util/reflect: rewrite struct merging with map

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

util/reflect/struct.go

@@ -0,0 +1,398 @@
+package reflect
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"reflect"
+	"regexp"
+	"strings"
+)
+
+var (
+	// ErrInvalidParam specifies invalid url query params
+	ErrInvalidParam = errors.New("invalid url query param provided")
+)
+
+var (
+	bracketSplitter = regexp.MustCompile(`\[|\]`)
+)
+
+// StructFields returns slice of struct fields
+func StructFields(src interface{}) ([]reflect.StructField, error) {
+	var fields []reflect.StructField
+
+	sv := reflect.ValueOf(src)
+	if sv.Kind() == reflect.Ptr {
+		sv = sv.Elem()
+	}
+	if sv.Kind() != reflect.Struct {
+		return nil, ErrInvalidStruct
+	}
+
+	typ := sv.Type()
+	for idx := 0; idx < typ.NumField(); idx++ {
+		fld := typ.Field(idx)
+		val := sv.Field(idx)
+		if !val.CanSet() || len(fld.PkgPath) != 0 {
+			continue
+		}
+		if val.Kind() == reflect.Struct {
+			infields, err := StructFields(val.Interface())
+			if err != nil {
+				return nil, err
+			}
+			fields = append(fields, infields...)
+		} else {
+			fields = append(fields, fld)
+		}
+	}
+
+	return fields, nil
+}
+
+// CopyDefaults for a from b
+// a and b should be pointers to the same kind of struct
+func CopyDefaults(a, b interface{}) {
+	pt := reflect.TypeOf(a)
+	t := pt.Elem()
+	va := reflect.ValueOf(a).Elem()
+	vb := reflect.ValueOf(b).Elem()
+	for i := 0; i < t.NumField(); i++ {
+		aField := va.Field(i)
+		if aField.CanSet() {
+			bField := vb.Field(i)
+			aField.Set(bField)
+		}
+	}
+}
+
+// CopyFrom sets the public members of a from b
+// a and b should be pointers to structs
+// a can be a different type from b
+// Only the Fields which have the same name and assignable type on a
+// and b will be set.
+func CopyFrom(a, b interface{}) {
+	ta := reflect.TypeOf(a).Elem()
+	tb := reflect.TypeOf(b).Elem()
+	va := reflect.ValueOf(a).Elem()
+	vb := reflect.ValueOf(b).Elem()
+	for i := 0; i < tb.NumField(); i++ {
+		bField := vb.Field(i)
+		tbField := tb.Field(i)
+		name := tbField.Name
+		aField := va.FieldByName(name)
+		taField, found := ta.FieldByName(name)
+		if found && aField.IsValid() && bField.IsValid() && aField.CanSet() && tbField.Type.AssignableTo(taField.Type) {
+			aField.Set(bField)
+		}
+	}
+}
+
+func StructURLValues(src interface{}, pref string, tags []string) (url.Values, error) {
+	data := url.Values{}
+
+	sv := reflect.ValueOf(src)
+	if sv.Kind() == reflect.Ptr {
+		sv = sv.Elem()
+	}
+	if sv.Kind() != reflect.Struct {
+		return nil, ErrInvalidStruct
+	}
+
+	typ := sv.Type()
+	for idx := 0; idx < typ.NumField(); idx++ {
+		fld := typ.Field(idx)
+		val := sv.Field(idx)
+		if !val.CanSet() || len(fld.PkgPath) != 0 || !val.IsValid() {
+			continue
+		}
+
+		var t *tag
+		for _, tn := range tags {
+			ts, ok := fld.Tag.Lookup(tn)
+			if !ok {
+				continue
+			}
+
+			tp := strings.Split(ts, ",")
+			// special
+			switch tn {
+			case "protobuf": // special
+				t = &tag{key: tn, name: tp[3][5:], opts: append(tp[:3], tp[4:]...)}
+			default:
+				t = &tag{key: tn, name: tp[0], opts: tp[1:]}
+			}
+			if t.name != "" {
+				break
+			}
+		}
+
+		if t.name == "" {
+			// fallback to lowercase
+			t.name = strings.ToLower(fld.Name)
+		}
+		if pref != "" {
+			t.name = pref + "." + t.name
+		}
+
+		if !val.IsValid() || val.IsZero() {
+			continue
+		}
+
+		switch val.Kind() {
+		case reflect.Struct, reflect.Ptr:
+			if val.IsNil() {
+				continue
+			}
+			ndata, err := StructURLValues(val.Interface(), t.name, tags)
+			if err != nil {
+				return ndata, err
+			}
+			for k, v := range ndata {
+				data[k] = v
+			}
+		default:
+			switch val.Kind() {
+			case reflect.Slice:
+				for i := 0; i < val.Len(); i++ {
+					va := val.Index(i)
