enable nip10 replies

you can now reply to notes

Signed-off-by: William Casarin <jb55@jb55.com>

src/post.rs

@@ -1,4 +1,5 @@
-use nostrdb::NoteBuilder;
+use nostrdb::{Note, NoteBuilder, NoteReply};
+use std::collections::HashSet;
 
 pub struct NewPost {
     pub content: String,
@@ -6,7 +7,7 @@ pub struct NewPost {
 }
 
 impl NewPost {
-    pub fn to_note(&self, seckey: &[u8; 32]) -> nostrdb::Note {
+    pub fn to_note(&self, seckey: &[u8; 32]) -> Note {
         NoteBuilder::new()
             .kind(1)
             .content(&self.content)
@@ -14,4 +15,73 @@ impl NewPost {
             .build()
             .expect("note should be ok")
     }
+
+    pub fn to_reply(&self, seckey: &[u8; 32], replying_to: &Note) -> Note {
+        let builder = NoteBuilder::new().kind(1).content(&self.content);
+
+        let nip10 = NoteReply::new(replying_to.tags());
+
+        let mut builder = if let Some(root) = nip10.root() {
+            builder
+                .start_tag()
+                .tag_str("e")
+                .tag_str(&hex::encode(root.id))
+                .tag_str("")
+                .tag_str("root")
+                .start_tag()
+                .tag_str("e")
+                .tag_str(&hex::encode(replying_to.id()))
+                .tag_str("")
+                .tag_str("reply")
+                .sign(seckey)
+        } else {
+            // we're replying to a post that isn't in a thread,
+            // just add a single reply-to-root tag
+            builder
+                .start_tag()
+                .tag_str("e")
+                .tag_str(&hex::encode(replying_to.id()))
+                .tag_str("")
+                .tag_str("root")
+                .sign(seckey)
+        };
+
+        let mut seen_p: HashSet<&[u8; 32]> = HashSet::new();
+
+        builder = builder
+            .start_tag()
+            .tag_str("p")
+            .tag_str(&hex::encode(replying_to.pubkey()));
+
+        seen_p.insert(replying_to.pubkey());
+
+        for tag in replying_to.tags() {
+            if tag.count() < 2 {
+                continue;
+            }
+
+            if tag.get_unchecked(0).variant().str() != Some("p") {
+                continue;
+            }
+
+            let id = if let Some(id) = tag.get_unchecked(1).variant().id() {
+                id
+            } else {
+                continue;
+            };
+
+            if seen_p.contains(id) {
+                continue;
+            }
+
+            seen_p.insert(id);
+
+            builder = builder.start_tag().tag_str("p").tag_str(&hex::encode(id));
+        }
+
+        builder
+            .sign(seckey)
+            .build()
+            .expect("expected build to work")
+    }
 }