Fix Lua API performance by caching

Fixes: #412

src/__cache__.lua

@@ -0,0 +1,25 @@
+-- Please ignore me and move on.
+-- Or if you insist, see https://github.com/sayanarijit/xplr/issues/412
+
+local xplr = xplr
+
+xplr.__CACHE__ = { directory_nodes = {} }
+
+function xplr.__CACHE__.set_directory_nodes(nodes)
+  xplr.__CACHE__.directory_nodes = nodes
+end
+
+function xplr.__CACHE__.call(fun, arg)
+  if arg.app and arg.app.directory_buffer then
+    arg.app.directory_buffer.nodes = xplr.__CACHE__.directory_nodes
+  elseif arg.directory_buffer then
+    arg.directory_buffer.nodes = xplr.__CACHE__.directory_nodes
+  end
+  return fun(arg)
+end
+
+function xplr.__CACHE__.caller(fun)
+  return function(arg)
+    return xplr.__CACHE__.call(fun, arg)
+  end
+end

src/app.rs

@@ -1133,6 +1133,7 @@ pub struct Command {
 
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
 pub enum MsgOut {
+    CacheDirectoryNodes(Vec<Node>),
     ExplorePwdAsync,
     ExploreParentsAsync,
     Refresh,
@@ -1246,12 +1247,29 @@ impl History {
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Serialize)]
+pub struct CachedDirectoryBuffer {
+    pub parent: String,
+    pub total: usize,
+    pub focus: usize,
+}
+
+impl CachedDirectoryBuffer {
+    pub fn new(buf: &DirectoryBuffer) -> Self {
+        Self {
+            parent: buf.parent.clone(),
+            total: buf.total,
+            focus: buf.focus,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize)]
 pub struct CallLuaArg {
     pub version: String,
     pub pwd: String,
     pub focused_node: Option<Node>,
-    pub directory_buffer: Option<DirectoryBuffer>,
+    pub directory_buffer: Option<CachedDirectoryBuffer>,
     pub selection: IndexSet<Node>,
     pub mode: Mode,
     pub layout: Layout,
@@ -2246,6 +2264,8 @@ impl App {
             dir.focused_node().map(|n| n.relative_path.clone()),
         )?;
         if dir.parent == self.pwd {
+            self.msg_out
+                .push_back(MsgOut::CacheDirectoryNodes(dir.nodes.clone()));
             self.directory_buffer = Some(dir);
         }
         Ok(self)
@@ -2741,7 +2761,10 @@ impl App {
             version: self.version.clone(),
             pwd: self.pwd.clone(),
             focused_node: self.focused_node().cloned(),
-            directory_buffer: self.directory_buffer.clone(),
+            directory_buffer: self
+                .directory_buffer
+                .as_ref()
+                .map(|buf| CachedDirectoryBuffer::new(buf)),
             selection: self.selection.clone(),
             mode: self.mode.clone(),
             layout: self.layout.clone(),

src/lua.rs

@@ -1,3 +1,4 @@
+use crate::app::Node;
 use crate::app::VERSION;
 use crate::config::Config;
 use anyhow::bail;
@@ -8,6 +9,7 @@ use serde::Deserialize;
 use std::fs;
 
 const DEFAULT_LUA_SCRIPT: &str = include_str!("init.lua");
+const INTERNAL_LUA_SCRIPT: &str = include_str!("__cache__.lua");
 const UPGRADE_GUIDE_LINK: &str = "https://xplr.dev/en/upgrade-guide.html";
 
 fn parse_version(version: &str) -> Result<(u16, u16, u16, Option<u16>)> {
@@ -49,30 +51,6 @@ pub fn check_version(version: &str, path: &str) -> Result<()> {
     }
 }
 
-fn resolve_fn_recursive<'lua, 'a>(
-    table: &mlua::Table<'lua>,
-    mut path: impl Iterator<Item = &'a str>,
-) -> Result<mlua::Function<'lua>> {
-    if let Some(nxt) = path.next() {
-        match table.get(nxt)? {
-            mlua::Value::Table(t) => resolve_fn_recursive(&t, path),
-            mlua::Value::Function(f) => Ok(f),
-            t => bail!("{:?} is not a function", t),
-        }
-    } else {
-        bail!("Invalid path")
-    }
-}
-
-/// This function resolves paths like `builtin.func_foo`, `custom.func_bar` into lua functions.
-pub fn resolve_fn<'lua>(
-    globals: &mlua::Table<'lua>,
-    path: &str,
-) -> Result<mlua::Function<'lua>> {
-    let path = format!("xplr.fn.{}", path);
-    resolve_fn_recursive(globals, path.split('.'))
-}
-
 /// Used to initialize Lua globals
 pub fn init(lua: &Lua) -> Result<Config> {
     let config = Config::default();
@@ -91,6 +69,7 @@ pub fn init(lua: &Lua) -> Result<Config> {
     globals.set("xplr", lua_xplr)?;
 
     lua.load(DEFAULT_LUA_SCRIPT).set_name("init")?.exec()?;
+    lua.load(INTERNAL_LUA_SCRIPT).set_name("internal")?.exec()?;
 
     let lua_xplr: mlua::Table = globals.get("xplr")?;
     let config: Config = lua.from_value(lua_xplr.get("config")?)?;
@@ -123,14 +102,26 @@ pub fn extend(lua: &Lua, path: &str) -> Result<Config> {
 pub fn call<'lua, R: Deserialize<'lua>>(
     lua: &'lua Lua,
     func: &str,
-    args: mlua::Value<'lua>,
+    arg: mlua::Value<'lua>,
 ) -> Result<R> {
-    let func = resolve_fn(&lua.globals(), func)?;
-    let res: mlua::Value = func.call(args)?;
+    let func = format!("xplr.__CACHE__.caller(xplr.fn.{})", func);
+    let caller: mlua::Function = lua.load(&func).eval()?;
+    let res: mlua::Value = caller.call(arg)?;
     let res: R = lua.from_value(res)?;
     Ok(res)
 }
 
+/// Used to cache the directory nodes.
+pub fn cache_directory_nodes<'lua>(
+    lua: &'lua Lua,
+    nodes: &[Node],
+) -> Result<()> {
+    let func = "xplr.__CACHE__.set_directory_nodes";
+    let func: mlua::Function = lua.load(func).eval()?;
+    func.call(lua.to_value(nodes)?)?;
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
 

src/runner.rs

@@ -38,13 +38,6 @@ fn call_lua(
     func: &str,
     _silent: bool,
 ) -> Result<Option<Vec<app::ExternalMsg>>> {
-    let _focus_index = app
-        .directory_buffer
-        .as_ref()
-        .map(|d| d.focus)
-        .unwrap_or_default()
-        .to_string();
-
     let arg = app.to_lua_arg();
     let arg = lua.to_value(&arg)?;
     lua::call(lua, func, arg)
@@ -280,6 +273,10 @@ impl Runner {
                                 tx_msg_in.send(task)?;
                             }
 
+                            CacheDirectoryNodes(nodes) => {
+                                lua::cache_directory_nodes(&lua, &nodes)?;
+                            }
+
                             Quit => {
                                 result = Ok(None);
                                 break 'outer;

src/ui.rs

@@ -1203,7 +1203,7 @@ impl From<TuiRect> for Rect {
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize)]
 pub struct ContentRendererArg {
     app: app::CallLuaArg,
     screen_size: Rect,