refactor: use new struct in backend

backend/cli/cli.go

@@ -0,0 +1,47 @@
+package cli
+
+import (
+	"flag"
+	"fmt"
+	"os"
+)
+
+// CLIArgs holds the arguments parsed from the command line, mirroring the
+// argparse result in the legacy coconut-leaf.py.
+type CLIArgs struct {
+	// Config is the path to the configuration file (the legacy CONFIG_TOML).
+	Config string
+	// Init indicates whether to initialize the calendar system before running.
+	Init bool
+}
+
+// Parse parses the command-line arguments via the standard flag package and
+// returns a *CLIArgs. When the required --config flag is missing, it prints the
+// usage and exits with status 2 (matching argparse's exit code).
+func Parse() *CLIArgs {
+	args := &CLIArgs{}
+
+	// Custom usage output mirroring the legacy ArgumentParser description banner.
+	flag.Usage = func() {
+		out := flag.CommandLine.Output()
+		fmt.Fprintln(out, "The server of light, self-host and multi-account calendar system.")
+		fmt.Fprintln(out)
+		fmt.Fprintf(out, "Usage of %s:\n", os.Args[0])
+		flag.PrintDefaults()
+	}
+
+	// --config maps to the legacy -c/--config (required), --init to -i/--init.
+	flag.StringVar(&args.Config, "config", "", "The configuration file `CONFIG_TOML` for coconut-leaf")
+	flag.BoolVar(&args.Init, "init", false, "Set for initialize the calendar system")
+
+	flag.Parse()
+
+	// The standard flag package has no built-in "required", so validate manually.
+	if args.Config == "" {
+		fmt.Fprintln(os.Stderr, "error: the required flag --config is not provided")
+		flag.Usage()
+		os.Exit(2)
+	}
+
+	return args
+}