use std::fmt;

#[derive(Debug, Clone, PartialEq)]
pub enum Error {
    Parse(ParseError),
    Context(ContextError),
    Eval(EvalError),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Error::Parse(parse_error) => write!(f, "{}", parse_error),
            Error::Context(context_error) => write!(f, "{}", context_error),
            Error::Eval(eval_error) => write!(f, "{}", eval_error),
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct ParseError {
    pub line: usize,
    pub message: String,
}

impl std::error::Error for ParseError {}

impl From<std::io::Error> for ParseError {
    fn from(err: std::io::Error) -> Self {
        ParseError {
            line: 0,
            message: err.to_string(),
        }
    }
}

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "parser (line {}): {}.", self.line + 1, self.message)
    }
}

#[derive(Debug, Clone, PartialEq)]
pub enum ContextErrorReason {
    Redefinition,
    UnknownVariable,
    BadScope,
    Label,
    Other,
}

#[derive(Debug, Clone, PartialEq)]
pub struct ContextError {
    pub line: usize,
    pub reason: ContextErrorReason,
    pub message: String,
}

impl std::error::Error for ContextError {}

// TODO: needed?
impl From<std::io::Error> for ContextError {
    fn from(err: std::io::Error) -> Self {
        ContextError {
            line: 0,
            reason: ContextErrorReason::Other,
            message: err.to_string(),
        }
    }
}

impl fmt::Display for ContextError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Context error (line {}): {}.",
            self.line + 1,
            self.message
        )
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct EvalError {
    pub line: usize,
    pub message: String,
}

impl std::error::Error for EvalError {}

impl From<std::io::Error> for EvalError {
    fn from(err: std::io::Error) -> Self {
        EvalError {
            line: 0,
            message: err.to_string(),
        }
    }
}

impl From<ContextError> for EvalError {
    fn from(err: ContextError) -> Self {
        EvalError {
            line: err.line,
            message: err.message,
        }
    }
}

impl fmt::Display for EvalError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Evaluation error (line {}): {}.",
            self.line + 1,
            self.message
        )
    }
}