#![no_std]
#![no_main]
#![feature(generic_associated_types)]
#![feature(type_alias_impl_trait)]

use core::mem;
use core::sync::atomic::{AtomicBool, Ordering};
use core::task::Waker;

use defmt::*;
use embassy::blocking_mutex::raw::ThreadModeRawMutex;
use embassy::channel::mpmc::Channel;
use embassy::executor::Spawner;
use embassy::util::Forever;
use embassy_net::tcp::TcpSocket;
use embassy_net::{PacketBox, PacketBoxExt, PacketBuf, Stack, StackResources};
use embassy_nrf::rng::Rng;
use embassy_nrf::usb::Driver;
use embassy_nrf::{interrupt, pac, peripherals, Peripherals};
use embassy_usb::{Builder, Config, UsbDevice};
use embassy_usb_ncm::{CdcNcmClass, Receiver, Sender, State};
use embedded_io::asynch::{Read, Write};
use {defmt_rtt as _, panic_probe as _};

type MyDriver = Driver<'static, peripherals::USBD>;

macro_rules! forever {
    ($val:expr) => {{
        type T = impl Sized;
        static FOREVER: Forever<T> = Forever::new();
        FOREVER.put_with(move || $val)
    }};
}

#[embassy::task]
async fn usb_task(mut device: UsbDevice<'static, MyDriver>) -> ! {
    device.run().await
}

#[embassy::task]
async fn usb_ncm_rx_task(mut class: Receiver<'static, MyDriver>) {
    loop {
        warn!("WAITING for connection");
        LINK_UP.store(false, Ordering::Relaxed);

        class.wait_connection().await.unwrap();

        warn!("Connected");
        LINK_UP.store(true, Ordering::Relaxed);

        loop {
            let mut p = unwrap!(PacketBox::new(embassy_net::Packet::new()));
            let n = match class.read_packet(&mut p[..]).await {
                Ok(n) => n,
                Err(e) => {
                    warn!("error reading packet: {:?}", e);
                    break;
                }
            };

            let buf = p.slice(0..n);
            if RX_CHANNEL.try_send(buf).is_err() {
                warn!("Failed pushing rx'd packet to channel.");
            }
        }
    }
}

#[embassy::task]
async fn usb_ncm_tx_task(mut class: Sender<'static, MyDriver>) {
    loop {
        let pkt = TX_CHANNEL.recv().await;
        if let Err(e) = class.write_packet(&pkt[..]).await {
            warn!("Failed to TX packet: {:?}", e);
        }
    }
}

#[embassy::task]
async fn net_task(stack: &'static Stack<Device>) -> ! {
    stack.run().await
}

#[embassy::main]
async fn main(spawner: Spawner, p: Peripherals) {
    let clock: pac::CLOCK = unsafe { mem::transmute(()) };
    let power: pac::POWER = unsafe { mem::transmute(()) };

    info!("Enabling ext hfosc...");
    clock.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
    while clock.events_hfclkstarted.read().bits() != 1 {}

    info!("Waiting for vbus...");
    while !power.usbregstatus.read().vbusdetect().is_vbus_present() {}
    info!("vbus OK");

    // Create the driver, from the HAL.
    let irq = interrupt::take!(USBD);
    let driver = Driver::new(p.USBD, irq);

    // Create embassy-usb Config
    let mut config = Config::new(0xc0de, 0xcafe);
    config.manufacturer = Some("Embassy");
    config.product = Some("USB-Ethernet example");
    config.serial_number = Some("12345678");
    config.max_power = 100;
    config.max_packet_size_0 = 64;

    // Required for Windows support.
    config.composite_with_iads = true;
    config.device_class = 0xEF;
    config.device_sub_class = 0x02;
    config.device_protocol = 0x01;

    struct Resources {
        device_descriptor: [u8; 256],
        config_descriptor: [u8; 256],
        bos_descriptor: [u8; 256],
        control_buf: [u8; 128],
        serial_state: State<'static>,
    }
    let res: &mut Resources = forever!(Resources {
        device_descriptor: [0; 256],
        config_descriptor: [0; 256],
        bos_descriptor: [0; 256],
        control_buf: [0; 128],
        serial_state: State::new(),
    });

    // Create embassy-usb DeviceBuilder using the driver and config.
    let mut builder = Builder::new(
        driver,
        config,
        &mut res.device_descriptor,
        &mut res.config_descriptor,
        &mut res.bos_descriptor,
        &mut res.control_buf,
        None,
    );

