phase1: go module skeleton with subcommand stubs

cmd/md-to-html/main.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/fserg/md-to-html/internal/version"
+)
+
+func main() {
+	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr))
+}
+
+func run(args []string, stdout, stderr io.Writer) int {
+	if len(args) == 0 {
+		printUsage(stdout)
+		return 0
+	}
+
+	switch args[0] {
+	case "-h", "--help", "help":
+		printUsage(stdout)
+		return 0
+	case "serve":
+		return runServe(args[1:], stdout)
+	case "cli":
+		return runCLI(args[1:], stdout, stderr)
+	case "version":
+		return runVersion(args[1:], stdout, stderr)
+	default:
+		fmt.Fprintf(stderr, "unknown subcommand %q\n\n", args[0])
+		printUsage(stderr)
+		return 2
+	}
+}
+
+func runServe(args []string, stdout io.Writer) int {
+	fs := flag.NewFlagSet("serve", flag.ContinueOnError)
+	fs.SetOutput(io.Discard)
+	if err := fs.Parse(args); err != nil {
+		return 2
+	}
+	fmt.Fprintln(stdout, "serve not implemented yet")
+	return 0
+}
+
+func runCLI(args []string, stdout, stderr io.Writer) int {
+	fs := flag.NewFlagSet("cli", flag.ContinueOnError)
+	fs.SetOutput(io.Discard)
+	if err := fs.Parse(args); err != nil {
+		return 2
+	}
+
+	if fs.NArg() != 1 {
+		fmt.Fprintln(stderr, "usage: md-to-html cli <file.md>")
+		return 2
+	}
+
+	fmt.Fprintf(stdout, "cli not implemented yet: %s\n", fs.Arg(0))
+	return 0
+}
+
+func runVersion(args []string, stdout, stderr io.Writer) int {
+	fs := flag.NewFlagSet("version", flag.ContinueOnError)
+	fs.SetOutput(io.Discard)
+	if err := fs.Parse(args); err != nil {
+		return 2
+	}
+
+	if fs.NArg() != 0 {
+		fmt.Fprintln(stderr, "usage: md-to-html version")
+		return 2
+	}
+
+	fmt.Fprintln(stdout, version.Version)
+	return 0
+}
+
+func printUsage(w io.Writer) {
+	fmt.Fprint(w, `Usage:
+  md-to-html serve
+  md-to-html cli <file.md>
+  md-to-html version
+
+Commands:
+  serve    Start the HTTP server stub
+  cli      Convert a Markdown file stub
+  version  Print the build version
+`)
+}