thag_rs 0.2.1

/// Example from the clap cookbook, not using the `clap-repl` crate.
///
/// The latest version of this example is `repl-derive.rs` in the [examples] folder
///  in the `clap` repository. At time of writing you can run it successfully just
/// by invoking its URL with the `thag_url` tool, like this:
///
/// ```bash
/// thag_url https://github.com/clap-rs/clap/blob/master/examples/repl-derive.rs
/// ```
///
/// Obviously this requires you to have first installed `thag_rs` with the `tools` feature.
///
/// Can't find a keybinding to navigate history, unlike `clap_repl_crate_rustyline.rs`.
//# Purpose: Demo building a repl using `clap` directly.
//# Categories: REPL, technique
use std::io::Write;

use clap::{Parser, Subcommand};

fn main() -> Result<(), String> {
    loop {
        let line = readline()?;
        let line = line.trim();
        if line.is_empty() {
            continue;
        }

        match respond(line) {
            Ok(quit) => {
                if quit {
                    break;
                }
            }
            Err(err) => {
                write!(std::io::stdout(), "{err}").map_err(|e| e.to_string())?;
                std::io::stdout().flush().map_err(|e| e.to_string())?;
            }
        }
    }

    println!();
    Ok(())
}

fn respond(line: &str) -> Result<bool, String> {
    let args = shlex::split(line).ok_or("error: Invalid quoting")?;
    let cli = Cli::try_parse_from(args).map_err(|e| e.to_string())?;
    match cli.command {
        Commands::Ping => {
            write!(std::io::stdout(), "Pong").map_err(|e| e.to_string())?;
            std::io::stdout().flush().map_err(|e| e.to_string())?;
        }
        Commands::Exit => {
            write!(std::io::stdout(), "Exiting ...").map_err(|e| e.to_string())?;
            std::io::stdout().flush().map_err(|e| e.to_string())?;
            return Ok(true);
        }
    }
    Ok(false)
}

#[derive(Debug, Parser)]
#[command(multicall = true)]
struct Cli {
    #[command(subcommand)]
    command: Commands,
}

#[derive(Debug, Subcommand)]
enum Commands {
    Ping,
    Exit,
}

fn readline() -> Result<String, String> {
    write!(std::io::stdout(), "$ ").map_err(|e| e.to_string())?;
    std::io::stdout().flush().map_err(|e| e.to_string())?;
    let mut buffer = String::new();
    std::io::stdin()
        .read_line(&mut buffer)
        .map_err(|e| e.to_string())?;
    Ok(buffer)
}