How to update WordPress data from App

/**
* WP-AppKit has no webservice dedicated to data update yet (this is one of the things on our roadmap).
* The now native WP Rest API can be used to achieve that by implementing your own ajax calls to the Rest API 
* that you would call manually from your WP-AppKit app. 
* But if you want to stay within WP-AppKit possibilities, you can use the WP-AppKit's "liveQuery" web service 
* which is designed to retrieve custom content from server but can also work to update data.
*
* The example here shows how to update a post meta from the app, but it can be transposed to update any WordPress data.
* Note: Sent data is not secured here. If you're on https, it's ok. If not, just be aware that the data sent is not encrypted,
* just like when you submit a form on a non https website.
*
* The App.liveQuery() webservice used here is pretty convenient to handle any custom request from app to server. 
* We haven't found time to write doc about it yet but we have hope it will come soon ;)
*/

/**
* First, on app side, here's what could be the function (defined and called in functions.js) 
* that sends our meta_data to the server:
*/

//In theme's functions.js:
//Send meta data to the server using the "liveQuery" webservice:
function sendMyPostMetaData( post_id, meta_data ) {
	
	//Define our custom query, that we will retrieve on server side
	//using the 'wpak_live_query' hook:

	//Query parameters sent to server (can be whatever you want):
	var query_args = {
		my_action: 'update_my_post_meta',
		my_post_id: post_id, //Set your own post id here
		my_meta_data: meta_data
	};

	//Define query options:
	var options = {
		auto_interpret_result: false, //This is to tell WPAK that we're doing our own custom query
		success: function( answer ) { //The meta update webservice call went ok
			if ( answer.my_result.ok === 1 ) {
				//Meta updated ok: 
				console.log( 'Meta updated successfully!', answer.my_result.my_feedback_data );
			} else {
				//Error when updating meta: display error:
				console.log( 'Meta update error: ', answer.my_result.error );
			}
		},
		error: function( error ) {
			//This is if the web service call failed
		}
	};

	//Send our meta update query to the server:
	App.liveQuery( query_args, options );
}


/**
* Then the corresponding PHP code on server side to update post meta data :
* put this in a PHP file in the "php" folder of your theme. If no "php" folder exists, create it. 
* The PHP file can be named whatever you like.
*/

//Catch the liveQuery call made in the app, update the post meta and return 
//some feedback to the app:
add_filter( 'wpak_live_query', 'update_my_meta', 10, 3 );
function update_my_meta( $service_answer, $query_params ) {
	//$query_params contains what was passed in liveQuery's "query_args"
	
	//Check that our 'my_action' action is called:
	if ( isset( $query_params['my_action'] ) && $query_params['my_action'] === 'update_my_post_meta' ) {
		
		//Prepare our custom answer:
		$result = array( 'ok' => 0, 'error' => '', 'my_feedback_data' => '' );
		
		//Check passed post ID and update the post meta if the corresponding post is OK:
		if ( !empty( $query_params['my_post_id'] ) ) {
			
			$post_id = (int)$query_params['my_post_id'];
			
			//Check that the post exists
			$my_post = get_post( $post_id );
			if ( $my_post && $my_post->post_type === 'post' ) {
				
				//Update our meta:
				if ( !empty( $query_params['my_meta_data'] )  ) {
					$my_meta_data = $query_params['my_meta_data']; //Probably do some sanitization on my_meta_data here!
					update_post_meta( $post_id, 'my_post_meta', $my_meta_data );
					
					//If everything went ok, set webservice answer to ok = 1:
					$result['ok'] = 1;
					$result['my_feedback_data'] = 'Everything went well :)';
				} else {
					$result['error'] = 'no-meta-data';
				}
				
			} else {
				$result['error'] = 'post-not-found';
			}
			
		} else {
			$result['error'] = 'no-post-id';
		}
		
		//Add your result to the web service answer:
		$service_answer['my_result'] = $result;
	}
	
	return $service_answer;
}