/**
 * 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 { MediaError } from "../../../errors";
import log from "../../../log";
import type { IIndexSegment } from "./index_helpers";
import { getIndexSegmentEnd } from "./index_helpers";

/**
 * Update a complete array of segments in a given timeline with a [generally]
 * smaller but [generally] newer set of segments.
 *
 * Returns a boolean:
 *   - If set to `true`, the old timeline was emptied and completely replaced by
 *     the content of the newer timeline.
 *     This could happen either if a problem happened while trying to update or
 *     when the update is actually bigger than what it is updating.
 *   - If set to `false`, the older timeline was either updated to add the newer
 *     segments, or untouched.
 *
 * @param {Array.<Object>} oldTimeline
 * @param {Array.<Object>} newTimeline
 * @returns {boolean}
 */
export default function updateSegmentTimeline(
  oldTimeline: IIndexSegment[],
  newTimeline: IIndexSegment[],
): boolean {
  if (oldTimeline.length === 0) {
    oldTimeline.push(...newTimeline);
    return true;
  } else if (newTimeline.length === 0) {
    return false;
  }

  const prevTimelineLength = oldTimeline.length;
  const newIndexStart = newTimeline[0].start;

  const oldLastElt = oldTimeline[prevTimelineLength - 1];
  const oldIndexEnd = getIndexSegmentEnd(oldLastElt, newTimeline[0]);
  if (oldIndexEnd < newIndexStart) {
    throw new MediaError(
      "MANIFEST_UPDATE_ERROR",
      "Cannot perform partial update: not enough data",
    );
  }

  for (let i = prevTimelineLength - 1; i >= 0; i--) {
    const currStart = oldTimeline[i].start;
    if (currStart === newIndexStart) {
      // replace that one and those after it
      const nbEltsToRemove = prevTimelineLength - i;
      oldTimeline.splice(i, nbEltsToRemove, ...newTimeline);
      return false;
    } else if (currStart < newIndexStart) {
      // first to be before
      const currElt = oldTimeline[i];
      if (currElt.start + currElt.duration > newIndexStart) {
        // The new Manifest overlaps a previous segment (weird)
        // In that improbable case, we'll just completely replace segments
        log.warn("RepresentationIndex: Manifest update removed all previous segments");
        oldTimeline.splice(0, prevTimelineLength, ...newTimeline);
        return true;
      } else if (currElt.repeatCount === undefined || currElt.repeatCount <= 0) {
        if (currElt.repeatCount < 0) {
          currElt.repeatCount =
            Math.floor((newIndexStart - currElt.start) / currElt.duration) - 1;
        }
        oldTimeline.splice(i + 1, prevTimelineLength - (i + 1), ...newTimeline);
        return false;
      }
      // else, there is a positive repeat we might want to update
      const eltLastTime = currElt.start + currElt.duration * (currElt.repeatCount + 1);
      if (eltLastTime <= newIndexStart) {
        // our new index comes directly after
        // put it after this one
        oldTimeline.splice(i + 1, prevTimelineLength - (i + 1), ...newTimeline);
        return false;
      }

      const newCurrRepeat = (newIndexStart - currElt.start) / currElt.duration - 1;
      if (newCurrRepeat % 1 === 0 && currElt.duration === newTimeline[0].duration) {
        const newRepeatCount =
          newTimeline[0].repeatCount < 0
            ? -1 // === maximum possible repeat
            : newTimeline[0].repeatCount + newCurrRepeat + 1;

        // replace that one and those after it
        oldTimeline.splice(i, prevTimelineLength - i, ...newTimeline);
        oldTimeline[i].start = currElt.start;
        oldTimeline[i].repeatCount = newRepeatCount;
        return false;
      }
      log.warn("RepresentationIndex: Manifest update removed previous segments");
      oldTimeline[i].repeatCount = Math.floor(newCurrRepeat);

      // put it after this one
      oldTimeline.splice(i + 1, prevTimelineLength - (i + 1), ...newTimeline);
      return false;
    }
  }

  // if we got here, it means that every segments in the previous manifest are
  // after the new one. This is unusual.
  // Either the new one has more depth or it's an older one.
  const prevLastElt = oldTimeline[oldTimeline.length - 1];
  const newLastElt = newTimeline[newTimeline.length - 1];
  if (prevLastElt.repeatCount !== undefined && prevLastElt.repeatCount < 0) {
    if (prevLastElt.start > newLastElt.start) {
      log.warn("RepresentationIndex: The new index is older than the previous one");
      return false;
    } else {
      // the new has more depth
      log.warn('RepresentationIndex: The new index is "bigger" than the previous one');
      oldTimeline.splice(0, prevTimelineLength, ...newTimeline);
      return true;
    }
  }
  const prevLastTime =
    prevLastElt.start + prevLastElt.duration * (prevLastElt.repeatCount + 1);
  const newLastTime =
    newLastElt.start + newLastElt.duration * (newLastElt.repeatCount + 1);
  if (prevLastTime >= newLastTime) {
    log.warn("RepresentationIndex: The new index is older than the previous one");
    return false;
  }

  // the new one has more depth. full update
  log.warn('RepresentationIndex: The new index is "bigger" than the previous one');
  oldTimeline.splice(0, prevTimelineLength, ...newTimeline);
  return true;
}