"use strict";

/**
 * Buffer Helper utils, providing methods dealing buffer length retrieval
*/

var BufferHelper = {
  isBuffered: function isBuffered(media, position) {
    if (media) {
      var buffered = media.buffered;
      for (var i = 0; i < buffered.length; i++) {
        if (position >= buffered.start(i) && position <= buffered.end(i)) {
          return true;
        }
      }
    }
    return false;
  },

  bufferInfo: function bufferInfo(media, pos, maxHoleDuration) {
    if (media) {
      var vbuffered = media.buffered,
          buffered = [],
          i;
      for (i = 0; i < vbuffered.length; i++) {
        buffered.push({ start: vbuffered.start(i), end: vbuffered.end(i) });
      }
      return this.bufferedInfo(buffered, pos, maxHoleDuration);
    } else {
      return { len: 0, start: pos, end: pos, nextStart: undefined };
    }
  },

  bufferedInfo: function bufferedInfo(buffered, pos, maxHoleDuration) {
    var buffered2 = [],

    // bufferStart and bufferEnd are buffer boundaries around current video position
    bufferLen,
        bufferStart,
        bufferEnd,
        bufferStartNext,
        i;
    // sort on buffer.start/smaller end (IE does not always return sorted buffered range)
    buffered.sort(function (a, b) {
      var diff = a.start - b.start;
      if (diff) {
        return diff;
      } else {
        return b.end - a.end;
      }
    });
    // there might be some small holes between buffer time range
    // consider that holes smaller than maxHoleDuration are irrelevant and build another
    // buffer time range representations that discards those holes
    for (i = 0; i < buffered.length; i++) {
      var buf2len = buffered2.length;
      if (buf2len) {
        var buf2end = buffered2[buf2len - 1].end;
        // if small hole (value between 0 or maxHoleDuration ) or overlapping (negative)
        if (buffered[i].start - buf2end < maxHoleDuration) {
          // merge overlapping time ranges
          // update lastRange.end only if smaller than item.end
          // e.g.  [ 1, 15] with  [ 2,8] => [ 1,15] (no need to modify lastRange.end)
          // whereas [ 1, 8] with  [ 2,15] => [ 1,15] ( lastRange should switch from [1,8] to [1,15])
          if (buffered[i].end > buf2end) {
            buffered2[buf2len - 1].end = buffered[i].end;
          }
        } else {
          // big hole
          buffered2.push(buffered[i]);
        }
      } else {
        // first value
        buffered2.push(buffered[i]);
      }
    }
    for (i = 0, bufferLen = 0, bufferStart = bufferEnd = pos; i < buffered2.length; i++) {
      var start = buffered2[i].start,
          end = buffered2[i].end;
      //logger.log('buf start/end:' + buffered.start(i) + '/' + buffered.end(i));
      if (pos + maxHoleDuration >= start && pos < end) {
        // play position is inside this buffer TimeRange, retrieve end of buffer position and buffer length
        bufferStart = start;
        bufferEnd = end;
        bufferLen = bufferEnd - pos;
      } else if (pos + maxHoleDuration < start) {
        bufferStartNext = start;
        break;
      }
    }
    return { len: bufferLen, start: bufferStart, end: bufferEnd, nextStart: bufferStartNext };
  }
};

module.exports = BufferHelper;