use embedded_hal::blocking::delay::{DelayMs, DelayUs};
use embedded_hal::blocking::i2c::Write;

use crate::{bus::DataBus, error::Result};

/// This module supports I2C backpacks with a MCP23008 IC, like
/// the one from adafruit.
/// Connections as follows:
///
/// <table>
/// <tr><th>MCP23008 pin</th><th>name</th><th>LCD pin</th></tr>
/// <tr><td>0</td><td>N/C</td><td></td></tr>
/// <tr><td>1</td><td>RS</td><td>4</td></tr>
/// <tr><td>2</td><td>E</td><td>6</td></tr>
/// <tr><td>3</td><td>DB4</td><td>11</td></tr>
/// <tr><td>4</td><td>DB5</td><td>12</td></tr>
/// <tr><td>5</td><td>DB6</td><td>13</td></tr>
/// <tr><td>6</td><td>DB7</td><td>14</td></tr>
/// <tr><td>7</td><td>Backlight</td><td></td></tr>
/// </table>

pub struct I2CMCP23008Bus<I2C: Write> {
    i2c_bus: I2C,
    address: u8,
}

const REG_IODIR : u8 = 0x00;
const REG_GPIO : u8 = 0x09;

impl<I2C: Write> I2CMCP23008Bus<I2C> {

    /// Create a new instance of the MCP23008 I2C driver. The address of those
    /// devices is 0b010_0xxx where x is configured by bootstrap pins.
    pub fn new(i2c_bus: I2C, address: u8) -> Result<I2CMCP23008Bus<I2C>> {
        let mut mcp23008 = I2CMCP23008Bus { i2c_bus, address };
        // Set to reset values according to datasheet
        mcp23008.write_reg(REG_IODIR, 0b1111_1111)?;
        for reg in 0x01usize..0x0A {
            mcp23008.write_reg(reg as u8, 0)?;
        }
        // Configure pins 1..=7 as outputs, see pin mapping above
        mcp23008.write_reg(REG_IODIR, 0b0000_0001)?;
        Ok(mcp23008)
    }

    fn write_reg(&mut self, reg: u8, value: u8) -> Result<()> {
        let data = [reg, value];
        self.i2c_bus.write(self.address, &data)
            .map_err(|_| crate::error::Error)
    }

    fn set_pins(&mut self, pins: u8) -> Result<()> {
        self.write_reg(REG_GPIO, pins)
    }

}

impl<I2C: Write> DataBus for I2CMCP23008Bus<I2C> {
    fn write<D: DelayUs<u16> + DelayMs<u8>>(
        &mut self,
        byte: u8,
        data: bool,
        delay: &mut D,
    ) -> Result<()> {
        let rs = if data { 0b10 } else { 0b00 };
        let en = 0b0000_0100;
        let backlight = 0b1000_0000; // always enable backlight

        let upper_nibble = (byte & 0xF0) >> 4;
        let lower_nibble = byte & 0x0F;

        // upper nibble: [d7 d6 d5 d4]
        // Pulse EN
        // lower nibble: [d3 d2 d1 d0]
        // Pulse EN

        let pins = rs | backlight | (upper_nibble << 3);
        self.set_pins(pins)?;

        delay.delay_ms(1);

        let pins = rs | en | backlight | (upper_nibble << 3);
        self.set_pins(pins)?;

        delay.delay_ms(1);

        let pins = rs | backlight | (lower_nibble << 3);
        self.set_pins(pins)?;

        delay.delay_ms(1);

        let pins = rs | en | backlight | (lower_nibble << 3);
        self.set_pins(pins)?;

        delay.delay_ms(1);

        let pins = backlight | (lower_nibble << 3);
        self.set_pins(pins)?;

        Ok(())
    }
}