--- /dev/null
+// Copyright 2017 Frank Schroeder. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package properties
+
+import (
+ "fmt"
+ "reflect"
+ "strconv"
+ "strings"
+ "time"
+)
+
+// Decode assigns property values to exported fields of a struct.
+//
+// Decode traverses v recursively and returns an error if a value cannot be
+// converted to the field type or a required value is missing for a field.
+//
+// The following type dependent decodings are used:
+//
+// String, boolean, numeric fields have the value of the property key assigned.
+// The property key name is the name of the field. A different key and a default
+// value can be set in the field's tag. Fields without default value are
+// required. If the value cannot be converted to the field type an error is
+// returned.
+//
+// time.Duration fields have the result of time.ParseDuration() assigned.
+//
+// time.Time fields have the vaule of time.Parse() assigned. The default layout
+// is time.RFC3339 but can be set in the field's tag.
+//
+// Arrays and slices of string, boolean, numeric, time.Duration and time.Time
+// fields have the value interpreted as a comma separated list of values. The
+// individual values are trimmed of whitespace and empty values are ignored. A
+// default value can be provided as a semicolon separated list in the field's
+// tag.
+//
+// Struct fields are decoded recursively using the field name plus "." as
+// prefix. The prefix (without dot) can be overridden in the field's tag.
+// Default values are not supported in the field's tag. Specify them on the
+// fields of the inner struct instead.
+//
+// Map fields must have a key of type string and are decoded recursively by
+// using the field's name plus ".' as prefix and the next element of the key
+// name as map key. The prefix (without dot) can be overridden in the field's
+// tag. Default values are not supported.
+//
+// Examples:
+//
+// // Field is ignored.
+// Field int `properties:"-"`
+//
+// // Field is assigned value of 'Field'.
+// Field int
+//
+// // Field is assigned value of 'myName'.
+// Field int `properties:"myName"`
+//
+// // Field is assigned value of key 'myName' and has a default
+// // value 15 if the key does not exist.
+// Field int `properties:"myName,default=15"`
+//
+// // Field is assigned value of key 'Field' and has a default
+// // value 15 if the key does not exist.
+// Field int `properties:",default=15"`
+//
+// // Field is assigned value of key 'date' and the date
+// // is in format 2006-01-02
+// Field time.Time `properties:"date,layout=2006-01-02"`
+//
+// // Field is assigned the non-empty and whitespace trimmed
+// // values of key 'Field' split by commas.
+// Field []string
+//
+// // Field is assigned the non-empty and whitespace trimmed
+// // values of key 'Field' split by commas and has a default
+// // value ["a", "b", "c"] if the key does not exist.
+// Field []string `properties:",default=a;b;c"`
+//
+// // Field is decoded recursively with "Field." as key prefix.
+// Field SomeStruct
+//
+// // Field is decoded recursively with "myName." as key prefix.
+// Field SomeStruct `properties:"myName"`
+//
+// // Field is decoded recursively with "Field." as key prefix
+// // and the next dotted element of the key as map key.
+// Field map[string]string
+//
+// // Field is decoded recursively with "myName." as key prefix
+// // and the next dotted element of the key as map key.
+// Field map[string]string `properties:"myName"`
+func (p *Properties) Decode(x interface{}) error {
+ t, v := reflect.TypeOf(x), reflect.ValueOf(x)
+ if t.Kind() != reflect.Ptr || v.Elem().Type().Kind() != reflect.Struct {
+ return fmt.Errorf("not a pointer to struct: %s", t)
+ }
+ if err := dec(p, "", nil, nil, v); err != nil {
+ return err
+ }
+ return nil
+}
+
+func dec(p *Properties, key string, def *string, opts map[string]string, v reflect.Value) error {
+ t := v.Type()
+
+ // value returns the property value for key or the default if provided.
+ value := func() (string, error) {
+ if val, ok := p.Get(key); ok {
+ return val, nil
+ }
+ if def != nil {
+ return *def, nil
+ }
+ return "", fmt.Errorf("missing required key %s", key)
+ }
+
+ // conv converts a string to a value of the given type.
+ conv := func(s string, t reflect.Type) (val reflect.Value, err error) {
+ var v interface{}
+
+ switch {
+ case isDuration(t):
+ v, err = time.ParseDuration(s)
+
+ case isTime(t):
+ layout := opts["layout"]
+ if layout == "" {
+ layout = time.RFC3339
+ }
+ v, err = time.Parse(layout, s)
+
+ case isBool(t):
+ v, err = boolVal(s), nil
+
+ case isString(t):
+ v, err = s, nil
+
+ case isFloat(t):
+ v, err = strconv.ParseFloat(s, 64)
+
+ case isInt(t):
+ v, err = strconv.ParseInt(s, 10, 64)
+
+ case isUint(t):
+ v, err = strconv.ParseUint(s, 10, 64)
+
+ default:
+ return reflect.Zero(t), fmt.Errorf("unsupported type %s", t)
+ }
+ if err != nil {
+ return reflect.Zero(t), err
+ }
+ return reflect.ValueOf(v).Convert(t), nil
+ }
+
+ // keydef returns the property key and the default value based on the
+ // name of the struct field and the options in the tag.
