package dynamodbattribute import ( "fmt" "reflect" "strconv" "time" "github.com/aws/aws-sdk-go/aws" "github.com/aws/aws-sdk-go/service/dynamodb" ) // An UnixTime provides aliasing of time.Time into a type that when marshaled // and unmarshaled with DynamoDB AttributeValues it will be done so as number // instead of string in seconds since January 1, 1970 UTC. // // This type is useful as an alternative to the struct tag `unixtime` when you // want to have your time value marshaled as Unix time in seconds intead of // the default time.RFC3339. // // Important to note that zero value time as unixtime is not 0 seconds // from January 1, 1970 UTC, but -62135596800. Which is seconds between // January 1, 0001 UTC, and January 1, 0001 UTC. type UnixTime time.Time // String calls the underlying time.Time.String to return a human readable representation func (e UnixTime) String() string { return time.Time(e).String() } // MarshalDynamoDBAttributeValue implements the Marshaler interface so that // the UnixTime can be marshaled from to a DynamoDB AttributeValue number // value encoded in the number of seconds since January 1, 1970 UTC. func (e UnixTime) MarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error { t := time.Time(e) s := strconv.FormatInt(t.Unix(), 10) av.N = &s return nil } // UnmarshalDynamoDBAttributeValue implements the Unmarshaler interface so that // the UnixTime can be unmarshaled from a DynamoDB AttributeValue number representing // the number of seconds since January 1, 1970 UTC. // // If an error parsing the AttributeValue number occurs UnmarshalError will be // returned. func (e *UnixTime) UnmarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error { t, err := decodeUnixTime(aws.StringValue(av.N)) if err != nil { return err } *e = UnixTime(t) return nil } // A Marshaler is an interface to provide custom marshaling of Go value types // to AttributeValues. Use this to provide custom logic determining how a // Go Value type should be marshaled. // // type ExampleMarshaler struct { // Value int // } // func (m *ExampleMarshaler) MarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error { // n := fmt.Sprintf("%v", m.Value) // av.N = &n // return nil // } type Marshaler interface { MarshalDynamoDBAttributeValue(*dynamodb.AttributeValue) error } // Marshal will serialize the passed in Go value type into a DynamoDB AttributeValue // type. This value can be used in DynamoDB API operations to simplify marshaling // your Go value types into AttributeValues. // // Marshal will recursively transverse the passed in value marshaling its // contents into a AttributeValue. Marshal supports basic scalars // (int,uint,float,bool,string), maps, slices, and structs. Anonymous // nested types are flattened based on Go anonymous type visibility. // // Marshaling slices to AttributeValue will default to a List for all // types except for []byte and [][]byte. []byte will be marshaled as // Binary data (B), and [][]byte will be marshaled as binary data set // (BS). // // `dynamodbav` struct tag can be used to control how the value will be // marshaled into a AttributeValue. // // // Field is ignored // Field int `dynamodbav:"-"` // // // Field AttributeValue map key "myName" // Field int `dynamodbav:"myName"` // // // Field AttributeValue map key "myName", and // // Field is omitted if it is empty // Field int `dynamodbav:"myName,omitempty"` // // // Field AttributeValue map key "Field", and // // Field is omitted if it is empty // Field int `dynamodbav:",omitempty"` // // // Field's elems will be omitted if empty // // only valid for slices, and maps. // Field []string `dynamodbav:",omitemptyelem"` // // // Field will be marshaled as a AttributeValue string // // only value for number types, (int,uint,float) // Field int `dynamodbav:",string"` // // // Field will be marshaled as a binary set // Field [][]byte `dynamodbav:",binaryset"` // // // Field will be marshaled as a number set // Field []int `dynamodbav:",numberset"` // // // Field will be marshaled as a string set // Field []string `dynamodbav:",stringset"` // // // Field will be marshaled as Unix time number in seconds. // // This tag is only valid with time.Time typed struct fields. // // Important to note that zero value time as unixtime is not 0 seconds // // from January 1, 1970 UTC, but -62135596800. Which is seconds between // // January 1, 0001 UTC, and January 1, 0001 UTC. // Field time.Time `dynamodbav:",unixtime"` // // The omitempty tag is only used during Marshaling and is ignored for // Unmarshal. Any zero value or a value when marshaled results in a // AttributeValue NULL will be added to AttributeValue Maps during struct // marshal. The