/**
 * Seed planning arithmetic (CONCEPT.md D38), independent of the database.
 */

/** The parts of `from`..`to` (inclusive) that no range in `covered` (inclusive pairs) overlaps, oldest first. */
export function uncovered(from: number, to: number, covered: [number, number][]): [number, number][] {
  const gaps: [number, number][] = []
  let next = from
  for (const [start, end] of [...covered].sort((a, b) => a[0] - b[0])) {
    if (end < next) continue
    if (start > to) break
    if (start > next) gaps.push([next, Math.min(start - 1, to)])
    next = Math.max(next, end + 1)
    if (next > to) return gaps
  }
  if (next <= to) gaps.push([next, to])
  return gaps
}

/** `gaps` cut into ranges of at most `size` articles, newest first (from the top of the newest gap down). */
export function cut(gaps: [number, number][], size: number): [number, number][] {
  const ranges: [number, number][] = []
  for (const [from, to] of [...gaps].sort((a, b) => b[1] - a[1])) {
    for (let end = to; end >= from; end -= size) ranges.push([Math.max(from, end - size + 1), end])
  }
  return ranges
}