Implement the command parser

Right now this just supports help and version, but will be getting new commands
shortly.

bridge/commandhandler.go

@@ -0,0 +1,112 @@
+package bridge
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/alecthomas/kong"
+	"github.com/google/shlex"
+
+	"maunium.net/go/maulogger/v2"
+	"maunium.net/go/mautrix/id"
+)
+
+type commandHandler struct {
+	bridge *Bridge
+	log    maulogger.Logger
+}
+
+func newCommandHandler(bridge *Bridge) *commandHandler {
+	return &commandHandler{
+		bridge: bridge,
+		log:    bridge.log.Sub("Commands"),
+	}
+}
+
+func commandsHelpPrinter(options kong.HelpOptions, ctx *kong.Context) error {
+	selected := ctx.Selected()
+
+	if selected == nil {
+		for _, cmd := range ctx.Model.Leaves(true) {
+			fmt.Fprintf(ctx.Stdout, " * %s - %s\n", cmd.Path(), cmd.Help)
+		}
+	} else {
+		fmt.Fprintf(ctx.Stdout, "%s - %s\n", selected.Path(), selected.Help)
+		if selected.Detail != "" {
+			fmt.Fprintf(ctx.Stdout, "\n%s\n", selected.Detail)
+		}
+		if len(selected.Positional) > 0 {
+			fmt.Fprintf(ctx.Stdout, "\nArguments:\n")
+			for _, arg := range selected.Positional {
+				fmt.Fprintf(ctx.Stdout, "%s %s\n", arg.Summary(), arg.Help)
+			}
+		}
+	}
+
+	return nil
+}
+
+func (h *commandHandler) handle(roomID id.RoomID, user *User, message string, replyTo id.EventID) {
+	cmd := commands{
+		globals: globals{
+			bot:     h.bridge.bot,
+			bridge:  h.bridge,
+			portal:  h.bridge.GetPortalByMXID(roomID),
+			handler: h,
+			roomID:  roomID,
+			user:    user,
+			replyTo: replyTo,
+		},
+	}
+
+	buf := &strings.Builder{}
+
+	parse, err := kong.New(
+		&cmd,
+		kong.Exit(func(int) {}),
+		kong.NoDefaultHelp(),
+		kong.Writers(buf, buf),
+		kong.Help(commandsHelpPrinter),
+	)
+
+	if err != nil {
+		h.log.Warnf("Failed to create argument parser for %q: %v", roomID, err)
+
+		cmd.globals.reply("unexpected error, please try again shortly")
+
+		return
+	}
+
+	args, err := shlex.Split(message)
+	if err != nil {
+		h.log.Warnf("Failed to split message %q: %v", message, err)
+
+		cmd.globals.reply("failed to process the command")
+
+		return
+	}
+
+	ctx, err := parse.Parse(args)
+	if err != nil {
+		h.log.Warnf("Failed to parse command %q: %v", message, err)
+
+		cmd.globals.reply("failed to process the command")
+
+		return
+	}
+
+	cmd.globals.context = ctx
+
+	err = ctx.Run(&cmd.globals)
+	if err != nil {
+		h.log.Warnf("Command %q failed: %v", message, err)
+
+		cmd.globals.reply("unexpected failure")
+
+		return
+	}
+
+	if buf.Len() > 0 {
+		cmd.globals.reply(buf.String())
+	}
+}