Initial commit

This is still experimental, though for now I've been able to implement a
few commands:

- cd:    changes the current working directory of the agent
- ls:    lists the directories and files in the current working directory
- ping:  responds with "pong"
- pwd:   prints the current working directory
- shell: executes an arbitrary command on the host

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "gsm-agent"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "gsm-agent"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

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+use std::cmp::Ordering;
+use std::env;
+use std::fs;
+use std::fs::DirEntry;
+use std::io::Read;
+use std::io::Write;
+use std::net::TcpListener;
+use std::net::TcpStream;
+use std::path::Path;
+use std::process::Command;
+
+fn main() {
+    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
+    for stream in listener.incoming() {
+        let stream = stream.unwrap();
+        handle_connection(stream);
+    }
+}
+
+fn cwd() -> String {
+    env::current_dir().unwrap().to_string_lossy().to_string()
+}
+
+fn handle_connection(mut stream: TcpStream) {
+    let mut buffer = [0; 1024];
+    stream.read(&mut buffer).unwrap();
+    let mut request: &str = &String::from_utf8(buffer.to_vec()).unwrap();
+    request = request.trim();
+    let trim_chars = [' ', '\n', '\0'];
+    request = request.trim_matches(&trim_chars[..]);
+    let mut command_iter = request.split_whitespace();
+    let command = command_iter.next().unwrap();
+    let response: String = match command {
+        "cd" => {
+            let path = Path::new(command_iter.next().unwrap());
+            env::set_current_dir(path).unwrap();
+            cwd()
+        }
+        "ls" => {
+            let mut files: Vec<String> = Vec::new();
+            let mut paths: Vec<DirEntry> =
+                fs::read_dir(cwd()).unwrap().map(|r| r.unwrap()).collect();
+            paths.sort_by(|a, b| {
+                let a_is_dir = a.file_type().unwrap().is_dir();
+                let b_is_dir = b.file_type().unwrap().is_dir();
+                if a_is_dir && !b_is_dir {
+                    Ordering::Less
+                } else if !a_is_dir && b_is_dir {
+                    Ordering::Greater
+                } else {
+                    a.file_name().cmp(&b.file_name())
+                }
+            });
+            for file in paths {
+                files.push(file.file_name().into_string().unwrap());
+            }
+            files.join("\n")
+        }
+        "ping" => String::from("pong"),
+        "pwd" => cwd(),
+        "shell" => String::from_utf8(
+            Command::new(command_iter.next().unwrap())
+                .args(command_iter)
+                .output()
+                .unwrap()
+                .stdout,
+        )
+        .unwrap(),
+        _ => {
+            format!(
+                "unknown command: {:?}",
+                request.split_whitespace().next().unwrap_or("")
+            )
+        }
+    };
+    stream.write(format!("{}\n", response).as_bytes()).unwrap();
+    stream.flush().unwrap();
+}