util/reflect: improve merge for map

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/reflect/reflect.go

@@ -2,7 +2,10 @@ package reflect
 
 import (
 	"errors"
+	"fmt"
 	"reflect"
+	"strconv"
+	"strings"
 )
 
 var (
@@ -119,3 +122,189 @@ func CopyFrom(a, b interface{}) {
 		}
 	}
 }
+
+func MergeMap(a interface{}, b map[string]interface{}) error {
+	var err error
+
+	// preprocess map
+	nb := make(map[string]interface{}, len(b))
+	for k, v := range b {
+		ps := strings.Split(k, ".")
+		if len(ps) == 1 {
+			nb[k] = v
+			continue
+		}
+		em := make(map[string]interface{})
+		em[ps[len(ps)-1]] = v
+		for i := len(ps) - 2; i > 0; i-- {
+			nm := make(map[string]interface{})
+			nm[ps[i]] = em
+			em = nm
+		}
+		if vm, ok := nb[ps[0]]; ok {
+			// nested map
+			nm := vm.(map[string]interface{})
+			for vk, vv := range em {
+				nm[vk] = vv
+			}
+			nb[ps[0]] = nm
+		} else {
+			nb[ps[0]] = em
+		}
+	}
+
+	ta := reflect.TypeOf(a)
+	if ta.Kind() == reflect.Ptr {
+		ta = ta.Elem()
+	}
+	va := reflect.ValueOf(a)
+	if va.Kind() == reflect.Ptr {
+		va = va.Elem()
+	}
+
+	for mk, mv := range nb {
+		vmv := reflect.ValueOf(mv)
+		//		tmv := reflect.TypeOf(mv)
+		name := strings.Title(mk)
+		fva := va.FieldByName(name)
+		fta, found := ta.FieldByName(name)
+		if !found || !fva.IsValid() || !fva.CanSet() || fta.PkgPath != "" {
+			continue
+		}
+		// fast path via direct assign
+		if vmv.Type().AssignableTo(fta.Type) {
+			fva.Set(vmv)
+			continue
+		}
+		switch getKind(fva) {
+		case reflect.Bool:
+			err = mergeBool(fva, vmv)
+		case reflect.String:
+			err = mergeString(fva, vmv)
+		case reflect.Int:
+			err = mergeInt(fva, vmv)
+		case reflect.Uint:
+			err = mergeUint(fva, vmv)
+		case reflect.Float64:
+			err = mergeFloat(fva, vmv)
+		}
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func mergeBool(va, vb reflect.Value) error {
+	switch getKind(vb) {
+	case reflect.Int:
+		if vb.Int() == 1 {
+			va.SetBool(true)
+		}
+	case reflect.Uint:
+		if vb.Uint() == 1 {
+			va.SetBool(true)
+		}
+	case reflect.Float64:
+		if vb.Float() == 1 {
+			va.SetBool(true)
+		}
+	case reflect.String:
+		if vb.String() == "1" || vb.String() == "true" {
+			vb.SetBool(true)
+		}
+	default:
+		return fmt.Errorf("cant merge %v %s with %v %s", va, va.Kind(), vb, vb.Kind())
+	}
+	return nil
+}
+
+func mergeString(va, vb reflect.Value) error {
+	switch getKind(vb) {
+	case reflect.Int:
+		va.SetString(fmt.Sprintf("%d", vb.Int()))
+	case reflect.Uint:
+		va.SetString(fmt.Sprintf("%d", vb.Uint()))
+	case reflect.Float64:
+		va.SetString(fmt.Sprintf("%f", vb.Float()))
+	case reflect.String:
+		va.Set(vb)
+	default:
+		return fmt.Errorf("cant merge %v %s with %v %s", va, va.Kind(), vb, vb.Kind())
+	}
+	return nil
+}
+
+func mergeInt(va, vb reflect.Value) error {
+	switch getKind(vb) {
+	case reflect.Int:
+		va.Set(vb)
+	case reflect.Uint:
+		va.SetInt(int64(vb.Uint()))
+	case reflect.Float64:
+		va.SetInt(int64(vb.Float()))
+	case reflect.String:
+		if f, err := strconv.ParseInt(vb.String(), 10, va.Type().Bits()); err != nil {
+			return err
+		} else {
+			va.SetInt(f)
+		}
+	default:
+		return fmt.Errorf("cant merge %v %s with %v %s", va, va.Kind(), vb, vb.Kind())
+	}
+	return nil
+}
+
+func mergeUint(va, vb reflect.Value) error {
+	switch getKind(vb) {
+	case reflect.Int:
+		va.SetUint(uint64(vb.Int()))
+	case reflect.Uint:
+		va.Set(vb)
+	case reflect.Float64:
+		va.SetUint(uint64(vb.Float()))
+	case reflect.String:
+		if f, err := strconv.ParseUint(vb.String(), 10, va.Type().Bits()); err != nil {
+			return err
+		} else {
+			va.SetUint(f)
+		}
+	default:
+		return fmt.Errorf("cant merge %v %s with %v %s", va, va.Kind(), vb, vb.Kind())
+	}
+	return nil
+}
+
+func mergeFloat(va, vb reflect.Value) error {
+	switch getKind(vb) {
+	case reflect.Int:
+		va.SetFloat(float64(vb.Int()))
+	case reflect.Uint:
+		va.SetFloat(float64(vb.Uint()))
+	case reflect.Float64:
+		va.Set(vb)
+	case reflect.String:
+		if f, err := strconv.ParseFloat(vb.String(), va.Type().Bits()); err != nil {
+			return err
+		} else {
+			va.SetFloat(f)
+		}
+	default:
+		return fmt.Errorf("cant merge %v %s with %v %s", va, va.Kind(), vb, vb.Kind())
+	}
+
+	return nil
+}
+
+func getKind(val reflect.Value) reflect.Kind {
+	kind := val.Kind()
+	switch {
+	case kind >= reflect.Int && kind <= reflect.Int64:
+		return reflect.Int
+	case kind >= reflect.Uint && kind <= reflect.Uint64:
+		return reflect.Uint
+	case kind >= reflect.Float32 && kind <= reflect.Float64:
+		return reflect.Float64
+	}
+	return kind
+}