    // WARNINGS for Android ethernet tethering:
    // - On Pixel 4a, it refused to work on Android 11, worked on Android 12.
    // - if the host's MAC address has the "locally-administered" bit set (bit 1 of first byte),
    //   it doesn't work! The "Ethernet tethering" option in settings doesn't get enabled.
    //   This is due to regex spaghetti: https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-mainline-12.0.0_r84/core/res/res/values/config.xml#417
    //   and this nonsense in the linux kernel: https://github.com/torvalds/linux/blob/c00c5e1d157bec0ef0b0b59aa5482eb8dc7e8e49/drivers/net/usb/usbnet.c#L1751-L1757

    // Our MAC addr.
    let our_mac_addr = [0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC];
    // Host's MAC addr. This is the MAC the host "thinks" its USB-to-ethernet adapter has.
    let host_mac_addr = [0x88, 0x88, 0x88, 0x88, 0x88, 0x88];

    // Create classes on the builder.
    let class = CdcNcmClass::new(&mut builder, &mut res.serial_state, host_mac_addr, 64);

    // Build the builder.
    let usb = builder.build();

    unwrap!(spawner.spawn(usb_task(usb)));

    let (tx, rx) = class.split();
    unwrap!(spawner.spawn(usb_ncm_rx_task(rx)));
    unwrap!(spawner.spawn(usb_ncm_tx_task(tx)));

    let config = embassy_net::ConfigStrategy::Dhcp;
    //let config = embassy_net::ConfigStrategy::Static(embassy_net::Config {
    //    address: Ipv4Cidr::new(Ipv4Address::new(10, 42, 0, 61), 24),
    //    dns_servers: Vec::new(),
    //    gateway: Some(Ipv4Address::new(10, 42, 0, 1)),
    //});

    // Generate random seed
    let mut rng = Rng::new(p.RNG, interrupt::take!(RNG));
    let mut seed = [0; 8];
    rng.blocking_fill_bytes(&mut seed);
    let seed = u64::from_le_bytes(seed);

    // Init network stack
    let device = Device { mac_addr: our_mac_addr };
    let stack = &*forever!(Stack::new(
        device,
        config,
        forever!(StackResources::<1, 2, 8>::new()),
        seed
    ));

    unwrap!(spawner.spawn(net_task(stack)));

    // And now we can use it!

    let mut rx_buffer = [0; 4096];
    let mut tx_buffer = [0; 4096];
    let mut buf = [0; 4096];

    loop {
        let mut socket = TcpSocket::new(stack, &mut rx_buffer, &mut tx_buffer);
        socket.set_timeout(Some(embassy_net::SmolDuration::from_secs(10)));

        info!("Listening on TCP:1234...");
        if let Err(e) = socket.accept(1234).await {
            warn!("accept error: {:?}", e);
            continue;
        }

        info!("Received connection from {:?}", socket.remote_endpoint());

        loop {
            let n = match socket.read(&mut buf).await {
                Ok(0) => {
                    warn!("read EOF");
                    break;
                }
                Ok(n) => n,
                Err(e) => {
                    warn!("read error: {:?}", e);
                    break;
                }
            };

            info!("rxd {:02x}", &buf[..n]);

            match socket.write_all(&buf[..n]).await {
                Ok(()) => {}
                Err(e) => {
                    warn!("write error: {:?}", e);
                    break;
                }
            };
        }
    }
}

static TX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
static RX_CHANNEL: Channel<ThreadModeRawMutex, PacketBuf, 8> = Channel::new();
static LINK_UP: AtomicBool = AtomicBool::new(false);

struct Device {
    mac_addr: [u8; 6],
}

impl embassy_net::Device for Device {
    fn register_waker(&mut self, waker: &Waker) {
        // loopy loopy wakey wakey
        waker.wake_by_ref()
    }

    fn link_state(&mut self) -> embassy_net::LinkState {
        match LINK_UP.load(Ordering::Relaxed) {
            true => embassy_net::LinkState::Up,
            false => embassy_net::LinkState::Down,
        }
    }

    fn capabilities(&self) -> embassy_net::DeviceCapabilities {
        let mut caps = embassy_net::DeviceCapabilities::default();
        caps.max_transmission_unit = 1514; // 1500 IP + 14 ethernet header
        caps.medium = embassy_net::Medium::Ethernet;
        caps
    }

    fn is_transmit_ready(&mut self) -> bool {
        true
    }

    fn transmit(&mut self, pkt: PacketBuf) {
        if TX_CHANNEL.try_send(pkt).is_err() {
            warn!("TX failed")
        }
    }

    fn receive<'a>(&mut self) -> Option<PacketBuf> {
        RX_CHANNEL.try_recv().ok()
    }

    fn ethernet_address(&self) -> [u8; 6] {
        self.mac_addr
    }
}