firestore.rules

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read: if
          true 
    }
    
    function userIsLoggedIn(){
      	return request.auth != null
      }
    function isNewResource(){
      return resource == null
    }
    function resourceBelongsToUser(){
      return request.auth.uid == resource.data.userId
    }
    
    //threads
    match /threads/{thread}{
    	function isOnlyAppendingPostAndContributor(){
 	 			return request.resource.data.diff(resource.data).affectedKeys().hasOnly(['posts', 'contributors'])
			}
      allow write: if
      	userIsLoggedIn() && (isNewResource() || resourceBelongsToUser())
      allow update: if
      	isOnlyAppendingPostAndContributor()
    }
    
    //posts
    match /posts/{post}{
      allow write: if
      	userIsLoggedIn() && (isNewResource() || resourceBelongsToUser())
    }
    
    // forums
    match /forums/{forum}{
  		function isOnlyAppendingThread(){
    		return request.resource.data.diff(resource.data).affectedKeys().hasOnly(['threads'])
  		}
  		allow update: if
    		userIsLoggedIn() && isOnlyAppendingThread()
		}
    
    // users
    match /users/{user}{
    	allow create: if
      	true
      allow update: if
      	request.auth.uid == resource.id 
    }
  }
}