#![no_std]

use embedded_hal::{
    delay::DelayNs,
    digital::{InputPin, OutputPin},
    spi::{Operation, SpiDevice},
};

const EPD_WIDTH: usize = 240;
const EPD_HEIGHT: usize = 320;
const EPD_ARRAY: usize = EPD_WIDTH * EPD_HEIGHT / 8;

pub struct EPaperDisplay<BusyPin, ResetPin, DcPin, SpiDevice, Delay> {
    busy: BusyPin,
    reset: ResetPin,
    dc: DcPin,
    spi: SpiDevice,
    delay: Delay,
}

pub enum InitError<ResetError, DcError, SpiError> {
    ResetError(ResetError),
    WriteError(WriteError<DcError, SpiError>),
}

pub enum WriteError<DcError, SpiError> {
    DcError(DcError),
    SpiError(SpiError),
}

pub struct Frame([u8; EPD_ARRAY]);

impl Frame {
    pub const fn new_white() -> Self {
        Self([0xff; EPD_ARRAY])
    }

    pub const fn new_black() -> Self {
        Self([0x00; EPD_ARRAY])
    }
}

pub struct DoubleFrame {
    old: Frame,
    new: Frame,
}

pub enum PixelColour {
    Black = 0,
    White = 1,
}

impl DoubleFrame {
    pub fn new(old: Frame, new: Frame) -> Self {
        Self { old, new }
    }

    pub fn draw_pixel(&mut self, x: usize, y: usize, colour: PixelColour) {

    }
}

impl<BusyPin: InputPin, ResetPin: OutputPin, DcPin: OutputPin, Spi: SpiDevice, Delay: DelayNs>
    EPaperDisplay<BusyPin, ResetPin, DcPin, Spi, Delay>
{
    pub fn new(
        busy: BusyPin,
        reset: ResetPin,
        dc: DcPin,
        spi: Spi,
        delay: Delay,
    ) -> Result<Self, InitError<ResetPin::Error, DcPin::Error, Spi::Error>> {
        let mut display = Self {
            busy,
            reset,
            dc,
            spi,
            delay,
        };
        display.init().map(|_| display)
    }

    fn write_command(&mut self, byte: u8) -> Result<(), WriteError<DcPin::Error, Spi::Error>> {
        self.dc.set_low().map_err(WriteError::DcError)?;
        self.spi
            .transaction(&mut [
                Operation::DelayNs(60),
                Operation::Write(&[byte]),
                Operation::DelayNs(20),
            ])
            .map_err(WriteError::SpiError)?;
        self.delay.delay_ns(40);
        Ok(())
    }

    fn write_data(&mut self, byte: u8) -> Result<(), WriteError<DcPin::Error, Spi::Error>> {
        self.dc.set_high().map_err(WriteError::DcError)?;
        self.spi
            .transaction(&mut [
                Operation::DelayNs(60),
                Operation::Write(&[byte]),
                Operation::DelayNs(20),
            ])
            .map_err(WriteError::SpiError)?;
        self.delay.delay_ns(40);
        Ok(())
    }

    fn wait_for_display(&mut self) {
        while self.busy.is_low().expect("Failed to read busy pin") {}
    }

    fn init(&mut self) -> Result<(), InitError<ResetPin::Error, DcPin::Error, Spi::Error>> {
        self.reset.set_low().map_err(InitError::ResetError)?;
        self.delay.delay_ms(10);
        self.reset.set_high().map_err(InitError::ResetError)?;
        self.delay.delay_ms(10);

        self.write_command(0x00).map_err(InitError::WriteError)?;
        self.write_data(0x1f).map_err(InitError::WriteError)?;
        self.write_command(0x04).map_err(InitError::WriteError)?;

        self.wait_for_display();

        Ok(())
    }

    fn clear_display(&mut self) {
        self.write_command(0x10);
        for _ in 0..EPD_ARRAY {
            self.write_data(0xff);
        }
        self.write_command(0x13);
        for _ in 0..EPD_ARRAY {
            self.write_data(0xff);
        }
        self.write_command(0x12);

        self.delay.delay_ms(1);
        self.wait_for_display();
    }

    pub fn draw_full_frame(&mut self, double_frame: &mut DoubleFrame) {
        self.write_command(0x10);
        for byte in double_frame.old.0 {
            self.write_data(byte);
        }
        self.write_command(0x13);
        for byte in double_frame.new.0 {
            self.write_data(byte);
        }
        self.write_command(0x12);
        double_frame.old.0 = double_frame.new.0;

        self.delay.delay_ms(1);
        self.wait_for_display();
    }
}