use minisql::type_system::DbType;
use nom::{
    branch::alt, bytes::complete::{tag, take_while}, character::{complete::{alphanumeric1, anychar, char, multispace0, multispace1}, is_alphanumeric}, combinator::peek, error::make_error, sequence::{delimited, terminated}, IResult, Parser
};

use crate::syntax::Condition;
use super::literal::parse_literal;

pub fn parse_table_name(input: &str) -> IResult<&str, &str> {
    alt((
        delimited(char('"'), alphanumeric1, char('"')),
        parse_identifier,
    ))(input)
}

pub fn parse_identifier(input: &str) -> IResult<&str, &str> {
    let (_, first) = peek(anychar)(input)?;
    if first.is_alphabetic() || first == '_' {
        take_while(|c: char| {
            is_alphanumeric(c as u8) || c == '_'
        })(input)
    } else {
        Err(nom::Err::Error(make_error(
            input,
            nom::error::ErrorKind::Alpha,
        )))
    }
}

pub fn parse_column_name(input: &str) -> IResult<&str, String> {
    terminated(parse_identifier, multispace0)(input).map(|(rest, name)| (rest, name.to_string()))
}

pub fn parse_db_type(input: &str) -> IResult<&str, DbType> {
    let (input, db_type) = alt(
        (
            tag("STRING")
                .map(|_| DbType::String),
            tag("INT")
                .map(|_| DbType::Int),
            tag("NUMBER")
                .map(|_| DbType::Number),
            tag("UUID")
                .map(|_| DbType::Uuid),
            delimited(tag("Option("), parse_db_type, tag(")"))
                .map(|ty| {
                    DbType::Option(Box::new(ty))
                })
        )
    )(input)?;
    Ok((input, db_type))
}

pub fn parse_condition(input: &str) -> IResult<&str, Option<Condition>> {
    match tag::<&str, &str, nom::error::Error<&str>>("WHERE")(input) {
        Ok((input, _)) => {
            let (input, _) = multispace1(input)?;
            let (input, condition) = parse_equality(input)?;
            Ok((input, Some(condition)))
        }
        Err(_) => Ok((input, None)),
    }
}

fn parse_equality(input: &str) -> IResult<&str, Condition> {
    let (input, column_name) = parse_column_name(input)?;
    let (input, _) = multispace0(input)?;
    let (input, _) = char('=')(input)?;
    let (input, _) = multispace0(input)?;
    let (input, lit) = parse_literal(input)?;
    Ok((input, Condition::Eq(column_name, lit)))
}

#[cfg(test)]
mod tests {
    use minisql::type_system::DbType;

    use crate::parsing::common::{parse_db_type, parse_equality, parse_identifier};
    use crate::parsing::literal::Literal;
    use crate::syntax::Condition;

    #[test]
    fn test_parse_equality() {
        match parse_equality("id   =   1") {
            Ok(("", Condition::Eq(column_name, value))) => {
                assert!(column_name.eq("id"));
                assert_eq!(value, Literal::Int(1))
            }
            _ => {
                panic!("should parse");
            }
        }
    }

    #[test]
    fn test_parse_db_type() {
        assert!(matches!(
            parse_db_type("INT").expect("should parse").1,
            DbType::Int
        ));
        assert!(matches!(
            parse_db_type("STRING").expect("should parse").1,
            DbType::String
        ));
        assert!(matches!(
            parse_db_type("UUID").expect("should parse").1,
            DbType::Uuid
        ));
        assert!(matches!(
            parse_db_type("NUMBER").expect("should parse").1,
            DbType::Number
        ));
        assert!(matches!(parse_db_type("Unknown"), Err(_)));
    }

    #[test]
    fn test_parse_identifier() {
        assert_eq!(
            parse_identifier("_variable__Test").expect("should parse").1,
            "_variable__Test"
        );
        assert!(matches!(
            parse_identifier("123_variable__Test"),
            Err(_)
        ));
    }

    #[test]
    fn test_parse_option_string_type() {
        assert_eq!(
            parse_db_type("Option(STRING)").expect("should parse").1,
            DbType::Option(Box::new(DbType::String))
        );
    }

    #[test]
    fn test_parse_nested_option_int_type() {
        assert_eq!(
            parse_db_type("Option(Option(Option(INT)))").expect("should parse").1,
            DbType::Option(Box::new(DbType::Option(Box::new(DbType::Option(Box::new(DbType::Int))))))
        );
    }
}