/**
 * 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 log from "../../../log";

const SEGMENT_ID = 0x18538067;
const INFO_ID = 0x1549a966;
const TIMECODESCALE_ID = 0x2ad7b1;
const DURATION_ID = 0x4489;
const CUES_ID = 0x1c53bb6b;
const CUE_POINT_ID = 0xbb;
const CUE_TIME_ID = 0xb3;
const CUE_TRACK_POSITIONS_ID = 0xb7;
const CUE_CLUSTER_POSITIONS_ID = 0xf1;

export interface ICuesSegment {
  time: number;
  duration: number;
  timescale: number;
  range: [number, number];
}

/**
 * Find the offsets of the value linked to the given element ID.
 * @param {number} elementID - ID for the searched element.
 * @param {Array.<number>} parents - eventual IDs of the parent elements. From
 * top level to lower level (from the furthest to the closest).
 * @param {Uint8Array} buffer - buffer where the ID will be searched
 * @param {Array.<number>} range - start and end offsets in the buffer where the
 * ID will be searched.
 * @returns {Array.<number>|null}
 */
function findNextElement(
  elementID: number,
  parents: number[],
  buffer: Uint8Array,
  [initialOffset, maxOffset]: [number, number],
): [number, number] | null {
  let currentOffset = initialOffset;
  while (currentOffset < maxOffset) {
    const parsedID = getEBMLID(buffer, currentOffset);
    if (parsedID === null) {
      return null;
    }

    const { value: ebmlTagID, length: ebmlTagLength } = parsedID;
    const sizeOffset = currentOffset + ebmlTagLength;
    const parsedValue = getEBMLValue(buffer, sizeOffset);
    if (parsedValue === null) {
      return null;
    }

    const { length: valueLengthLength, value: valueLength } = parsedValue;
    const valueOffset = sizeOffset + valueLengthLength;
    const valueEndOffset = valueOffset + valueLength;
    if (ebmlTagID === elementID) {
      return [valueOffset, valueEndOffset];
    } else if (parents.length > 0) {
      for (let i = 0; i < parents.length; i++) {
        if (ebmlTagID === parents[i]) {
          const newParents = parents.slice(i + 1, parents.length);
          return findNextElement(elementID, newParents, buffer, [
            valueOffset,
            valueEndOffset,
          ]);
        }
      }
    }
    currentOffset = valueEndOffset;
  }
  return null;
}

/**
 * Return the timecode scale (basically timescale) of the whole file.
 * @param {Uint8Array} buffer
 * @param {number} initialOffset
 * @returns {number|null}
 */
export function getTimeCodeScale(
  buffer: Uint8Array,
  initialOffset: number,
): number | null {
  const timeCodeScaleOffsets = findNextElement(
    TIMECODESCALE_ID,
    [SEGMENT_ID, INFO_ID],
    buffer,
    [initialOffset, buffer.length],
  );
  if (timeCodeScaleOffsets === null) {
    return null;
  }
  const length = timeCodeScaleOffsets[1] - timeCodeScaleOffsets[0];
  return 1e9 / bytesToNumber(buffer, timeCodeScaleOffsets[0], length);
}

/**
 * Return the duration of the concerned media.
 * @param {Uint8Array} buffer
 * @param {number} initialOffset
 * @returns {number|null}
 */
function getDuration(buffer: Uint8Array, initialOffset: number): number | null {
  const timeCodeScaleOffsets = findNextElement(
    DURATION_ID,
    [SEGMENT_ID, INFO_ID],
    buffer,
    [initialOffset, buffer.length],
  );
  if (timeCodeScaleOffsets === null) {
    return null;
  }

  const length = timeCodeScaleOffsets[1] - timeCodeScaleOffsets[0];
  if (length === 4) {
    return get_IEEE754_32Bits(buffer, timeCodeScaleOffsets[0]);
  } else if (length === 8) {
    return get_IEEE754_64Bits(buffer, timeCodeScaleOffsets[0]);
  }
  return null;
}

