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

use defmt::{panic, *};
use embassy_executor::executor::Spawner;
use embassy_executor::time::{Duration, Timer};
use embassy_stm32::gpio::{Level, Output, Speed};
use embassy_stm32::time::Hertz;
use embassy_stm32::usb::{Driver, Instance};
use embassy_stm32::{interrupt, Config};
use embassy_usb::driver::EndpointError;
use embassy_usb::Builder;
use embassy_usb_serial::{CdcAcmClass, State};
use futures::future::join;
use {defmt_rtt as _, panic_probe as _};

fn config() -> Config {
    let mut config = Config::default();
    config.rcc.hse = Some(Hertz(8_000_000));
    config.rcc.sys_ck = Some(Hertz(48_000_000));
    config.rcc.pclk1 = Some(Hertz(24_000_000));
    config
}

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    let mut p = embassy_stm32::init(config());
    info!("Hello World!");

    {
        // BluePill board has a pull-up resistor on the D+ line.
        // Pull the D+ pin down to send a RESET condition to the USB bus.
        // This forced reset is needed only for development, without it host
        // will not reset your device when you upload new firmware.
        let _dp = Output::new(&mut p.PA12, Level::Low, Speed::Low);
        Timer::after(Duration::from_millis(10)).await;
    }

    // Create the driver, from the HAL.
    let irq = interrupt::take!(USB_LP_CAN1_RX0);
    let driver = Driver::new(p.USB, irq, p.PA12, p.PA11);

    // Create embassy-usb Config
    let config = embassy_usb::Config::new(0xc0de, 0xcafe);
    //config.max_packet_size_0 = 64;

    // 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 = Builder::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?;
    }
}