Implement the command parser

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

bridge/commands.go

@@ -0,0 +1,81 @@
+package bridge
+
+import (
+	"fmt"
+
+	"github.com/alecthomas/kong"
+
+	"maunium.net/go/mautrix/appservice"
+	"maunium.net/go/mautrix/event"
+	"maunium.net/go/mautrix/format"
+	"maunium.net/go/mautrix/id"
+
+	"gitlab.com/beeper/discord/consts"
+	"gitlab.com/beeper/discord/version"
+)
+
+type globals struct {
+	context *kong.Context
+
+	bridge  *Bridge
+	bot     *appservice.IntentAPI
+	portal  *Portal
+	handler *commandHandler
+	roomID  id.RoomID
+	user    *User
+	replyTo id.EventID
+}
+
+func (g *globals) reply(msg string) {
+	content := format.RenderMarkdown(msg, true, false)
+	content.MsgType = event.MsgNotice
+	intent := g.bot
+
+	if g.portal != nil && g.portal.IsPrivateChat() {
+		intent = g.portal.MainIntent()
+	}
+
+	_, err := intent.SendMessageEvent(g.roomID, event.EventMessage, content)
+	if err != nil {
+		g.handler.log.Warnfln("Failed to reply to command from %q: %v", g.user.MXID, err)
+	}
+}
+
+type commands struct {
+	globals
+
+	Help    helpCmd    `kong:"cmd,help='Displays this message.'"`
+	Version versionCmd `kong:"cmd,help='Displays the version of the bridge.'"`
+}
+
+type helpCmd struct {
+	Command []string `kong:"arg,optional,help='The command to get help on.'"`
+}
+
+func (c *helpCmd) Run(g *globals) error {
+	ctx, err := kong.Trace(g.context.Kong, c.Command)
+	if err != nil {
+		return err
+	}
+
+	if ctx.Error != nil {
+		return err
+	}
+
+	err = ctx.PrintUsage(true)
+	if err != nil {
+		return err
+	}
+
+	fmt.Fprintln(g.context.Stdout)
+
+	return nil
+}
+
+type versionCmd struct{}
+
+func (c *versionCmd) Run(g *globals) error {
+	fmt.Fprintln(g.context.Stdout, consts.Name, version.String)
+
+	return nil
+}