Handle links to images and other files

[skiadas]

We need to:

• [ ] locate the resource in the Moodle files
• [ ] save it as its own document in appropriate filesystem location
• [ ] replace text reference to it
• [ ] log file creation somewhere?

[skiadas]

Some details:

• File references are found in the questions.xml file, and they look like this: @@PLUGINFILE@@/Screen%20Shot%202020-03-22%20at%209.43.06%20AM.png or @@PLUGINFILE@@/length_main.png?time=1586707802344
• The files.xml file contains information about these files, in <file> entries:
  • A <contenthash> entry there identifies the resource and its content uniquely, something like: 3f6936cd31ef70a593d22af181563df3f1c034ac
  • Other useful entries: filename, filepath, filesize, mimetype, timecreated and timemodified
  • itemid matches the questionid where the image appeared.
  • There may be multiple files with the same name.
  • Hopefully files are uniquely identified by their "itemid" plus name? Otherwise we have multiple files references by the same name in the same location, which could be problematic.
• The actual contents are in the files directory, in subdirectories based on the first 2 letters of the content hash, and the actual filenames are the contenthash itself.

We should start with a FileManager class:

• At construction it processes the files.xml file and stores information about the various files that are available.
• Somehow has information about how we would like the various file assets to be stored when they have to be stored.
• Upon request for a file, it creates the appropriate file with the appropriate filename in the file system and returns a Path to it.
• Optionally, the actual creation of the files is perhaps delayed to happen on mass at the end?