use embedded_hal::spi::{Operation, SpiDevice};
use anyhow::{ensure, Result};
use crate::hardware::error::SpiError;

pub struct Mcp3208<SPI> {
    spi: SPI,
    vref: f64
}

impl<SPI> Mcp3208<SPI>
where
    SPI : SpiDevice<u8>,
    SPI::Error : Send,
    SPI::Error : Sync,
    SPI::Error : 'static,
{
    pub fn new(spi: SPI, vref: f64) -> Self {
        Self {
            spi,
            vref
        }
    }

    pub fn read_single(&mut self, channel: u8) -> Result<f64> {
        ensure!(channel < 8, "Invalid Channel {channel}");

        // We don't care what the third byte written is
        let mut write_bits = [0b00000110, 0b00000000, 0b00000000];
        write_bits[0] |= (channel.unbounded_shr(2)) & 0xFF;
        write_bits[1] |= (channel.unbounded_shl(6)) & 0xFF;

        let mut read_bits = [0u8; 3];
        self.spi.transfer(&mut read_bits, &write_bits).map_err(SpiError)?;

        let value: u16 = u16::from_be_bytes([read_bits[1], read_bits[2]]) & 0x0FFF;

        Ok(((value as f64) / (0xFFF as f64)) * self.vref)
    }
}