chore: I have no fucking idea

This is vibecoded shit but i can't be bothered to do it myself.
Nobody else besides me is gonna be using this, and this wont ever be
extended or anything, so I just don't care.

ntfy.go

@@ -0,0 +1,159 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+	"time"
+
+	"maunium.net/go/mautrix/appservice"
+	"maunium.net/go/mautrix/id"
+)
+
+const (
+	defaultNtfyURL    = "https://ntfy.sh"
+	connectTimeout    = 10 * time.Second
+	initialBackoff    = 1 * time.Second
+	maxBackoff        = 2 * time.Minute
+	scannerBufSize    = 64 * 1024
+	maxScannerBufSize = 1024 * 1024
+)
+
+type NtfyEvent struct {
+	ID      string `json:"id"`
+	Time    int64  `json:"time"`
+	Event   string `json:"event"`
+	Topic   string `json:"topic"`
+	Message string `json:"message"`
+	Title   string `json:"title"`
+}
+
+type NtfyClient struct {
+	baseURL    string
+	httpClient *http.Client
+}
+
+func NewNtfyClient(baseURL string) *NtfyClient {
+	if baseURL == "" {
+		baseURL = defaultNtfyURL
+	}
+	return &NtfyClient{
+		baseURL: strings.TrimRight(baseURL, "/"),
+		httpClient: &http.Client{
+			Timeout: connectTimeout,
+		},
+	}
+}
+
+func (c *NtfyClient) PublishToNtfy(topic, message string) error {
+	url := fmt.Sprintf("%s/%s", c.baseURL, topic)
+
+	req, err := http.NewRequest("POST", url, bytes.NewReader([]byte(message)))
+	if err != nil {
+		return fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "text/plain")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("publish request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("ntfy returned %d: %s", resp.StatusCode, string(body))
+	}
+	return nil
+}
+
+func (c *NtfyClient) Listen(ctx context.Context, topic, matrixRoomID string, intent *appservice.IntentAPI) {
+	backoff := initialBackoff
+
+	for {
+		err := c.stream(ctx, topic, matrixRoomID, intent)
+
+		select {
+		case <-ctx.Done():
+			log.Printf("[ntfy] listener for topic %q stopped", topic)
+			return
+		default:
+		}
+
+		if err != nil {
+			log.Printf("[ntfy] topic %q disconnected: %v, reconnecting in %v", topic, err, backoff)
+		} else {
+			log.Printf("[ntfy] topic %q stream closed, reconnecting in %v", topic, backoff)
+			backoff = initialBackoff
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(backoff):
+		}
+
+		backoff *= 2
+		if backoff > maxBackoff {
+			backoff = maxBackoff
+		}
+	}
+}
+
+func (c *NtfyClient) stream(ctx context.Context, topic, matrixRoomID string, intent *appservice.IntentAPI) error {
+	url := fmt.Sprintf("%s/%s/json", c.baseURL, topic)
+
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return fmt.Errorf("create request: %w", err)
+	}
+
+	streamClient := &http.Client{Timeout: 0}
+	resp, err := streamClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("GET %s: %w", url, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("GET %s returned %d", url, resp.StatusCode)
+	}
+
+	scanner := bufio.NewScanner(resp.Body)
+	scanner.Buffer(make([]byte, 0, scannerBufSize), maxScannerBufSize)
+
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		if len(line) == 0 {
+			continue
+		}
+
+		var ntfyEvt NtfyEvent
+		if err := json.Unmarshal(line, &ntfyEvt); err != nil {
+			continue
+		}
+		if ntfyEvt.Event != "message" || ntfyEvt.Message == "" {
+			continue
+		}
+
+		body := ntfyEvt.Message
+		if ntfyEvt.Title != "" {
+			body = fmt.Sprintf("**%s**\n%s", ntfyEvt.Title, body)
+		}
+
+		if _, err := intent.SendText(ctx, id.RoomID(matrixRoomID), body); err != nil {
+			log.Printf("[ntfy] send to room %s failed: %v", matrixRoomID, err)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return fmt.Errorf("scanner: %w", err)
+	}
+	return nil
+}