extern crate getopts;
extern crate byteorder;

use std::env;
use std::fs;
use std::io::BufReader;
use std::io::prelude::*;
use std::i32;
use std::io::Cursor;

use getopts::Options;
use byteorder::{ReadBytesExt, WriteBytesExt, LittleEndian};


fn main() {
    let args: Vec<String> = env::args().collect();

    let mut opts = Options::new();

    opts.optflag("c", "", "Compress file");
    opts.optflag("x", "", "Extract file");

    let matches = match opts.parse(&args[1..]) {
        Ok(m) => { m }
        Err(f) => { panic!(f.to_string()) }
    };

    if matches.opt_present("c") {
        let input = &matches.free[0];
        let output = &matches.free[1];

        create(&input, &output);
    }
    else if matches.opt_present("x") {
        let input = &matches.free[0];
        let output = &matches.free[1];

        extract(&input, &output)
    }
}

fn create(input: &String, output: &String) {
    let mut output_file = fs::File::create(output).unwrap();

    let input_file = fs::File::open(input).unwrap();
    let input_buf = BufReader::new(input_file);

    let mut i : i32 = 0;

    for b in input_buf.bytes() {
        let b = b.unwrap();

        for n in 0..i32::MAX {
            if b == get_byte(n) {
                i = n;
                break;
            }
        }

        let mut index : Vec<u8> = vec![];

        index.write_i32::<LittleEndian>(i).unwrap();

        output_file.write_all(&index).unwrap();
    }
}

fn extract(input: &String, output: &String) {
    let mut output_file = fs::File::create(output).unwrap();
    let mut input_file = fs::File::open(input).unwrap();

    let mut buf = vec![0; 4];

    loop {
        let size = input_file.read(&mut buf).unwrap();

        if size <= 0 {
            break;
        }

        let mut c = Cursor::new(&buf);
        let index = c.read_i32::<LittleEndian>().unwrap();

        output_file.write_all(&[get_byte(index)]).unwrap();
    }
}

fn get_byte(id: i32) -> u8 {
    let pid : f64 = 4.0 * series(1, id) - 2.0 * series(4, id) - series(5, id) - series(6, id);

    let mut y : f64 = (pid - (pid as i32) as f64 + 1.0).abs();

    y = 16.0 * (y - y.floor());

    let first : u8 = y as u8;

    y = 16.0 * (y - y.floor());

    let second : u8 = y as u8;

    (first << 4) | second
}

fn series(m: i32, id: i32) -> f64 {
    const EPS : f64 = 1e-17;

    let mut ak : f64;
    let mut s : f64 = 0.0;
    let mut t : f64;

    for k in 0..id {
      ak = (8 * k + m) as f64;
      t = expm((id - k) as f64, ak);

      s = s + t / ak;
      s = s - (s as i32) as f64;
    }

    for k in id..id + 101 {
      ak = (8 * k + m) as f64;
      t = 16f64.powi(id - k) / ak;

      if t < EPS {
          break;
      }

      s = s + t;
      s = s - (s as i32) as f64;
    }

    s
}

fn expm(p: f64, ak: f64) -> f64 {
    const NTP : usize = 25;

    let mut tp = vec![1f64; NTP];
    let mut i : i32 = 0;
    let mut p1 : f64 = p;
    let mut pt : f64;
    let mut r : f64 = 1.0;

    for n in 1..NTP {
        tp[n] = 2.0 * tp[n - 1];
    }

    if ak == 1.0 {
        return 0.0;
    }

    for n in 0..NTP {
        if tp[n] > p {
            i = n as i32;
            break;
        }
    }

    pt = tp[(i - 1) as usize];

    for _ in 1..i + 1 {
      if p1 >= pt {
        r = 16.0 * r;
        r = r - ((r / ak) as i32) as f64 * ak;

        p1 = p1 - pt;
      }

      pt = 0.5 * pt;

      if pt >= 1.0 {
        r = r * r;
        r = r - ((r / ak) as i32) as f64 * ak;
      }
    }

    r
}