use crate::ShellError;
use std::io::{BufRead, BufReader, Read};

pub struct BufferedReader<R: Read> {
    input: BufReader<R>,
    error: bool,
}

impl<R: Read> BufferedReader<R> {
    pub fn new(input: BufReader<R>) -> Self {
        Self {
            input,
            error: false,
        }
    }

    pub fn into_inner(self) -> BufReader<R> {
        self.input
    }
}

impl<R: Read> Iterator for BufferedReader<R> {
    type Item = Result<Vec<u8>, ShellError>;

    fn next(&mut self) -> Option<Self::Item> {
        // Don't try to read more data if an error occurs
        if self.error {
            return None;
        }

        let buffer = self.input.fill_buf();
        match buffer {
            Ok(s) => {
                let result = s.to_vec();

                let buffer_len = s.len();

                if buffer_len == 0 {
                    None
                } else {
                    self.input.consume(buffer_len);

                    Some(Ok(result))
                }
            }
            Err(e) => {
                self.error = true;
                Some(Err(ShellError::IOError { msg: e.to_string() }))
            }
        }
    }
}