT, "testkey4", "help", "4")
+	if err := as.Parse(); err == nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGet(t *testing.T) {
+	as := NewArgSet()
+	as.Append(INT, "testkey1", "help", 1)
+	as.Append(INT, "testkey2", "help", 2)
+	as.Append(INT, "testkey3", "help", 3)
+	if err := as.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	if as.Get("testkey1") == nil {
+		t.Errorf("cannot get parsed at %q", "testkey1")
+	}
+}

type.go

@@ -1,5 +1,10 @@
 package args
 
+import (
+	"fmt"
+	"time"
+)
+
 type Type int
 
 const (
@@ -8,3 +13,18 @@ const (
 	BOOL     = Type(iota)
 	DURATION = Type(iota)
 )
+
+func (t Type) String() string {
+	var i interface{} = nil
+	switch t {
+	case INT:
+		i = 1
+	case STRING:
+		i = ""
+	case BOOL:
+		i = false
+	case DURATION:
+		i = time.Duration(0)
+	}
+	return fmt.Sprintf("%T", i)
+}

type_test.go

@@ -0,0 +1,18 @@
+package args
+
+import "testing"
+
+func TestType(t *testing.T) {
+	if INT.String() != "int" {
+		t.Errorf("wrong string for INT")
+	}
+	if STRING.String() != "string" {
+		t.Errorf("wrong string for STRING")
+	}
+	if BOOL.String() != "bool" {
+		t.Errorf("wrong string for BOOL")
+	}
+	if DURATION.String() != "time.Duration" {
+		t.Errorf("wrong string for DURATION")
+	}
+}