#![allow(unused_parens)]

use std::io::prelude::*;
use std::fs::File;
use std::env::args;

fn main()
{
	let argv = args().collect::<Vec<String>>();
	if argv.len() != 4
	{
		eprintln!("usage: upsample <factor> <input.dat> <output.dat>");
		return;
	}

	// deal with command-line arguments first, before anything big happens
	let factor = argv[1].parse::<usize>().unwrap();
	let mut input_file = File::open(&argv[2]).unwrap();
	let mut output_file = File::create(&argv[3]).unwrap();
	
	// read the input file
	let mut input_data:Vec<u8> = Vec::new();
	input_file.read_to_end(&mut input_data).unwrap();

	// decode the input data
	let mut input:Vec<f32> = Vec::with_capacity(input_data.len()/4);
	for chunk in input_data.chunks_exact(4)
	{
		let mut samplebuffer:[u8;4] = [0x00; 4];
		samplebuffer.copy_from_slice(chunk);
		input.push(f32::from_be_bytes(samplebuffer));
	}

	// actually do the processing
	let output_size = (input.len()-1)*factor;
	let mut output:Vec<f32> = Vec::with_capacity(output_size);
	let ffac = factor as f32;
	for t in 0..input.len()-1
	{
		for iu in 0..factor
		{
			let u = iu as f32;
			output.push(
				input[t] * (ffac-u)/ffac
				+
				input[t+1] * u/ffac
			);
		}
	}
	output.push(input[input.len()-1]);

	// encode the output data
	let mut output_data:Vec<u8> = Vec::with_capacity(output.len()*4);
	for point in output.iter()
	{
		output_data.extend_from_slice(&point.to_be_bytes());
	}
	
	// write the output file
	output_file.write_all(&output_data).unwrap();
}