import {
  continuousVirtualWindow,
  groupEventsByDay,
  layoutTimedEventsForDay,
  moveEventToDay,
  rangeForMode,
  resizeEventToTime,
} from "../src/features/calendar/calendarViewModel.ts";

function assert(condition: unknown, message: string): void {
  if (!condition) throw new Error(message);
}

function event(
  id: string,
  start: Date,
  end: Date,
  allDay = false,
) {
  return {
    id,
    calendar_id: "calendar-1",
    summary: id,
    start_at: start.toISOString(),
    end_at: end.toISOString(),
    all_day: allDay,
  } as never;
}

const focus = new Date(2026, 6, 15, 12);
const month = rangeForMode("month", focus, {
  before: 8,
  after: 12,
});
assert(
  (month.end.getTime() - month.start.getTime()) / 86_400_000 === 42,
  "month view should retain its six-week window",
);

const virtual = continuousVirtualWindow(
  100,
  { scrollTop: 20 * 92, height: 8 * 92 },
  3,
);
assert(virtual.start === 17, "virtualization should retain overscan above");
assert(virtual.end === 31, "virtualization should retain overscan below");
assert(
  virtual.topSpacerHeight + virtual.bottomSpacerHeight > 0,
  "virtualization should preserve offscreen geometry",
);

const day = new Date(2026, 6, 7);
const parallel = [0, 1, 2, 3].map((index) =>
  event(
    `event-${index}`,
    new Date(2026, 6, 7, 9),
    new Date(2026, 6, 7, 10),
  ),
);
const layout = layoutTimedEventsForDay(parallel, day);
assert(
  layout.items.length === 2 && layout.overflows.length === 1,
  "parallel events should use bounded columns plus one overflow control",
);
assert(
  layout.overflows[0].events.length === 2,
  "overflow should retain every hidden event",
);

const allDay = event(
  "all-day",
  new Date(2026, 6, 7),
  new Date(2026, 6, 9),
  true,
);
const grouped = groupEventsByDay([allDay]);
assert(grouped.size === 2, "all-day end dates should remain exclusive");
const moved = moveEventToDay(allDay, new Date(2026, 6, 20));
assert(
  moved.endAt?.getDate() === 22,
  "moving an all-day event should preserve its duration",
);

const timed = event(
  "timed",
  new Date(2026, 6, 7, 10),
  new Date(2026, 6, 7, 11),
);
const resized = resizeEventToTime(timed, "end", day, 9 * 60);
assert(
  resized.endAt !== null &&
    resized.endAt.getTime() > resized.startAt.getTime(),
  "resizing must not invert an event",
);

console.log("Calendar view model interaction checks passed.");