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package ext
import (
"compress/gzip"
"compress/lzw"
"errors"
"io"
"log/slog"
"net/http"
"strconv"
"strings"
"git.gabrielgio.me/cerrado/pkg/u"
"github.com/andybalholm/brotli"
"github.com/klauspost/compress/zstd"
)
var (
invalidParamErr = errors.New("Invalid weighted param")
)
type CompressionResponseWriter struct {
innerWriter http.ResponseWriter
compressWriter io.Writer
}
func Compress(next func(w http.ResponseWriter, r *http.Request)) func(w http.ResponseWriter, r *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
if accept, ok := r.Header["Accept-Encoding"]; ok {
if compress, algo := GetCompressionWriter(u.FirstOrZero(accept), w); algo != "" {
defer compress.Close()
w.Header().Add("Content-Encoding", algo)
w = &CompressionResponseWriter{
innerWriter: w,
compressWriter: compress,
}
}
}
next(w, r)
}
}
func GetCompressionWriter(header string, inner io.Writer) (io.WriteCloser, string) {
c := GetCompression(header)
switch c {
case "br":
return GetBrotliWriter(inner), c
case "gzip":
return GetGZIPWriter(inner), c
case "compress":
return GetLZWWriter(inner), c
case "zstd":
return GetZSTDWriter(inner), c
default:
return nil, ""
}
}
func (c *CompressionResponseWriter) Header() http.Header {
return c.innerWriter.Header()
}
func (c *CompressionResponseWriter) Write(b []byte) (int, error) {
return c.compressWriter.Write(b)
}
func (c *CompressionResponseWriter) WriteHeader(statusCode int) {
c.innerWriter.WriteHeader(statusCode)
}
func GetCompression(header string) string {
c := "*"
q := 0.0
if header == "" {
return c
}
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding
for _, e := range strings.Split(header, ",") {
ps := strings.Split(e, ";")
if len(ps) == 2 {
w, err := getWeighedValue(ps[1])
if err != nil {
slog.Error(
"Error parsing weighting from Accept-Encoding",
"error", err,
)
continue
}
// gettting weighting value
if w > q {
q = w
c = strings.Trim(ps[0], " ")
}
} else {
if 1 > q {
q = 1
c = strings.Trim(ps[0], " ")
}
}
}
return c
}
func GetGZIPWriter(w io.Writer) io.WriteCloser {
// error can be ignored here since it will only err when compression level
// is not valid
r, _ := gzip.NewWriterLevel(w, gzip.BestCompression)
return r
}
func GetBrotliWriter(w io.Writer) io.WriteCloser {
return brotli.NewWriterLevel(w, brotli.BestCompression)
}
func GetZSTDWriter(w io.Writer) io.WriteCloser {
// error can be ignored here since it will only opts are given
r, _ := zstd.NewWriter(w)
return r
}
func GetLZWWriter(w io.Writer) io.WriteCloser {
return lzw.NewWriter(w, lzw.LSB, 8)
}
func getWeighedValue(part string) (float64, error) {
ps := strings.SplitN(part, "=", 2)
if len(ps) != 2 {
return 0, invalidParamErr
}
if name := strings.TrimSpace(ps[0]); name == "q" {
w, err := strconv.ParseFloat(ps[1], 64)
if err != nil {
return 0, err
}
return w, nil
}
return 0, invalidParamErr
}
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