omitemptyelem tag works the same as omitempty except it // applies to maps and slices instead of struct fields, and will not be // included in the marshaled AttributeValue Map, List, or Set. // // For convenience and backwards compatibility with ConvertTo functions // json struct tags are supported by the Marshal and Unmarshal. If // both json and dynamodbav struct tags are provided the json tag will // be ignored in favor of dynamodbav. // // All struct fields and with anonymous fields, are marshaled unless the // any of the following conditions are meet. // // - the field is not exported // - json or dynamodbav field tag is "-" // - json or dynamodbav field tag specifies "omitempty", and is empty. // // Pointer and interfaces values encode as the value pointed to or contained // in the interface. A nil value encodes as the AttributeValue NULL value. // // Channel, complex, and function values are not encoded and will be skipped // when walking the value to be marshaled. // // When marshaling any error that occurs will halt the marshal and return // the error. // // Marshal cannot represent cyclic data structures and will not handle them. // Passing cyclic structures to Marshal will result in an infinite recursion. func Marshal(in interface{}) (*dynamodb.AttributeValue, error) { return NewEncoder().Encode(in) } // MarshalMap is an alias for Marshal func which marshals Go value // type to a map of AttributeValues. // // This is useful for DynamoDB APIs such as PutItem. func MarshalMap(in interface{}) (map[string]*dynamodb.AttributeValue, error) { av, err := NewEncoder().Encode(in) if err != nil || av == nil || av.M == nil { return map[string]*dynamodb.AttributeValue{}, err } return av.M, nil } // MarshalList is an alias for Marshal func which marshals Go value // type to a slice of AttributeValues. func MarshalList(in interface{}) ([]*dynamodb.AttributeValue, error) { av, err := NewEncoder().Encode(in) if err != nil || av == nil || av.L == nil { return []*dynamodb.AttributeValue{}, err } return av.L, nil } // A MarshalOptions is a collection of options shared between marshaling // and unmarshaling type MarshalOptions struct { // States that the encoding/json struct tags should be supported. // if a `dynamodbav` struct tag is also provided the encoding/json // tag will be ignored. // // Enabled by default. SupportJSONTags bool // Support other custom struct tag keys, such as `yaml` or `toml`. // Note that values provided with a custom TagKey must also be supported // by the (un)marshalers in this package. TagKey string // EnableEmptyCollections modifies how structures, maps, and slices are (un)marshalled. // When set to true empty collection values will be preserved as their respective // empty DynamoDB AttributeValue type when set to true. // // Disabled by default. EnableEmptyCollections bool } // An Encoder provides marshaling Go value types to AttributeValues. type Encoder struct { MarshalOptions // Empty strings, "", will be marked as NULL AttributeValue types. // Will not apply to lists, sets, or maps. Use the struct tag `omitemptyelem` // to skip empty (zero) values in lists, sets and maps. // // Enabled by default. NullEmptyString bool // Empty byte slices, len([]byte{}) == 0, will be marked as NULL AttributeValue types. // Will not apply to lists, sets, or maps. Use the struct tag `omitemptyelem` // to skip empty (zero) values in lists, sets and maps. // // Enabled by default. NullEmptyByteSlice bool } // NewEncoder creates a new Encoder with default configuration. Use // the `opts` functional options to override the default configuration. func NewEncoder(opts ...func(*Encoder)) *Encoder { e := &Encoder{ MarshalOptions: MarshalOptions{ SupportJSONTags: true, }, NullEmptyString: true, NullEmptyByteSlice: true, } for _, o := range opts { o(e) } return e } // Encode will marshal a Go value type to an AttributeValue. Returning // the AttributeValue constructed or error. func (e *Encoder) Encode(in interface{}) (*dynamodb.AttributeValue, error) { av := &dynamodb.AttributeValue{} if err := e.encode(av, reflect.ValueOf(in), tag{}); err != nil { return nil, err } return av, nil } func (e *Encoder) encode(av *dynamodb.AttributeValue, v reflect.Value, fieldTag tag) error { // We should check for omitted values first before dereferencing. if fieldTag.OmitEmpty && emptyValue(v, e.EnableEmptyCollections) { encodeNull(av) return nil } // Handle both pointers and interface conversion into types v = valueElem(v) if v.Kind() != reflect.Invalid { if used, err := tryMarshaler(av, v); used { return err } } switch v.Kind() { case reflect.Invalid: encodeNull(av) case reflect.Struct: return e.encodeStruct(av, v, fieldTag) case reflect.Map: return e.encodeMap(av, v, fieldTag) case reflect.Slice, reflect.Array: return e.encodeSlice(av, v, fieldTag) case reflect.Chan, reflect.Func, reflect.UnsafePointer: // do nothing for unsupported types default: return e.encodeScalar(av, v, fieldTag) } return nil } func (e *Encoder) encodeStruct(av *dynamodb.AttributeValue, v reflect.Value, fieldTag tag) error { // To maintain backwards compatibility with ConvertTo family of methods which // converted time.Time structs to strings if v.Type().ConvertibleTo(timeType) { var t time.Time t = v.Convert(timeType).Interface().