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use std::error::{Error as StdError};
use std::fmt;
use csv::{DeserializeErrorKind, ErrorKind, Error as CsvError};

#[derive(Debug)]
pub enum Error {
    Csv(String, CsvError),
    FieldError(String, u64, DeserializeErrorKind, Option<String>),
    LineError(String, ErrorKind)
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::Csv(ref filename, ref err) => write!(f, "error parsing {} - {}", filename, format!("{}", err)),
            Error::FieldError(ref filename, ref lineno, ref errk, ref field) => match *field {
                Some(ref fieldname) => {
                    write!(f, "error parsing {} in {}:{} - {}", fieldname, filename, lineno, format!("{}", errk))
                }
                None => write!(f, "error parsing {}:{} - {}", filename, lineno, format!("{}", errk))
            },
            Error::LineError(ref filename, ref err) => match *err {
                // TODO: Find out when position can be None
                ErrorKind::UnequalLengths{ref pos, ref expected_len, ref len} => write!(f, "error parsing {}:{} - expected {} fields but got {} fields", filename, pos.as_ref().unwrap().line(), expected_len, len),
                ErrorKind::Utf8{ref pos, ref err} => write!(f, "error parsing {}:{} - {:?}", filename, pos.as_ref().unwrap().line(), err),
                _ => write!(f, "error parsing {} - {:?}", filename, err)
            }
        }
    }
}

impl StdError for Error {
    fn description(&self) -> &str {
        use self::Error::*;
        match *self {
            Csv(_, ref err) => err.description(),
            FieldError(..) => "error processing field of a line",
            LineError(..) => "error processing line"
        }
    }

    fn cause(&self) -> Option<&StdError> {
        use self::Error::*;
        match *self {
            Csv(_, ref err) => Some(err),
            // ErrorKinds don't implement std::error::Error, need to keep original error
            FieldError(..) => None,
            LineError(..) => None
        }
    }
}