v0.0.479 AccessStruct

reflectext/structAccess.go

@@ -0,0 +1,185 @@
+package reflectext
+
+import (
+	"errors"
+	"gogs.mikescher.com/BlackForestBytes/goext/langext"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+var ErrAccessStructInvalidFieldType = errors.New("invalid field type")
+var ErrAccessStructFieldInPathWasNil = errors.New("a field in the path was nil")
+var ErrAccessStructInvalidArrayIndex = errors.New("invalid array index")
+var ErrAccessStructInvalidMapKey = errors.New("invalid map key")
+var ErrAccessStructArrayAccess = errors.New("trying to access array")
+var ErrAccessStructMapAccess = errors.New("trying to access map")
+var ErrAccessStructMissingField = errors.New("missing field")
+
+type AccessStructOpt struct {
+	ReturnNilOnMissingFields          bool    // return nil (instead of error) when a field in the path is missing (aka the supplied path is wrong)
+	ReturnNilOnNilPtrFields           bool    // return nil (instead of error) when a field in the path is nil
+	ReturnNilOnWrongFinalFieldType    bool    // return nil (instead of error) when the (final) field is not of the requested generic type
+	ReturnNilOnWrongIntermedFieldType bool    // return nil (instead of error) when the intermediate field has an invalid type
+	ReturnNilOnInvalidArrayIndizes    bool    // return nil (instead of error) when trying to acces an array with an invalid index (not a number or out of range)
+	ReturnNilOnMissingMapKeys         bool    // return nil (instead of error) when trying to access a map with a missing key
+	UsedTagForKeys                    *string // Use this tag for key names in the struct (instead of the StructField.Name)
+	PreventArrayAccess                bool    // do not access array indizes - throw an error instead
+	PreventMapAccess                  bool    // do not access maps - throw an error instead
+}
+
+func AccessJSONStruct[TResult any](v any, path string) (TResult, error) {
+	return AccessStructByStringPath[TResult](v, path, AccessStructOpt{UsedTagForKeys: langext.Ptr("json")})
+}
+
+func AccessStruct[TResult any](v any, path string) (TResult, error) {
+	return AccessStructByStringPath[TResult](v, path, AccessStructOpt{})
+}
+
+func AccessStructByArrayPath[TResult any](v any, path []string, opts ...AccessStructOpt) (TResult, error) {
+	opt := AccessStructOpt{}
+	if len(opts) > 0 {
+		opt = opts[0]
+	}
+
+	resultVal, err := accessStructByPath(reflect.ValueOf(v), path, opt)
+	if err != nil {
+		return *new(TResult), err
+	}
+
+	if resultValCast, ok := resultVal.(TResult); ok {
+		return resultValCast, nil
+	} else if opt.ReturnNilOnWrongFinalFieldType {
+		return *new(TResult), nil
+	} else {
+		return *new(TResult), ErrAccessStructInvalidFieldType
+	}
+}
+
+func AccessStructByStringPath[TResult any](v any, path string, opts ...AccessStructOpt) (TResult, error) {
+	opt := AccessStructOpt{}
+	if len(opts) > 0 {
+		opt = opts[0]
+	}
+	arrpath := strings.Split(path, ".")
+
+	resultVal, err := accessStructByPath(reflect.ValueOf(v), arrpath, opt)
+	if err != nil {
+		return *new(TResult), err
+	}
+
+	if resultValCast, ok := resultVal.(TResult); ok {
+		return resultValCast, nil
+	} else if opt.ReturnNilOnWrongFinalFieldType {
+		return *new(TResult), nil
+	} else {
+		return *new(TResult), ErrAccessStructInvalidFieldType
+	}
+}
+
+func accessStructByPath(val reflect.Value, path []string, opt AccessStructOpt) (any, error) {
+	if len(path) == 0 {
+		return val.Interface(), nil
+	}
+
+	currPath := path[0]
+
+	if val.Kind() == reflect.Ptr {
+		if val.IsNil() {
+			if opt.ReturnNilOnNilPtrFields {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructFieldInPathWasNil
+			}
+		}
+		return accessStructByPath(val.Elem(), path, opt)
+	}
+
+	if val.Kind() == reflect.Array || val.Kind() == reflect.Slice {
+		if opt.PreventArrayAccess {
+			return nil, ErrAccessStructArrayAccess
+		}
+
+		if val.IsNil() {
+			if opt.ReturnNilOnNilPtrFields {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructFieldInPathWasNil
+			}
+		}
+
+		arrIdx, err := strconv.ParseInt(currPath, 10, 64)
+		if err != nil {
+			if opt.ReturnNilOnInvalidArrayIndizes {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructInvalidArrayIndex
+			}
+		}
+		if arrIdx < 0 || int(arrIdx) >= val.Len() {
+			if opt.ReturnNilOnInvalidArrayIndizes {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructInvalidArrayIndex
+			}
+		}
+		return accessStructByPath(val.Index(int(arrIdx)), path[1:], opt)
+	}
+
+	if val.Kind() == reflect.Map {
+		if opt.PreventMapAccess {
+			return nil, ErrAccessStructMapAccess
+		}
+
+		if val.IsNil() {
+			if opt.ReturnNilOnNilPtrFields {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructFieldInPathWasNil
+			}
+		}
+
+		mapval := val.MapIndex(reflect.ValueOf(currPath))
+		if !mapval.IsValid() || mapval.IsZero() {
+			if opt.ReturnNilOnMissingMapKeys {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructInvalidMapKey
+			}
+		}
+
+		return accessStructByPath(mapval, path[1:], opt)
+	}
+
+	if val.Kind() == reflect.Struct {
+		if opt.UsedTagForKeys != nil {
+			for i := 0; i < val.NumField(); i++ {
+				if val.Type().Field(i).Tag.Get(*opt.UsedTagForKeys) == currPath {
+					return accessStructByPath(val.Field(i), path[1:], opt)
+				}
+			}
+			if opt.ReturnNilOnMissingFields {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructMissingField
+			}
+		} else {
+			for i := 0; i < val.NumField(); i++ {
+				if val.Type().Field(i).Name == currPath {
+					return accessStructByPath(val.Field(i), path[1:], opt)
+				}
+			}
+			if opt.ReturnNilOnMissingFields {
+				return nil, nil
+			} else {
+				return nil, ErrAccessStructMissingField
+			}
+		}
+	}
+
+	if opt.ReturnNilOnWrongIntermedFieldType {
+		return nil, nil
+	} else {
+		return nil, ErrAccessStructMissingField
+	}
+}