use nom::
{
	IResult,
	branch::alt,
	bytes::complete::{escaped_transform, tag},
	character::complete::{digit1, multispace0, none_of},
	combinator::{map, map_res, opt, recognize},
	multi::{many1, separated_list},
	sequence::{delimited, pair, preceded, terminated},
};

use super::{Declarations, function_or_predicate_name, word_boundary, variable_name};

// TODO: avoid code duplication
fn true_(i: &str) -> IResult<&str, crate::Formula>
{
	map
	(
		terminated
		(
			tag("true"),
			word_boundary,
		),
		|_| crate::Formula::true_(),
	)(i)
}

fn false_(i: &str) -> IResult<&str, crate::Formula>
{
	map
	(
		terminated
		(
			tag("false"),
			word_boundary,
		),
		|_| crate::Formula::false_(),
	)(i)
}

pub fn boolean(i: &str) -> IResult<&str, crate::Formula>
{
	alt
	((
		true_,
		false_,
	))(i)
}

/*fn formula_parenthesized<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Formula>
{
	delimited
	(
		terminated
		(
			tag("("),
			multispace0,
		),
		|i| formula(i, d),
		preceded
		(
			multispace0,
			tag(")"),
		),
	)(i)
}

fn term_precedence_0<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Term>
{
	alt
	((
		boolean,
		special_integer,
		integer,
		map
		(
			|i| function(i, d),
			crate::Term::Function,
		),
		string,
		map
		(
			|i| variable(i, d),
			crate::Term::Variable,
		),
		|i| absolute_value(i, d),
		|i| term_parenthesized(i, d),
	))(i)
}

fn term_precedence_1<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Term>
{
	alt
	((
		|i| negative(i, d),
		|i| term_precedence_0(i, d),
	))(i)
}

fn term_precedence_2<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Term>
{
	alt
	((
		map
		(
			pair
			(
				many1
				(
					terminated
					(
						|i| term_precedence_1(i, d),
						delimited
						(
							multispace0,
							tag("**"),
							multispace0,
						),
					)
				),
				|i| term_precedence_1(i, d),
			),
			|(arguments, last_argument)| arguments.into_iter().rev().fold(last_argument,
				|accumulator, argument|
					crate::Term::exponentiate(Box::new(argument), Box::new(accumulator))),
		),
		|i| term_precedence_1(i, d),
	))(i)
}

fn term_precedence_3<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Term>
{
	alt
	((
		map
		(
			pair
			(
				|i| term_precedence_2(i, d),
				many1
				(
					pair
					(
						delimited
						(
							multispace0,
							alt
							((
								tag("*"),
								tag("/"),
								tag("%"),
							)),
							multispace0,
						),
						|i| term_precedence_2(i, d),
					)
				),
			),
			|(first_argument, arguments)| arguments.into_iter().fold(first_argument,
				|accumulator, (operator, argument)|
				match operator
				{
					"*" => crate::Term::multiply(Box::new(accumulator), Box::new(argument)),
					"/" => crate::Term::divide(Box::new(accumulator), Box::new(argument)),
					"%" => crate::Term::modulo(Box::new(accumulator), Box::new(argument)),
					// TODO: handle appropriately
					_ => panic!("test"),
				})
		),
		|i| term_precedence_2(i, d),
	))(i)
}

fn term_precedence_4<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Term>
{
	alt
	((
		map
		(
			pair
			(
				|i| term_precedence_3(i, d),
				many1
				(
					pair
					(
						delimited
						(
							multispace0,
							alt
							((
								tag("+"),
								tag("-"),
							)),
							multispace0,
						),
						|i| term_precedence_3(i, d),
					)
				),
			),
			|(first_argument, arguments)| arguments.into_iter().fold(first_argument,
				|accumulator, (operator, argument)|
				match operator
				{
					"+" => crate::Term::add(Box::new(accumulator), Box::new(argument)),
					"-" => crate::Term::subtract(Box::new(accumulator), Box::new(argument)),
					// TODO: handle appropriately
					_ => panic!("test"),
				})
		),
		|i| term_precedence_3(i, d),
	))(i)
}

pub fn formula<'a>(i: &'a str, d: &Declarations) -> IResult<&'a str, crate::Formula>
{
	formula_precedence_4(i, d)
}*/

#[cfg(test)]
mod tests
{
	use crate::parse::formulas::*;
	use crate::{Formula, VariableDeclaration, VariableDeclarationStack};

	/*fn formula(i: &str) -> Formula
	{
		crate::parse::formula(i, &Declarations::new()).unwrap().1
	}

	fn format_formula(i: &str) -> String
	{
		format!("{}", formula(i))
	}

	#[test]
	fn parse_formula_boolean()
	{
		assert_eq!(formula("true"), Formula::true_());
		assert_eq!(formula("false"), Formula::false_());
	}*/

	#[test]
	fn parse_boolean()
	{
		assert_eq!(boolean("true"), Ok(("", Formula::true_())));
		assert_eq!(boolean("false"), Ok(("", Formula::false_())));
		assert_eq!(boolean("true false"), Ok((" false", Formula::true_())));
		assert_eq!(boolean("false true"), Ok((" true", Formula::false_())));
		assert_eq!(boolean("true,"), Ok((",", Formula::true_())));
		assert_eq!(boolean("false,"), Ok((",", Formula::false_())));
		assert!(boolean("truefalse").is_err());
		assert!(boolean("falsetrue").is_err());
		assert!(boolean("truea").is_err());
		assert!(boolean("falsea").is_err());
		assert!(boolean("a").is_err());
		assert!(boolean("-").is_err());
		assert!(boolean(" ").is_err());
	}
}