use std::time::Duration;

use anyhow::Context;
use metrics::{describe_gauge, gauge, Gauge};
use serialport::SerialPort;

pub struct Pli {
    port: Box<dyn SerialPort>,
    voltage_gauge: Gauge,
    duty_cycle: Gauge,
}

impl Pli {
    pub fn new(serial_port: String, baud_rate: u32) -> anyhow::Result<Self> {
        let port = serialport::new(serial_port, baud_rate)
            .timeout(Duration::from_millis(250))
            .open()?;

        describe_gauge!("pl_battery_voltage", "Battery voltage");
        let voltage_gauge = gauge!("pl_battery_voltage");
        describe_gauge!("pl_duty_cycle", "Duty cycle");
        let duty_cycle = gauge!("pl_duty_cycle");

        Ok(Self {
            port,
            voltage_gauge,
            duty_cycle,
        })
    }

    pub fn refresh(&mut self) {
        if let Ok(batv) = self.read_ram(50) {
            self.voltage_gauge.set(((batv * 4) as f64) / 10.);
        }
        if let Ok(duty_cycle) = self.read_ram(39) {
            self.duty_cycle.set((duty_cycle as f64) / 255.);
        }
    }

    fn send_command(&mut self, req: [u8; 4]) {
        self.port
            .write_all(&req)
            .expect("failed to write to serial port");
    }

    fn receive<const LENGTH: usize>(&mut self) -> [u8; LENGTH] {
        let mut buf = [0; LENGTH];
        match self.port.read_exact(&mut buf) {
            Ok(_) => {}
            Err(e) => log::error!("PLI serial read error: {e:#?}"),
        }
        buf
    }

    fn read_ram(&mut self, address: u8) -> anyhow::Result<u8> {
        self.send_command(command(20, address, 0));
        let buf: [u8; 2] = self.receive();
        if buf[0] == 200 { Some(buf[1]) } else { None }
            .context(format!("Error from PLI: {}", buf[0]))
    }
}

fn command(operation: u8, address: u8, data: u8) -> [u8; 4] {
    [operation, address, data, !operation]
}