feat: use enum_dispatch for command dispatch and add Open command

Replace manual dynamic dispatch using Box <dyn Runnable> with enum_dispatch
for improved performance and cleaner code.

Add a new Open command to allow opening the TUI as the default behavior
when no subcommand is provided.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-26B-A4B-it-GGUF:UD-Q5_K_XL)

Cargo.lock

@@ -339,6 +339,18 @@ version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
+[[package]]
+name = "enum_dispatch"
+version = "0.3.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa18ce2bc66555b3218614519ac839ddb759a7d6720732f979ef8d13be147ecd"
+dependencies = [
+ "once_cell",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "equivalent"
 version = "1.0.2"
@@ -494,6 +506,7 @@ dependencies = [
  "crossterm",
  "csv",
  "dirs",
+ "enum_dispatch",
  "flate2",
  "indexmap",
  "proptest",

Cargo.toml

@@ -23,6 +23,7 @@ unicode-width = "0.2"
 dirs = "5"
 csv = "1"
 clap = { version = "4.6.0", features = ["derive"] }
+enum_dispatch = "0.3.13"
 
 [dev-dependencies]
 proptest = "1"

flake.nix

@@ -42,6 +42,7 @@
           pkgs.pkg-config
           pkgs.rust-analyzer
           crate2nix.packages.${system}.default
+          pkgs.cargo-expand
         ];
         RUST_BACKTRACE = "1";
       };

src/main.rs

@@ -14,6 +14,7 @@ use std::path::PathBuf;
 
 use anyhow::{Context, Result};
 use clap::{Parser, Subcommand};
+use enum_dispatch::enum_dispatch;
 
 use draw::run_tui;
 use model::Model;
@@ -29,7 +30,13 @@ struct Cli {
     command: Option<Commands>,
 }
 
+#[enum_dispatch]
+trait Runnable {
+    fn run(self, model_file: Option<PathBuf>) -> Result<()>;
+}
+
 #[derive(Subcommand)]
+#[enum_dispatch(Runnable)]
 enum Commands {
     /// Import JSON or CSV data, then open TUI (or save with --output)
     Import(ImportArgs),
@@ -37,6 +44,8 @@ enum Commands {
     Cmd(CmdArgs),
     /// Run commands from a script file headless
     Script(ScriptArgs),
+    /// Open the TUI (default when no subcommand given)
+    Open(OpenTui),
 }
 
 #[derive(clap::Args)]
@@ -105,23 +114,10 @@ struct ScriptArgs {
     file: Option<PathBuf>,
 }
 
-trait Runnable {
+#[derive(clap::Args)]
-    fn run(self: Box<Self>, model_file: Option<PathBuf>) -> Result<()>;
-}
-
-impl From<Commands> for Box<dyn Runnable> {
-    fn from(cmd: Commands) -> Self {
-        match cmd {
-            Commands::Import(args) => Box::new(args),
-            Commands::Cmd(args) => Box::new(args),
-            Commands::Script(args) => Box::new(args),
-        }
-    }
-}
-
 struct OpenTui;
 impl Runnable for OpenTui {
-    fn run(self: Box<Self>, model_file: Option<PathBuf>) -> Result<()> {
+    fn run(self, model_file: Option<PathBuf>) -> Result<()> {
         let model = get_initial_model(&model_file)?;
         run_tui(model, model_file, None)
     }
@@ -129,15 +125,12 @@ impl Runnable for OpenTui {
 
 fn main() -> Result<()> {
     let cli = Cli::parse();
-    let cmd: Box<dyn Runnable> = cli
+    let cmd = cli.command.unwrap_or(Commands::Open(OpenTui));
-        .command
-        .map(|c| -> Box<dyn Runnable> { c.into() })
-        .unwrap_or_else(|| Box::new(OpenTui));
     cmd.run(cli.file)
 }
 
 impl Runnable for ImportArgs {
-    fn run(self: Box<Self>, model_file: Option<PathBuf>) -> Result<()> {
+    fn run(self, model_file: Option<PathBuf>) -> Result<()> {
         if self.files.is_empty() {
             anyhow::bail!("No files specified for import");
         }
@@ -164,13 +157,13 @@ impl Runnable for ImportArgs {
 }
 
 impl Runnable for CmdArgs {
-    fn run(self: Box<Self>, _model_file: Option<PathBuf>) -> Result<()> {
+    fn run(self, _model_file: Option<PathBuf>) -> Result<()> {
         run_headless_commands(&self.json, &self.file)
     }
 }
 
 impl Runnable for ScriptArgs {
-    fn run(self: Box<Self>, _model_file: Option<PathBuf>) -> Result<()> {
+    fn run(self, _model_file: Option<PathBuf>) -> Result<()> {
         run_headless_script(&self.path, &self.file)
     }
 }