first commit

cli/help.go

@@ -0,0 +1,107 @@
+package cli
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Version is the program version, overridable at build time via -ldflags.
+var Version = "0.1.0"
+
+// PrintVersion writes the version banner.
+func PrintVersion(w io.Writer) {
+	fmt.Fprintf(w, "got %s — a Rob-Pike-style command-line downloader in Go\n", Version)
+}
+
+// PrintHelp writes usage. A bare -h/--help (empty tag) shows only the Basic
+// group, keeping the default terse; --help=all shows every group and
+// --help=<group> (basic/http/bittorrent/advanced) filters to one.
+func PrintHelp(w io.Writer, tag string) {
+	all := tag == "all"
+	// Empty tag means a bare -h/--help: default to the Basic group only.
+	bare := tag == ""
+	want, filtered := tagByName(tag)
+	if bare {
+		want, filtered = Basic, true
+	}
+	if !all && !bare && !filtered {
+		fmt.Fprintf(w, "got: unknown help tag %q (use all|basic|http|bittorrent|advanced)\n\n", tag)
+	}
+	fmt.Fprint(w, `Usage: got [OPTIONS] URI | magnet:... | file.torrent ...
+
+A multi-protocol download tool: segmented HTTP(S) and BitTorrent.
+
+`)
+	for _, group := range []Tag{Basic, HTTP, BitTorrent, Advanced} {
+		if filtered && !all && group != want {
+			continue
+		}
+		fmt.Fprintf(w, "%s options:\n", title(group.String()))
+		for i := range options {
+			o := &options[i]
+			if o.Tag != group {
+				continue
+			}
+			fmt.Fprintf(w, "  %s  %s\n", flagLabel(o), o.Help)
+		}
+		fmt.Fprintln(w)
+	}
+	// Only the full listing (all groups) repeats the meta flags.
+	if all || !filtered {
+		fmt.Fprint(w, "  -h, --help[=TAG]  show help (TAG: all|basic|http|bittorrent|advanced)\n")
+		fmt.Fprint(w, "  -v, --version     show version\n\n")
+	}
+	if bare {
+		fmt.Fprint(w, "Showing basic options. Use --help=all for every option, or --help=advanced for advanced ones.\n")
+	}
+}
+
+// title upper-cases the first letter of a single word.
+func title(s string) string {
+	if s == "" {
+		return s
+	}
+	return strings.ToUpper(s[:1]) + s[1:]
+}
+
+func tagByName(name string) (Tag, bool) {
+	switch name {
+	case "basic":
+		return Basic, true
+	case "http":
+		return HTTP, true
+	case "bittorrent", "bt":
+		return BitTorrent, true
+	case "advanced":
+		return Advanced, true
+	default:
+		return Basic, false
+	}
+}
+
+// flagLabel renders the "-x, --long=ARG" column for one option.
+func flagLabel(o *Opt) string {
+	var b strings.Builder
+	if o.Short != 0 {
+		fmt.Fprintf(&b, "-%c, ", o.Short)
+	} else {
+		b.WriteString("    ")
+	}
+	b.WriteString("--" + o.Long)
+	switch o.Kind {
+	case Bool:
+		// no argument shown
+	case Size:
+		b.WriteString("=SIZE")
+	case Int:
+		b.WriteString("=N")
+	case Float:
+		b.WriteString("=RATIO")
+	case Enum:
+		b.WriteString("=" + strings.Join(o.Enum, "|"))
+	default:
+		b.WriteString("=VAL")
+	}
+	return b.String()
+}