use std::convert::TryFrom;
use std::error::Error;
use std::fmt::Display;
use std::str::FromStr;

#[derive(Debug, Eq, PartialEq)]
pub enum ParseStatusError {
    InvalidReplyKind,
    InvalidCategory,
    MissingErrNr,
}

impl Display for ParseStatusError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

impl Error for ParseStatusError {
    fn description(&self) -> &str {
        match self {
            Self::InvalidReplyKind => "Invalid reply kind",
            Self::InvalidCategory => "Invalid error category",
            Self::MissingErrNr => "Missing or invalid error number",
        }
    }
}

#[derive(Debug, Eq, PartialEq, Clone)]
pub enum ReplyKind {
    PositivePreliminary,
    PositiveCompletion,
    PositiveIntermediate,
    NegativeTransient,
    NegativePermanent,
}

impl TryFrom<char> for ReplyKind {
    type Error = ParseStatusError;

    fn try_from(value: char) -> Result<Self, Self::Error> {
        match value {
            '1' => Ok(ReplyKind::PositivePreliminary),
            '2' => Ok(ReplyKind::PositiveCompletion),
            '3' => Ok(ReplyKind::PositiveIntermediate),
            '4' => Ok(ReplyKind::NegativeTransient),
            '5' => Ok(ReplyKind::NegativePermanent),
            _ => Err(ParseStatusError::InvalidReplyKind),
        }
    }
}

impl Display for ReplyKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            match self {
                ReplyKind::PositivePreliminary => '1',
                ReplyKind::PositiveCompletion => '2',
                ReplyKind::PositiveIntermediate => '3',
                ReplyKind::NegativeTransient => '4',
                ReplyKind::NegativePermanent => '5',
            }
        )
    }
}

#[derive(Debug, Eq, PartialEq, Clone)]
pub enum Category {
    Syntax,
    Information,
    Connection,
    Authentication,
    Unspecified,
    System,
    Nonstandard,
}

impl TryFrom<char> for Category {
    type Error = ParseStatusError;

    fn try_from(value: char) -> Result<Self, Self::Error> {
        match value {
            '0' => Ok(Category::Syntax),
            '1' => Ok(Category::Information),
            '2' => Ok(Category::Connection),
            '3' => Ok(Category::Authentication),
            '4' => Ok(Category::Unspecified),
            '5' => Ok(Category::System),
            '8' => Ok(Category::Nonstandard),
            _ => Err(ParseStatusError::InvalidCategory),
        }
    }
}

impl Display for Category {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            match self {
                Category::Syntax => '0',
                Category::Information => '1',
                Category::Connection => '2',
                Category::Authentication => '3',
                Category::Unspecified => '4',
                Category::System => '5',
                Category::Nonstandard => '8',
            }
        )
    }
}

#[derive(Debug, Eq, PartialEq, Clone)]
pub struct Status(pub ReplyKind, pub Category, pub u8);

impl FromStr for Status {
    type Err = ParseStatusError;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let chars: Vec<char> = s.chars().collect();

        let reply = chars.get(0).ok_or(ParseStatusError::InvalidReplyKind)?;
        let category = chars.get(1).ok_or(ParseStatusError::InvalidCategory)?;

        let errnr: u8 = if let Some(ref c) = chars.get(2) {
            let tmp = c.to_digit(10).ok_or(ParseStatusError::MissingErrNr)?;
            u8::try_from(tmp).map_err(|_| ParseStatusError::MissingErrNr)?
        } else {
            return Err(ParseStatusError::MissingErrNr);
        };

        Ok(Status(
            ReplyKind::try_from(*reply)?,
            Category::try_from(*category)?,
            errnr,
        ))
    }
}

impl Display for Status {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}{}{}", self.0, self.1, self.2)
    }
}

impl Status {
    pub fn is_positive(&self) -> bool {
        match self.0 {
            ReplyKind::PositiveCompletion
            | ReplyKind::PositiveIntermediate
            | ReplyKind::PositivePreliminary => true,
            _ => false,
        }
    }

    pub fn is_start(&self) -> bool {
        *self == Status(ReplyKind::PositiveCompletion, Category::Connection, 0)
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn basic_parsing() {
        let ok = Status::from_str("250").unwrap();

        assert_eq!(
            ok,
            Status(ReplyKind::PositiveCompletion, Category::System, 0)
        );
    }

    #[test]
    fn invalid_reply() {
        if let Err(ParseStatusError::InvalidReplyKind) = Status::from_str("700") {
            // Do nothing
        } else {
            panic!();
        }
    }

    #[test]
    fn invalid_category() {
        if let Err(ParseStatusError::InvalidCategory) = Status::from_str("170") {
            // Do nothing
        } else {
            panic!();
        }
    }

    #[test]
    fn missing_errno() {
        if let Err(ParseStatusError::MissingErrNr) = Status::from_str("17") {
            // Do nothing
        } else {
            panic!();
        }
    }
}