use std::{
    io::Write,
    sync::{Arc, RwLock},
    time::Duration,
};

use anyhow::Context;
use metrics::{describe_gauge, gauge, Gauge};
use serde::{Deserialize, Serialize};
use serialport::SerialPort;
use termcolor::WriteColor;

pub struct Pli {
    pub state: Arc<RwLock<PlState>>,
    port: Box<dyn SerialPort>,
    voltage_gauge: Gauge,
    duty_cycle: Gauge,
    internal_charge_current: Gauge,
    internal_load_current: Gauge,
    regulator_gauges: RegulatorGauges,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub struct PlState {
    pub battery_voltage: f64,
    pub duty_cycle: f64,
    pub internal_charge_current: f64,
    pub internal_load_current: f64,
    pub regulator_state: RegulatorState,
}

impl Default for PlState {
    fn default() -> Self {
        Self {
            battery_voltage: Default::default(),
            duty_cycle: Default::default(),
            internal_charge_current: Default::default(),
            internal_load_current: Default::default(),
            regulator_state: RegulatorState::Absorption,
        }
    }
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum RegulatorState {
    Boost,
    Equalise,
    Absorption,
    Float,
}

impl From<u8> for RegulatorState {
    fn from(value: u8) -> Self {
        match value & 0b11 {
            0b00 => Self::Boost,
            0b01 => Self::Equalise,
            0b10 => Self::Absorption,
            0b11 => Self::Float,
            _ => unreachable!(),
        }
    }
}

struct RegulatorGauges {
    boost: Gauge,
    equalise: Gauge,
    absorption: Gauge,
    float: Gauge,
}

impl RegulatorGauges {
    fn new() -> Self {
        describe_gauge!("pl_regulator", "Regulator state");
        let boost = gauge!("pl_regulator", "state" => "boost");
        let equalise = gauge!("pl_regulator", "state" => "equalise");
        let absorption = gauge!("pl_regulator", "state" => "absorption");
        let float = gauge!("pl_regulator", "state" => "float");
        Self {
            boost,
            equalise,
            absorption,
            float,
        }
    }

    fn set(&mut self, state: &RegulatorState) {
        match state {
            RegulatorState::Boost => {
                self.boost.set(1.);
                self.equalise.set(0.);
                self.absorption.set(0.);
                self.float.set(0.);
            }
            RegulatorState::Equalise => {
                self.boost.set(0.);
                self.equalise.set(1.);
                self.absorption.set(0.);
                self.float.set(0.);
            }
            RegulatorState::Absorption => {
                self.boost.set(0.);
                self.equalise.set(0.);
                self.absorption.set(1.);
                self.float.set(0.);
            }
            RegulatorState::Float => {
                self.boost.set(0.);
                self.equalise.set(0.);
                self.absorption.set(0.);
                self.float.set(1.);
            }
        }
    }
}

#[derive(Debug, Clone, Copy)]
pub enum PliRequest {
    ReadRam(u8),
}

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");
        describe_gauge!("pl_internal_charge_current", "Internal charge current");
        let internal_charge_current = gauge!("pl_internal_charge_current");
        describe_gauge!("pl_internal_load_current", "Internal load current");
        let internal_load_current = gauge!("pl_internal_load_current");

        Ok(Self {
            state: Arc::new(RwLock::new(Default::default())),
            port,
            voltage_gauge,
            duty_cycle,
            internal_charge_current,
            internal_load_current,
            regulator_gauges: RegulatorGauges::new(),
        })
    }

    pub fn refresh(&mut self) {
        if let Ok(new_state) = self.read_state() {
            self.voltage_gauge.set(new_state.battery_voltage);
            self.duty_cycle.set(new_state.duty_cycle);
            self.internal_charge_current
                .set(new_state.internal_charge_current);
            self.internal_load_current
                .set(new_state.internal_load_current);
            self.regulator_gauges.set(&new_state.regulator_state);

            *self.state.write().expect("PLI state handler panicked!!") = new_state;
        }
    }

    pub fn process_request(&mut self, message: PliRequest) {
        match message {
            PliRequest::ReadRam(address) => match self.read_ram(address) {
                Ok(data) => {
                    let mut stdout =
                        termcolor::StandardStream::stdout(termcolor::ColorChoice::Always);
                    let _ = stdout.set_color(
                        termcolor::ColorSpec::new().set_fg(Some(termcolor::Color::Green)),
                    );
                    if writeln!(&mut stdout, "Read RAM at {address}: data {data}").is_err() {
                        log::warn!(
                            "Failed to set stdout colour\nRead RAM at {address}: data {data}"
                        );
                    };
                }
                Err(e) => log::error!("RAM read error: {e:?}"),
            },
        }
    }

    fn read_state(&mut self) -> anyhow::Result<PlState> {
        Ok(PlState {
            battery_voltage: (self.read_ram(PlRamAddress::Batv)? as f64) * (4. / 10.),
            duty_cycle: (self.read_ram(PlRamAddress::Dutycyc)? as f64) / 255.,
            internal_charge_current: (self.read_ram(PlRamAddress::Cint)? as f64) * (4. / 10.),
            internal_load_current: (self.read_ram(PlRamAddress::Lint)? as f64) * (4. / 10.),
            regulator_state: self.read_ram(PlRamAddress::Rstate)?.into(),
        })
    }

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

enum PlRamAddress {
    Dutycyc,
    Batv,
    Rstate,
    Cint,
    Lint,
}

impl From<PlRamAddress> for u8 {
    fn from(value: PlRamAddress) -> Self {
        match value {
            PlRamAddress::Dutycyc => 39,
            PlRamAddress::Batv => 50,
            PlRamAddress::Rstate => 101,
            PlRamAddress::Cint => 213,
            PlRamAddress::Lint => 217,
        }
    }
}

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