module.exports = grammar({
    name: "TestLang",
    rules: {
        source_file: $ => repeat($._definition),

        _definition: $ => choice(
            $.function_definition
            //TODO others
        ),

        function_definition: $ => seq(
            'fn',
            $.identifier,
            $.parameter_list,
            field("return_type", optional($._type)),
            $.block,
        ),
        parameter_list: $ => seq("(", /* TODO */ ")"),

        block: $ => seq(
            "{",
            choice(
                repeat($._statement),
                "",
            ),
            "}"
        ),

        _statement: $ => choice(
            $._return_statement
        ),

        _return_statement: $ => seq("return", $._expression, ";"),

        _expression: $ => choice($.identifier, $.unary, $.binary),

        unary: $ => prec(4, choice(seq("-", $._expression), seq("!", $._expression))),
        binary: $ => choice(prec.left(2, seq($._expression, "*", $._expression)), prec.left(1, seq($._expression, "+", $._expression))),

        _type: $ => "bool",
        _type: $ => choice(
            $.primitive_type,
        ),
        primitive_type: $ => choice("bool", "int"),

        identifier: $ => /[a-z]+/,
    }
});