/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import type { IParsedAdaptation } from "../types";

/**
 * Returns "last time of reference" from the adaptation given, considering a
 * dynamic content.
 * Undefined if a time could not be found.
 * Null if the Adaptation has no segments (it could be that it didn't started or
 * that it already finished for example).
 *
 * We consider the earliest last time from every representations in the given
 * adaptation.
 * @param {Object} adaptation
 * @returns {Number|undefined|null}
 */
export default function getLastPositionFromAdaptation(
  adaptation: IParsedAdaptation,
): number | undefined | null {
  const { representations } = adaptation;
  let min: null | number = null;
  for (const representation of representations) {
    const lastPosition = representation.index.getLastAvailablePosition();
    if (lastPosition === undefined) {
      // we cannot tell
      return undefined;
    }
    if (lastPosition !== null) {
      min = min === null ? lastPosition : Math.min(min, lastPosition);
    }
  }
  if (min === null) {
    // It means that all positions were null === no segments (yet?)
    return null;
  }
  return min;
}