From b9f3007d9eca3ecb42a2d05fe44f9cae9a795cc1 Mon Sep 17 00:00:00 2001
From: fdai7451 <ruben.otto@informatik.hs-fulda.de>
Date: Thu, 19 Jan 2023 14:20:26 +0100
Subject: [PATCH] feat: use trait to define builtins

---
 Cargo.lock           |  7 +++++++
 Cargo.toml           |  1 +
 src/builtins/cd.rs   | 14 +++++++++++---
 src/builtins/exit.rs |  9 +++++++--
 src/builtins/mod.rs  | 20 ++++++++++++++------
 5 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index cd9af18..aab23d0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -169,10 +169,17 @@ dependencies = [
  "static_assertions",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f61fba1741ea2b3d6a1e3178721804bb716a68a6aeba1149b5d52e3d464ea66"
+
 [[package]]
 name = "pmuw-project"
 version = "0.1.0"
 dependencies = [
+ "once_cell",
  "rustyline",
  "shlex",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index c097580..91d07aa 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,5 +4,6 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+once_cell = "1.17"
 rustyline = "10.1.0"
 shlex = "1.1"
diff --git a/src/builtins/cd.rs b/src/builtins/cd.rs
index 14230fa..c840d80 100644
--- a/src/builtins/cd.rs
+++ b/src/builtins/cd.rs
@@ -1,8 +1,16 @@
+use crate::builtins::Builtin;
 use std::env::set_current_dir;
 
 use crate::error::ShellError;
 
-pub fn run(args: Vec<String>) -> Result<(), ShellError> {
-    set_current_dir(args.get(0).unwrap());
-    Ok(())
+pub struct Cd;
+
+impl Builtin for Cd {
+    fn execute(&mut self, args: Vec<String>) -> Result<(), ShellError> {
+        let Some(first) = args.get(0) else {
+            return Err(ShellError::ExecuteFailure("no argument given".to_string()))
+        };
+
+        set_current_dir(first).map_err(|e| ShellError::ExecuteFailure(e.to_string()))
+    }
 }
diff --git a/src/builtins/exit.rs b/src/builtins/exit.rs
index 8bf4196..c71586a 100644
--- a/src/builtins/exit.rs
+++ b/src/builtins/exit.rs
@@ -1,5 +1,10 @@
+use crate::builtins::Builtin;
 use crate::error::ShellError;
 
-pub fn run() -> Result<(), ShellError> {
-    Err(ShellError::Exit)
+pub struct Exit;
+
+impl Builtin for Exit {
+    fn execute(&mut self, _: Vec<String>) -> Result<(), ShellError> {
+        Err(ShellError::Exit)
+    }
 }
diff --git a/src/builtins/mod.rs b/src/builtins/mod.rs
index c02da93..ac07bb9 100644
--- a/src/builtins/mod.rs
+++ b/src/builtins/mod.rs
@@ -1,18 +1,26 @@
 use crate::error::ShellError;
+use once_cell::unsync::Lazy;
 mod cd;
 mod exit;
 
-const BUILTINS: &[&str] = &["exit", "cd"];
+trait Builtin: Sync + Send {
+    fn execute(&mut self, args: Vec<String>) -> Result<(), ShellError>;
+}
+
+const BUILTINS: Lazy<Vec<(&str, Box<dyn Builtin>)>> =
+    Lazy::new(|| vec![("cd", Box::new(cd::Cd)), ("exit", Box::new(exit::Exit))]);
 
 pub fn is_builtin(keyword: &str) -> bool {
-    BUILTINS.contains(&keyword)
+    BUILTINS.iter().find(|(k, _)| k == &keyword).is_some()
 }
 
+#[allow(const_item_mutation)]
 pub fn execute_builtin(keyword: &str, args: Vec<String>) -> Result<(), ShellError> {
-    match keyword {
-        "exit" => exit::run()?,
-        "cd" => cd::run(args)?,
-        _ => {}
+    if let Some(builtin) = BUILTINS
+        .iter_mut()
+        .find_map(|(k, c)| if k == &keyword { Some(c) } else { None })
+    {
+        builtin.execute(args)?
     }
     Ok(())
 }