ETag middleware

[ebebbington]

Original issue: https://github.com/drashland/deno-drash/issues/17

Ported over here because @crookse decided to make it a middleware instead (which is a good call), because it means it's usuable by users, but doesn't affect drash's performance at all - win win scenario

What

Add a new middleware for supporting the ETag header

Why

• Improves caching = improves request speed
• Will not affect Drash's performance because Drash wouldn't have it built into the source code

How

• File structure would look like:

deno-drash-middleware/
    etag/ <-- etag code here
        tests/
        deps.ts
        some_related_file.ts
        another_related_file.ts
        mod.ts
        README.md
    ...

• Users would import the middleware like:

import { ETag } from "https://deno.land/x/drash-middleware@v{version}/etag/mod.ts"

• Place third-party modules in your middleware directory's deps.ts file (if used)

• Any Deno std module that's required by your package can be exported from the repo's root deps.ts file so that all middleware can import std modules from that single file.

Acceptance Criteria

• README.md file showing how to use the middleware. Drash is a documentation-driven codebase, so the documentation is very important.

• Develop ETag functionality

• Tests

[diveDylan]

@ebebbington got it. ✋

[ebebbington]

@diveDylan Nice one! Be sure to read contributing for more information on tackling issues

[ebebbington]

We're just in the process of updating the contributing documentation, just waiting for drashland/deno-drash-middleware#9 to be closed and it should give more information hoping its helpful :)

[diveDylan]

ye... I have read the doc for coding. It seems has a lot work on compare the cache state fresh or stale before set Etag on the response headers.

[ebebbington]

I think how it would work is:

1. If request has no etag and is a GET (avoid POST, DELETE, PUT due to dynamic data?):
   1.1. set etag with hashed timestamp, request method and url
2. if request etag has expired (using decoded timestamp from the header)
   2.1. 'refresh', and go to point 1.1

Though i am not sure and might. be looking in the wrong direction, the implementation of ETag is confusing to me

[ebebbington]

Heres some resources if it helps:

https://en.wikipedia.org/wiki/HTTP_ETag

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag

If you want to discuss it in more detail then feel free to join our discord

[diveDylan]

@ebebbington i have read all the doc on your list before 😄

[ebebbington]

Just thought it's worth mentioning!:)

[diveDylan]

@ebebbington haha. it is indeed!:)

[ebebbington]

@diveDylan have you made any progress on this?

[diveDylan]

@diveDylan have you made any progress on this?

sorry, i forget this! I will join the discord and read contributing line. It is too late ...