// Copyright 2019 Robin Krahl <robin.krahl@ireas.org>
// SPDX-License-Identifier: GPL-3.0-or-later

use core::iter::Iterator;

use hal::stm32::CRC;

pub trait Crc {
    fn get(&self, data: &[u8]) -> u32 {
        self.get_u32(data.chunks(4).map(slice_to_u32))
    }

    fn get_u32<I: Iterator<Item = u32>>(&self, iter: I) -> u32;
}

pub struct Stm32Crc {
    crc: CRC,
}

impl Stm32Crc {
    pub fn new(crc: CRC) -> Self {
        Self { crc }
    }

    fn write(&self, val: u32) {
        self.crc.dr.write(|w| w.dr().bits(val));
    }

    fn read(&self) -> u32 {
        self.crc.dr.read().dr().bits()
    }

    fn reset(&self) {
        self.crc.cr.write(|w| w.reset().reset());
    }
}

impl Crc for Stm32Crc {
    fn get_u32<I: Iterator<Item = u32>>(&self, iter: I) -> u32 {
        self.reset();
        iter.for_each(|val| self.write(val));
        self.read()
    }
}

fn slice_to_u32(data: &[u8]) -> u32 {
    data.iter()
        .enumerate()
        .fold(0, |acc, (idx, val)| acc + (u32::from(*val) << (idx * 8)))
}