use std::fs;
use std::io::{Seek, Write};
use std::path::Path;

use chrono::{DateTime, Datelike, Utc};
use serde::{Deserialize, Serialize};

use gps_parser;
use ina3221;

#[derive(Serialize, Deserialize, Debug)]
struct Sample {
    value: f64,
    unit: String,
}

#[derive(Serialize, Deserialize, Debug)]
struct CvsData {
    lat: f64,
    lon: f64,
    timestamp: String,
    speed: Sample,
    rpm: Sample,
    current: Sample,
    voltage: Sample,
}

#[derive(serde::Deserialize)]
struct Opts {
    log_path: String,
    i2c_dev: String,
    i2c_slave_address: u16,
    gps_dev: String,
    shunt_resistor: f64,
}

fn read_opts(path: &str) -> Opts {
    let opts_str = fs::read_to_string(path).expect("Unable to read log file");
    return  serde_json::from_str(&opts_str).unwrap();
}

fn update_date(datetime: DateTime<Utc>, year: i32, month: u32, day: u32) -> DateTime<Utc> {
    let mut res = datetime;

    res = match res.with_year(year) {
        Some(value) => value,
        _none => datetime,
    };
    res = match res.with_month(month) {
        Some(value) => value,
        _none => datetime,
    };
    res = match res.with_day(day) {
        Some(value) => value,
        _none => datetime,
    };
    return res;
}

fn log_sample(log_path: &str, sample: CvsData) {
    let path = Path::new(log_path);
    let mut log_json: Vec<CvsData> = Vec::new();
    let mut file: fs::File;
    if path.exists() {
        file = fs::OpenOptions::new().read(true).write(true).create(true).truncate(false).append(false).open(log_path).unwrap();
        let log_str = fs::read_to_string(path).expect("Unable to read log file");
        log_json = serde_json::from_str(&log_str).unwrap();
        file.set_len(0).unwrap();
        file.rewind().unwrap();
    } else {
        file = fs::File::create(log_path).expect("Unable to create file");
    }
    log_json.push(sample);
    let j = match serde_json::to_string(&log_json) {
        Ok(value) => value,
        Err(error) => panic!("Unable to make JSON from struct {:?}", error),
    };
    file.write_all(j.as_bytes()).expect("Unable to write JSON string to file");
}

fn main() {
    let opts = read_opts("/etc/cvs-monitor/config.json");
    let path = Path::new(&opts.log_path);
    if !path.exists() {
        match fs::create_dir(&opts.log_path) {
            Ok(()) => {},
            Err(err) => panic!("Can't create dir \"{}\" ({})", opts.log_path, err),
        };
    }
    let now = Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Secs, true);
    let log_file: String = opts.log_path + &now + ".json";

    let mut gps_parser = gps_parser::GpsParser::new(&opts.gps_dev);
    let mut ina = ina3221::Ina3221::new(opts.i2c_slave_address, &opts.i2c_dev, opts.shunt_resistor);


    loop {
        let speed = Sample {
            value: 0.0,
            unit: "km/h".to_string(),
        };
        let rpm = Sample {
            value: 0.0,
            unit: "T/min".to_string(),
        };
        let current = Sample {
            value: 0.0,
            unit: "A".to_string(),
        };
        let voltage = Sample {
            value: 0.0,
            unit: "V".to_string(),
        };

        let mut sample = CvsData {
            lat: 0.0,
            lon: 0.0,
            timestamp: Utc::now().to_rfc3339(),
            speed,
            rpm,
            current,
            voltage,
        };

        let gps = match gps_parser.parse_nmea() {
            Ok(value) => value,
            Err(_) => continue
        };
        sample.lat = gps.lat;
        sample.lon = gps.lon;
        sample.speed.value = gps.speed;
        sample.rpm.value = sample.speed.value * 1000.0 / (60.0 * 2.2);

        let mut tmp  = gps.timestamp;
        tmp = update_date(tmp, Utc::now().year(), Utc::now().month(), Utc::now().day());
        sample.timestamp = tmp.to_rfc3339();
        let current = match ina.current(ina3221::Channel::One) {
            Ok(value) => value,
            Err(_error) => 0.0,
        };
        sample.current.value = current;
        let voltage = match ina.bus_voltage(ina3221::Channel::One) {
            Ok(value) => value,
            Err(_error) => 0.0,
        };
        sample.voltage.value = voltage;

        log_sample(&log_file, sample);
    }
}