/**
 * @param {Uint8Array} buffer
 * @param {number} initialOffset
 * @returns {Array.<Object>|null}
 */
export function getSegmentsFromCues(
  buffer: Uint8Array,
  initialOffset: number,
): ICuesSegment[] | null {
  const segmentRange = findNextElement(SEGMENT_ID, [], buffer, [
    initialOffset,
    buffer.length,
  ]);
  if (segmentRange === null) {
    return null;
  }

  const [segmentRangeStart, segmentRangeEnd] = segmentRange;

  const timescale = getTimeCodeScale(buffer, segmentRangeStart);
  if (timescale === null) {
    return null;
  }

  const duration = getDuration(buffer, segmentRangeStart);
  if (duration === null) {
    return null;
  }

  const cuesRange = findNextElement(CUES_ID, [], buffer, [
    segmentRangeStart,
    segmentRangeEnd,
  ]);
  if (cuesRange === null) {
    return null;
  }

  const rawInfos: Array<{
    time: number;
    duration?: number;
    rangeStart: number;
  }> = [];

  let currentOffset = cuesRange[0];
  while (currentOffset < cuesRange[1]) {
    const cuePointRange = findNextElement(CUE_POINT_ID, [], buffer, [
      currentOffset,
      cuesRange[1],
    ]);

    if (cuePointRange === null) {
      break;
    }

    const cueTimeRange = findNextElement(CUE_TIME_ID, [], buffer, [
      cuePointRange[0],
      cuePointRange[1],
    ]);
    if (cueTimeRange === null) {
      return null;
    }
    const time = bytesToNumber(
      buffer,
      cueTimeRange[0],
      cueTimeRange[1] - cueTimeRange[0],
    );

    const cueOffsetRange = findNextElement(
      CUE_CLUSTER_POSITIONS_ID,
      [CUE_TRACK_POSITIONS_ID],
      buffer,
      [cuePointRange[0], cuePointRange[1]],
    );
    if (cueOffsetRange === null) {
      return null;
    }

    const rangeStart =
      bytesToNumber(buffer, cueOffsetRange[0], cueOffsetRange[1] - cueOffsetRange[0]) +
      segmentRangeStart;
    rawInfos.push({ time, rangeStart });

    currentOffset = cuePointRange[1];
  }

  const segments: ICuesSegment[] = [];

  for (let i = 0; i < rawInfos.length; i++) {
    const currentSegment = rawInfos[i];
    if (i === rawInfos.length - 1) {
      segments.push({
        time: currentSegment.time,
        timescale,
        duration: i === 0 ? duration : duration - currentSegment.time,
        range: [currentSegment.rangeStart, Infinity],
      });
    } else {
      segments.push({
        time: currentSegment.time,
        timescale,
        duration: rawInfos[i + 1].time - currentSegment.time,
        range: [currentSegment.rangeStart, rawInfos[i + 1].rangeStart - 1],
      });
    }
  }

  return segments;
}

function getLength(buffer: Uint8Array, offset: number): number | undefined {
  for (let length = 1; length <= 8; length++) {
    if (buffer[offset] >= Math.pow(2, 8 - length)) {
      return length;
    }
  }
  return undefined;
}

function getEBMLID(
  buffer: Uint8Array,
  offset: number,
): { length: number; value: number } | null {
  const length = getLength(buffer, offset);
  if (length === undefined) {
    log.warn("webm: unrepresentable length");
    return null;
  }
  if (offset + length > buffer.length) {
    log.warn("webm: impossible length");
    return null;
  }

  let value = 0;
  for (let i = 0; i < length; i++) {
    value = buffer[offset + i] * Math.pow(2, (length - i - 1) * 8) + value;
  }
  return { length, value };
}

function getEBMLValue(
  buffer: Uint8Array,
  offset: number,
): { length: number; value: number } | null {
  const length = getLength(buffer, offset);
  if (length === undefined) {
    log.warn("webm: unrepresentable length");
    return null;
  }
  if (offset + length > buffer.length) {
    log.warn("webm: impossible length");
    return null;
  }

  let value =
    (buffer[offset] & ((1 << (8 - length)) - 1)) * Math.pow(2, (length - 1) * 8);
  for (let i = 1; i < length; i++) {
    value = buffer[offset + i] * Math.pow(2, (length - i - 1) * 8) + value;
  }
  return { length, value };
}

/**
 * Convert a IEEE754 32 bits floating number as an Uint8Array into its
 * corresponding Number.
 * @param {Uint8Array} buffer
 * @param {number} offset
 * @returns {number}
 */
function get_IEEE754_32Bits(buffer: Uint8Array, offset: number): number {
  return new DataView(buffer.buffer).getFloat32(offset);
}

/**
 * Convert a IEEE754 64 bits floating number as an Uint8Array into its
 * corresponding Number.
 * @param {Uint8Array} buffer
 * @param {number} offset
 * @returns {number}
 */
function get_IEEE754_64Bits(buffer: Uint8Array, offset: number): number {
  return new DataView(buffer.buffer).getFloat64(offset);
}

function bytesToNumber(buffer: Uint8Array, offset: number, length: number): number {
  let value = 0;
  for (let i = 0; i < length; i++) {
    value = buffer[offset + i] * Math.pow(2, (length - i - 1) * 8) + value;
  }
  return value;
}