use crate::pac::CRC as PAC_CRC;
use crate::pac::crc::vals;
use crate::peripherals::CRC;
use crate::rcc::sealed::RccPeripheral;

pub struct Crc {
    _peripheral: CRC,
    _config: CrcConfig,
}

pub enum CrcConfigError {
    InvalidPolynomial
}

pub struct CrcConfig {
    reverse_in: CrcInputReverseConfig,
    reverse_out: bool,
    poly_size: PolySize,
    crc_init_value: u32,
    crc_poly: u32,
}

pub enum CrcInputReverseConfig {
    None,
    Byte,
    Halfword,
    Word,
}

impl CrcConfig {
    pub fn new(reverse_in: CrcInputReverseConfig, reverse_out: bool, poly_size: PolySize, crc_init_value: u32, crc_poly: u32) -> Result<Self, CrcConfigError> {
        // As Per RM0091 (DocID018940 Rev 9), Even polynomials are not supported.
        if crc_poly % 2 == 0 {
            Err(CrcConfigError::InvalidPolynomial)
        } else {
            Ok(CrcConfig { reverse_in, reverse_out, poly_size, crc_init_value, crc_poly })
        }
    }
}

pub enum PolySize {
    Width7,
    Width8,
    Width16,
    Width32,
}

impl Crc {
    /// Instantiates the CRC32 peripheral and initializes it to default values.
    pub fn new(peripheral: CRC, init_value: u32, config: CrcConfig) -> Self {
        // Note: enable and reset come from RccPeripheral.
        // enable CRC clock in RCC.
        CRC::enable();
        // Reset CRC to default values.
        CRC::reset();
        let mut instance = Self {
            _peripheral: peripheral,
            _config: config
        };
        unimplemented!();
        // instance.init();
        // instance
    }

    // Configure device settings
    fn configure_revout(&mut self) {
        unsafe {
            PAC_CRC.cr().modify(|w| {w.set_rev_out(
                match self._config.reverse_out {
                    true => {vals::RevOut::REVERSED}
                    false => {vals::RevOut::NORMAL}
                }
            )})
        }
    }

    fn configure_revin(&mut self) {
        unsafe {
            PAC_CRC.cr().modify(|w| {w.set_rev_in(
                match self._config.reverse_in {
                    CrcInputReverseConfig::None => {vals::RevIn::NORMAL}
                    CrcInputReverseConfig::Byte => {vals::RevIn::BYTE}
                    CrcInputReverseConfig::Halfword => {vals::RevIn::HALFWORD}
                    CrcInputReverseConfig::Word => {vals::RevIn::WORD}
                }
            )})
        }
    }

    fn configure_polysize(&mut self) {
        unsafe {
            PAC_CRC.cr().modify(|w| {w.set_polysize(
                match self._config.poly_size {
                    PolySize::Width7 => {vals::Polysize::POLYSIZE7}
                    PolySize::Width8 => {vals::Polysize::POLYSIZE8}
                    PolySize::Width16 => {vals::Polysize::POLYSIZE16}
                    PolySize::Width32 => {vals::Polysize::POLYSIZE32}
                }
            )})
        }
    }

    pub fn reset(&mut self) {
        unsafe { PAC_CRC.cr().modify(|w| w.set_reset(true)); }
    }

    fn set_crc_init(&mut self, value: u32) {
        unsafe {
            PAC_CRC.init().write_value(value)
        }
    }

}