+					//if va.Type().Elem().Kind() != reflect.Ptr {
+					if va.Kind() != reflect.Ptr {
+						data.Set(t.name, fmt.Sprintf("%v", va.Interface()))
+						continue
+					}
+					switch va.Type().Elem().String() {
+					case "wrapperspb.BoolValue", "wrapperspb.BytesValue", "wrapperspb.StringValue":
+						if eva := reflect.Indirect(va).FieldByName("Value"); eva.IsValid() {
+							data.Add(t.name, fmt.Sprintf("%v", eva.Interface()))
+						}
+					case "wrapperspb.DoubleValue", "wrapperspb.FloatValue":
+						if eva := reflect.Indirect(va).FieldByName("Value"); eva.IsValid() {
+							data.Add(t.name, fmt.Sprintf("%v", eva.Interface()))
+						}
+					case "wrapperspb.Int32Value", "wrapperspb.Int64Value":
+						if eva := reflect.Indirect(va).FieldByName("Value"); eva.IsValid() {
+							data.Add(t.name, fmt.Sprintf("%v", eva.Interface()))
+						}
+					case "wrapperspb.UInt32Value", "wrapperspb.UInt64Value":
+						if eva := reflect.Indirect(va).FieldByName("Value"); eva.IsValid() {
+							data.Add(t.name, fmt.Sprintf("%v", eva.Interface()))
+						}
+					default:
+						data.Add(t.name, fmt.Sprintf("%v", val.Index(i).Interface()))
+					}
+				}
+			default:
+				data.Set(t.name, fmt.Sprintf("%v", val.Interface()))
+			}
+		}
+	}
+	return data, nil
+}
+
+// URLMap returns map of url query params
+func URLMap(query string) (map[string]interface{}, error) {
+	var (
+		mp interface{} = make(map[string]interface{})
+	)
+
+	params := strings.Split(query, "&")
+
+	for _, part := range params {
+		tm, err := queryToMap(part)
+		if err != nil {
+			return nil, err
+		}
+		mp = merge(mp, tm)
+	}
+
+	return mp.(map[string]interface{}), nil
+}
+
+// FlattenMap expand key.subkey to nested map
+func FlattenMap(a map[string]interface{}) map[string]interface{} {
+	// preprocess map
+	nb := make(map[string]interface{}, len(a))
+	for k, v := range a {
+		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
+		}
+	}
+	return nb
+}
+
+/*
+	case reflect.String:
+		fn := func(c rune) bool { return c == ',' || c == ';' || c == ' ' }
+		slice := strings.FieldsFunc(vb.String(), fn)
+		if va.IsNil() {
+			va.Set(reflect.MakeSlice(va.Type(), len(slice), len(slice)))
+		}
+*/
+
+func btSplitter(str string) []string {
+	r := bracketSplitter.Split(str, -1)
+	for idx, s := range r {
+		if len(s) == 0 {
+			if len(r) > idx+1 {
+				copy(r[idx:], r[idx+1:])
+				r = r[:len(r)-1]
+			}
+		}
+	}
+	return r
+}
+
+// queryToMap turns something like a[b][c]=4 into
+//   map[string]interface{}{
+//     "a": map[string]interface{}{
+// 		  "b": map[string]interface{}{
+// 			  "c": 4,
+// 		  },
+// 	  },
+//   }
+func queryToMap(param string) (map[string]interface{}, error) {
+	rawKey, rawValue, err := splitKeyAndValue(param)
+	if err != nil {
+		return nil, err
+	}
+	rawValue, err = url.QueryUnescape(rawValue)
+	if err != nil {
+		return nil, err
+	}
+	rawKey, err = url.QueryUnescape(rawKey)
+	if err != nil {
+		return nil, err
+	}
+
+	pieces := btSplitter(rawKey)
+	key := pieces[0]
+
+	// If len==1 then rawKey has no [] chars and we can just
+	// decode this as key=value into {key: value}
+	if len(pieces) == 1 {
+		return map[string]interface{}{
+			key: rawValue,
+		}, nil
+	}
+
+	// If len > 1 then we have something like a[b][c]=2
+	// so we need to turn this into {"a": {"b": {"c": 2}}}
+	// To do this we break our key into two pieces:
+	//   a and b[c]
+	// and then we set {"a": queryToMap("b[c]", value)}
+	ret := make(map[string]interface{})
+	ret[key], err = queryToMap(buildNewKey(rawKey) + "=" + rawValue)
+	if err != nil {
+		return nil, err
+	}
+
+	// When URL params have a set of empty brackets (eg a[]=1)
+	// it is assumed to be an array. This will get us the
+	// correct value for the array item and return it as an
+	// []interface{} so that it can be merged properly.
