use crate::lisp::{
    expr::{Arity, LispExpr},
    lex::{Span, SpanDisplay},
    number::LispNumber,
};

use std::{fmt, io};

#[derive(Debug)]
pub enum LispError {
    Parse(ParseError),
    Eval(EvalError),
    Stringified(String),
}

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

impl fmt::Display for LispError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Parse(p) => write!(f, "parse error: {}", p.kind),
            Self::Eval(e) => write!(f, "eval error: {}", e),
            Self::Stringified(s) => write!(f, "{}", s),
        }
    }
}

#[derive(Debug, PartialEq, Clone)]
pub struct ParseError {
    pub span: Span,
    pub kind: ParseErrorKind,
}

impl ParseError {
    pub fn new(span: Span, kind: ParseErrorKind) -> Self {
        Self { span, kind }
    }
    pub fn display(&self, text: &str, file_name: &str) -> String {
        let SpanDisplay { line, col, .. } = SpanDisplay::highlight_span(self.span, text, file_name);
        format!(
            "in file `{}`; line {}, col {}: {}",
            file_name, line, col, self.kind
        )
    }
}

#[derive(Debug, PartialEq, Clone)]
pub enum ParseErrorKind {
    InvalidLiteral,
    InvalidToken,
    InvalidChar(char),
    LiteralParseError,
    MissingCloseParen,
    UnbalancedComma,
    UnexpectedEof,
    UnexpectedToken {
        expected: &'static str,
        found: &'static str,
    },
    UnmatchedParen,
    UnterminatedString,
}

impl fmt::Display for ParseErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ParseErrorKind::InvalidChar(ch) => write!(f, "invalid character {}", ch),
            ParseErrorKind::InvalidToken => write!(f, "invalid token"),
            ParseErrorKind::UnexpectedEof => write!(f, "unexpected end of file"),
            ParseErrorKind::InvalidLiteral => write!(f, "invalid literal"),
            ParseErrorKind::UnmatchedParen => write!(f, "unmatched `)`"),
            ParseErrorKind::UnbalancedComma => write!(f, "unbalanced comma"),
            ParseErrorKind::UnexpectedToken { expected, found } => {
                write!(
                    f,
                    "unexpected token, got `{}`, expected `{}`",
                    found, expected
                )
            }
            ParseErrorKind::LiteralParseError => write!(f, "error parsing literal"),
            ParseErrorKind::MissingCloseParen => write!(f, "missing `)`"),
            ParseErrorKind::UnterminatedString => write!(f, "unterminated string literal"),
        }
    }
}

impl From<ParseError> for LispError {
    fn from(p: ParseError) -> Self {
        LispError::Parse(p)
    }
}

#[derive(Debug)]
pub enum EvalError {
    ArgumentCount(Arity),
    BadForm,
    UnboundVariable(String),
    DivByZero,
    TypeMismatch,
    NoFileName,
    FileError(io::Error),
    AccessEmptyList,
    InvalidCoordinates((LispNumber, LispNumber)),
    AssertionError { expected: LispExpr, got: LispExpr },
    ScriptLoadError(io::Error),
    CustomInternal(&'static str),
    Custom(String),
}

impl fmt::Display for EvalError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::ArgumentCount(i) => {
                write!(f, "invalid number of arguments, expected ")?;
                match i {
                    Arity::Exact(a) => write!(f, "exactly {} argument(s)", a),
                    Arity::Atleast(a) => write!(f, "atleast {} argument(s)", a),
                    Arity::Atmost(a) => write!(f, "atmost {} argument(s)", a),
                    Arity::Range(low, high) => {
                        write!(f, "between {} and {} argument(s)", low, high)
                    }
                    Arity::None => write!(f, "any number of arguments"),
                }
            }
            Self::BadForm => write!(f, "bad expression form"),
            Self::UnboundVariable(s) => write!(f, "unbound variable {}", s),
            Self::TypeMismatch => write!(f, "mismatched types"),
            Self::DivByZero => write!(f, "attempt to divide by zero"),
            Self::NoFileName => write!(f, "no file name specified"),
            Self::FileError(e) => write!(f, "file error: {}", e),
            Self::AccessEmptyList => write!(f, "attempted to access empty list"),
            Self::InvalidCoordinates((x, y)) => write!(f, "invalid coordinates: {} {}", x, y),
            Self::AssertionError { expected, got } => {
                write!(f, "assertion error: expected `{}` got `{}`", expected, got)
            }
            Self::ScriptLoadError(s) => write!(f, "error while loading script: {}", s),
            Self::CustomInternal(s) => write!(f, "{}", s),
            Self::Custom(s) => write!(f, "error: {}", s),
        }
    }
}

impl From<EvalError> for LispError {
    fn from(e: EvalError) -> Self {
        LispError::Eval(e)
    }
}