use std::env;
use std::io::{self, Write};
use std::sync::{Arc, Mutex};
mod path;
mod poem;
use poem::{read::Readable, recite::Reciteable, Poem};
mod compose;
use compose::Environment;

/// Starts the main shell loop
///
/// # Arguments
/// * `away` - A mutex, indicating whether or not user is at the prompt
/// * `env` - The global shell state
///
/// # Examples
/// ```
/// fn main() {
///     let mut env = compose::env();
///     let mut away = Arc::new(Mutex::new(false));
///     ...
///     repl(&mut away, &mut env);
/// }
/// ```
fn repl(away: &mut Arc<Mutex<bool>>, env: &mut Environment) {
    // Initial path refresh on startup
    env.bins = path::refresh();

    // Main shell loop
    loop {
        // Get the prompt
        let prompt = match env::var("PS1") {
            Ok(val) => val,
            Err(_) => String::from("|> "),
        };

        // Output the prompt
        print!("{}", prompt);
        io::stdout().flush().unwrap();

        // At the prompt
        *away.lock().unwrap() = false;

        // Wait for user input
        let mut poetry = String::new();
        let bytes = io::stdin()
            .read_line(&mut poetry)
            .expect("dwvsh: error: unable to evaluate the input string");

        // Check if we've reached EOF (i.e. <C-d>)
        if bytes == 0 {
            println!();
            break;
        }

        // Trim the input
        let poetry = String::from(poetry.trim());

        // Skip parsing if there is no poetry
        if poetry.is_empty() {
            continue;
        }

        // Not at the prompt
        *away.lock().unwrap() = true;

        // Parse the poem
        let poem = Poem::read(poetry, env);
        let poem = match poem {
            Ok(poem) => poem,
            Err(e) => {
                eprintln!("dwvsh: {}", e.to_string().to_lowercase());
                continue;
            }
        };

        // Recite the poem
        match poem.recite(env) {
            Ok(_) => {}
            Err(e) => eprintln!("dwvsh: {}", e.to_string().to_lowercase()),
        }
    }
}

/// Shell entry
///
/// Shell setup and entry
fn main() {
    // Compose the environment for dwvsh
    let mut env = compose::env();

    // Handle signals
    let mut away = Arc::new(Mutex::new(true));
    unsafe {
        let away = Arc::clone(&away);
        signal_hook::low_level::register(signal_hook::consts::SIGINT, move || {
            if *away.lock().unwrap() {
                println!();
            } else {
                let prompt = match env::var("PS1") {
                    Ok(val) => val,
                    Err(_) => String::from("|> "),
                };
                print!("\n{}", prompt);
                io::stdout().flush().unwrap();
            }
        })
        .unwrap();
    };

    // Begin evaluating commands
    repl(&mut away, &mut env);
}