Add reducer

main.go

@@ -87,8 +87,11 @@ func main() {
 		}
 		fileName = path.Base(filePath)
 		src = f
-	} else {
+	} else if !stdinIsTty && len(args) == 0 {
 		src = os.Stdin
+	} else {
+		reduce(args)
+		return
 	}
 
 	data, err := io.ReadAll(src)

reduce.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	_ "embed"
+	"fmt"
+	"os"
+	"os/exec"
+	"path"
+)
+
+//go:embed npm/index.js
+var src []byte
+
+func reduce(fns []string) {
+	script := path.Join(os.TempDir(), fmt.Sprintf("fx-%v.js", version))
+	_, err := os.Stat(script)
+	if os.IsNotExist(err) {
+		err := os.WriteFile(script, src, 0644)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	deno := false
+	bin, err := exec.LookPath("node")
+	if err != nil {
+		if err != nil {
+			bin, err = exec.LookPath("deno")
+			if err != nil {
+				_, _ = fmt.Fprintf(os.Stderr, "Node.js or Deno is required to run fx with reducers.\n")
+				os.Exit(1)
+			}
+			deno = true
+		}
+	}
+
+	var args []string
+	if deno {
+		args = []string{"run", "-A", script}
+	} else {
+		args = []string{script}
+	}
+	args = append(args, fns...)
+
+	cmd := exec.Command(bin, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err = cmd.Run()
+
+	switch err := err.(type) {
+	case nil:
+		os.Exit(0)
+	case *exec.ExitError:
+		os.Exit(err.ExitCode())
+	default:
+		panic(err)
+	}
+}

version.go

@@ -1,3 +1,3 @@
 package main
 
-const version = "30"
+const version = "30.0.0"