//! Tests for the row arithmetic that pins the inline viewport to the
//! bottom of the screen: where its top belongs, and how much of the
//! screen above has to scroll to get there without overwriting anything.

use super::{Move, clear_from, next_top, pinned_top, scroll_up_needed};

#[test]
fn a_viewport_shorter_than_the_screen_sits_flush_with_the_last_row() {
    assert_eq!(pinned_top(24, 4), 20);
}

#[test]
fn a_viewport_as_tall_as_the_screen_starts_at_row_zero() {
    assert_eq!(pinned_top(24, 24), 0);
}

#[test]
fn a_viewport_taller_than_the_screen_clamps_to_row_zero() {
    assert_eq!(pinned_top(10, 24), 0);
}

#[test]
fn a_viewport_that_grows_moves_its_top_up_to_the_pinned_row() {
    assert_eq!(next_top(24, 6, 20), 18);
}

#[test]
fn a_viewport_that_shrinks_keeps_its_top_where_it_is() {
    assert_eq!(next_top(24, 4, 18), 18);
}

#[test]
fn a_viewport_that_keeps_its_height_keeps_its_top() {
    assert_eq!(next_top(24, 4, 20), 20);
}

#[test]
fn room_below_the_current_row_needs_no_scroll() {
    assert_eq!(scroll_up_needed(5, 20), 0);
}

#[test]
fn a_pinned_top_exactly_at_the_current_row_needs_no_scroll() {
    assert_eq!(scroll_up_needed(10, 10), 0);
}

#[test]
fn a_pinned_top_above_the_current_row_scrolls_the_difference() {
    assert_eq!(scroll_up_needed(15, 5), 10);
}

#[test]
fn a_viewport_that_moves_down_clears_from_the_row_it_came_from() {
    assert_eq!(clear_from(15, 25), 15);
}

#[test]
fn a_viewport_that_moves_up_clears_from_the_row_it_lands_on() {
    assert_eq!(clear_from(15, 5), 5);
}

#[test]
fn a_resize_that_grows_scrolls_the_screen_and_clears_from_the_row_it_lands_on() {
    assert_eq!(
        Move::resize(24, 6, 20),
        Move {
            scroll: 2,
            clear: 18,
            top: 18,
            rows: 6
        }
    );
}

#[test]
fn a_resize_that_shrinks_keeps_its_top_and_clears_the_rows_below_it() {
    assert_eq!(
        Move::resize(24, 4, 18),
        Move {
            scroll: 0,
            clear: 18,
            top: 18,
            rows: 4
        }
    );
}

#[test]
fn a_repin_that_moves_down_clears_from_the_row_it_came_from() {
    assert_eq!(
        Move::repin(24, 4, 18),
        Move {
            scroll: 0,
            clear: 18,
            top: 20,
            rows: 4
        }
    );
}

#[test]
fn a_repin_that_moves_up_scrolls_the_screen_by_as_much_as_the_top_moves() {
    assert_eq!(
        Move::repin(24, 8, 20),
        Move {
            scroll: 4,
            clear: 16,
            top: 16,
            rows: 8
        }
    );
}