text: /**
   * @license
   * Copyright 2016 Google Inc.
   *
   * 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.
   */
  
  goog.provide('shaka.text.TextEngine');
  
  goog.require('goog.asserts');
  goog.require('shaka.util.Error');
  goog.require('shaka.util.IDestroyable');
  
  
  
  /**
   * Manages text parsers and cues.
   *
   * @param {shaka.extern.TextDisplayer} displayer
   * @struct
   * @constructor
   * @implements {shaka.util.IDestroyable}
   */
  shaka.text.TextEngine = function(displayer) {
    /** @private {shaka.extern.TextParser} */
    this.parser_ = null;
  
    /** @private {shaka.extern.TextDisplayer} */
    this.displayer_ = displayer;
  
    /** @private {number} */
    this.timestampOffset_ = 0;
  
    /** @private {number} */
    this.appendWindowStart_ = 0;
  
    /** @private {number} */
    this.appendWindowEnd_ = Infinity;
  
    /** @private {?number} */
    this.bufferStart_ = null;
  
    /** @private {?number} */
    this.bufferEnd_ = null;
  };
  
  
  /** @private {!Object.<string, !shaka.extern.TextParserPlugin>} */
  shaka.text.TextEngine.parserMap_ = {};
  
  
  /**
   * @param {string} mimeType
   * @param {!shaka.extern.TextParserPlugin} plugin
   * @export
   */
  shaka.text.TextEngine.registerParser = function(mimeType, plugin) {
    shaka.text.TextEngine.parserMap_[mimeType] = plugin;
  };
  
  
  /**
   * @param {string} mimeType
   * @export
   */
  shaka.text.TextEngine.unregisterParser = function(mimeType) {
    delete shaka.text.TextEngine.parserMap_[mimeType];
  };
  
  
  /**
   * @param {string} mimeType
   * @return {boolean}
   */
  shaka.text.TextEngine.isTypeSupported = function(mimeType) {
    return !!shaka.text.TextEngine.parserMap_[mimeType];
  };
  
  
  /** @override */
  shaka.text.TextEngine.prototype.destroy = function() {
    this.parser_ = null;
    this.displayer_ = null;
  
    return Promise.resolve();
  };
  
  
  /**
   * @param {shaka.extern.TextDisplayer} displayer
   * @export
   */
  shaka.text.TextEngine.prototype.setDisplayer = function(displayer) {
    this.displayer_ = displayer;
  };
  
  
  /**
   * Initialize the parser.  This can be called multiple times, but must be called
   * at least once before appendBuffer.
   *
   * @param {string} mimeType
   */
  shaka.text.TextEngine.prototype.initParser = function(mimeType) {
    let factory = shaka.text.TextEngine.parserMap_[mimeType];
    goog.asserts.assert(
        factory,
        'Text type negotiation should have happened already');
    this.parser_ = new factory();
  };
  
  
  /**
   * Parse the start time from the text media segment, if possible.
   *
   * @param {!ArrayBuffer} buffer
   * @return {number}
   * @throws {shaka.util.Error} on failure
   */
  shaka.text.TextEngine.prototype.getStartTime = function(buffer) {
    goog.asserts.assert(this.parser_, 'The parser should already be initialized');
  
    /** @type {shaka.extern.TextParser.TimeContext} **/
    let time = {
      periodStart: 0,
      segmentStart: null,
      segmentEnd: 0
    };
  
    // Parse the buffer and extract the first cue start time.
    try {
      let allCues = this.parser_.parseMedia(new Uint8Array(buffer), time);
      return allCues[0].startTime;
    } catch (exception) {
      // This could be a failure from the parser itself (init segment required)
      // or an exception from allCues.length being zero.
      throw new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.TEXT,
          shaka.util.Error.Code.UNABLE_TO_EXTRACT_CUE_START_TIME,
          exception);
    }
  };
  
  
  /**
   * @param {!ArrayBuffer} buffer
   * @param {?number} startTime
   * @param {?number} endTime
   * @return {!Promise}
   */
  shaka.text.TextEngine.prototype.appendBuffer =
      function(buffer, startTime, endTime) {
    goog.asserts.assert(this.parser_, 'The parser should already be initialized');
  
    // Start the operation asynchronously to avoid blocking the caller.
    return Promise.resolve().then(function() {
      // Check that TextEngine hasn't been destroyed.
      if (!this.parser_ || !this.displayer_) return;
  
      if (startTime == null || endTime == null) {
        this.parser_.parseInit(new Uint8Array(buffer));
        return;
      }
  
