fix(electron): correctly read/write file with no encoding

[D34THWINGS]

I was working with the Filesystem plugin and some data URL files encoded in base64 and I stumbled upon the fact that Electron bridge is not implemented like the Android and iOS one. I simply cannot store a PDF file because it always encrypt as UTF8 and break the file.

On iOS and Android, the default encoding when writing files is base64. If a data URL is detected it deletes its header before converting it to binary. When reading, if no encoding is given, the same thing happens the other way, it converts binary to base64.

This is a breaking change for Electron users but ATM, Electron filesystem plugin does not behave at all like iOS and Android.

[jcesarmobile]

Thanks for the PR, but it doesn't build because data is string and don't let you switch it to Buffer (line 65).
Also you are always removing whatever there is before the ,, even if it has encoding, that will remove part of texts that have , on it.

The code should look like:

      let data = options.data;
      if (!options.encoding) {
        data = options.data.indexOf(',') >= 0 ? options.data.split(',')[1] : options.data;
      }
      let writeData = options.encoding ? data : Buffer.from(data, 'base64');
      this.NodeFS.writeFile(lookupPath, writeData, options.encoding || 'binary', (err:any) => {

[jcesarmobile]

write is fine now, but read is returning the converted string, not the original base64 written string.
In example, if I write "e", in the file it's written as "hello", and if I read it, I get "hello" too, but I should get "e" as that's what I wrote. On Android and iOS it works like that.
So I think it should be something like this:

Suggested change

	resolve({ data: options.encoding ? data : data.toString('base64') });
	resolve({ data: options.encoding ? data : Buffer.from(data).toString('base64') });

[D34THWINGS]

It bugs me because fs.readFile returns a Buffer to the callback so I shouldn't have wrap it again in a Buffer 🤔

[jcesarmobile]

Looks like it returns a string if you pass 'binary' as encoding, but returns a Buffer if you pass null as encoding. At least that's what I'm getting.

[D34THWINGS]

The trick was to add 'binary' as encoding when using Buffer.from. Works now! But I also saw that the data:application/pdf;base64, is not stripped on web. Should I fix it in this PR? Or should I make another one?

[jcesarmobile]

better a new one

[jcesarmobile]

Added another comment

[jcesarmobile]

I don't see any difference in using Buffer.from(data, 'binary').toString('base64') as you did or Buffer.from(data).toString('base64') as I suggested, both work for me, so I'll merge, thanks!