label_printer/ntfy/ntfy.go

package ntfy

import (
	"context"
	"encoding/json"
	"fmt"
	"image"
	_ "image/gif"
	_ "image/jpeg"
	_ "image/png"
	"log"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"github.com/lestrrat-go/dither"
	"github.com/nfnt/resize"
	_ "golang.org/x/image/webp"
	"nhooyr.io/websocket"

	"git.sr.ht/~guacamolie/faxmachine/config"
	"git.sr.ht/~guacamolie/faxmachine/escpos"
	"git.sr.ht/~guacamolie/faxmachine/printjob"
)

type Instance struct {
	logger      *slog.Logger
	host        string
	accessToken string
	topics      map[string]config.Topic
}

func NewInstance(conf config.Ntfy, logger *slog.Logger) *Instance {
	return &Instance{
		host:        conf.Host,
		accessToken: conf.AccessToken,
		topics:      conf.Topics,
		logger:      logger,
	}
}

type message struct {
	Event      string     `json:"event"`
	Topic      string     `json:"topic"`
	Message    string     `json:"message"`
	Time       int64      `json:"time"`
	Attachment attachment `json:"attachment"`
}

type attachment struct {
	Name string `json:"name"`
	Type string `json:"type"`
	Size int    `json:"size"`
	URL  string `json:"url"`
}

func (i *Instance) Subscribe(ctx context.Context, queue chan<- printjob.Job) error {
	topicNames := make([]string, 0, len(i.topics))
	for k := range i.topics {
		topicNames = append(topicNames, k)
	}
	uri := fmt.Sprintf("wss://%s/%s/ws", i.host, strings.Join(topicNames, ","))

	header := make(http.Header)
	if i.accessToken != "" {
		header.Set("Authorization", fmt.Sprintf("Bearer %s", i.accessToken))
	}

	conn, _, err := websocket.Dial(ctx, uri, &websocket.DialOptions{
		HTTPHeader: header,
	})
	if err != nil {
		return fmt.Errorf("couldn't connect to instance: %v", err)
	}

	go i.drain(ctx, conn, queue)

	return nil
}

func (i *Instance) drain(ctx context.Context, conn *websocket.Conn, queue chan<- printjob.Job) {
	for {
		_, data, err := conn.Read(ctx)
		if err != nil {
			log.Printf("failed to read: %v\n", err)
			return
		}

		var msg message
		if err := json.Unmarshal(data, &msg); err != nil {
			log.Printf("failed to unmarshal: %v\n", err)
			return
		}

		if msg.Event != "message" {
			continue
		}

		sender := i.topics[msg.Topic].Name

		i.logger.Info("received print job",
			slog.Group("topic",
				slog.String("topic", msg.Topic),
				slog.String("name", sender),
			),
			slog.Group("message",
				slog.String("message", msg.Message),
				slog.String("attachment", msg.Attachment.URL),
			),
		)

		select {
		case queue <- &job{sender, msg}:
		default:
		}
	}
}

type job struct {
	sender string
	msg    message
}

func (j *job) Sender() string {
	return j.msg.Topic
}

func (j *job) Time() time.Time {
	return time.Unix(j.msg.Time, 0)
}

func (j *job) Description() string {
	switch {
	case j.msg.Message != "":
		return j.msg.Message
	case j.msg.Attachment.Name != "":
		return j.msg.Attachment.Name
	default:
		return ""
	}
}

func (j *job) Print(ctx context.Context, p *escpos.Printer) error {
	text := j.msg.Message

	if len(text) > 2000 {
		text = text[:2000]
	}

	if strings.HasPrefix(text, "You received a file: ") {
		text = ""
	}

	text, _ = strings.CutPrefix(text, "[guac::prefix]")

	if j.msg.Attachment.URL != "" {
		resp, err := http.Get(j.msg.Attachment.URL)
		if err != nil {
			return fmt.Errorf("failed to get attachment: %w", err)
		}

		img, _, err := image.Decode(resp.Body)
		if err != nil {
			return fmt.Errorf("failed to decode image: %w", err)
		}
		img = resize.Resize(512, 0, img, resize.Lanczos3)
		img = dither.Monochrome(dither.FloydSteinberg, img, 1.18)

		if err := p.PrintImage(img); err != nil {
			return fmt.Errorf("failed to print image: %w", err)
		}
	}

	if text != "" {
		fmt.Fprintf(p, "\n%s\n", text)
	}

	return nil
}

func (j *job) OnPrinted(ctx context.Context) {
	// Nothing to do since we can't reply to the job submitter.
}

func (j *job) OnShredded(ctx context.Context, err error) {
	// Nothing to do since we can't reply to the job submitter.
}