public class TenantDetailTriggerHandler() {

public static void addTenant(Map <ID, Tenant_Details__c> newTenMap, Map <ID, Tenant_Details__c> oldTenMap) {


//Within one SOQL, I am not only capturing the tenant records but also each of their associated child objects (room detail records). I assume there is a one to many relationship from tenant to room detail. If I am wrong please inform me.

//This SOQL may give an error since I haven't tested it out. Writing these types of SOQL
//can be tricky but worth it in the end. 
List<Tenant_Details__c> tenantDetailList = [select Contribution__c, Stays_in__c, (SELECT ID, Rent__c, Sharing_Capacity__c, Present_Tenant_Count__c from Room_Detailss__r) from Tenant_Details__c where id in :newTenMap.keyset()];
    
    List<Tenant_Details__c> tenantDetailListToUpdate = new List<Tenant_Details__c>();
    List<Room_Details__c> roomDetailListToUpdate = new List<Room_Details__c>();
    

    for(Tenant_Details__c tenant : tenantDetailList)
    {
      
        //This SOQL is what was causing an error and limiting how many records code be processed
        //I moved this code above the for loop and commented it out
        //Room_Details__c rooms=[select Rent__c, Sharing_Capacity__c, //Present_Tenant_Count__c from Room_Details__c where id = :tenant.Stays_in__c];
        
       for (Room_Details__c oneRoom : tenant.Room_Details__c) {


        //Changed all references of "rooms" to "oneRoom"
        System.debug('Trigger.isInsert');
        System.debug('Previous tenant count:'+oneRoom.Present_Tenant_Count__c);
        if(oneRoom.Present_Tenant_Count__c<oneRoom.Sharing_Capacity__c)
        {
            oneRoom.Present_Tenant_Count__c=oneRoom.Present_Tenant_Count__c+1;//3. updating tenant count 
            
        }
        else
        {
            System.debug('Maximum tenant count reached');

            //Replaced "Trigger.oldMap" with "oldTenMap"
            //After reviewing this again, this may also give an error. The reason is when we pass the room
//id as an argument in the get method, it'll return NullException since the Trigger.oldMap is a map of the //Tenant_Details__c object and not the Room_Details__c object.
//To resolve this, you should replace "oldTenMap.get(oneRoom.Id)" with just "oneRoom" 
            oldTenMap.get(oneRoom.Id).addError('Cannot add tenants to this room.');//4. add error on max capacity
        }
        
        //5. increase rent of each tenant
        System.debug('New tenant count: '+rooms.Present_Tenant_Count__c);
        Double contri = rooms.Rent__c/rooms.Present_Tenant_Count__c;
        tenant.Contribution__c=contri;     
        
        for(Tenant_Details__c allTenants:[select Contribution__c from Tenant_Details__c where Stays_in__c=:tenant.Stays_in__c])
        {
            allTenants.Contribution__c=contri;
            tenantDetailListToUpdate.add(allTenants);
        }
		
        roomDetailListToUpdate.add(rooms);
    }
    update roomDetailListToUpdate;
    update tenantDetailListToUpdate;	
}
}
}

trigger TenantDetailTrigger on Tenant_Details__c (after insert) 
{   
    TenantDetailTriggerHandler.addTenant(Trigger.newMap, Trigger.oldMap);
}