/**
 * 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 { ITNode } from "../../../../../../utils/xml-parser";
import type { IIndexSegment } from "../../../../utils/index_helpers";
import convertElementsToIndexSegment from "./convert_element_to_index_segment";
import type { IParsedS } from "./parse_s_element";
import { parseSElementNode } from "./parse_s_element";

/**
 * Allows to generate the "timeline" for the "Timeline" RepresentationIndex.
 * Call this function when the timeline is unknown.
 * This function was added to only perform that task lazily, i.e. only when
 * first needed.
 * @param {Array.<Object>} elements - All S nodes constituting
 * the corresponding SegmentTimeline node.
 * @returns {Array.<Object>}
 */
export default function constructTimelineFromElements(
  elements: ITNode[],
): IIndexSegment[] {
  const initialTimeline: IParsedS[] = [];
  for (let i = 0; i < elements.length; i++) {
    initialTimeline.push(parseSElementNode(elements[i]));
  }
  const timeline: IIndexSegment[] = [];
  for (let i = 0; i < initialTimeline.length; i++) {
    const item = initialTimeline[i];
    const previousItem =
      timeline[timeline.length - 1] === undefined ? null : timeline[timeline.length - 1];
    const nextItem = initialTimeline[i + 1] === undefined ? null : initialTimeline[i + 1];
    const timelineElement = convertElementsToIndexSegment(item, previousItem, nextItem);
    if (timelineElement !== null) {
      timeline.push(timelineElement);
    }
  }
  return timeline;
}