use serial::SerialPort;
use std::io::BufRead;
use std::io::BufReader;
use std::io::Result as IoResult;

use walkdir::WalkDir;
fn main() {
    let helptext = "Argument 1 is serial port (for example /dev/ttyACM0, Argument 2 is the directory with the music, no stars.";
    let mut args = std::env::args_os();
    let _selfname = args.next();
    let serialport = args.next().expect(helptext);
    let musicdir = args.next().expect(helptext);

    println!("opening serial port");

    let mut port = serial::open(&serialport).expect("could not open serial port");
    port.reconfigure(&|settings| {
        settings.set_baud_rate(serial::Baud115200)?;
        settings.set_char_size(serial::Bits8);
        settings.set_parity(serial::ParityNone);
        settings.set_stop_bits(serial::Stop1);
        settings.set_flow_control(serial::FlowNone);
        Ok(())
    })
    .expect("could not configure port");
    port.set_timeout(std::time::Duration::from_secs(30))
        .expect("could not set timeout");

    println!("serial port opened");

    println!("skimming music dir");

    let walker = WalkDir::new(musicdir).into_iter();
    let walker = walker.filter_entry(|e| {
        e.file_name()
            .to_str()
            .map(|s| !s.starts_with('.'))
            .unwrap_or(true)
    });
    let mut music = Vec::new();
    for entry in walker {
        match entry {
            Err(e) => eprintln!("error when reading music dir, continuing: {:?}", e),
            Ok(entry) => {
                if entry.file_type().is_file()
                    && entry.path().extension() != Some(std::ffi::OsStr::new("jpg"))
                {
                    music.push(Some(entry.path().to_owned()));
                }
            }
        }
    }
    println!("music dir skimmed");
    use rand::seq::SliceRandom;
    use rand::SeedableRng;
    let mut rng = rand::rngs::SmallRng::seed_from_u64(0);
    music.shuffle(&mut rng);
    println!("loaded {} \"songs\"", music.len());

    println!("checked all songs");
    println!("opening audio output");
    let (_stream, stream_handle) = rodio::OutputStream::try_default()
        .expect("could not open audio output, or could not find any");
    let mut sink = rodio::Sink::try_new(&stream_handle).expect("could not create sink");
    println!("audio output opened");

    #[derive(Clone, Copy, Debug)]
    struct Hyst {
        max: usize,
        prechoice: usize,
        /// value when the choice was last changed
        prechoice_val: usize,
        /// value of last read
        preval: usize,
        /// number of times the same (but changed) value has been read
        stability: usize,
    }

    let equality_range = 1;
    let stability_tresh = 7;

    let hyst = Hyst {
        // wage has valid range 0-5000
        max: 5000,
        prechoice: 0,
        prechoice_val: 0,
        preval: 0,
        stability: 0,
    };

    let musiclen = music.len();

    let read_delay = std::time::Duration::from_millis(100);
    // first remove noise
    let iter = PortIter::new(port, read_delay)
        .unwrap()
        .map(|e| e.unwrap())
        .scan(hyst, |hyst, el| {
            // 8888 is empty screen, 69696969 is EEEE
            if el == 8888 || el == 69_69_69_69 {
                return Some(None)
            }
            hyst.max = hyst.max.max(el);
            let absdiff = el.max(hyst.prechoice_val) - el.min(hyst.prechoice_val);
            if absdiff > equality_range {
                // build stability if value has not changed since last time
                if hyst.preval == el {
                    hyst.stability += 1;
                } else {
                    hyst.stability = 0;
                }
                hyst.preval = el;

                // once we are stable
                if hyst.stability > stability_tresh {
                    let choice = (el * (musiclen - 1)) / hyst.max;
                    // make sure the choice actually changed
                    if choice != hyst.prechoice {
                        hyst.prechoice = choice;
                        hyst.stability = 0;
                        hyst.prechoice_val = el;
                        println!("pushing choice {}", choice);
                        return Some(Some((el, hyst.max)));
                    }
                }
            }
            Some(None)
        });

    // next: turn de-noised into a decoder
    let iter = iter
        // skip thing the denoiser denoised
        .flatten()
        .map(|(e, max)| {
        let decoder;
        // re-run until we hit actually valid music files
        loop {
            let base = (e * (music.len() - 1)) / max;
            let mut delta: isize = 0;
            let choicef;
            let choice;
            // search for non-deleted paths in a cyclic pattern around base choice
            // (0, -1, 1, -2, 2...)
            loop {
                let modchoice = if delta > 0 {
                    let c = base + (delta as usize);
                    delta = -delta;
                    c
                } else {
                    let c = base - (delta as usize);
                    delta = (-delta) + 1;
                    c
                };
                println!("trying {} next delta {}", modchoice, delta);
                if let Some(Some(c)) = music.get(modchoice) {
                    choicef = c;
                    choice = modchoice;
                    break;
                }
            }
            // try to decode
            let c = || -> Result<rodio::Decoder<_>, ()> {
                let f = std::fs::File::open(choicef).map_err(|_| ())?;
                let rdr = BufReader::new(f);
                rodio::Decoder::new(rdr).map_err(|_| ())
            };
            match (c)() {
                Ok(d) => {
                    decoder = d;
                    println!("playing {:?}", choicef);
                    break;
                }
                Err(()) => {
                    eprintln!("{:?} was not actually music", choicef);
                    music[choice] = None;
                }
            }
        }
        decoder
    });
    // now just play the decoder
    for decoder in iter {
        let newsink = rodio::Sink::try_new(&stream_handle).expect("could not create sink");
        newsink.append(decoder);

        sink.stop();
        sink = newsink;
    }
}

#[derive(Debug)]
enum PortIterErr {
    Io(std::io::Error),
    Parse(std::num::ParseIntError),
}

impl From<std::io::Error> for PortIterErr {
    fn from(e: std::io::Error) -> Self {
        Self::Io(e)
    }
}
impl From<std::num::ParseIntError> for PortIterErr {
    fn from(e: std::num::ParseIntError) -> Self {
        Self::Parse(e)
    }
}

struct PortIter<S: SerialPort> {
    port: BufReader<S>,
    delay: std::time::Duration,
}
impl<S: SerialPort> PortIter<S> {
    fn new(mut p: S, delay: std::time::Duration) -> IoResult<Self> {
        p.write_all(b"r")?;
        Ok(Self {
            port: BufReader::new(p),
            delay,
        })
    }
}
impl<S: SerialPort> Iterator for PortIter<S> {
    type Item = Result<usize, PortIterErr>;
    fn next(&mut self) -> Option<Result<usize, PortIterErr>> {
        let mut buf = String::new();
        let r = self.port.read_line(&mut buf);
        match r {
            Ok(0) => return None,
            Err(e) => return Some(Result::Err(e.into())),
            Ok(_) => (),
        };

        let num = match buf.trim().parse::<usize>() {
            Err(e) => return Some(Result::Err(e.into())),
            Ok(num) => num,
        };
        match self.port.get_mut().write_all(b"r") {
            Ok(_) => (),
            Err(e) => return Some(Result::Err(e.into())),
        }

        std::thread::sleep(self.delay);
        Some(Result::Ok(num))
    }
}