use std::io::Read;
use std::fs::File;
use Result;
use binread::BinReadable;

pub struct IJVMReader {
    pointer: usize,
    source: Vec<u8>
}

impl IJVMReader {
    pub fn new(path: &str) -> Result<IJVMReader> {
        let file = match File::open(path) {
            Ok(file) => file,
            Err(_) => return Err("Could not open file"),
        };
        let abc: Vec<u8> = file.bytes().map(|e| e.unwrap()).collect();
        Ok(IJVMReader {
            pointer: 0,
            source: abc
        })
    }

    pub fn new_from_slice(source: &[u8]) -> IJVMReader {
        IJVMReader {
            pointer: 0,
            source: source.to_vec(),
        }
    }
}

impl BinReadable for IJVMReader {
    fn get(&mut self) -> Result<u8> {
        if self.pointer >= self.source.len() {
            return Err("EOF reached")
        }
        let byte = self.source[self.pointer];
        self.pointer += 1;
        Ok(byte)
    }

    fn cur(&self) -> usize {
        self.pointer
    }

    fn len(&self) -> usize {
        self.source.len()
    }

    fn slice(&mut self, len: usize) -> &[u8] {
        let slice = &self.source[self.pointer..self.pointer+len];
        self.pointer += len;
        slice
    }
}