module.exports = grammar({
	name: 'lila',

	word: $ => $.identifier,

	rules: {
		source_file: $ => repeat($._definition),

		_definition: $ => choice(
			$.function_definition
		),

		function_definition: $ => seq(
			'func',
			field('name', $.identifier),
			field('parameters', $.parameters),
			field('return_type', optional($._type)),
			field('body', $.block),
		),

		parameters: $ => seq(
			'(',
			optional(seq(
				repeat(seq($.parameter, ',')),
				seq($.parameter, optional(',')),
			)),
			')',
		),

		parameter: $ => seq(
			$.identifier,
			' ',
			$._type,
		),

		block: $ => seq(
			'{',
			repeat($._statement),
			optional($._expression),
			'}',
		),

		_statement: $ => choice(
			$.return_statement,
			$.assign_statement,
			$.if_statement,
		),

		if_statement: $ => seq(
			'if',
			field('condition', $._expression),
			field('body', $.block),
			';'
		),

		if_expression: $ => seq(
			'if',
			field('condition', $._expression),
			field('body', $.block),
			field('else',
				seq('else', choice(
					$._expression,
					$.block,
				))
			),
		),

		return_statement: $ => seq(
			'return',
			optional($._expression),
			';',
		),

		assign_statement: $ => seq(
			$.identifier,
			'=',
			$._expression,
			';',
		),

		_expression: $ => choice(
			$.unary_expression,
			$.binary_expression,
			$.if_expression,
			$.boolean_literal,
			$.integer_literal,
			$.identifier,
		),

		unary_expression: $ => prec(10, choice(
			seq('-', $._expression),
			seq('!', $._expression),
		)),

		binary_expression: $ => choice(
			prec.left(4, seq($._expression, '*', $._expression)),
			prec.left(3, seq($._expression, '+', $._expression)),
			prec.left(2, seq($._expression, '||', $._expression)),
			prec.left(1, seq($._expression, '&&', $._expression)),
		),

		identifier: $ => /[a-z_]+[a-zA-Z0-9_]*/,

		integer_literal: $ => /\d+/,

		boolean_literal: $ => choice('true', 'false'),

		//string_literal: $ => /"[]"/,

		_type: $ => choice(
			$.primitive_type,
		),

		primitive_type: $ => choice(
			'bool',
			'int',
			'uint',
		),
	}
});