//! A platform agnostic driver to interface with the MAX7219 (LED matrix display driver)
//!
//! This driver was built using [`embedded-hal-async`] traits.
//!
//! [`embedded-hal-async`]: https://docs.rs/embedded-hal-async/~1.0

#![deny(unsafe_code)]
#![deny(warnings)]
#![no_std]

use embedded_hal_async::spi::SpiDevice;

/// Digits per display
pub const NUM_DIGITS: usize = 8;

/// Possible command register values on the display chip.
#[derive(Clone, Copy)]
pub enum Register {
    Noop = 0x00,
    Digit0 = 0x01,
    Digit1 = 0x02,
    Digit2 = 0x03,
    Digit3 = 0x04,
    Digit4 = 0x05,
    Digit5 = 0x06,
    Digit6 = 0x07,
    Digit7 = 0x08,
    DecodeMode = 0x09,
    Intensity = 0x0A,
    ScanLimit = 0x0B,
    Power = 0x0C,
    DisplayTest = 0x0F,
}

impl From<Register> for u8 {
    fn from(command: Register) -> u8 {
        command as u8
    }
}

/// Decode modes for BCD encoded input.
#[derive(Copy, Clone)]
pub enum DecodeMode {
    /// No decode for BCD encoded input.
    NoDecode = 0x00,
    CodeBDigit0 = 0x01,
    CodeBDigits3_0 = 0x0F,
    CodeBDigits7_0 = 0xFF,
}

/// A MAX7219 chip.
///
/// Currently, this driver does not support daisy-chaining multiple MAX7219 chips.
pub struct Max7219<SPI> {
    pub spi: SPI,
}

impl<SPI> Max7219<SPI>
where
    SPI: SpiDevice,
{
    /// Write a byte to a register on the display chip.
    async fn write_reg(&mut self, register: impl Into<u8>, data: u8) -> Result<(), SPI::Error> {
        self.spi.write(&[register.into(), data]).await
    }

    /// Power on the display.
    pub async fn power_on(&mut self) -> Result<(), SPI::Error> {
        self.write_reg(Register::Power, 0x01).await
    }

    /// Power off the display.
    pub async fn power_off(&mut self) -> Result<(), SPI::Error> {
        self.write_reg(Register::Power, 0x00).await
    }

    /// Clear the display by setting all digits to empty.
    pub async fn clear(&mut self) -> Result<(), SPI::Error> {
        self.write_raw(&[0; NUM_DIGITS]).await
    }

    /// Set intensity level on the display,from `0x00` (dimmest) to `0x0F` (brightest).
    pub async fn set_intensity(&mut self, intensity: u8) -> Result<(), SPI::Error> {
        self.write_reg(Register::Intensity, intensity).await
    }

    /// Set decode mode to be used on input sent to the display chip.
    ///
    /// See [`DecodeMode`] for more information.
    pub async fn set_decode_mode(&mut self, mode: DecodeMode) -> Result<(), SPI::Error> {
        self.write_reg(Register::DecodeMode, mode as u8).await
    }

    /// Write a byte to a digit on the display.
    ///
    /// A typical 7-segment display has the following layout:
    ///
    /// ```txt
    ///     A
    ///    ---
    /// F |   | B
    ///   | G |
    ///    ---
    /// E |   | C
    ///   | D |
    ///    ---  . DP
    /// ```
    ///
    /// | Byte        | 7  | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
    /// |-------------|----|---|---|---|---|---|---|---|
    /// | **Segment** | DP | A | B | C | D | E | F | G |
    ///
    /// To display the number `5`, for example, the byte `0b0101_1011` would be
    /// sent to the display.
    #[inline]
    pub async fn write_digit_bytes(&mut self, digit: u8, value: u8) -> Result<(), SPI::Error> {
        self.write_reg(digit + 1, value).await
    }

    /// Write byte string to the display
    ///
    /// # Arguments
    ///
    /// * `string` - the byte string to send 8 bytes long. Unknown characters result in question mark.
    /// * `dots` - u8 bit array specifying where to put dots in the string (1 = dot, 0 = not)
    pub async fn write_str(
        &mut self,
        string: &[u8; NUM_DIGITS],
        dots: u8,
    ) -> Result<(), SPI::Error> {
        for (i, b) in string.iter().enumerate() {
            let reg = NUM_DIGITS as u8 - i as u8; // reverse order
            let dot = (dots >> (reg - 1)) & 1 == 1;
            self.write_reg(reg, ssb_byte(*b, dot)).await?;
        }

        Ok(())
    }

    /// Write a right justified integer with sign.
    pub async fn write_integer(&mut self, value: i32) -> Result<(), SPI::Error> {
        let mut buf = [0u8; 8];
        let j = base_10_bytes(value, &mut buf);
        buf = pad_left(j);
        self.write_str(&buf, 0b00000000).await
    }

    /// Write a right justified hex formatted integer with sign.
    pub async fn write_hex(&mut self, value: u32) -> Result<(), SPI::Error> {
        let mut buf = [0u8; 8];
        let j = hex_bytes(value, &mut buf);
        buf = pad_left(j);
        self.write_str(&buf, 0b00000000).await
    }

