Bellhop/internal/bot/bot.go

// Package bot wires Matrix command messages to the *arr clients.
//
// Commands take the form "<prefix><cmd> <query>" (e.g. "!movie dune"). The
// dispatcher parses the message, picks the *arr client by command name,
// performs a lookup, and adds the top hit. The reply is posted back into a
// thread rooted at the request event so a busy room stays readable.
package bot

import (
	"context"
	"fmt"
	"html"
	"log/slog"
	"strings"
	"time"

	"bellhop/internal/arr"

	"maunium.net/go/mautrix/id"
)

// Replier sends a threaded reply into roomID under rootEventID. The ctx
// governs cancellation/deadline so shutdown propagates through replies.
type Replier interface {
	PostThreadedReply(ctx context.Context, roomID id.RoomID, rootEventID id.EventID, plain, htmlBody string) error
}

// Services holds the configured *arr clients. Any field may be nil; commands
// that target an unconfigured service reply with "not configured".
type Services struct {
	Radarr arr.Client
	Sonarr arr.Client
	Lidarr arr.Client
}

// Dispatcher routes parsed commands to services and posts replies.
type Dispatcher struct {
	baseCtx  context.Context
	prefix   string
	services Services
	replier  Replier
	timeout  time.Duration
}

// New builds a Dispatcher. prefix is the leading character(s) on a command
// (e.g. "!"); a zero value defaults to "!". baseCtx becomes the parent of
// every per-command context so app shutdown cancels in-flight handlers.
func New(baseCtx context.Context, prefix string, services Services, replier Replier) *Dispatcher {
	if prefix == "" {
		prefix = "!"
	}
	if baseCtx == nil {
		baseCtx = context.Background()
	}
	return &Dispatcher{
		baseCtx:  baseCtx,
		prefix:   prefix,
		services: services,
		replier:  replier,
		timeout:  60 * time.Second,
	}
}

// Handle is the matrix.MessageHandler entry point. It parses body, dispatches
// the command, and posts a reply. Non-command messages are ignored silently.
func (d *Dispatcher) Handle(roomID id.RoomID, eventID id.EventID, sender id.UserID, body string) {
	cmd, query, ok := parseCommand(d.prefix, body)
	if !ok {
		return
	}

	slog.Info("bot: command received", "room", roomID, "sender", sender, "cmd", cmd, "query", query)

	ctx, cancel := context.WithTimeout(d.baseCtx, d.timeout)
	defer cancel()

	plain, htmlBody := d.dispatch(ctx, cmd, query)
	if err := d.replier.PostThreadedReply(ctx, roomID, eventID, plain, htmlBody); err != nil {
		slog.Error("bot: reply failed", "room", roomID, "err", err)
	}
}

// parseCommand pulls (cmd, query) out of a body like "!movie dune". Returns
// ok=false when the message is not a command for us.
func parseCommand(prefix, body string) (cmd, query string, ok bool) {
	body = strings.TrimSpace(body)
	if !strings.HasPrefix(body, prefix) {
		return "", "", false
	}
	rest := strings.TrimSpace(body[len(prefix):])
	if rest == "" {
		return "", "", false
	}
	parts := strings.SplitN(rest, " ", 2)
	cmd = strings.ToLower(parts[0])
	if len(parts) == 2 {
		query = strings.TrimSpace(parts[1])
	}
	return cmd, query, true
}

func (d *Dispatcher) dispatch(ctx context.Context, cmd, query string) (plain, htmlBody string) {
	switch cmd {
	case "help":
		return d.help()
	case "movie":
		return d.run(ctx, "movie", "Radarr", d.services.Radarr, query)
	case "tv":
		return d.run(ctx, "tv", "Sonarr", d.services.Sonarr, query)
	case "music":
		return d.run(ctx, "music", "Lidarr", d.services.Lidarr, query)
	default:
		msg := fmt.Sprintf("Unknown command %q. Try %shelp.", cmd, d.prefix)
		return msg, html.EscapeString(msg)
	}
}

func (d *Dispatcher) run(ctx context.Context, cmd, service string, client arr.Client, query string) (plain, htmlBody string) {
	if client == nil {
		msg := fmt.Sprintf("%s is not configured.", service)
		return msg, html.EscapeString(msg)
	}
	if query == "" {
		msg := fmt.Sprintf("Usage: %s%s <query>", d.prefix, cmd)
		return msg, html.EscapeString(msg)
	}

	results, err := client.Search(ctx, query)
	if err != nil {
		slog.Error("bot: search failed", "service", service, "query", query, "err", err)
		msg := fmt.Sprintf("%s search failed: %v", service, err)
		return msg, html.EscapeString(msg)
	}
	if len(results) == 0 {
		msg := fmt.Sprintf("No %s results for %q.", service, query)
		return msg, html.EscapeString(msg)
	}

	top := results[0]
	if top.Exists {
		msg := fmt.Sprintf("%s already has %s in the library.", service, formatTitle(top))
		return msg, html.EscapeString(msg)
	}
	if err := client.Add(ctx, top); err != nil {
		slog.Error("bot: add failed", "service", service, "title", top.Title, "err", err)
		msg := fmt.Sprintf("%s: failed to add %s: %v", service, formatTitle(top), err)
		return msg, html.EscapeString(msg)
	}

	plain = fmt.Sprintf("Added to %s: %s", service, formatTitle(top))
	htmlBody = fmt.Sprintf("Added to <b>%s</b>: %s", html.EscapeString(service), html.EscapeString(formatTitle(top)))
	return plain, htmlBody
}

func (d *Dispatcher) help() (string, string) {
	lines := []string{
		"Bellhop commands:",
		fmt.Sprintf("  %smovie <query>  — add the top Radarr hit", d.prefix),
		fmt.Sprintf("  %stv <query>     — add the top Sonarr hit", d.prefix),
		fmt.Sprintf("  %smusic <query>  — add the top Lidarr hit", d.prefix),
		fmt.Sprintf("  %shelp           — show this message", d.prefix),
	}
	plain := strings.Join(lines, "\n")
	htmlBody := "<pre>" + html.EscapeString(plain) + "</pre>"
	return plain, htmlBody
}

func formatTitle(r arr.Result) string {
	if r.Year > 0 {
		return fmt.Sprintf("%s (%d)", r.Title, r.Year)
	}
	return r.Title
}