token_serializer: introduce TokenWriter

This simplifies token serialization

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

crates/notedeck_columns/src/storage/mod.rs

@@ -5,4 +5,4 @@ mod token_parser;
 pub use decks::{load_decks_cache, save_decks_cache, DECKS_CACHE_FILE};
 pub use migration::{deserialize_columns, COLUMNS_FILE};
 
-pub use token_parser::{ParseError, TokenParser, TokenSerializable};
+pub use token_parser::{ParseError, TokenParser, TokenSerializable, TokenWriter};

crates/notedeck_columns/src/storage/token_parser.rs

@@ -25,6 +25,42 @@ pub enum ParseError<'a> {
     EOF,
 }
 
+pub struct TokenWriter {
+    delim: &'static str,
+    tokens_written: usize,
+    buf: Vec<u8>,
+}
+
+impl Default for TokenWriter {
+    fn default() -> Self {
+        Self::new(":")
+    }
+}
+
+impl TokenWriter {
+    pub fn new(delim: &'static str) -> Self {
+        let buf = vec![];
+        let tokens_written = 0;
+        Self {
+            buf,
+            tokens_written,
+            delim,
+        }
+    }
+
+    pub fn write_token(&mut self, token: &str) {
+        if self.tokens_written > 0 {
+            self.buf.extend_from_slice(self.delim.as_bytes())
+        }
+        self.buf.extend_from_slice(token.as_bytes());
+        self.tokens_written += 1;
+    }
+
+    pub fn buffer(&self) -> &[u8] {
+        &self.buf
+    }
+}
+
 #[derive(Clone)]
 pub struct TokenParser<'a> {
     tokens: &'a [&'a str],
@@ -146,7 +182,7 @@ pub trait TokenSerializable: Sized {
     /// Return a list of serialization plans for a type. We do this for
     /// type safety and assume constructing these types are lightweight
     fn parse<'a>(parser: &mut TokenParser<'a>) -> Result<Self, ParseError<'a>>;
-    fn serialize(&self, write_token: fn(&str) -> Result<(), std::io::Error>) -> Result<(), std::io::Error>;
+    fn serialize(&self, writer: &mut TokenWriter);
 }
 
 #[cfg(test)]

crates/notedeck_columns/src/ui/add_column.rs

@@ -11,7 +11,7 @@ use nostrdb::{Ndb, Transaction};
 use crate::{
     login_manager::AcquireKeyState,
     route::Route,
-    storage::{ParseError, TokenParser, TokenSerializable},
+    storage::{ParseError, TokenParser, TokenSerializable, TokenWriter},
     timeline::{kind::ListKind, PubkeySource, Timeline, TimelineKind},
     ui::anim::ICON_EXPANSION_MULTIPLE,
     Damus,
@@ -111,14 +111,10 @@ impl AddColumnRoute {
 }
 
 impl TokenSerializable for AddColumnRoute {
-    fn serialize(
-        &self,
-        write_token: fn(&str) -> Result<(), std::io::Error>,
-    ) -> Result<(), std::io::Error> {
+    fn serialize(&self, writer: &mut TokenWriter) {
         for token in self.tokens() {
-            write_token(token)?;
+            writer.write_token(token);
         }
-        Ok(())
     }
 
     fn parse<'a>(parser: &mut TokenParser<'a>) -> Result<Self, ParseError<'a>> {