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use std::io::prelude::*;
use std::io::{BufReader, Lines};
use std::env;

use errors::*;
use parse;

pub struct Iter<R> {
    lines: Lines<BufReader<R>>,
}

impl<R: Read> Iter<R> {
    pub fn new(reader: R) -> Iter<R> {
        Iter {
            lines: BufReader::new(reader).lines(),
        }
    }

    pub fn load(self) -> Result<()> {
        for item in self {
            let (key, value) = item?;
            if env::var(&key).is_err() {
                env::set_var(&key, value);
            }
        }

        Ok(())
    }
}

impl<R: Read> Iterator for Iter<R> {
    type Item = Result<(String, String)>;

    fn next(&mut self) -> Option<Self::Item> {
        loop {
            let line = match self.lines.next() {
                Some(Ok(line)) => line,
                Some(Err(err)) => return Some(Err(Error::Io(err))),
                None => return None,
            };

            match parse::parse_line(&line) {
                Ok(Some(result)) => return Some(Ok(result)),
                Ok(None) => {}
                Err(err) => return Some(Err(err)),
            }
        }
    }
}