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rewriter.go
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/
rewriter.go
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package proxy
import (
"bytes"
"github.com/valyala/bytebufferpool"
"github.com/valyala/fasthttp"
)
var (
contentEncodingGzip = []byte("gzip")
contentEncodingDeflate = []byte("deflate")
contentEncodingBr = []byte("br")
)
var (
contentTypePlain = []byte("text/plain")
contentTypeHTML = []byte("text/html")
contentTypeCSS = []byte("text/css")
contentTypeJS = []byte("text/javascript")
contentTypeJSAlt = []byte("application/javascript")
contentTypeJSXAlt = []byte("application/x-javascript")
contentTypeJSON = []byte("application/json")
contentTypeXML = []byte("application/xml")
contentTypeXHTML = []byte("application/xhtml")
)
type replacePair struct {
from, to []byte
}
type BodyRewriter struct {
contentTypes [][]byte
replaceRules []*replacePair
BasePath string
RewriteBaseURL bool
}
func NewBodyRewriter() *BodyRewriter {
return &BodyRewriter{
contentTypes: [][]byte{
contentTypePlain,
contentTypeHTML,
contentTypeCSS,
contentTypeJS,
contentTypeJSAlt,
contentTypeJSXAlt,
contentTypeJSON,
contentTypeXML,
contentTypeXHTML,
},
RewriteBaseURL: true,
replaceRules: make([]*replacePair, 0),
}
}
var responseBodyPool bytebufferpool.Pool
// AddReplace adds a replacement in response body from upstream.
func (r *BodyRewriter) AddReplace(from, to []byte) {
if r.replaceRules == nil {
r.replaceRules = make([]*replacePair, 0, 1)
}
r.replaceRules = append(r.replaceRules, &replacePair{from, to})
}
func getDecodedBody(resp *fasthttp.Response) []byte {
enc := resp.Header.Peek("Content-Encoding")
if bytes.Equal(enc, contentEncodingGzip) {
b, err := resp.BodyGunzip()
if err != nil {
return nil
}
return b
}
if bytes.Equal(enc, contentEncodingDeflate) {
b, err := resp.BodyInflate()
if err != nil {
return nil
}
return b
}
if bytes.Equal(enc, contentEncodingBr) {
b, err := resp.BodyUnbrotli()
if err != nil {
return nil
}
return b
}
return resp.Body()
}
func setEncodedBody(resp *fasthttp.Response, body []byte) {
if len(body) == 0 {
resp.ResetBody()
return
}
enc := resp.Header.Peek("Content-Encoding")
if bytes.Equal(enc, contentEncodingGzip) {
w := responseBodyPool.Get()
body = fasthttp.AppendGzipBytes(w.B, body)
resp.SetBody(body)
responseBodyPool.Put(w)
return
}
if bytes.Equal(enc, contentEncodingDeflate) {
w := responseBodyPool.Get()
body = fasthttp.AppendDeflateBytes(w.B, body)
resp.SetBody(body)
responseBodyPool.Put(w)
return
}
if bytes.Equal(enc, contentEncodingBr) {
w := responseBodyPool.Get()
body = fasthttp.AppendBrotliBytes(w.B, body)
resp.SetBody(body)
responseBodyPool.Put(w)
return
}
resp.SetBody(body)
}
func trimScheme(url []byte) []byte {
i := bytes.IndexByte(url, ':')
if i == -1 {
return url
}
return url[i+1:]
}
// Enabled checks if the rewriter is enabled.
func (r *BodyRewriter) Enabled() bool {
return len(r.replaceRules) > 0 || r.RewriteBaseURL
}
// RewriteResponse rewrites response body.
func (r *BodyRewriter) RewriteResponse(baseURL, upstream []byte, resp *fasthttp.Response) {
if !r.Enabled() {
return
}
ct := resp.Header.ContentType()
isRewritable := false
for _, ctb := range r.contentTypes {
if bytes.HasPrefix(ct, ctb) {
isRewritable = true
break
}
}
if !isRewritable {
return
}
body := getDecodedBody(resp)
if len(body) == 0 {
return
}
for _, v := range r.replaceRules {
body = bytes.ReplaceAll(body, v.from, v.to)
}
if r.RewriteBaseURL {
baseURL = bytes.TrimRight(baseURL, "/")
upstream = bytes.TrimRight(upstream, "/")
body = bytes.ReplaceAll(body, upstream, baseURL)
body = bytes.ReplaceAll(body, trimScheme(upstream), trimScheme(baseURL))
}
setEncodedBody(resp, body)
}