    /// Write a raw value to the display.
    pub async fn write_raw(&mut self, raw: &[u8; NUM_DIGITS]) -> Result<(), SPI::Error> {
        for (n, b) in raw.iter().enumerate() {
            self.write_digit_bytes(n as u8, *b).await?;
        }
        Ok(())
    }

    /// Enable or disable the display test mode.
    pub async fn set_test(&mut self, enable: bool) -> Result<(), SPI::Error> {
        self.write_reg(Register::DisplayTest, if enable { 0x01 } else { 0x00 })
            .await
    }

    /// Create a new instance of the MAX7219 driver.
    ///
    /// After creating a new instance, you should call the [`Max7219::init`]
    /// method to initialize the display.
    pub const fn new(spi: SPI) -> Self {
        Self { spi }
    }

    /// Set the number of digits to scan (display). The value should be between 1 and 8.
    pub async fn set_scan_limit(&mut self, limit: u8) -> Result<(), SPI::Error> {
        self.write_reg(Register::ScanLimit, limit - 1).await
    }

    /// Initialize the display with the default settings.
    pub async fn init(&mut self) -> Result<(), SPI::Error> {
        self.set_test(false).await?;
        self.set_scan_limit(NUM_DIGITS as u8).await?;
        self.set_decode_mode(DecodeMode::NoDecode).await?;
        self.clear().await?;
        self.power_off().await?;
        self.power_on().await?;

        Ok(())
    }
}

///
/// Translate alphanumeric ASCII bytes into segment set bytes
///
fn ssb_byte(b: u8, dot: bool) -> u8 {
    let mut result = match b as char {
        ' ' => 0b0000_0000, // "blank"
        '.' => 0b1000_0000,
        '-' => 0b0000_0001, // -
        '_' => 0b0000_1000, // _
        '0' => 0b0111_1110,
        '1' => 0b0011_0000,
        '2' => 0b0110_1101,
        '3' => 0b0111_1001,
        '4' => 0b0011_0011,
        '5' => 0b0101_1011,
        '6' => 0b0101_1111,
        '7' => 0b0111_0000,
        '8' => 0b0111_1111,
        '9' => 0b0111_1011,
        'a' | 'A' => 0b0111_0111,
        'b' => 0b0001_1111,
        'c' | 'C' => 0b0100_1110,
        'd' => 0b0011_1101,
        'e' | 'E' => 0b0100_1111,
        'f' | 'F' => 0b0100_0111,
        'g' | 'G' => 0b0101_1110,
        'h' | 'H' => 0b0011_0111,
        'i' | 'I' => 0b0011_0000,
        'j' | 'J' => 0b0011_1100,
        // K undoable
        'l' | 'L' => 0b0000_1110,
        // M undoable
        'n' | 'N' => 0b0001_0101,
        'o' | 'O' => 0b0111_1110,
        'p' | 'P' => 0b0110_0111,
        'q' => 0b0111_0011,
        'r' | 'R' => 0b0000_0101,
        's' | 'S' => 0b0101_1011,
        // T undoable
        'u' | 'U' => 0b0011_1110,
        // V undoable
        // W undoable
        // X undoable
        // Y undoable
        // Z undoable
        _ => 0b1110_0101, // ?
    };

    if dot {
        result |= 0b1000_0000; // turn "." on
    }

    result
}

/// Convert the integer into an integer byte Sequence
fn base_10_bytes(mut n: i32, buf: &mut [u8]) -> &[u8] {
    let mut sign: bool = false;
    if n == 0 {
        return b"0";
    }
    //don't overflow the display
    if !(-9999999..=99999999).contains(&n) {
        return b"Err";
    }
    if n < 0 {
        n = -n;
        sign = true;
    }
    let mut i = 0;
    while n > 0 {
        buf[i] = (n % 10) as u8 + b'0';
        n /= 10;
        i += 1;
    }
    if sign {
        buf[i] = b'-';
        i += 1;
    }
    let slice = &mut buf[..i];
    slice.reverse();
    &*slice
}

/// Convert the integer into a hexidecimal byte sequence
fn hex_bytes(mut n: u32, buf: &mut [u8]) -> &[u8] {
    if n == 0 {
        return b"0";
    }
    let mut i = 0;
    while n > 0 {
        let digit = (n % 16) as u8;
        buf[i] = match digit {
            0 => b'0',
            1 => b'1',
            2 => b'2',
            3 => b'3',
            4 => b'4',
            5 => b'5',
            6 => b'6',
            7 => b'7',
            8 => b'8',
            9 => b'9',
            10 => b'a',
            11 => b'b',
            12 => b'c',
            13 => b'd',
            14 => b'e',
            15 => b'f',
            _ => b'?',
        };
        n /= 16;
        i += 1;
    }
    let slice = &mut buf[..i];
    slice.reverse();
    &*slice
}

/// Take a byte slice and pad the left hand side
fn pad_left(val: &[u8]) -> [u8; 8] {
    assert!(val.len() <= 8);
    let size: usize = 8;
    let pos: usize = val.len();
    let mut cur: usize = 1;
    let mut out: [u8; 8] = *b"        ";
    while cur <= pos {
        out[size - cur] = val[pos - cur];
        cur += 1;
    }
    out
}