package api import ( "bytes" "encoding/base64" "fmt" "net/http" "github.com/diamondburned/arikawa/v2/utils/json" "github.com/pkg/errors" ) var ErrInvalidImageCT = errors.New("unknown image content-type") var ErrInvalidImageData = errors.New("invalid image data") type ErrImageTooLarge struct { Size, Max int } func (err ErrImageTooLarge) Error() string { return fmt.Sprintf("Image is %.02fkb, larger than %.02fkb", float64(err.Size)/1000, float64(err.Max)/1000) } // Image wraps around the Data URI Scheme that Discord uses: // https://discordapp.com/developers/docs/reference#image-data type Image struct { // ContentType is optional and will be automatically detected. However, it // should always return "image/jpeg," "image/png" or "image/gif". ContentType string // Just raw content of the file. Content []byte } func DecodeImage(data []byte) (*Image, error) { parts := bytes.SplitN(data, []byte{';'}, 2) if len(parts) < 2 { return nil, ErrInvalidImageData } if !bytes.HasPrefix(parts[0], []byte("data:")) { return nil, errors.Wrap(ErrInvalidImageData, "invalid header") } if !bytes.HasPrefix(parts[1], []byte("base64,")) { return nil, errors.Wrap(ErrInvalidImageData, "invalid base64") } var b64 = parts[1][len("base64,"):] var img = Image{ ContentType: string(parts[0][len("data:"):]), Content: make([]byte, base64.StdEncoding.DecodedLen(len(b64))), } base64.StdEncoding.Decode(img.Content, b64) return &img, nil } func (i Image) Validate(maxSize int) error { if maxSize > 0 && len(i.Content) > maxSize { return ErrImageTooLarge{len(i.Content), maxSize} } switch i.ContentType { case "image/png", "image/jpeg", "image/gif": return nil default: return ErrInvalidImageCT } } func (i Image) Encode() ([]byte, error) { if i.ContentType == "" { var max = 512 if len(i.Content) < max { max = len(i.Content) } i.ContentType = http.DetectContentType(i.Content[:max]) } if err := i.Validate(0); err != nil { return nil, err } b64enc := make([]byte, base64.StdEncoding.EncodedLen(len(i.Content))) base64.StdEncoding.Encode(b64enc, i.Content) return bytes.Join([][]byte{ []byte("data:"), []byte(i.ContentType), []byte(";base64,"), b64enc, }, nil), nil } var _ json.Marshaler = (*Image)(nil) var _ json.Unmarshaler = (*Image)(nil) func (i Image) MarshalJSON() ([]byte, error) { if len(i.Content) == 0 { return []byte("null"), nil } b, err := i.Encode() if err != nil { return nil, err } return bytes.Join([][]byte{{'"'}, b, {'"'}}, nil), nil } func (i *Image) UnmarshalJSON(v []byte) error { // Trim string v = bytes.Trim(v, `"`) // Accept a nil image. if string(v) == "null" { return nil } img, err := DecodeImage(v) if err != nil { return err } *i = *img return nil }