update: refactor config

- Explicitly specify all of the valid options for Update
- Seperate the config from File() and Units()
- Add YAML tags for the fields

config/config.go

@@ -0,0 +1,66 @@
+package config
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// IsZero returns whether or not the parameter is the zero value for its type.
+// If the parameter is a struct, only the exported fields are considered.
+func IsZero(c interface{}) bool {
+	return isZero(reflect.ValueOf(c))
+}
+
+// AssertValid checks the fields in the structure and makes sure that they
+// contain valid values as specified by the 'valid' flag. Empty fields are
+// implicitly valid.
+func AssertValid(c interface{}) error {
+	ct := reflect.TypeOf(c)
+	cv := reflect.ValueOf(c)
+	for i := 0; i < ct.NumField(); i++ {
+		ft := ct.Field(i)
+		if !isFieldExported(ft) {
+			continue
+		}
+
+		valid := ft.Tag.Get("valid")
+		val := cv.Field(i)
+		if !isValid(val, valid) {
+			return fmt.Errorf("invalid value \"%v\" for option %q (valid options: %q)", val.Interface(), ft.Name, valid)
+		}
+	}
+	return nil
+}
+
+func isZero(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Struct:
+		vt := v.Type()
+		for i := 0; i < v.NumField(); i++ {
+			if isFieldExported(vt.Field(i)) && !isZero(v.Field(i)) {
+				return false
+			}
+		}
+		return true
+	default:
+		return v.Interface() == reflect.Zero(v.Type()).Interface()
+	}
+}
+
+func isFieldExported(f reflect.StructField) bool {
+	return f.PkgPath == ""
+}
+
+func isValid(v reflect.Value, valid string) bool {
+	if valid == "" || isZero(v) {
+		return true
+	}
+	vs := fmt.Sprintf("%v", v.Interface())
+	for _, valid := range strings.Split(valid, ",") {
+		if vs == valid {
+			return true
+		}
+	}
+	return false
+}

config/config_test.go

@@ -0,0 +1,63 @@
+package config
+
+import (
+	"errors"
+	"reflect"
+	"testing"
+)
+
+func TestIsZero(t *testing.T) {
+	for _, tt := range []struct {
+		c     interface{}
+		empty bool
+	}{
+		{struct{}{}, true},
+		{struct{ a, b string }{}, true},
+		{struct{ A, b string }{}, true},
+		{struct{ A, B string }{}, true},
+		{struct{ A string }{A: "hello"}, false},
+		{struct{ A int }{}, true},
+		{struct{ A int }{A: 1}, false},
+	} {
+		if empty := IsZero(tt.c); tt.empty != empty {
+			t.Errorf("bad result (%q): want %q, got %q", tt.c, tt.empty, empty)
+		}
+	}
+}
+
+func TestAssertValid(t *testing.T) {
+	for _, tt := range []struct {
+		c   interface{}
+		err error
+	}{
+		{struct{}{}, nil},
+		{struct {
+			A, b string `valid:"1,2"`
+		}{}, nil},
+		{struct {
+			A, b string `valid:"1,2"`
+		}{A: "1", b: "2"}, nil},
+		{struct {
+			A, b string `valid:"1,2"`
+		}{A: "1", b: "hello"}, nil},
+		{struct {
+			A, b string `valid:"1,2"`
+		}{A: "hello", b: "2"}, errors.New("invalid value \"hello\" for option \"A\" (valid options: \"1,2\")")},
+		{struct {
+			A, b int `valid:"1,2"`
+		}{}, nil},
+		{struct {
+			A, b int `valid:"1,2"`
+		}{A: 1, b: 2}, nil},
+		{struct {
+			A, b int `valid:"1,2"`
+		}{A: 1, b: 9}, nil},
+		{struct {
+			A, b int `valid:"1,2"`
+		}{A: 9, b: 2}, errors.New("invalid value \"9\" for option \"A\" (valid options: \"1,2\")")},
+	} {
+		if err := AssertValid(tt.c); !reflect.DeepEqual(tt.err, err) {
+			t.Errorf("bad result (%q): want %q, got %q", tt.c, tt.err, err)
+		}
+	}
+}

config/etc_hosts.go

@@ -0,0 +1,3 @@
+package config
+
+type EtcHosts string

config/update.go

@@ -0,0 +1,7 @@
+package config
+
+type Update struct {
+	RebootStrategy string `yaml:"reboot-strategy" env:"REBOOT_STRATEGY" valid:"best-effort,etcd-lock,reboot,off"`
+	Group          string `yaml:"group"           env:"GROUP"`
+	Server         string `yaml:"server"          env:"SERVER"`
+}