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