      /** @type {shaka.extern.TextParser.TimeContext} **/
      let time = {
        periodStart: this.timestampOffset_,
        segmentStart: this.timestampOffset_ + startTime,
        segmentEnd: this.timestampOffset_ + endTime
      };
  
      // Parse the buffer and add the new cues.
      let allCues = this.parser_.parseMedia(new Uint8Array(buffer), time);
      let cuesToAppend = allCues.filter(function(cue) {
        return cue.startTime >= this.appendWindowStart_ &&
               cue.startTime < this.appendWindowEnd_;
      }.bind(this));
  
      this.displayer_.append(cuesToAppend);
  
      // NOTE: We update the buffered range from the start and end times passed
      // down from the segment reference, not with the start and end times of the
      // parsed cues.  This is important because some segments may contain no
      // cues, but we must still consider those ranges buffered.
      if (this.bufferStart_ == null) {
        this.bufferStart_ = Math.max(startTime, this.appendWindowStart_);
      } else {
        // We already had something in buffer, and we assume we are extending the
        // range from the end.
        goog.asserts.assert((startTime - this.bufferEnd_) <= 1,
                            'There should not be a gap in text references >1s');
      }
      this.bufferEnd_ = Math.min(endTime, this.appendWindowEnd_);
    }.bind(this));
  };
  
  
  /**
   * @param {number} start
   * @param {number} end
   * @return {!Promise}
   */
  shaka.text.TextEngine.prototype.remove = function(start, end) {
    // Start the operation asynchronously to avoid blocking the caller.
    return Promise.resolve().then(function() {
      if (this.displayer_ && this.displayer_.remove(start, end)) {
        if (this.bufferStart_ == null) {
          goog.asserts.assert(this.bufferEnd_ == null,
                              'end must be null if start is null');
        } else {
          goog.asserts.assert(this.bufferEnd_ != null,
                              'end must be non-null if start is non-null');
  
          // Update buffered range.
          if (end <= this.bufferStart_ || start >= this.bufferEnd_) {
            // No intersection.  Nothing was removed.
          } else if (start <= this.bufferStart_ && end >= this.bufferEnd_) {
            // We wiped out everything.
            this.bufferStart_ = this.bufferEnd_ = null;
          } else if (start <= this.bufferStart_ && end < this.bufferEnd_) {
            // We removed from the beginning of the range.
            this.bufferStart_ = end;
          } else if (start > this.bufferStart_ && end >= this.bufferEnd_) {
            // We removed from the end of the range.
            this.bufferEnd_ = start;
          } else {
            // We removed from the middle?  StreamingEngine isn't supposed to.
            goog.asserts.assert(
                false, 'removal from the middle is not supported by TextEngine');
          }
        }
      }
    }.bind(this));
  };
  
  
  /** @param {number} timestampOffset */
  shaka.text.TextEngine.prototype.setTimestampOffset =
      function(timestampOffset) {
    this.timestampOffset_ = timestampOffset;
  };
  
  
  /**
   * @param {number} appendWindowStart
   * @param {number} appendWindowEnd
   */
  shaka.text.TextEngine.prototype.setAppendWindow =
      function(appendWindowStart, appendWindowEnd) {
    this.appendWindowStart_ = appendWindowStart;
    this.appendWindowEnd_ = appendWindowEnd;
  };
  
  
  /**
   * @return {?number} Time in seconds of the beginning of the buffered range,
   *   or null if nothing is buffered.
   */
  shaka.text.TextEngine.prototype.bufferStart = function() {
    return this.bufferStart_;
  };
  
  
  /**
   * @return {?number} Time in seconds of the end of the buffered range,
   *   or null if nothing is buffered.
   */
  shaka.text.TextEngine.prototype.bufferEnd = function() {
    return this.bufferEnd_;
  };
  
  
  /**
   * @param {number} t A timestamp
   * @return {boolean}
   */
  shaka.text.TextEngine.prototype.isBuffered = function(t) {
    return t >= this.bufferStart_ && t < this.bufferEnd_;
  };
  
  
  /**
   * @param {number} t A timestamp
   * @return {number} Number of seconds ahead of 't' we have buffered
   */
  shaka.text.TextEngine.prototype.bufferedAheadOf = function(t) {
    if (this.bufferEnd_ == null || this.bufferEnd_ < t) return 0;
  
    goog.asserts.assert(
        this.bufferStart_ != null, 'start should not be null if end is not null');
  
    return this.bufferEnd_ - Math.max(t, this.bufferStart_);
  };
  
  
  /**
   * Append cues to text displayer.
   *
   * @param {!Array.<!shaka.text.Cue>} cues
   * @export
   */
  shaka.text.TextEngine.prototype.appendCues = function(cues) {
    this.displayer_.append(cues);
  };
  