private withRtpHeaderExtension()

in src/sdp/SDP.ts [421:478]
49 lines of code
17 McCabe index (conditional complexity)

  private withRtpHeaderExtension(previousSdp: SDP, url: string): SDP {
    // According to https://webrtc.googlesource.com/src/+/b62ee8ce94e5f10e0a94d6f112e715cc4d0cd9dc,
    // RTP header extension ID change would result in a hard failure. Therefore if the extension exists
    // in the previous SDP, use the same extension ID to avoid the failure. Otherwise use a new ID
    const previousId = previousSdp ? previousSdp.getRtpHeaderExtensionId(url) : -1;
    const id =
      previousId === -1 ? this.getUniqueRtpHeaderExtensionId(SDP.splitLines(this.sdp)) : previousId;

    const sections = SDP.splitSections(this.sdp);
    const newSections = [];
    for (let section of sections) {
      if (/^m=video/.test(section) && SDP.getRtpHeaderExtensionIdInSection(section, url) === -1) {
        // Add RTP header extension when it does not already exist
        const srcLines: string[] = SDP.splitLines(section);
        const dstLines: string[] = [];
        if (id === -1 || this.hasRtpHeaderExtensionId(id)) {
          // if all ids are used or the id is already used, we won't add new line to it
          newSections.push(section);
          continue;
        }

        for (const line of srcLines) {
          dstLines.push(line);
          if (/^a=sendrecv/.test(line.trim())) {
            const targetLine = `a=extmap:` + id + ` ` + url;
            dstLines.push(targetLine);
          }
        }
        section = dstLines.join(SDP.CRLF) + SDP.CRLF;
      } else if (
        previousId !== -1 &&
        /^m=video/.test(section) &&
        SDP.getRtpHeaderExtensionIdInSection(section, url) !== previousId
      ) {
        // Override extension ID if it does not match previous SDP
        const srcLines: string[] = SDP.splitLines(section);
        const dstLines: string[] = [];
        for (const line of srcLines) {
          if (/^a=extmap:/.test(line.trim())) {
            const headerExtension = line.split('a=extmap:')[1].split(' ');
            if (headerExtension[1] === url) {
              if (!this.hasRtpHeaderExtensionId(previousId)) {
                // If previous ID is used by another extension, remove it from this SDP
                const targetLine = `a=extmap:` + previousId + ` ` + url;
                dstLines.push(targetLine);
              }
              continue;
            }
          }
          dstLines.push(line);
        }
        section = dstLines.join(SDP.CRLF) + SDP.CRLF;
      }
      newSections.push(section);
    }
    const newSdp = newSections.join('');
    return new SDP(newSdp);
  }