use clap::Parser;
use dotenv::dotenv;
use std::io::Write;
use thermaldecoder::{Header, HDR_SIZE};
use v4l::video::Output;

#[derive(Parser, Debug)]
#[command(version, about, long_about = None)]
struct Args {
    #[arg(short, long, default_value_t = false)]
    temperature: bool,
    #[arg(short, long, default_value = "/dev/video0")]
    device: String,
}

fn pixel_to_celcius(x: u16) -> u16 {
    let x: f64 = x.into();
    let x = x / 256.0;
    let t = (-1.665884e-08) * x.powf(4.)
        + (1.347094e-05) * x.powf(3.)
        + (-4.396264e-03) * x.powf(2.)
        + (9.506939e-01) * x
        + (-6.353247e+01);
    (t * 256.0) as u16
}

fn main() -> anyhow::Result<()> {
    let args = Args::parse();
    dotenv().ok();
    let device = match std::env::var("THERMALCAM_IFACE=enp1s0f0") {
        Ok(d) => {
            let device = pcap::Device::list()
                .expect("device list failed")
                .into_iter()
                .find(|x| x.name == d)
                .expect(&format!("could not find device {}", d));
            device
        }
        Err(_) => pcap::Device::lookup()
            .expect("device lookup failed")
            .expect("no device available"),
    };
    // get the default Device

    println!("Using device {}", device.name);
    let output = args.device;
    println!("Using output v4l2loopback device {}", output);

    const WIDTH: usize = 288;
    const HEIGHT: usize = 384;
    let fourcc_repr = [
        b'Y', // | 0b10000000
        b'1', b'6',
        b' ', // Note: not using b' ' | 0x80, (V4L2_PIX_FMT_Y16_BE)
              // because VID_S_FMT ioctl returns EINVAL, so just swap the bytes here
    ];
    let fourcc = v4l::format::FourCC { repr: fourcc_repr };
    let mut out = v4l::Device::with_path(output)?;
    // To find the fourcc code, use v4l2-ctl --list-formats-out /dev/video0
    // (or read the source :)
    let format = v4l::Format::new(WIDTH as u32, HEIGHT as u32, fourcc);
    Output::set_format(&out, &format)?;

    // Setup Capture
    let mut cap = pcap::Capture::from_device(device)
        .unwrap()
        .immediate_mode(true)
        .open()
        .unwrap();

    // get a packet and print its bytes
    const PACKET_LEN: usize = 6972;
    const FRAME_LEN: usize = WIDTH * HEIGHT * 2;
    let mut frame = [0u8; FRAME_LEN];
    let mut len = 0;
    while let Ok(p) = cap.next_packet() {
        let data = p.data;
        if data.len() != PACKET_LEN {
            continue;
        }
        let data = &data[0x2a..];
        let header = match Header::read(data) {
            Ok(header) => header,
            Err(_) => continue,
        };
        let data = &data[HDR_SIZE..];
        if (header.part == 0 && len > 0)
            // do not write out of bounds - would panic, instead just skip
            || (data.len() + len > FRAME_LEN)
        {
            if len == FRAME_LEN {
                // swap the bytes, we are using LE, not BE, 16 bit grayscale
                // possibly limitation of current v4l2loopback or v4l rust wrapper or libv4l2
                let mut swapped = [0u8; FRAME_LEN];
                for i in 0..FRAME_LEN / 2 {
                    let mut pixel = u16::from_be_bytes([frame[i * 2], frame[i * 2 + 1]]);
                    if args.temperature {
                        pixel = pixel_to_celcius(pixel);
                    }
                    let pixel_swapped = pixel.to_le_bytes();
                    swapped[i * 2..i * 2 + 2].copy_from_slice(&pixel_swapped);
                }
                out.write_all(&swapped[..])?;
            }
            len = 0;
        }
        frame[len..len + data.len()].copy_from_slice(data);
        len += data.len();
    }
    Ok(())
}