initial commit

opener.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+)
+
+// hostOpen launches the platform's "open" handler for target (a URL, file path,
+// or opaque string) without blocking. Errors after launch are logged, not
+// returned, since the GUI handler is fire-and-forget.
+//
+// It resolves the opener via realOpenerPath so a host that also shadows
+// `xdg-open`/`open` with this binary doesn't recurse back into client mode.
+func hostOpen(target string) error {
+	name, args := openCommand(target)
+	bin, err := realOpenerPath(name)
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command(bin, args...)
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("start %s: %w", bin, err)
+	}
+	go func() {
+		if err := cmd.Wait(); err != nil {
+			log.Printf("open %q exited: %v", target, err)
+		}
+	}()
+	return nil
+}
+
+func openCommand(target string) (string, []string) {
+	switch runtime.GOOS {
+	case "darwin":
+		return "open", []string{target}
+	case "windows":
+		return "rundll32", []string{"url.dll,FileProtocolHandler", target}
+	default:
+		return "xdg-open", []string{target}
+	}
+}
+
+// defaultOpenerName is the platform's native opener, used as the fallback target
+// when we were invoked as `open-proxy open` rather than under a shadowed name.
+func defaultOpenerName() string {
+	if runtime.GOOS == "darwin" {
+		return "open"
+	}
+	return "xdg-open"
+}
+
+// localOpen runs the real opener (the next `name` on $PATH that isn't us) for
+// arg. Used as the client-side fallback when the host is unreachable.
+func localOpen(name, arg string) error {
+	bin, err := realOpenerPath(name)
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command(bin, arg)
+	cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
+	return cmd.Run()
+}
+
+// realOpenerPath finds an executable named `name` on $PATH that is not this
+// binary (so a symlink shadowing `xdg-open`/`open` doesn't recurse into us).
+func realOpenerPath(name string) (string, error) {
+	self := selfFileInfo()
+	for _, dir := range filepath.SplitList(os.Getenv("PATH")) {
+		if dir == "" {
+			continue
+		}
+		cand := filepath.Join(dir, name)
+		info, err := os.Stat(cand) // follows symlinks
+		if err != nil || info.IsDir() || info.Mode()&0o111 == 0 {
+			continue
+		}
+		// Compare by file identity (device+inode), not path string: a symlink or
+		// hardlink pointing back at this binary is recognized as us regardless of
+		// how its path is spelled or whether $PATH entries are relative.
+		if self != nil && os.SameFile(self, info) {
+			continue
+		}
+		return cand, nil
+	}
+	return "", fmt.Errorf("no real %q found on PATH", name)
+}
+
+func selfFileInfo() os.FileInfo {
+	exe, err := os.Executable()
+	if err != nil {
+		return nil
+	}
+	info, err := os.Stat(exe)
+	if err != nil {
+		return nil
+	}
+	return info
+}