use thiserror::Error;

use crate::interpreter::Primitive;
use crate::lexer::Token;
use crate::misc::CodePos;
use crate::parser::expr::{BinaryOp, UnaryOp};

#[derive(Error, Debug)]
pub enum LexerError {
    #[error("Unexpected character '{c}' at {code_pos}.")]
    UnexpectedCharacter { c: char, code_pos: CodePos },
    #[error("Unterminated string literal starting at {code_pos}.")]
    UnterminatedStringLiteral { code_pos: CodePos },
    #[error("Unterminated block comment starting at {code_pos}.")]
    UnterminatedBlockComment { code_pos: CodePos },
    #[error("Invalid number literal {lexeme} at {code_pos}: {msg}")]
    InvalidNumberLiteral {
        lexeme: String,
        msg: String,
        code_pos: CodePos,
    },
}

#[derive(Error, Debug)]
pub enum ParserError {
    #[error("Token stream ended unexpectedly.")]
    TokenStreamEnded,
    #[error("Unexpected token {token} at {0}.", token.code_pos())]
    UnexpectedToken { token: Token },
}

#[derive(Error, Debug)]
pub enum EvalError {
    #[error("Unary operator {op} had invalid argument {arg}")]
    UnaryOpInvalidArgument { op: UnaryOp, arg: Primitive },
    #[error("Binary operator {op} had invalid arguments {left} and {right}")]
    BinaryOpInvalidArguments {
        left: Primitive,
        op: BinaryOp,
        right: Primitive,
    },
    #[error("Division by zero")]
    DivisionByZero,
}

#[derive(Error, Debug)]
pub enum LoxError {
    #[error("{0}", format_lexer_errors(inner))]
    LexerError { inner: Vec<LexerError> },
    #[error("{inner}")]
    ParserError { inner: ParserError },
    #[error("{inner}")]
    EvalError { inner: EvalError },
}

fn format_lexer_errors(lexer_errs: &Vec<LexerError>) -> String {
    let msg = if lexer_errs.len() == 1 {
        format!("{}", lexer_errs[0])
    } else {
        let msgs: Vec<String> = lexer_errs.iter().map(|err| format!("{}", err)).collect();
        msgs.join("\n")
    };

    msg
}

impl From<Vec<LexerError>> for LoxError {
    fn from(lexer_errs: Vec<LexerError>) -> Self {
        LoxError::LexerError { inner: lexer_errs }
    }
}

impl From<ParserError> for LoxError {
    fn from(parser_err: ParserError) -> Self {
        LoxError::ParserError { inner: parser_err }
    }
}

impl From<EvalError> for LoxError {
    fn from(eval_err: EvalError) -> Self {
        LoxError::EvalError { inner: eval_err }
    }
}