Add support for content negotiation #28

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1. kovshenin commented on Mar 13, 2023

   

   kovshenin

   on Mar 13, 2023

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   Hi @ocean90, thanks for your comment!

   Unfortunately the Accept header isn't a great one to vary on as there is too much difference between different browsers, and even browser versions. For example for this issue page on GitHub in Chrome I get:

   Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
   

   And in Safari I get:

   Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
   

   This kind of variance will kill cache efficiency, so blindly varying on this header is not a great idea.

   What you can do for ActivityPub is normalize and filter the header, and set a specific variant flag with a custom cache config. For example:

   // Do some string manipulation with $_SERVER['HTTP_ACCEPT']
   $config['variants']['activity-pub'] = $result_from_manipulation;
   return $config;
   

   I know some users do this to detect requests from smartphones based on the User-Agent header, which is also not a great one to vary on, without converting it to a less variable 1/0 or mobile/desktop value.

   If you're looking for more information about custom cache configuration, my friend @roytanck published a post a while ago: https://roytanck.com/2022/01/13/tweaking-surge-by-adding-a-configuration-file/

   Hope that helps!
2. ocean90 commented on Mar 13, 2023

   

   ocean90

   on Mar 13, 2023

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   Thanks for the quick feedback. I was aware of the custom configuration file but wasn't sure if variants is what I was looking for. I'll give this a try!

   👍React with 👍1Reacted by Konstantin Kovshenin
3. ocean90 commented on Mar 14, 2023

   

   ocean90

   on Mar 14, 2023

   Last edited by ocean90

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   Got it working with the following config for variants:

   // Content negotiation.
   $representation = 'generic'; // Or just 'html'.
   if ( isset( $_SERVER['HTTP_ACCEPT'] ) ) {
   	$accept = strtolower( $_SERVER['HTTP_ACCEPT'] );
   
   	if ( str_contains( $accept, 'text/html' ) ) {
   		$representation = 'html';
   	} elseif (
   		// Based on https://github.com/pfefferle/wordpress-activitypub/blob/abef17b9ad5d8e346aca92008e3b2b13aaa4ebf4/includes/class-activitypub.php#L67-L84.
   		str_contains( $accept, 'application/json' ) ||
   		str_contains( $accept, 'application/activity+json' ) ||
   		str_contains( $accept, 'application/ld+json' )
   	) {
   		$representation = 'json';
   	}
   }
   $config['variants']['representation'] = $representation;
   unset( $accept, $representation );
   
   return $config;

   Thanks again!
4. ocean90

   closed this as completedon Mar 14, 2023
5. kovshenin commented on Mar 15, 2023

   

   kovshenin

   on Mar 15, 2023

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   Nice, thanks for sharing @ocean90! Also IIRC you have to return $config as it's passed on to a variable which is then merged with the main config:

   surge/include/common.php

   Lines 53 to 56 in b0f2a2d

   	// Run a custom configuration file.
   	if ( defined( 'WP_CACHE_CONFIG' ) ) {
   	$_config = ( function( $config ) {
   	$_config = (array) include( WP_CACHE_CONFIG );
6. ocean90 commented on Mar 15, 2023

   

   ocean90

   on Mar 15, 2023

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   Right, I already had that in my config. Updated above in case anyone wants to copy it as is.

   🎉React with 🎉2Reacted by Konstantin Kovshenin and Matthias Pfefferle