import strings

fn myprintln[T](data T, mut str strings.Builder) T {
    $if T is $array {
        str.write_string('array: [')
        for i, elem in data {
            myprintln(elem, mut str)
            if i < data.len - 1 {
                str.write_string(', ')
            }
        }
        str.write_string(']')
    } $else $if T is $map {
        str.write_string('map: {')
        for key, val in data {
            str.write_string('(key) ')
            myprintln(key, mut str)
            str.write_string(' -> (value) ')
            myprintln(val, mut str)
        }
        str.write_string('}')
    } $else {
        str.write_string(data.str())
    }
    return data
}

struct Test {
mut:
    s strings.Builder
}

fn test_recursive_array() {
    mut t := Test{}
    myprintln([[1], [2], [3]], mut t.s)
    assert t.s.str() == 'array: [array: [1], array: [2], array: [3]]'
}

fn test_recursive_map() {
    mut t2 := Test{}
    myprintln({
        'a': [1, 2, 3]
        'b': [1000]
    }, mut t2.s)
    assert t2.s.str() == 'map: {(key) a -> (value) array: [1, 2, 3](key) b -> (value) array: [1000]}'
}