71 lines
1.5 KiB
Go
71 lines
1.5 KiB
Go
package urlenc
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import (
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"bytes"
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"compress/flate"
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"encoding/base64"
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"io"
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"sort"
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"strings"
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"oss.terrastruct.com/util-go/xdefer"
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"oss.terrastruct.com/d2/d2graph"
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)
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var compressionDict = "->" +
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"<-" +
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"--" +
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"<->"
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func init() {
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var common []string
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for k := range d2graph.ReservedKeywords {
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common = append(common, k)
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}
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sort.Strings(common)
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for _, k := range common {
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compressionDict += k
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}
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}
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// Encode takes a D2 script and encodes it as a compressed base64 string for embedding in URLs.
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func Encode(raw string) (_ string, err error) {
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defer xdefer.Errorf(&err, "failed to encode d2 script")
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b := &bytes.Buffer{}
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zw, err := flate.NewWriterDict(b, flate.DefaultCompression, []byte(compressionDict))
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if err != nil {
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return "", err
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}
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if _, err := io.Copy(zw, strings.NewReader(raw)); err != nil {
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return "", err
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}
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if err := zw.Close(); err != nil {
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return "", err
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}
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encoded := base64.URLEncoding.EncodeToString(b.Bytes())
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return encoded, nil
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}
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// Decode decodes a compressed base64 D2 string.
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func Decode(encoded string) (_ string, err error) {
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defer xdefer.Errorf(&err, "failed to decode d2 script")
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b64Decoded, err := base64.URLEncoding.DecodeString(encoded)
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if err != nil {
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return "", err
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}
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zr := flate.NewReaderDict(bytes.NewReader(b64Decoded), []byte(compressionDict))
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var b bytes.Buffer
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if _, err := io.Copy(&b, zr); err != nil {
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return "", err
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}
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if err := zr.Close(); err != nil {
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return "", nil
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}
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return b.String(), nil
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}
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