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

use core::mem;
use defmt::{info, panic};
use embassy::executor::Spawner;
use embassy_nrf::interrupt;
use embassy_nrf::pac;
use embassy_nrf::usb::{Driver, Instance};
use embassy_nrf::Peripherals;
use embassy_usb::driver::EndpointError;
use embassy_usb::{Config, UsbDeviceBuilder};
use embassy_usb_serial::{CdcAcmClass, State};
use futures::future::join;

use defmt_rtt as _; // global logger
use panic_probe as _;

#[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 config = Config::new(0xc0de, 0xcafe);

    // Create embassy-usb DeviceBuilder using the driver and config.
    // It needs some buffers for building the descriptors.
    let mut device_descriptor = [0; 256];
    let mut config_descriptor = [0; 256];
    let mut bos_descriptor = [0; 256];
    let mut control_buf = [0; 7];

    let mut state = State::new();

    let mut builder = UsbDeviceBuilder::new(
        driver,
        config,
        &mut device_descriptor,
        &mut config_descriptor,
        &mut bos_descriptor,
        &mut control_buf,
        None,
    );

    // Create classes on the builder.
    let mut class = CdcAcmClass::new(&mut builder, &mut state, 64);

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

    // Run the USB device.
    let usb_fut = usb.run();

    // Do stuff with the class!
    let echo_fut = async {
        loop {
            class.wait_connection().await;
            info!("Connected");
            let _ = echo(&mut class).await;
            info!("Disconnected");
        }
    };

    // Run everything concurrently.
    // If we had made everything `'static` above instead, we could do this using separate tasks instead.
    join(usb_fut, echo_fut).await;
}

struct Disconnected {}

impl From<EndpointError> for Disconnected {
    fn from(val: EndpointError) -> Self {
        match val {
            EndpointError::BufferOverflow => panic!("Buffer overflow"),
            EndpointError::Disabled => Disconnected {},
        }
    }
}

async fn echo<'d, T: Instance + 'd>(
    class: &mut CdcAcmClass<'d, Driver<'d, T>>,
) -> Result<(), Disconnected> {
    let mut buf = [0; 64];
    loop {
        let n = class.read_packet(&mut buf).await?;
        let data = &buf[..n];
        info!("data: {:x}", data);
        class.write_packet(data).await?;
    }
}