+ keydef := func(f reflect.StructField) (string, *string, map[string]string) {
+ _key, _opts := parseTag(f.Tag.Get("properties"))
+
+ var _def *string
+ if d, ok := _opts["default"]; ok {
+ _def = &d
+ }
+ if _key != "" {
+ return _key, _def, _opts
+ }
+ return f.Name, _def, _opts
+ }
+
+ switch {
+ case isDuration(t) || isTime(t) || isBool(t) || isString(t) || isFloat(t) || isInt(t) || isUint(t):
+ s, err := value()
+ if err != nil {
+ return err
+ }
+ val, err := conv(s, t)
+ if err != nil {
+ return err
+ }
+ v.Set(val)
+
+ case isPtr(t):
+ return dec(p, key, def, opts, v.Elem())
+
+ case isStruct(t):
+ for i := 0; i < v.NumField(); i++ {
+ fv := v.Field(i)
+ fk, def, opts := keydef(t.Field(i))
+ if !fv.CanSet() {
+ return fmt.Errorf("cannot set %s", t.Field(i).Name)
+ }
+ if fk == "-" {
+ continue
+ }
+ if key != "" {
+ fk = key + "." + fk
+ }
+ if err := dec(p, fk, def, opts, fv); err != nil {
+ return err
+ }
+ }
+ return nil
+
+ case isArray(t):
+ val, err := value()
+ if err != nil {
+ return err
+ }
+ vals := split(val, ";")
+ a := reflect.MakeSlice(t, 0, len(vals))
+ for _, s := range vals {
+ val, err := conv(s, t.Elem())
+ if err != nil {
+ return err
+ }
+ a = reflect.Append(a, val)
+ }
+ v.Set(a)
+
+ case isMap(t):
+ valT := t.Elem()
+ m := reflect.MakeMap(t)
+ for postfix := range p.FilterStripPrefix(key + ".").m {
+ pp := strings.SplitN(postfix, ".", 2)
+ mk, mv := pp[0], reflect.New(valT)
+ if err := dec(p, key+"."+mk, nil, nil, mv); err != nil {
+ return err
+ }
+ m.SetMapIndex(reflect.ValueOf(mk), mv.Elem())
+ }
+ v.Set(m)
+
+ default:
+ return fmt.Errorf("unsupported type %s", t)
+ }
+ return nil
+}
+
+// split splits a string on sep, trims whitespace of elements
+// and omits empty elements
+func split(s string, sep string) []string {
+ var a []string
+ for _, v := range strings.Split(s, sep) {
+ if v = strings.TrimSpace(v); v != "" {
+ a = append(a, v)
+ }
+ }
+ return a
+}
+
+// parseTag parses a "key,k=v,k=v,..."
+func parseTag(tag string) (key string, opts map[string]string) {
+ opts = map[string]string{}
+ for i, s := range strings.Split(tag, ",") {
+ if i == 0 {
+ key = s
+ continue
+ }
+
+ pp := strings.SplitN(s, "=", 2)
+ if len(pp) == 1 {
+ opts[pp[0]] = ""
+ } else {
+ opts[pp[0]] = pp[1]
+ }
+ }
+ return key, opts
+}
+
+func isArray(t reflect.Type) bool { return t.Kind() == reflect.Array || t.Kind() == reflect.Slice }
+func isBool(t reflect.Type) bool { return t.Kind() == reflect.Bool }
+func isDuration(t reflect.Type) bool { return t == reflect.TypeOf(time.Second) }
+func isMap(t reflect.Type) bool { return t.Kind() == reflect.Map }
+func isPtr(t reflect.Type) bool { return t.Kind() == reflect.Ptr }
+func isString(t reflect.Type) bool { return t.Kind() == reflect.String }
+func isStruct(t reflect.Type) bool { return t.Kind() == reflect.Struct }
+func isTime(t reflect.Type) bool { return t == reflect.TypeOf(time.Time{}) }
+func isFloat(t reflect.Type) bool {
+ return t.Kind() == reflect.Float32 || t.Kind() == reflect.Float64
+}
+func isInt(t reflect.Type) bool {
+ return t.Kind() == reflect.Int || t.Kind() == reflect.Int8 || t.Kind() == reflect.Int16 || t.Kind() == reflect.Int32 || t.Kind() == reflect.Int64
+}
+func isUint(t reflect.Type) bool {
+ return t.Kind() == reflect.Uint || t.Kind() == reflect.Uint8 || t.Kind() == reflect.Uint16 || t.Kind() == reflect.Uint32 || t.Kind() == reflect.Uint64
+}
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