use std::error;
use std::io::Read;
use std::path;
use std::process;

use clap::Parser;

use piston::EventLoop;
use piston::EventSettings;
use piston::Events;
use piston::RenderEvent;

use piston_window as pw;
use piston_window::PistonWindow;
use piston_window::WindowSettings;

#[derive(Debug, Parser)]
#[command(author, version, about, long_about = None)]
struct Cli {
    /// Executable to run
    executable: path::PathBuf,
    /// Number of pixels in a row
    cols: usize,
    /// Number of rows in a frame
    rows: usize,
    /// Free-format argument to pass to the executable
    arg: String,
    /// Frame rate for displaying
    #[arg(short, long, default_value_t = 25)]
    frame_rate: u64,
    /// Turn debugging information on
    #[arg(short, long, action = clap::ArgAction::Count)]
    debug: u8,
}

fn main() -> Result<(), Box<dyn error::Error>> {
    let cli = Cli::parse();
    if cli.debug >= 2 {
        eprintln!("CLI: {:?}", cli);
    }

    let mut child = process::Command::new(&cli.executable)
        .arg(cli.cols.to_string())
        .arg(cli.rows.to_string())
        .arg(cli.arg)
        .stdout(process::Stdio::piped())
        .spawn()?;
    if cli.debug >= 1 {
        eprintln!(
            "Running {} as a child process with pid {}",
            cli.executable.display(),
            child.id()
        );
    }

    let mut stdout = child
        .stdout
        .take()
        .ok_or("opening child process stdout failed")?;

    // TODO support also RGBW
    let colors = 3;
    // TODO check for overflow and excessive size
    let buffer_size = cli.cols * cli.rows * colors;
    let mut buffer = vec![0_u8; buffer_size];
    let mut frame_count = 0;

    let mut window: PistonWindow = WindowSettings::new(
        format!("pixelfoo-viewer {}", cli.executable.display()),
        [1600, 800],
    )
    .exit_on_esc(true)
    .build()?;

    let mut events = Events::new(EventSettings::new().ups(cli.frame_rate));

    let x_size = cli.cols;
    let y_size = cli.rows;
    while let Some(event) = events.next(&mut window) {
        if let Some(args) = event.render_args() {
            window.draw_2d(&event, |context, graphics, _device| {
                // let [vsx, vsy] = context.get_view_size();
                let [vsx, vsy] = args.viewport().window_size;

                // Compute cell size
                let csx = vsx / (x_size as f64);
                let csy = vsy / (y_size as f64);
                let cs = csx.min(csy);

                pw::clear([0.0, 0.0, 0.0, 1.0], graphics);

                stdout.read_exact(&mut buffer).expect("pipe read failed");
                if cli.debug >= 3 {
                    eprintln!("Received frame {}", frame_count);
                }

                for y in 0..y_size {
                    for x in 0..x_size {
                        let i = colors * (y * x_size + x);
                        let r = f32::from(buffer[i + 0]) / 255.0;
                        let g = f32::from(buffer[i + 1]) / 255.0;
                        let b = f32::from(buffer[i + 2]) / 255.0;
                        let color = [r, g, b, 1.0];
                        let rectangle = [(x as f64) * cs, (y as f64) * cs, cs, cs];
                        pw::rectangle(color, rectangle, context.transform, graphics);
                    }
                }
            });
        }
        frame_count += 1;
    }
    child.kill()?;

    Ok(())
}