nostr: add Event::hashtags method

Ref #460 (comment)

Signed-off-by: Yuki Kishimoto <yukikishimoto@protonmail.com>

CHANGELOG.md

@@ -51,6 +51,7 @@
 * nostr: add support to `nrelay` NIP-19 entity ([Yuki Kishimoto])
 * nostr: add `Event::get_tag_content` method ([Yuki Kishimoto])
 * nostr: add `Event::get_tags_content` method ([Yuki Kishimoto])
+* nostr: add `Event::hashtags` method ([Yuki Kishimoto])
 * pool: allow to set event limits per kind ([Yuki Kishimoto])
 * pool: log warn when high latency ([Yuki Kishimoto])
 * sdk: add support to automatic authentication to relays (NIP-42) ([Yuki Kishimoto])

bindings/nostr-ffi/src/event/mod.rs

@@ -220,6 +220,13 @@ impl Event {
             .collect()
     }
 
+    /// Extract hashtags from tags (`t` tag)
+    ///
+    /// **This method extract ONLY supported standard variants**
+    pub fn hashtags(&self) -> Vec<String> {
+        self.inner.hashtags().map(|t| t.to_owned()).collect()
+    }
+
     #[inline]
     #[uniffi::constructor]
     pub fn from_json(json: &str) -> Result<Self> {

bindings/nostr-js/src/event/mod.rs

@@ -113,6 +113,13 @@ impl JsEvent {
         self.inner.verify().is_ok()
     }
 
+    /// Extract hashtags from tags (`t` tag)
+    ///
+    /// **This method extract ONLY supported standard variants**
+    pub fn hashtags(&self) -> Vec<String> {
+        self.inner.hashtags().map(|t| t.to_owned()).collect()
+    }
+
     #[wasm_bindgen(js_name = fromJson)]
     pub fn from_json(json: &str) -> Result<JsEvent> {
         Ok(Self {

crates/nostr/src/event/mod.rs

@@ -511,6 +511,17 @@ impl Event {
         })
     }
 
+    /// Extract hashtags from tags (`t` tag)
+    ///
+    /// **This method extract ONLY `TagStandard::Hashtag`**
+    #[inline]
+    pub fn hashtags(&self) -> impl Iterator<Item = &String> {
+        self.iter_tags().filter_map(|t| match t.as_standardized() {
+            Some(TagStandard::Hashtag(hashtag)) => Some(hashtag),
+            _ => None,
+        })
+    }
+
     pub(crate) fn build_tags_indexes(&self) -> TagsIndexes {
         let mut idx: TagsIndexes = TagsIndexes::new();
         for (single_letter_tag, content) in self