(time.Time) if fieldTag.AsUnixTime { return UnixTime(t).MarshalDynamoDBAttributeValue(av) } s := t.Format(time.RFC3339Nano) av.S = &s return nil } av.M = map[string]*dynamodb.AttributeValue{} fields := unionStructFields(v.Type(), e.MarshalOptions) for _, f := range fields.All() { if f.Name == "" { return &InvalidMarshalError{msg: "map key cannot be empty"} } fv, found := encoderFieldByIndex(v, f.Index) if !found { continue } elem := &dynamodb.AttributeValue{} err := e.encode(elem, fv, f.tag) if err != nil { return err } skip, err := keepOrOmitEmpty(f.OmitEmpty, elem, err) if err != nil { return err } else if skip { continue } av.M[f.Name] = elem } if len(av.M) == 0 && !e.EnableEmptyCollections { encodeNull(av) } return nil } func (e *Encoder) encodeMap(av *dynamodb.AttributeValue, v reflect.Value, fieldTag tag) error { av.M = map[string]*dynamodb.AttributeValue{} for _, key := range v.MapKeys() { keyName := fmt.Sprint(key.Interface()) if keyName == "" { return &InvalidMarshalError{msg: "map key cannot be empty"} } elemVal := v.MapIndex(key) elem := &dynamodb.AttributeValue{} err := e.encode(elem, elemVal, tag{}) skip, err := keepOrOmitEmpty(fieldTag.OmitEmptyElem, elem, err) if err != nil { return err } else if skip { continue } av.M[keyName] = elem } if v.IsNil() || (len(av.M) == 0 && !e.EnableEmptyCollections) { encodeNull(av) } return nil } func (e *Encoder) encodeSlice(av *dynamodb.AttributeValue, v reflect.Value, fieldTag tag) error { if v.Kind() == reflect.Array && v.Len() == 0 && e.EnableEmptyCollections && fieldTag.OmitEmpty { encodeNull(av) return nil } switch v.Type().Elem().Kind() { case reflect.Uint8: slice := reflect.MakeSlice(byteSliceType, v.Len(), v.Len()) reflect.Copy(slice, v) b := slice.Bytes() if (v.Kind() == reflect.Slice && v.IsNil()) || (len(b) == 0 && !e.EnableEmptyCollections && e.NullEmptyByteSlice) { encodeNull(av) return nil } av.B = append([]byte{}, b...) default: var elemFn func(dynamodb.AttributeValue) error if fieldTag.AsBinSet || v.Type() == byteSliceSlicetype { // Binary Set av.BS = make([][]byte, 0, v.Len()) elemFn = func(elem dynamodb.AttributeValue) error { if elem.B == nil { return &InvalidMarshalError{msg: "binary set must only contain non-nil byte slices"} } av.BS = append(av.BS, elem.B) return nil } } else if fieldTag.AsNumSet { // Number Set av.NS = make([]*string, 0, v.Len()) elemFn = func(elem dynamodb.AttributeValue) error { if elem.N == nil { return &InvalidMarshalError{msg: "number set must only contain non-nil string numbers"} } av.NS = append(av.NS, elem.N) return nil } } else if fieldTag.AsStrSet { // String Set av.SS = make([]*string, 0, v.Len()) elemFn = func(elem dynamodb.AttributeValue) error { if elem.S == nil { return &InvalidMarshalError{msg: "string set must only contain non-nil strings"} } av.SS = append(av.SS, elem.S) return nil } } else { // List av.L = make([]*dynamodb.AttributeValue, 0, v.Len()) elemFn = func(elem dynamodb.AttributeValue) error { av.L = append(av.L, &elem) return nil } } if n, err := e.encodeList(v, fieldTag, elemFn); err != nil { return err } else if (v.Kind() == reflect.Slice && v.IsNil()) || (n == 0 && !e.EnableEmptyCollections) { encodeNull(av) } } return nil } func (e *Encoder) encodeList(v reflect.Value, fieldTag tag, elemFn func(dynamodb.AttributeValue) error) (int, error) { count := 0 for i := 0; i < v.Len(); i++ { elem := dynamodb.AttributeValue{} err := e.encode(&elem, v.Index(i), tag{OmitEmpty: fieldTag.OmitEmptyElem}) skip, err := keepOrOmitEmpty(fieldTag.OmitEmptyElem, &elem, err) if err != nil { return 0, err } else if skip { continue } if err := elemFn(elem); err != nil { return 0, err } count++ } return count, nil } func (e *Encoder) encodeScalar(av *dynamodb.AttributeValue, v reflect.Value, fieldTag tag) error { if v.Type() == numberType { s := v.String() if fieldTag.AsString { av.S = &s } else { av.N = &s } return nil } switch v.Kind() { case reflect.Bool: av.BOOL = new(bool) *av.BOOL = v.Bool() case reflect.String: if err := e.encodeString(av, v); err != nil { return err } default: // Fallback to encoding numbers, will