use crate::pac::crc::vals;
use crate::pac::CRC as PAC_CRC;
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,
    #[cfg(crc_v3)]
    poly_size: PolySize,
    crc_init_value: u32,
    #[cfg(crc_v3)]
    crc_poly: u32,
}

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

impl CrcConfig {
    pub fn new(
        reverse_in: CrcInputReverseConfig,
        reverse_out: bool,
        #[cfg(crc_v3)]
        poly_size: PolySize,
        crc_init_value: u32,
        #[cfg(crc_v3)]
        crc_poly: u32,
    ) -> Result<Self, CrcConfigError> {
        // As Per RM0091 (DocID018940 Rev 9), Even polynomials are not supported.
        #[cfg(crc_v3)]
        if crc_poly % 2 == 0 {
            return Err(CrcConfigError::InvalidPolynomial);
        }
        Ok(CrcConfig {
            reverse_in,
            reverse_out,
            #[cfg(crc_v3)]
            poly_size,
            crc_init_value,
            #[cfg(crc_v3)]
            crc_poly,
        })
    }
}

#[cfg(crc_v3)]
pub enum PolySize {
    Width7,
    Width8,
    Width16,
    Width32,
}

impl Crc {
    /// Instantiates the CRC32 peripheral and initializes it to default values.
    pub fn new(peripheral: CRC, 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,
        };
        CRC::reset();
        instance.reconfigure();
        instance.reset();
        instance
    }

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

    /// Reconfigures the CRC peripheral. Doesn't reset.
    fn reconfigure(&mut self) {
        unsafe {
            // Init CRC value
            PAC_CRC.init().write_value(self._config.crc_init_value);
            #[cfg(crc_v3)]
                PAC_CRC.pol().write_value(self._config.crc_poly);

            // configure CR components
            // (reverse I/O, polysize, poly)
            PAC_CRC.cr().modify(|w| {
                // configure reverse output
                w.set_rev_out(match self._config.reverse_out {
                    true => vals::RevOut::REVERSED,
                    false => vals::RevOut::NORMAL,
                });
                // configure reverse input
                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,
                });
                // configure the polynomial.
                #[cfg(crc_v3)]
                    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,
                });
            })
        }

        self.reset();
    }

    /// Feeds a byte into the CRC peripheral. Returns the computed checksum.
    pub fn feed_byte(&mut self, byte: u8) -> u32 {
        unsafe {
            PAC_CRC.dr8().write_value(byte as u32);
            PAC_CRC.dr().read()
        }
    }

    /// Feeds an slice of bytes into the CRC peripheral. Returns the computed checksum.
    pub fn feed_bytes(&mut self, bytes: &[u8]) -> u32 {
        for byte in bytes {
            unsafe { PAC_CRC.dr8().write_value(*byte as u32); }
        }
        unsafe {
            PAC_CRC.dr().read()
        }
    }
    /// Feeds a halfword into the CRC peripheral. Returns the computed checksum.
    pub fn feed_halfword(&mut self, byte: u16) -> u32 {
        unsafe {
            PAC_CRC.dr16().write_value(byte as u32);
            PAC_CRC.dr().read()
        }
    }
    /// Feeds an slice of halfwords into the CRC peripheral. Returns the computed checksum.
    pub fn feed_halfwords(&mut self, bytes: &[u16]) -> u32 {
        for byte in bytes {
            unsafe { PAC_CRC.dr16().write_value(*byte as u32); }
        }
        unsafe {
            PAC_CRC.dr().read()
        }
    }
    /// Feeds a halfword into the CRC peripheral. Returns the computed checksum.
    pub fn feed_word(&mut self, byte: u32) -> u32 {
        unsafe {
            PAC_CRC.dr().write_value(byte as u32);
            PAC_CRC.dr().read()
        }
    }
    /// Feeds an slice of halfwords into the CRC peripheral. Returns the computed checksum.
    pub fn feed_words(&mut self, bytes: &[u32]) -> u32 {
        for byte in bytes {
            unsafe { PAC_CRC.dr().write_value(*byte as u32); }
        }
        unsafe {
            PAC_CRC.dr().read()
        }
    }
}