use ariprog::{
  common_difference,
  common_difference_and_first_term,
  first_term,
  how_many_terms,
  nth_term,
  insert_arithmetic_means,
  NthTerm
};

#[test]
fn it_gets_common_difference() {
  assert_eq!(common_difference(15.0, 10.0), 5.0);
  assert_eq!(common_difference(10.0, 8.0), 2.0);
}

#[test]
fn it_gets_nth_term() {
  assert_eq!(nth_term(1.0, 2.0, 20.0), 39.0);
  assert_eq!(nth_term(0.0, 2.0, 103.0), 204.0);
}

#[test]
fn it_gets_first_term() {
  assert_eq!(first_term(39.0, 2.0, 20.0), 1.0);
  assert_eq!(first_term(204.0, 2.0, 103.0), 0.0);
}

#[test]
fn it_inserts_arithmetic_means() {
  assert_eq!(
    insert_arithmetic_means(6, 14.0, 98.0),
    vec![14.0, 26.0, 38.0, 50.0, 62.0, 74.0, 86.0, 98.0]
  );
  assert_eq!(
    insert_arithmetic_means(3, 1.0, 13.0),
    vec![1.0, 4.0, 7.0, 10.0, 13.0]
  );
}

#[test]
fn it_gets_the_number_of_terms() {
    assert_eq!(
        how_many_terms(5.0, 785.0, 5.0),
        157
    );
    assert_eq!(
        how_many_terms(0.0, 1000.0, 2.0),
        501
    );
}

#[test]
fn it_gets_common_difference_and_first_term() {
    assert_eq!(
        common_difference_and_first_term(
            NthTerm { value: 64.0, position: 8.0 },
            NthTerm { value: 32.0, position: 4.0 }
        ),
        (8.0, 8.0)
    );
    assert_eq!(
        common_difference_and_first_term(
            NthTerm { value: 1000.0, position: 501.0 },
            NthTerm { value: 998.0, position: 500.0 }
        ),
        (2.0, 0.0)
    )
}