/// Support for the Cirque Pinnacle 1CA027.
use core::cmp::{max, min};
use embedded_hal::{digital::v2::OutputPin, spi};
use nb;

/// Default I²C address.
#[allow(unused)]
const I2C_ADDR: u8 = 0x2a;

// the maximum reportable units
const MAX_X: u16 = 2048;
const MAX_Y: u16 = 1536;

// the lowest reachable units
const CLAMP_X_MIN: u16 = 127;
const CLAMP_Y_MIN: u16 = 63;

// the highest reachable units
const CLAMP_X_MAX: u16 = 1919;
const CLAMP_Y_MAX: u16 = 1471;

// masks for register access protocol
const WRITE_MASK: u8 = 0x80;
const READ_MASK: u8 = 0xa0;

fn clamp<T: Ord>(val: T, low: T, high: T) -> T {
    min(max(low, val), high)
}

/// Register Access Protocol addresses.
#[allow(unused)]
#[repr(u8)]
enum RAPAddress {
    FirmwareID = 0x00,
    FirmwareVersion = 0x01,
    Status1 = 0x02,
    SysConfig1 = 0x03,
    FeedConfig1 = 0x04,
    FeedConfig2 = 0x05,
    FeedConfig3 = 0x06,
    CalConfig1 = 0x07,
    PS2AuxControl = 0x08,
    SampleRate = 0x09,
    ZIdle = 0x0a,
    ZScaler = 0x0b,
    SleepInterval = 0x0c,
    SleepTimer = 0x0d,
    DynamicEMIAdjustThreshold = 0x0e,
    Reserved1 = 0x0f,
    Reserved2 = 0x10,
    Reserved3 = 0x11,
    PacketByte0 = 0x12,
    PacketByte1 = 0x13,
    PacketByte2 = 0x14,
    PacketByte3 = 0x15,
    PacketByte4 = 0x16,
    PacketByte5 = 0x17,
    PortAGPIOControl = 0x18,
    PortAGPIOData = 0x19,
    PortBGPIOControlAndData = 0x1a,
    ExtendedRegisterAccessValue = 0x1b,
    ExtendedRegisterAccessHigh = 0x1c,
    ExtendedRegisterAccessLow = 0x1d,
    ExtendedRegisterAccessControl = 0x1e,
    ProductID = 0x1f,
}

// TODO: figure out how to use the
// embedded_hal::blocking::spi::{Transfer, Write} traits instead of
// doing it ourselves.
trait SPIWriter<Word>: spi::FullDuplex<Word> {
    fn write(&mut self, buf: &[Word]) -> nb::Result<(), Self::Error>;
    fn transfer(&mut self, buf: &mut [Word]) -> nb::Result<(), Self::Error>;
}

impl<T, Word> SPIWriter<Word> for T
where
    T: spi::FullDuplex<Word>,
    Word: Copy,
{
    fn write(&mut self, buf: &[Word]) -> nb::Result<(), Self::Error> {
        for i in buf {
            nb::block!(self.send(*i))?;
            _ = nb::block!(self.read())?;
        }
        Ok(())
    }

    fn transfer(&mut self, buf: &mut [Word]) -> nb::Result<(), Self::Error> {
        for i in buf.iter_mut() {
            nb::block!(self.send(*i))?;
            *i = nb::block!(self.read())?;
        }
        Ok(())
    }
}

#[allow(unused)]
#[derive(Debug)]
pub struct TouchData {
    x: u16,
    y: u16,
    z: u8,
    buttons: u8,
    is_pressed: bool,
}

impl TouchData {
    pub fn clamp(&mut self) {
        self.x = clamp(self.x, CLAMP_X_MIN, CLAMP_X_MAX);
        self.y = clamp(self.y, CLAMP_Y_MIN, CLAMP_Y_MAX);
    }

    pub fn scale_to(&mut self, width: u16, height: u16) {
        let width_factor: f32 = f32::from(width) / f32::from(CLAMP_X_MAX - CLAMP_X_MIN);
        let height_factor: f32 = f32::from(height) / f32::from(CLAMP_Y_MAX - CLAMP_Y_MIN);

