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)
	if m := metavar(o); m != "" {
		b.WriteString("=" + m)
	}
	return b.String()
}

// metavar is the placeholder shown after a value-taking flag, e.g. the "N" in
// "--split=N". An explicit Opt.Metavar wins; otherwise it derives from the Kind.
// Bool takes no value, so its metavar is empty and no "=ARG" is printed.
func metavar(o *Opt) string {
	if o.Metavar != "" {
		return o.Metavar
	}
	switch o.Kind {
	case Bool:
		return ""
	case Size:
		return "SIZE"
	case Int:
		return "N"
	case Float:
		return "RATIO"
	case Enum:
		return strings.Join(o.Enum, "|")
	default:
		return "VAL"
	}
}