/**
 * @fileOverview
 *
 * 有序维护选区
 */

export interface Identifiable {
  id: string | number;
}

/**
 * 保证 selection 保持与 records 有相同的偏序关系，查找插入位置
 */
function findInsertPosition<T extends Identifiable>(
  records: T[],
  selection: T[],
  item: T
): number {
  const recordIndex = records.indexOf(item);
  let ri = 0;
  let si = 0;
  while (records[ri] && selection[si]) {
    if (ri === recordIndex) break;
    if (records[ri] === selection[si] || records[ri].id === selection[si].id) {
      si += 1;
    }
    ri += 1;
  }
  return si;
}

/**
 * 插入到选区中，保持与 records 相同的偏序顺序
 */
export function selectionInsert<T extends Identifiable>(
  records: T[],
  selection: T[],
  item: T
): T[] {
  const newSelection = selection ? selection.slice() : [];
  const index = newSelection.indexOf(item);

  if (index === -1) {
    const insertIndex = findInsertPosition(records, newSelection, item);
    newSelection.splice(insertIndex, 0, item);
  }

  return newSelection;
}

/**
 * 从选取中删除
 */
export function selectionRemove<T extends Identifiable>(
  records: T[],
  selection: T[],
  item: T
): T[] {
  const newSelection = selection.slice();
  const index = newSelection.indexOf(item);

  if (index > -1) {
    newSelection.splice(index, 1);
  }

  return newSelection;
}