        self.clamp();
        self.x -= CLAMP_X_MIN;
        self.y -= CLAMP_Y_MIN;

        assert!(!width_factor.is_nan() && width_factor.is_finite());
        assert!(!height_factor.is_nan() && height_factor.is_finite());
        unsafe {
            self.x = (f32::from(self.x) * width_factor).to_int_unchecked();
            self.y = (f32::from(self.y) * height_factor).to_int_unchecked();
        }
    }
}

pub struct Cirque<C>
where
    C: OutputPin,
{
    cs_pin: C,
    sysclk_speed: u32,
}

impl<C> Cirque<C>
where
    C: OutputPin,
{
    pub fn new<S>(cs_pin: C, spi: &mut S, sysclk_speed: u32) -> nb::Result<Self, S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        let mut res = Self {
            cs_pin,
            sysclk_speed,
        };
        res.init(spi)?;
        Ok(res)
    }

    fn init<S>(&mut self, spi: &mut S) -> nb::Result<(), S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        self.cs_pin.set_high().ok();

        // spin until power on reset is flagged.
        // while self.read_flags(spi)? & 0x8 != 0x8 {}
        self.clear_flags(spi)?;

        self.wr(spi, RAPAddress::SysConfig1, 0x00)?;
        self.wr(spi, RAPAddress::FeedConfig2, 0x1e)?;
        self.wr(spi, RAPAddress::FeedConfig1, 0x03)?;
        self.wr(spi, RAPAddress::ZIdle, 0x05)?;

        Ok(())
    }

    // clears the hardware data ready flag
    fn clear_flags<S>(&mut self, spi: &mut S) -> nb::Result<(), S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        self.wr(spi, RAPAddress::Status1, 0x00)?;

        cortex_m::asm::delay(50 * self.sysclk_speed / 1_000_000);

        Ok(())
    }

    fn read_flags<S>(&mut self, spi: &mut S) -> nb::Result<u8, S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        let mut flags: [u8; 1] = [0xfb; 1];
        self.rd(spi, RAPAddress::Status1, &mut flags)?;
        Ok(flags[0])
    }

    pub fn poll<S>(&mut self, spi: &mut S) -> nb::Result<TouchData, S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        if self.read_flags(spi)? & 0x4 == 0x4 {
            Ok(self.read_coords(spi)?)
        } else {
            Err(nb::Error::WouldBlock)
        }
    }

    fn read_coords<S>(&mut self, spi: &mut S) -> nb::Result<TouchData, S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        let mut buf: [u8; 6] = [0xfc; 6];
        self.rd(spi, RAPAddress::PacketByte0, &mut buf)?;
        self.clear_flags(spi)?;

        let x = buf[2] as u16 | ((buf[4] as u16 & 0x0f) << 8);
        let y = buf[3] as u16 | ((buf[4] as u16 & 0xf0) << 4);
        let z = buf[5] & 0x3f;
        let buttons = 0;
        let is_pressed = x != 0;

        assert!(x < MAX_X);
        assert!(y < MAX_Y);

        Ok(TouchData {
            x,
            y,
            z,
            buttons,
            is_pressed,
        })
    }

    fn rd<S>(&mut self, spi: &mut S, addr: RAPAddress, buf: &mut [u8]) -> nb::Result<(), S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        let addr = addr as u8 | READ_MASK;
        self.cs_pin.set_low().ok();
        let res = spi
            .write(&[addr, 0xfc, 0xfc])
            .and_then(|_| spi.transfer(buf));
        self.cs_pin.set_high().ok();

        res
    }

    fn wr<S>(&mut self, spi: &mut S, addr: RAPAddress, data: u8) -> nb::Result<(), S::Error>
    where
        S: spi::FullDuplex<u8>,
    {
        let addr = addr as u8 | WRITE_MASK;
        self.cs_pin.set_low().ok();
        let res = spi.write(&[addr, data]);
        self.cs_pin.set_high().ok();

        res
    }
}