return invalid type if not supported if err := e.encodeNumber(av, v); err != nil { return err } if fieldTag.AsString && av.NULL == nil && av.N != nil { av.S = av.N av.N = nil } } return nil } func (e *Encoder) encodeNumber(av *dynamodb.AttributeValue, v reflect.Value) error { if used, err := tryMarshaler(av, v); used { return err } var out string switch v.Kind() { case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: out = encodeInt(v.Int()) case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64: out = encodeUint(v.Uint()) case reflect.Float32: out = encodeFloat(v.Float(), 32) case reflect.Float64: out = encodeFloat(v.Float(), 64) default: return &unsupportedMarshalTypeError{Type: v.Type()} } av.N = &out return nil } func (e *Encoder) encodeString(av *dynamodb.AttributeValue, v reflect.Value) error { if used, err := tryMarshaler(av, v); used { return err } switch v.Kind() { case reflect.String: s := v.String() if len(s) == 0 && e.NullEmptyString { encodeNull(av) } else { av.S = &s } default: return &unsupportedMarshalTypeError{Type: v.Type()} } return nil } func encodeInt(i int64) string { return strconv.FormatInt(i, 10) } func encodeUint(u uint64) string { return strconv.FormatUint(u, 10) } func encodeFloat(f float64, bitSize int) string { return strconv.FormatFloat(f, 'f', -1, bitSize) } func encodeNull(av *dynamodb.AttributeValue) { t := true *av = dynamodb.AttributeValue{NULL: &t} } // encoderFieldByIndex finds the field with the provided nested index func encoderFieldByIndex(v reflect.Value, index []int) (reflect.Value, bool) { for i, x := range index { if i > 0 && v.Kind() == reflect.Ptr && v.Type().Elem().Kind() == reflect.Struct { if v.IsNil() { return reflect.Value{}, false } v = v.Elem() } v = v.Field(x) } return v, true } func valueElem(v reflect.Value) reflect.Value { switch v.Kind() { case reflect.Interface, reflect.Ptr: for v.Kind() == reflect.Interface || v.Kind() == reflect.Ptr { v = v.Elem() } } return v } func emptyValue(v reflect.Value, emptyCollections bool) bool { switch v.Kind() { case reflect.Array: return v.Len() == 0 && !emptyCollections case reflect.Map, reflect.Slice: return v.IsNil() || (v.Len() == 0 && !emptyCollections) case reflect.String: return v.Len() == 0 case reflect.Bool: return !v.Bool() case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: return v.Int() == 0 case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: return v.Uint() == 0 case reflect.Float32, reflect.Float64: return v.Float() == 0 case reflect.Interface, reflect.Ptr: return v.IsNil() } return false } func tryMarshaler(av *dynamodb.AttributeValue, v reflect.Value) (bool, error) { if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() { v = v.Addr() } if v.Type().NumMethod() == 0 { return false, nil } if m, ok := v.Interface().(Marshaler); ok { return true, m.MarshalDynamoDBAttributeValue(av) } return false, nil } func keepOrOmitEmpty(omitEmpty bool, av *dynamodb.AttributeValue, err error) (bool, error) { if err != nil { if _, ok := err.(*unsupportedMarshalTypeError); ok { return true, nil } return false, err } if av.NULL != nil && omitEmpty { return true, nil } return false, nil } // An InvalidMarshalError is an error type representing an error // occurring when marshaling a Go value type to an AttributeValue. type InvalidMarshalError struct { emptyOrigError msg string } // Error returns the string representation of the error. // satisfying the error interface func (e *InvalidMarshalError) Error() string { return fmt.Sprintf("%s: %s", e.Code(), e.Message()) } // Code returns the code of the error, satisfying the awserr.Error // interface. func (e *InvalidMarshalError) Code() string { return "InvalidMarshalError" } // Message returns the detailed message of the error, satisfying // the awserr.Error interface. func (e *InvalidMarshalError) Message() string { return e.msg } // An unsupportedMarshalTypeError represents a Go value type // which cannot be marshaled into an AttributeValue and should // be skipped by the marshaler. type unsupportedMarshalTypeError struct { emptyOrigError Type reflect.Type } // Error returns the string representation of the error. // satisfying the error interface func (e *unsupportedMarshalTypeError) Error() string { return fmt.Sprintf("%s: %s", e.Code(), e.Message()) } // Code returns the code of the error, satisfying the awserr.Error // interface. func (e *unsupportedMarshalTypeError) Code() string { return "unsupportedMarshalTypeError" } // Message returns the detailed message of the error, satisfying // the awserr.Error interface. func (e *unsupportedMarshalTypeError) Message() string { return "Go value type " + e.Type.String() + " is not supported" }