75 lines
2.0 KiB
Go
75 lines
2.0 KiB
Go
package proxy
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import (
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"net/http"
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"net/http/httputil"
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"net/url"
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"strings"
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)
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// NewReverseProxy builds a reverse proxy to target base URL with path rewriting:
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// stripPrefix (/api/{alias}) + pathPrefix (/v1) + remainder, joined onto target via url.JoinPath
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// (e.g. https://host/api/ + v1 + users → https://host/api/v1/users).
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func NewReverseProxy(target *url.URL, stripPrefix, pathPrefix string, setAuth string) *httputil.ReverseProxy {
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proxy := httputil.NewSingleHostReverseProxy(target)
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orig := proxy.Director
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targetQuery := target.RawQuery
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proxy.Director = func(req *http.Request) {
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p := req.URL.Path
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if !strings.HasPrefix(p, stripPrefix) {
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orig(req)
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if setAuth != "" {
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req.Header.Set("Authorization", setAuth)
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}
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// Server-side requests carry RequestURI; client RoundTrip rejects it with URL.Host set.
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req.RequestURI = ""
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req.Header.Del("Host")
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req.Host = req.URL.Host
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return
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}
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rest := strings.TrimPrefix(p, stripPrefix)
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rest = strings.TrimPrefix(rest, "/")
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joined := buildUpstreamURL(target, pathPrefix, rest)
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req.URL.Scheme = joined.Scheme
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req.URL.Host = joined.Host
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req.URL.Path = joined.Path
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req.URL.RawPath = joined.RawPath
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req.URL.Opaque = ""
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// Match Host header to authority; clear stale map entry (e.g. from httptest.NewRequest).
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req.Header.Del("Host")
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req.Host = req.URL.Host
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if targetQuery == "" || req.URL.RawQuery == "" {
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req.URL.RawQuery = targetQuery + req.URL.RawQuery
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} else {
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req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
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}
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if setAuth != "" {
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req.Header.Set("Authorization", setAuth)
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}
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req.RequestURI = ""
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}
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return proxy
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}
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func buildUpstreamURL(target *url.URL, pathPrefix, rest string) *url.URL {
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rel := strings.Trim(pathPrefix, "/")
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if rest != "" {
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if rel != "" {
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rel = rel + "/" + rest
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} else {
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rel = rest
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}
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}
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var parts []string
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for _, seg := range strings.Split(rel, "/") {
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if seg != "" {
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parts = append(parts, seg)
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}
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}
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if len(parts) == 0 {
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out := *target
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return &out
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}
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return target.JoinPath(parts...)
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}
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