/**
 * @file m3u8/parser.js
 */
import Stream from './stream' ;
import LineStream from './line-stream';
import ParseStream from './parse-stream';

/**
 * A parser for M3U8 files. The current interpretation of the input is
 * exposed as a property `manifest` on parser objects. It's just two lines to
 * create and parse a manifest once you have the contents available as a string:
 *
 * ```js
 * var parser = new m3u8.Parser();
 * parser.push(xhr.responseText);
 * ```
 *
 * New input can later be applied to update the manifest object by calling
 * `push` again.
 *
 * The parser attempts to create a usable manifest object even if the
 * underlying input is somewhat nonsensical. It emits `info` and `warning`
 * events during the parse if it encounters input that seems invalid or
 * requires some property of the manifest object to be defaulted.
 *
 * @class Parser
 * @extends Stream
 */
export default class Parser extends Stream {
  constructor() {
    super();
    this.lineStream = new LineStream();
    this.parseStream = new ParseStream();
    this.lineStream.pipe(this.parseStream);
    /* eslint-disable consistent-this */
    const self = this;
    /* eslint-enable consistent-this */
    const uris = [];
    let currentUri = {};
    // if specified, the active EXT-X-MAP definition
    let currentMap;
    // if specified, the active decryption key
    let key;
    const noop = function() {};
    const defaultMediaGroups = {
      'AUDIO': {},
      'VIDEO': {},
      'CLOSED-CAPTIONS': {},
      'SUBTITLES': {}
    };
    // group segments into numbered timelines delineated by discontinuities
    let currentTimeline = 0;

    // the manifest is empty until the parse stream begins delivering data
    this.manifest = {
      allowCache: true,
      discontinuityStarts: [],
      segments: []
    };

    // update the manifest with the m3u8 entry from the parse stream
    this.parseStream.on('data', function(entry) {
      let mediaGroup;
      let rendition;

      ({
        tag() {
          // switch based on the tag type
          (({
            'allow-cache'() {
              this.manifest.allowCache = entry.allowed;
              if (!('allowed' in entry)) {
                this.trigger('info', {
                  message: 'defaulting allowCache to YES'
                });
                this.manifest.allowCache = true;
              }
            },
            byterange() {
              const byterange = {};

              if ('length' in entry) {
                currentUri.byterange = byterange;
                byterange.length = entry.length;

                if (!('offset' in entry)) {
                  this.trigger('info', {
                    message: 'defaulting offset to zero'
                  });
                  entry.offset = 0;
                }
              }
              if ('offset' in entry) {
                currentUri.byterange = byterange;
                byterange.offset = entry.offset;
              }
            },
            endlist() {
              this.manifest.endList = true;
            },
            inf() {
              if (!('mediaSequence' in this.manifest)) {
                this.manifest.mediaSequence = 0;
                this.trigger('info', {
                  message: 'defaulting media sequence to zero'
                });
              }
              if (!('discontinuitySequence' in this.manifest)) {
                this.manifest.discontinuitySequence = 0;
                this.trigger('info', {
                  message: 'defaulting discontinuity sequence to zero'
                });
              }
              if (entry.duration > 0) {
                currentUri.duration = entry.duration;
              }

              if (entry.duration === 0) {
                currentUri.duration = 0.01;
                this.trigger('info', {
                  message: 'updating zero segment duration to a small value'
                });
              }

              this.manifest.segments = uris;
            },
            key() {
              if (!entry.attributes) {
                this.trigger('warn', {
                  message: 'ignoring key declaration without attribute list'
                });
                return;
              }
              // clear the active encryption key
              if (entry.attributes.METHOD === 'NONE') {
                key = null;
                return;
              }
              if (!entry.attributes.URI) {
                this.trigger('warn', {
                  message: 'ignoring key declaration without URI'
                });
                return;
              }
              if (!entry.attributes.METHOD) {
                this.trigger('warn', {
                  message: 'defaulting key method to AES-128'
                });
              }

              // setup an encryption key for upcoming segments
              key = {
                method: entry.attributes.METHOD || 'AES-128',
                uri: entry.attributes.URI
              };

              if (typeof entry.attributes.IV !== 'undefined') {
                key.iv = entry.attributes.IV;
              }
            },
            'media-sequence'() {
              if (!isFinite(entry.number)) {
                this.trigger('warn', {
                  message: 'ignoring invalid media sequence: ' + entry.number
                });
                return;
              }
              this.manifest.mediaSequence = entry.number;
            },
            'discontinuity-sequence'() {
              if (!isFinite(entry.number)) {
                this.trigger('warn', {
                  message: 'ignoring invalid discontinuity sequence: ' + entry.number
                });
                return;
              }
              this.manifest.discontinuitySequence = entry.number;
              currentTimeline = entry.number;
            },
            'playlist-type'() {
              if (!(/VOD|EVENT/).test(entry.playlistType)) {
                this.trigger('warn', {
                  message: 'ignoring unknown playlist type: ' + entry.playlist
                });
                return;
              }
              this.manifest.playlistType = entry.playlistType;
            },
            map() {
              currentMap = {};
              if (entry.uri) {
                currentMap.uri = entry.uri;
              }
              if (entry.byterange) {
                currentMap.byterange = entry.byterange;
              }
            },
            'stream-inf'() {
              this.manifest.playlists = uris;
              this.manifest.mediaGroups =
                this.manifest.mediaGroups || defaultMediaGroups;

