feat(ntfy): add the HTTP client, stream manager, and account discovery

Speak the ntfy JSON API directly: subscribe, publish, group topics that share a server and credentials, reconnect with backoff and a since cursor, and list account subscriptions, reservations, and ACL grants.

internal/ntfy/event.go

@@ -0,0 +1,72 @@
+package ntfy
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+// Event is one NDJSON object from GET /topic/json.
+type Event struct {
+	ID         string          `json:"id"`
+	Time       int64           `json:"time"`
+	Expires    int64           `json:"expires,omitempty"`
+	Event      string          `json:"event"`
+	Topic      string          `json:"topic"`
+	Message    string          `json:"message"`
+	Title      string          `json:"title"`
+	Tags       []string        `json:"tags"`
+	Priority   int             `json:"priority"`
+	Click      string          `json:"click"`
+	SequenceID string          `json:"sequence_id,omitempty"`
+	Attachment *Attachment     `json:"attachment,omitempty"`
+	Actions    json.RawMessage `json:"actions,omitempty"`
+}
+
+// Attachment describes a file linked from a message.
+type Attachment struct {
+	Name    string `json:"name"`
+	URL     string `json:"url"`
+	Type    string `json:"type,omitempty"`
+	Size    int64  `json:"size,omitempty"`
+	Expires int64  `json:"expires,omitempty"`
+}
+
+// ParseLine decodes one NDJSON line. ok is false for blank lines.
+func ParseLine(line []byte) (Event, bool, error) {
+	line = bytes.TrimSpace(line)
+	if len(line) == 0 {
+		return Event{}, false, nil
+	}
+	var ev Event
+	if err := json.Unmarshal(line, &ev); err != nil {
+		return Event{}, false, err
+	}
+	if ev.Event == "" {
+		return Event{}, false, fmt.Errorf("missing event")
+	}
+	return ev, true, nil
+}
+
+// ReadLines yields each decoded event until EOF or a read error.
+// Malformed JSON is reported and skipped so one bad line does not kill the stream.
+func ReadLines(r io.Reader, yield func(Event) error, onBad func(error)) error {
+	sc := newScanner(r)
+	for sc.Scan() {
+		ev, ok, err := ParseLine(sc.Bytes())
+		if err != nil {
+			if onBad != nil {
+				onBad(err)
+			}
+			continue
+		}
+		if !ok {
+			continue
+		}
+		if err := yield(ev); err != nil {
+			return err
+		}
+	}
+	return sc.Err()
+}