#!/usr/bin/env rust-script

use std::{fmt, fs::read_to_string, str::FromStr};

const BASE_PATH: &str = "/sys/class/power_supply/BAT1/";
const CURRENT_NOW_PATH: &str = "current_now";
const VOLTAGE_NOW_PATH: &str = "voltage_now";
const STATUS_PATH: &str = "status";
const FACTOR: f32 = 1e6_f32;

#[derive(Debug)]
enum Status {
    Charging,
    Discharging,
    NotCharging,
}

impl FromStr for Status {
    type Err = &'static str;

    fn from_str(input: &str) -> Result<Status, Self::Err> {
        match input {
            "Charging" => Ok(Status::Charging),
            "Discharging" => Ok(Status::Discharging),
            "Not charging" => Ok(Status::NotCharging),
            _ => Err("unknown state"),
        }
    }
}

impl fmt::Display for Status {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self, f)
    }
}

fn fetch_and_trim_into<T: FromStr<Err = impl fmt::Debug>>(path: &str) -> T {
    let mut content = read_to_string(BASE_PATH.to_owned() + path).unwrap();
    content.pop();
    T::from_str(&content).unwrap()
}

fn fetch_bat_info(path: &str) -> f32 {
    let value: f32 = fetch_and_trim_into(path);
    value / FACTOR
}

fn main() {
    let current_now: f32 = fetch_bat_info(CURRENT_NOW_PATH);
    let voltage_now: f32 = fetch_bat_info(VOLTAGE_NOW_PATH);
    let watts: f32 = current_now * voltage_now;
    let status: Status = fetch_and_trim_into(STATUS_PATH);

    println!(
        "voltage: {:.4}\ncurrent: {:.4}\nwatts: {:.4}\nstatus: {}",
        voltage_now, current_now, watts, status
    );
}