【RFC】add metadata to FileBox

[windmemory]

Hi @zixia ,

I am working on sending voice message to other people in wechaty, and I realized that the voice length has to be passed when we send out voice message. And this information is pretty hard to be retrieved from the data, so I think it makes sense to add a metadata field in FileBox so for voice message that I received, I can persist the voice length in the metadata, then when use the FileBox voice file to send message, I can retrieve it from the FileBox object itself.

Currently I observed that there is a mimeType field in FileBox, and it is used only for url related FileBox object, I can possibly save the voice length inside that, or put it into the file name, but that is all work around, not elegant solutions. So I think the metadata field will be the final solution to my problem.

Please let me know your thought.

[huan]

It's a reasonable request, and it should be considering all the possible file box types.

I'll think about it and reply to you later. Before we have a metadata for FileBox, please keep using your workaround(which I feel it will work great).

[huan]

Do you have any idea about how the new metadata() method should be designed, especially in your use case?

If you have any, a PR is welcome to demonstrate what you need, and we can go on discussing about it based on your PR.

[windmemory]

Actually for my use case, I just need a key-value pair in side the metadata field. Like:

const f: FileBox = magicMethodGetMeOneFileBoxObject()
f.metadata.voiceLength = 9129392

So it could just be an Object for my use case. But you can make it more sophisticate to serve more file type.

[huan]

You should get your metadata property with wechaty@0.19.117 (which will require the file-box@0.8.23)

[windmemory]

That was blazing fast for adding features :)

I had some additional thoughts about this feature, I came up with this idea when I was laying on bed last night, so sorry for late statement of this idea.

It would be better to have metadata that added by the original creator of the object, and can not be modified afterwards, so it would carry the most reliable information with it, since it was added by the owner of the object. For my case, I would like to add the voiceLength to the metadata and don't want people to modify that value, so I think this feature is valuable to me. And I can imagine other use cases that people who created the object want to keep some information with the object.

I think we can pass an Metadata object in the constructor, and the object passed in can not be modified, example code below:

const meta = { zelda: 'breath of the wind' }
const f = FileBox.fromBase64(data, meta)

// When try to modify the data
f.metadata.zelda = 'game over'
// Expect an error thrown out

Probably we can use deep-froze on the Metadata object or do a recursively Object.freeze() on the Metadata.

What do you think about this?

[huan]

It's fast because this feature makes sense for the use cases.

I feel it's enough to use just Object.freeze() instead of doing a recursively because it will be too expensive.

Should be ready for use with the code from the latest master branch. (v0.8.24 or above)

[huan]

Could you please help me to add a documentation entry in README for the new metadata usage?

[windmemory]

PRed: #4

Please revise the PR if you see anything improper, I am closing this issue since the feature is implemented.