#![feature(integer_atomics, nll)]

extern crate num_traits;
extern crate memmap;

use num_traits::{NumAssignOps, PrimInt, sign::Unsigned};
use memmap::MmapMut;
use std::error::Error as StdError;
use std::fmt;
use std::fs::OpenOptions;
use std::ops::{BitAndAssign, BitOrAssign, BitXorAssign};
use std::mem::{align_of, size_of};
use std::sync::atomic::{AtomicU32, Ordering};

type Result<T> = std::result::Result<T, Box<StdError>>;

#[derive(Debug)]
enum Error {
    SomeErr,
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "SomeErr")
    }
}

impl StdError for Error {
    fn description(&self) -> &str {
        "SomeErr"
    }
}

//////////////////////////////
// Define AtomicUnsigned trait

trait AtomicUnsigned {
    type AtomicPrimitive;
    type Primitive: PrimInt + Unsigned + NumAssignOps + BitAndAssign + BitOrAssign + BitXorAssign;

    // ... re-export atomic integer API for example:
    fn load(&self, order: Ordering) -> Self::Primitive;
    fn store(&self, val: Self::Primitive, order: Ordering);
}

impl AtomicUnsigned for AtomicU32 {
    type AtomicPrimitive = AtomicU32;
    type Primitive = u32;

    fn load(&self, order: Ordering) -> Self::Primitive {
        self.load(order)
    }

    fn store(&self, val: Self::Primitive, order: Ordering) {
        self.store(val, order)
    }
}

///////////////////////////////////////
// Define hardware register memory map structure

const GPIO_REGISTER_COUNT: usize = 41;  // from BCM 2835 datasheet

trait GpioMmap {
    type Register: AtomicUnsigned;
    const DEVICE_ID: &'static str;
    const BASE_ADDR: usize;
    // ...

    fn new() -> Result<Self> where Self: std::marker::Sized;
    fn registers(&self) -> &[Self::Register; GPIO_REGISTER_COUNT];

}

/////////////////////////////////////////////////////////////
// Specialize register memory map for Raspberry Pi 3 platform

struct Rpi3RaspbianGpioMmap {
    mmap: MmapMut,
}

impl GpioMmap for Rpi3RaspbianGpioMmap {
    type Register = AtomicU32;
    const DEVICE_ID: &'static str = "/tmp/foo";
    const BASE_ADDR: usize = 0x0000; // per BCM2835 datasheet (could not locate BCM2837 datasheet)

    fn new() -> Result<Self> where Self: std::marker::Sized {
        let fd = OpenOptions::new()
                       .read(true)
                       .write(true)
                       .create(true)
                       .open(&Self::DEVICE_ID)?;
        fd.set_len((GPIO_REGISTER_COUNT * size_of::<Self::Register>()) as u64)?;

        let mmap = unsafe { MmapMut::map_mut(&fd)? };

        let mmap_size = mmap.len() * size_of::<u8>();
        if mmap_size != GPIO_REGISTER_COUNT * size_of::<Self::Register>() {
            return Err(Box::new(Error::SomeErr));
        };

        let mmap_addr = mmap.as_ptr() as usize;
        let register_align = align_of::<Self::Register>();
        if mmap_addr % register_align != 0 {
            return Err(Box::new(Error::SomeErr));
        }

        Ok(Self {
            mmap,
        })
    }

    fn registers(&self) -> &[Self::Register; GPIO_REGISTER_COUNT] {
        unsafe {
            &*(self.mmap.as_ptr() as *const Self::Register as *const [Self::Register; GPIO_REGISTER_COUNT])
        }
    }
}

////////////////////////
// Define HAL Components interface

trait Chal {
    type GpioMmap: GpioMmap;

    fn new(gpio_mmap: Self::GpioMmap) -> Self;
    //...
}

/////////////////////////////////////////////////////////
// Specialize HAL Components interface for Raspberry Pi 3

struct GpioControlSet {
    pub fn_ctrl_reg_offset:   usize,
    pub fn_ctrl_field_mask:   u32,
    //...
}

struct Rpi3Chal<G = Rpi3RaspbianGpioMmap> where G: GpioMmap,
                                                <G as GpioMmap>::Register: AtomicUnsigned<Primitive = u32> {
    gpio_mmap: <Rpi3Chal<G> as Chal>::GpioMmap,
    gpio_control_sets: [GpioControlSet; 1],
    //...
}

impl<G> Chal for Rpi3Chal<G> where G: GpioMmap,
//                                   <<G as GpioMmap>::Register as AtomicUnsigned>::Primitive: From<u32> {
                                   <G as GpioMmap>::Register: AtomicUnsigned<Primitive = u32> {
    type GpioMmap = G;

    fn new(gpio_mmap: Self::GpioMmap) -> Self {
        let gpio_control_set = GpioControlSet {
            fn_ctrl_reg_offset: 8,  // made-up value
            fn_ctrl_field_mask: 0b111 << 16, //made-up value
        };

        let chal = Self {
            gpio_mmap,
            gpio_control_sets: [gpio_control_set],
        };
        chal.init()
    }
}

impl<G> Rpi3Chal<G> where G: GpioMmap,
                          <G as GpioMmap>::Register: AtomicUnsigned<Primitive = u32> {
    fn init(self) -> Self {
        let led_gpio = &self.gpio_control_sets[0];
        let mut temp = self.gpio_mmap.registers()[led_gpio.fn_ctrl_reg_offset].load(Ordering::Relaxed); // <- returns AtomicUnsigned::Primitive
        temp &= !led_gpio.fn_ctrl_field_mask;                                                           // <- returns u32
        //...
        self.gpio_mmap.registers()[led_gpio.fn_ctrl_reg_offset].store(temp, Ordering::Relaxed);
        self
    }
}

fn main() {
    let _ = inner_main();
}

fn inner_main() -> Result<()> {
    let chal = Rpi3Chal::new(Rpi3RaspbianGpioMmap::new()?);

    Ok(())
}