package middleware
import (
"fmt"
"html"
"net/http"
"strings"
)
// GoImport serves the `` tag required by `go install` /
// `go get` to resolve the vanity path `atcr.io/...` to the source repository.
//
// Go tooling requests `https://atcr.io/?go-get=1` and expects an HTML
// document with a meta tag of the form:
//
//
//
// The meta tag must be present on every subpath under the module root, so this
// runs as middleware at the top of the chain and short-circuits any request
// carrying `?go-get=1`.
//
// For non-go-get requests on paths that look like Go module subpaths
// (/cmd/, /pkg/, /internal/, /scanner/), the middleware redirects to the
// corresponding source-tree URL in the git host so a browser visit doesn't
// 404. The redirect template mirrors the `go-source` meta tag's
// `{repoURL}/tree/main{/dir}` form.
func GoImport(modulePath, repoURL string) func(http.Handler) http.Handler {
body := fmt.Sprintf(
`go get %s`,
html.EscapeString(modulePath),
html.EscapeString(repoURL),
html.EscapeString(modulePath),
html.EscapeString(repoURL),
html.EscapeString(repoURL),
html.EscapeString(repoURL),
html.EscapeString(modulePath),
)
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.URL.Query().Get("go-get") == "1" {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
w.Header().Set("Cache-Control", "public, max-age=300")
_, _ = w.Write([]byte(body))
return
}
// Browser visits to recognizable Go subpaths get redirected to
// the repo source tree instead of falling through to the
// appview router (which 404s for these paths).
if isGoModuleSubpath(r.URL.Path) {
target := repoURL + "/tree/main" + r.URL.Path
http.Redirect(w, r, target, http.StatusFound)
return
}
next.ServeHTTP(w, r)
})
}
}
// isGoModuleSubpath reports whether p looks like a Go module source path
// (under cmd/, pkg/, internal/, or scanner/). The check is intentionally
// narrow so the redirect doesn't hijack other appview routes.
func isGoModuleSubpath(p string) bool {
switch {
case strings.HasPrefix(p, "/cmd/"),
strings.HasPrefix(p, "/pkg/"),
strings.HasPrefix(p, "/internal/"):
return true
}
return false
}