LZMA errors if run without Web Workers

[danielghost]

Subject of the issue/enhancement/features

If a course is run in an environment without Web Workers, e.g. offline via a mobile app, the course errors on load: Uncaught TypeError: window.LZMAFactory is not a function

For some reason the LZMA library seems to have been modified to declare LZMAFactory, but hasn't implemented this for all possible conditions when the library is initialised.

Your environment

• since https://github.com/adaptlearning/adapt-contrib-spoor/commit/b7fc02f5e0472b009ef371ad7b6058bee8e0ce62

Proposed solution

Use the latest libraries files:

• https://github.com/LZMA-JS/LZMA-JS/blob/master/src/lzma-min.js
• https://github.com/LZMA-JS/LZMA-JS/blob/master/src/lzma_worker-min.js

Modify https://github.com/adaptlearning/adapt-contrib-spoor/blob/master/js/serializers/SCORMSuspendData.js#L6 to use window.LZMA and prefix all LZMA compress and decompress references accordingly. Alternatively prefix these methods with window.LZMA directly and delete the LZMAWorker property.

[danielghost]

Seems like lzma-min file was modified to add the LZMAFactory method so lzma-min-worker wouldn't override the LZMA method once loaded, which would prevent the use of Web Workers. Assigning LZMAFactory also maintains the ability for https://github.com/adaptlearning/adapt-contrib-spoor/blob/master/js/serializers/SCORMSuspendData.js#L1144 to be run synchronously.

Ideally the implementation would change to https://gist.github.com/danielghost/045520d0d04c9cef70f36386e78c9a9a, but this would then require deserialize to become asynchronous, causing breaking changes to other methods throughout the framework, so they expect a returned Promise.

For now we will just fix the missing LZMAFactory method when Web Workers are not implemented.