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

use defmt::{panic, *};
use embassy_executor::Spawner;
use embassy_stm32::rcc::{AHBPrescaler, APBPrescaler, Hse, HseMode, Pll, PllSource, Sysclk, VoltageScale};
use embassy_stm32::time::Hertz;
use embassy_stm32::usb::{Driver, Instance};
use embassy_stm32::{bind_interrupts, pac, peripherals, usb, Config};
use embassy_usb::class::cdc_acm::{CdcAcmClass, State};
use embassy_usb::driver::EndpointError;
use embassy_usb::Builder;
use futures::future::join;
use {defmt_rtt as _, panic_probe as _};

bind_interrupts!(struct Irqs {
    USB_DRD_FS => usb::InterruptHandler<peripherals::USB>;
});

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    let mut config = Config::default();
    config.rcc.hsi = None;
    config.rcc.hsi48 = true; // needed for usb
    config.rcc.hse = Some(Hse {
        freq: Hertz(8_000_000),
        mode: HseMode::BypassDigital,
    });
    config.rcc.pll1 = Some(Pll {
        source: PllSource::Hse,
        prediv: 2,
        mul: 125,
        divp: Some(2), // 250mhz
        divq: None,
        divr: None,
    });
    config.rcc.ahb_pre = AHBPrescaler::Div2;
    config.rcc.apb1_pre = APBPrescaler::Div4;
    config.rcc.apb2_pre = APBPrescaler::Div2;
    config.rcc.apb3_pre = APBPrescaler::Div4;
    config.rcc.sys = Sysclk::Pll1P;
    config.rcc.voltage_scale = VoltageScale::Scale0;
    let p = embassy_stm32::init(config);

    info!("Hello World!");

    pac::RCC.ccipr4().write(|w| {
        w.set_usbsel(pac::rcc::vals::Usbsel::HSI48);
    });

    // Create the driver, from the HAL.
    let driver = Driver::new(p.USB, Irqs, p.PA12, p.PA11);

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

    // Required for windows compatibility.
    // https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.9.1/kconfig/CONFIG_CDC_ACM_IAD.html#help
    config.device_class = 0xEF;
    config.device_sub_class = 0x02;
    config.device_protocol = 0x01;
    config.composite_with_iads = true;

    // 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; 64];

    let mut state = State::new();

    let mut builder = Builder::new(
        driver,
        config,
        &mut device_descriptor,
        &mut config_descriptor,
        &mut bos_descriptor,
        &mut control_buf,
    );

    // 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?;
    }
}