              if (!entry.attributes) {
                this.trigger('warn', {
                  message: 'ignoring empty stream-inf attributes'
                });
                return;
              }

              if (!currentUri.attributes) {
                currentUri.attributes = {};
              }
              Object.assign(currentUri.attributes, entry.attributes);
            },
            media() {
              this.manifest.mediaGroups =
                this.manifest.mediaGroups || defaultMediaGroups;

              if (!(entry.attributes &&
                    entry.attributes.TYPE &&
                    entry.attributes['GROUP-ID'] &&
                    entry.attributes.NAME)) {
                this.trigger('warn', {
                  message: 'ignoring incomplete or missing media group'
                });
                return;
              }

              // find the media group, creating defaults as necessary
              const mediaGroupType = this.manifest.mediaGroups[entry.attributes.TYPE];

              mediaGroupType[entry.attributes['GROUP-ID']] =
                mediaGroupType[entry.attributes['GROUP-ID']] || {};
              mediaGroup = mediaGroupType[entry.attributes['GROUP-ID']];

              // collect the rendition metadata
              rendition = {
                default: (/yes/i).test(entry.attributes.DEFAULT)
              };
              if (rendition.default) {
                rendition.autoselect = true;
              } else {
                rendition.autoselect = (/yes/i).test(entry.attributes.AUTOSELECT);
              }
              if (entry.attributes.LANGUAGE) {
                rendition.language = entry.attributes.LANGUAGE;
              }
              if (entry.attributes.URI) {
                rendition.uri = entry.attributes.URI;
              }
              if (entry.attributes['INSTREAM-ID']) {
                rendition.instreamId = entry.attributes['INSTREAM-ID'];
              }
              if (entry.attributes.CHARACTERISTICS) {
                rendition.characteristics = entry.attributes.CHARACTERISTICS;
              }
              if (entry.attributes.FORCED) {
                rendition.forced = (/yes/i).test(entry.attributes.FORCED);
              }

              // insert the new rendition
              mediaGroup[entry.attributes.NAME] = rendition;
            },
            discontinuity() {
              currentTimeline += 1;
              currentUri.discontinuity = true;
              this.manifest.discontinuityStarts.push(uris.length);
            },
            'program-date-time'() {
              this.manifest.dateTimeString = entry.dateTimeString;
              this.manifest.dateTimeObject = entry.dateTimeObject;
            },
            targetduration() {
              if (!isFinite(entry.duration) || entry.duration < 0) {
                this.trigger('warn', {
                  message: 'ignoring invalid target duration: ' + entry.duration
                });
                return;
              }
              this.manifest.targetDuration = entry.duration;
            },
            totalduration() {
              if (!isFinite(entry.duration) || entry.duration < 0) {
                this.trigger('warn', {
                  message: 'ignoring invalid total duration: ' + entry.duration
                });
                return;
              }
              this.manifest.totalDuration = entry.duration;
            },
            'cue-out'() {
              currentUri.cueOut = entry.data;
            },
            'cue-out-cont'() {
              currentUri.cueOutCont = entry.data;
            },
            'cue-in'() {
              currentUri.cueIn = entry.data;
            }
          })[entry.tagType] || noop).call(self);
        },
        uri() {
          currentUri.uri = entry.uri;
          uris.push(currentUri);

          // if no explicit duration was declared, use the target duration
          if (this.manifest.targetDuration &&
              !('duration' in currentUri)) {
            this.trigger('warn', {
              message: 'defaulting segment duration to the target duration'
            });
            currentUri.duration = this.manifest.targetDuration;
          }
          // annotate with encryption information, if necessary
          if (key) {
            currentUri.key = key;
          }
          currentUri.timeline = currentTimeline;
          // annotate with initialization segment information, if necessary
          if (currentMap) {
            currentUri.map = currentMap;
          }

          // prepare for the next URI
          currentUri = {};
        },
        comment() {
          // comments are not important for playback
        }
      })[entry.type].call(self);
    });

  }

  /**
   * Parse the input string and update the manifest object.
   *
   * @param {String} chunk a potentially incomplete portion of the manifest
   */
  push(chunk) {
    this.lineStream.push(chunk);
  }

  /**
   * Flush any remaining input. This can be handy if the last line of an M3U8
   * manifest did not contain a trailing newline but the file has been
   * completely received.
   */
  end() {
    // flush any buffered input
    this.lineStream.push('\n');
  }

}
