Flag flyer language in Nostr events

docs/nostr-static-client-spec.md

@@ -61,6 +61,14 @@ Required tags:
 - `["t", "voxvera"]`
 - `["t", "flyer"]`
 
+Recommended language tags:
+
+- `["language", "<lang>"]`
+- `["L", "ISO-639-1"]`
+- `["l", "<lang>", "ISO-639-1"]`
+
+The payload `lang` field is authoritative. The language tags exist for relay/search metadata and as a fallback for older events whose payload omitted `lang`.
+
 Payload:
 
 ```json
@@ -118,6 +126,9 @@ Nostr editor/viewer controls and Nostr-specific flyer labels come from `NOSTR_UI
 
 Language changes should:
 
+- publish the selected flyer language in payload `lang`
+- publish matching Nostr language tags
+- infer language from event tags if a fetched payload omits `lang`
 - update default flyer content while the flyer is still using default content
 - preserve user-authored or fetched event content
 - update editor/viewer tool labels

site/nostr/nostr-client.js

@@ -751,6 +751,7 @@ Join us in a revolution that values truth and transparency. Together, we can bui
 
   function buildUnsignedEvent(payload) {
     const folderName = slugify(payload.folder_name);
+    const lang = supportedLang(payload.lang || FALLBACK_LANG);
     return {
       kind: EVENT_KIND,
       created_at: Math.floor(Date.now() / 1000),
@@ -759,7 +760,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
         ["t", "voxvera"],
         ["t", "flyer"],
         ["title", payload.headline || payload.title || folderName],
-        ["language", payload.lang || "en"]
+        ["language", lang],
+        ["L", "ISO-639-1"],
+        ["l", lang, "ISO-639-1"]
       ],
       content: JSON.stringify(payload)
     };
@@ -1011,10 +1014,21 @@ Join us in a revolution that values truth and transparency. Together, we can bui
     const hasTag = (name, value) => Array.isArray(event.tags) && event.tags.some((tag) => tag[0] === name && tag[1] === value);
     if (!hasTag("t", "voxvera") || !hasTag("t", "flyer")) throw new Error("Event is missing VoxVera flyer tags.");
     const payload = JSON.parse(event.content);
+    const taggedLang = languageFromTags(event.tags);
+    if (!payload.lang && taggedLang) {
+      payload.lang = taggedLang;
+    }
     validatePayload(payload);
     return payload;
   }
 
+  function languageFromTags(tags) {
+    if (!Array.isArray(tags)) return "";
+    const languageTag = tags.find((tag) => Array.isArray(tag) && tag[0] === "language" && tag[1]);
+    const labelTag = tags.find((tag) => Array.isArray(tag) && tag[0] === "l" && tag[1]);
+    return supportedLang((languageTag && languageTag[1]) || (labelTag && labelTag[1]) || "");
+  }
+
   function makeQrSvg(value) {
     if (!value) return "";
     if (typeof qrcode !== "function") {

tests/test_nostr_schema.py

@@ -29,7 +29,14 @@ def _event(payload=None, **overrides):
     event = {
         "kind": 30078,
         "content": json.dumps(payload or _payload()),
-        "tags": [["d", "voxvera:nostr-flyer"], ["t", "voxvera"], ["t", "flyer"]],
+        "tags": [
+            ["d", "voxvera:nostr-flyer"],
+            ["t", "voxvera"],
+            ["t", "flyer"],
+            ["language", "en"],
+            ["L", "ISO-639-1"],
+            ["l", "en", "ISO-639-1"],
+        ],
     }
     event.update(overrides)
     return event
@@ -43,6 +50,21 @@ def test_validate_accepts_nostr_event_payload():
     assert validate_event_source(_event())["content"] == "This flyer came from a Nostr event."
 
 
+def test_validate_uses_language_tag_when_payload_lang_is_missing():
+    payload = _payload()
+    payload.pop("lang")
+    event = _event(payload, tags=[
+        ["d", "voxvera:nostr-flyer"],
+        ["t", "voxvera"],
+        ["t", "flyer"],
+        ["language", "es"],
+        ["L", "ISO-639-1"],
+        ["l", "es", "ISO-639-1"],
+    ])
+
+    assert validate_event_source(event)["lang"] == "es"
+
+
 def test_normalize_maps_to_flyer_config_defaults():
     defaults = {
         "folder_name": "voxvera",

voxvera/nostr/schema.py

@@ -137,6 +137,10 @@ def _extract_payload(source: dict[str, Any]) -> dict[str, Any]:
         raise NostrValidationError(f"Nostr event content is not valid JSON: {exc.msg}") from exc
     if not isinstance(payload, dict):
         raise NostrValidationError("Nostr event content must decode to a JSON object.")
+    if not payload.get("lang"):
+        tagged_lang = _language_from_tags(source.get("tags", []))
+        if tagged_lang:
+            payload["lang"] = tagged_lang
     return payload
 
 
@@ -182,6 +186,16 @@ def _has_tag(source: dict[str, Any], name: str, value: str) -> bool:
     return any(isinstance(tag, list) and len(tag) >= 2 and tag[0] == name and tag[1] == value for tag in tags)
 
 
+def _language_from_tags(tags: Any) -> str:
+    if not isinstance(tags, list):
+        return ""
+    for tag_name in ("language", "l"):
+        for tag in tags:
+            if isinstance(tag, list) and len(tag) >= 2 and tag[0] == tag_name:
+                return _normalize_lang(str(tag[1]))
+    return ""
+
+
 def _normalize_lang(lang: str) -> str:
     return lang if lang in SUPPORTED_LANGS else "en"