+	if pieces[1] == "" {
+		temp := ret[key].(map[string]interface{})
+		ret[key] = []interface{}{temp[""]}
+	}
+	return ret, nil
+}
+
+// buildNewKey will take something like:
+// origKey = "bar[one][two]"
+// pieces = [bar one two ]
+// and return "one[two]"
+func buildNewKey(origKey string) string {
+	pieces := btSplitter(origKey)
+
+	ret := origKey[len(pieces[0])+1:]
+	ret = ret[:len(pieces[1])] + ret[len(pieces[1])+1:]
+	return ret
+}
+
+// splitKeyAndValue splits a URL param at the last equal
+// sign and returns the two strings. If no equal sign is
+// found, the ErrInvalidParam error is returned.
+func splitKeyAndValue(param string) (string, string, error) {
+	li := strings.LastIndex(param, "=")
+	if li == -1 {
+		return "", "", ErrInvalidParam
+	}
+	return param[:li], param[li+1:], nil
+}
+
+// merge merges a with b if they are either both slices
+// or map[string]interface{} types. Otherwise it returns b.
+func merge(a interface{}, b interface{}) interface{} {
+	if av, aok := a.(map[string]interface{}); aok {
+		if bv, bok := b.(map[string]interface{}); bok {
+			return mergeMapIface(av, bv)
+		}
+	}
+	if av, aok := a.([]interface{}); aok {
+		if bv, bok := b.([]interface{}); bok {
+			return mergeSliceIface(av, bv)
+		}
+	}
+
+	va := reflect.ValueOf(a)
+	vb := reflect.ValueOf(b)
+	if (va.Type().Kind() == reflect.Slice) && (va.Type().Elem().Kind() == vb.Type().Kind() || vb.Type().ConvertibleTo(va.Type().Elem())) {
+		va = reflect.Append(va, vb.Convert(va.Type().Elem()))
+		return va.Interface()
+	}
+
+	return b
+}
+
+// mergeMap merges a with b, attempting to merge any nested
+// values in nested maps but eventually overwriting anything
+// in a that can't be merged with whatever is in b.
+func mergeMapIface(a map[string]interface{}, b map[string]interface{}) map[string]interface{} {
+	for bK, bV := range b {
+		if aV, ok := a[bK]; ok {
+			if (reflect.ValueOf(aV).Type().Kind() == reflect.ValueOf(bV).Type().Kind()) ||
+				((reflect.ValueOf(aV).Type().Kind() == reflect.Slice) && reflect.ValueOf(aV).Type().Elem().Kind() == reflect.ValueOf(bV).Type().Kind()) {
+				nV := []interface{}{aV, bV}
+				a[bK] = nV
+			} else {
+				a[bK] = merge(a[bK], bV)
+			}
+		} else {
+			a[bK] = bV
+		}
+	}
+	return a
+}
+
+// mergeSlice merges a with b and returns the result.
+func mergeSliceIface(a []interface{}, b []interface{}) []interface{} {
+	a = append(a, b...)
+	return a
+}
+
+type tag struct {
+	key  string
+	name string
+	opts []string
+}