//! # Pico USB 'Twitchy' Mouse Example
//!
//! Creates a USB HID Class Poiting device (i.e. a virtual mouse) on a Pico
//! board, with the USB driver running in the main thread.
//!
//! It generates movement reports which will twitch the cursor up and down by a
//! few pixels, several times a second.
//!
//! See the `Cargo.toml` file for Copyright and licence details.
//!
//! This is a port of
//! https://github.com/atsamd-rs/atsamd/blob/master/boards/itsybitsy_m0/examples/twitching_usb_mouse.rs

#![no_std]
#![no_main]

// The macro for our start-up function
use cortex_m_rt::entry;

// The macro for marking our interrupt functions
use pico::hal::pac::interrupt;

// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;

// Pull in any important traits
use embedded_time::fixed_point::FixedPoint;
use pico::hal::prelude::*;

// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use pico::hal::pac;

// A shorter alias for the Hardware Abstraction Layer, which provides
// higher-level drivers.
use pico::hal;

// USB Device support
use usb_device::{class_prelude::*, prelude::*};

// USB Human Interface Device (HID) Class support
use usbd_hid::descriptor::generator_prelude::*;
use usbd_hid::descriptor::MouseReport;
use usbd_hid::hid_class::HIDClass;

/// The linker will place this boot block at the start of our program image. We
/// need this to help the ROM bootloader get our code up and running.
#[link_section = ".boot2"]
#[used]
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;

/// The USB Device Driver (shared with the interrupt).
static mut USB_DEVICE: Option<UsbDevice<hal::usb::UsbBus>> = None;

/// The USB Bus Driver (shared with the interrupt).
static mut USB_BUS: Option<UsbBusAllocator<hal::usb::UsbBus>> = None;

/// The USB Human Interface Device Driver (shared with the interrupt).
static mut USB_HID: Option<HIDClass<hal::usb::UsbBus>> = None;

/// Entry point to our bare-metal application.
///
/// The `#[entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables are initialised.
///
/// The function configures the RP2040 peripherals, then submits cursor movement
/// updates periodically.
#[entry]
fn main() -> ! {
    // Grab our singleton objects
    let mut pac = pac::Peripherals::take().unwrap();

    // Set up the watchdog driver - needed by the clock setup code
    let mut watchdog = hal::watchdog::Watchdog::new(pac.WATCHDOG);

    // Configure the clocks
    //
    // Our default is 12 MHz crystal input, 125 MHz system clock
    let clocks = hal::clocks::init_clocks_and_plls(
        pico::XOSC_CRYSTAL_FREQ,
        pac.XOSC,
        pac.CLOCKS,
        pac.PLL_SYS,
        pac.PLL_USB,
        &mut pac.RESETS,
        &mut watchdog,
    )
    .ok()
    .unwrap();

    // Set up the USB driver
    let usb_bus = UsbBusAllocator::new(hal::usb::UsbBus::new(
        pac.USBCTRL_REGS,
        pac.USBCTRL_DPRAM,
        clocks.usb_clock,
        true,
        &mut pac.RESETS,
    ));
    unsafe {
        // Note (safety): This is safe as interrupts haven't been started yet
        USB_BUS = Some(usb_bus);
    }

    // Grab a reference to the USB Bus allocator. We promising to the compiler
    // not to take mutable access to this global variable whilst this reference
    // exists!
    let bus_ref = unsafe { USB_BUS.as_ref().unwrap() };

    // Set up the USB HID Class Device driver, providing Mouse Reports
    let usb_hid = HIDClass::new(bus_ref, MouseReport::desc(), 60);
    unsafe {
        // Note (safety): This is safe as interrupts haven't been started yet.
        USB_HID = Some(usb_hid);
    }

    // Create a USB device with a fake VID and PID
    let usb_dev = UsbDeviceBuilder::new(bus_ref, UsbVidPid(0x16c0, 0x27da))
        .manufacturer("Fake company")
        .product("Twitchy Mousey")
        .serial_number("TEST")
        .device_class(0xEF) // misc
        .build();
    unsafe {
        // Note (safety): This is safe as interrupts haven't been started yet
        USB_DEVICE = Some(usb_dev);
    }

    unsafe {
        // Enable the USB interrupt
        pac::NVIC::unmask(hal::pac::Interrupt::USBCTRL_IRQ);
    };
    let core = pac::CorePeripherals::take().unwrap();
    let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());

    // Move the cursor up and down every 200ms
    loop {
        delay.delay_ms(100);

        let rep_up = MouseReport {
            x: 0,
            y: 4,
            buttons: 0,
            wheel: 0,
        };
        push_mouse_movement(rep_up).ok().unwrap_or(0);

        delay.delay_ms(100);

        let rep_down = MouseReport {
            x: 0,
            y: -4,
            buttons: 0,
            wheel: 0,
        };
        push_mouse_movement(rep_down).ok().unwrap_or(0);
    }
}

/// Submit a new mouse movement report to the USB stack.
///
/// We do this with interrupts disabled, to avoid a race hazard with the USB IRQ.
fn push_mouse_movement(report: MouseReport) -> Result<usize, usb_device::UsbError> {
    cortex_m::interrupt::free(|_| unsafe {
        // Now interrupts are disabled, grab the global variable and, if
        // available, send it a HID report
        USB_HID.as_mut().map(|hid| hid.push_input(&report))
    })
    .unwrap()
}

/// This function is called whenever the USB Hardware generates an Interrupt
/// Request.
#[allow(non_snake_case)]
#[interrupt]
unsafe fn USBCTRL_IRQ() {
    // Handle USB request
    let usb_dev = USB_DEVICE.as_mut().unwrap();
    let usb_hid = USB_HID.as_mut().unwrap();
    usb_dev.poll(&mut [usb_hid]);
}

// End of file