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#![doc(html_root_url = "https://docs.rs/rfc2047-decoder/0.1.2")]

use std::{error, fmt, result};

mod evaluator;
mod lexer;
mod parser;

/// Errors can come from the lexer or the parser.
/// Lexer errors are related to invalid syntaxes.
/// Parser and Evaluator errors are related to decoding issues.
#[derive(Debug)]
pub enum Error {
    RunLexerError(lexer::Error),
    RunParserError(parser::Error),
    RunEvaluatorError(evaluator::Error),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Error::RunLexerError(err) => err.fmt(f),
            Error::RunParserError(err) => err.fmt(f),
            Error::RunEvaluatorError(err) => err.fmt(f),
        }
    }
}

impl error::Error for Error {
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
        None
    }
}

impl From<lexer::Error> for Error {
    fn from(err: lexer::Error) -> Error {
        Error::RunLexerError(err)
    }
}

impl From<parser::Error> for Error {
    fn from(err: parser::Error) -> Error {
        Error::RunParserError(err)
    }
}

impl From<evaluator::Error> for Error {
    fn from(err: evaluator::Error) -> Error {
        Error::RunEvaluatorError(err)
    }
}

/// Wrapper around `std::result::Result`.
pub type Result<T> = result::Result<T, Error>;

/// Decode a RFC 2047 MIME Message Header.
///
/// ```rust
/// fn main() {
///     match rfc2047_decoder::decode("=?utf8?q?str_with_spaces?=".as_bytes()) {
///         Ok(s) => println!("{}", s),
///         Err(err) => panic!(err),
///     }
/// }
/// ```
///
/// # Errors
///
/// The function can return an error if the lexer,
/// the parser or the evaluator encounters an error.
pub fn decode(encoded_str: &[u8]) -> Result<String> {
    let tokens = lexer::run(&encoded_str)?;
    let ats = parser::run(&tokens)?;
    let decoded_str = evaluator::run(&ats)?;

    Ok(decoded_str)
}

#[cfg(test)]
mod tests {
    use crate::decode;

    fn assert_ok(decoded_str: &str, encoded_str: &str) {
        assert!(if let Ok(s) = decode(encoded_str.as_bytes()) {
            s == decoded_str
        } else {
            false
        });
    }

    #[test]
    fn clear_empty() {
        assert_ok("", "");
    }

    #[test]
    fn clear_with_str() {
        assert_ok("str", "str");
    }

    #[test]
    fn clear_with_spaces() {
        assert_ok("str with spaces", "str with spaces");
    }

    #[test]
    fn utf8_qs_empty() {
        assert_ok("", "=?UTF-8?Q??=");
    }

    #[test]
    fn utf8_qs_with_str() {
        assert_ok("str", "=?UTF-8?Q?str?=");
    }

    #[test]
    fn utf8_qs_with_spaces() {
        assert_ok("str with spaces", "=?utf8?q?str_with_spaces?=");
    }

    #[test]
    fn utf8_qs_with_spec_chars() {
        assert_ok(
            "str with special çhàrß",
            "=?utf8?q?str_with_special_=C3=A7h=C3=A0r=C3=9F?=",
        );
    }

    #[test]
    fn utf8_qs_double() {
        assert_ok("strstr", "=?UTF-8?Q?str?=\r\n =?UTF-8?Q?str?=");
        assert_ok("strstr", "=?UTF-8?Q?str?=\n =?UTF-8?Q?str?=");
        assert_ok("strstr", "=?UTF-8?Q?str?= =?UTF-8?Q?str?=");
        assert_ok("strstr", "=?UTF-8?Q?str?==?UTF-8?Q?str?=");
    }

    #[test]
    fn utf8_b64_empty() {
        assert_ok("", "=?UTF-8?B??=");
    }

    #[test]
    fn utf8_b64_with_str() {
        assert_ok("str", "=?UTF-8?B?c3Ry?=");
    }

    #[test]
    fn utf8_b64_with_spaces() {
        assert_ok("str with spaces", "=?utf8?b?c3RyIHdpdGggc3BhY2Vz?=");
    }

    #[test]
    fn utf8_b64_with_spec_chars() {
        assert_ok(
            "str with special çhàrß",
            "=?utf8?b?c3RyIHdpdGggc3BlY2lhbCDDp2jDoHLDnw==?=",
        );
    }
}