QQQ-21 add safelyGetPage; add stepType

src/main/java/com/kingsrook/qqq/backend/core/actions/RunBackendStepAction.java

@@ -28,6 +28,7 @@ import java.util.List;
 import java.util.Map;
 import com.kingsrook.qqq.backend.core.callbacks.QProcessCallback;
 import com.kingsrook.qqq.backend.core.exceptions.QException;
+import com.kingsrook.qqq.backend.core.exceptions.QUserFacingException;
 import com.kingsrook.qqq.backend.core.interfaces.BackendStep;
 import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepRequest;
 import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepResult;
@@ -128,14 +129,18 @@ public class RunBackendStepAction
          QProcessCallback callback = runBackendStepRequest.getCallback();
          if(callback == null)
          {
-            throw (new QException("Function is missing values for fields, but no callback was present to request fields from a user"));
+            throw (new QUserFacingException("Missing values for one or more fields",
+               new QException("Function is missing values for fields, but no callback was present to request fields from a user")));
          }
 
          Map<String, Serializable> fieldValues = callback.getFieldValues(fieldsToGet);
-         for(Map.Entry<String, Serializable> entry : fieldValues.entrySet())
+         if(fieldValues != null)
          {
-            runBackendStepRequest.addValue(entry.getKey(), entry.getValue());
-            // todo - check to make sure got values back?
+            for(Map.Entry<String, Serializable> entry : fieldValues.entrySet())
+            {
+               runBackendStepRequest.addValue(entry.getKey(), entry.getValue());
+               // todo - check to make sure got values back?
+            }
          }
       }
    }
@@ -164,7 +169,8 @@ public class RunBackendStepAction
             QProcessCallback callback = runBackendStepRequest.getCallback();
             if(callback == null)
             {
-               throw (new QException("Function is missing input records, but no callback was present to get a query filter from a user"));
+               throw (new QUserFacingException("Missing input records.",
+                  new QException("Function is missing input records, but no callback was present to request fields from a user")));
             }
 
             queryRequest.setFilter(callback.getQueryFilter());

src/main/java/com/kingsrook/qqq/backend/core/model/metadata/processes/QBackendStepMetaData.java

@@ -42,6 +42,16 @@ public class QBackendStepMetaData extends QStepMetaData
 
 
 
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   public QBackendStepMetaData()
+   {
+      setStepType("backend");
+   }
+
+
+
    /*******************************************************************************
     ** Setter for label
     **

src/main/java/com/kingsrook/qqq/backend/core/model/metadata/processes/QFrontendStepMetaData.java

@@ -40,6 +40,16 @@ public class QFrontendStepMetaData extends QStepMetaData
 
 
 
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   public QFrontendStepMetaData()
+   {
+      setStepType("frontend");
+   }
+
+
+
    /*******************************************************************************
     ** Getter for formFields
     **

src/main/java/com/kingsrook/qqq/backend/core/model/metadata/processes/QStepMetaData.java

@@ -25,17 +25,21 @@ package com.kingsrook.qqq.backend.core.model.metadata.processes;
 import java.util.ArrayList;
 import java.util.List;
 import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.kingsrook.qqq.backend.core.model.metadata.QFieldMetaData;
+import com.kingsrook.qqq.backend.core.model.metadata.serialization.QStepMetaDataDeserializer;
 
 
 /*******************************************************************************
  ** Meta-Data to define a step in a process in a QQQ instance.
  **
  *******************************************************************************/
+@JsonDeserialize(using = QStepMetaDataDeserializer.class)
 public class QStepMetaData
 {
    private String name;
    private String label;
+   private String stepType;
 
 
 
@@ -127,4 +131,25 @@ public class QStepMetaData
       return (new ArrayList<>());
    }
 
+
+
+   /*******************************************************************************
+    ** Getter for stepType
+    **
+    *******************************************************************************/
+   public String getStepType()
+   {
+      return stepType;
+   }
+
+
+
+   /*******************************************************************************
+    ** Setter for stepType
+    **
+    *******************************************************************************/
+   public void setStepType(String stepType)
+   {
+      this.stepType = stepType;
+   }
 }

src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java

@@ -22,6 +22,7 @@
 package com.kingsrook.qqq.backend.core.utils;
 
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.LinkedList;
@@ -332,4 +333,77 @@ public class CollectionUtils
       return (rs.toString());
    }
 
+
+
+   /*******************************************************************************
+    ** Get a sub-list, safely - i.e., w/o worrying if your indexes are too big.
+    *******************************************************************************/
+   public static <T> List<T> safelyGetPage(List<T> list, Integer skip, Integer limit)
+   {
+      //////////////////////////////////////////////////////////
+      // throw if the user requested a negative skip or limit //
+      //////////////////////////////////////////////////////////
+      if(skip != null && skip < 0)
+      {
+         throw (new IllegalArgumentException("Skip may not be negative (was " + skip + ")"));
+      }
+      if(limit != null && limit < 0)
+      {
+         throw (new IllegalArgumentException("Limit may not be negative (was " + limit + ")"));
+      }
+
+      ///////////////////////////////////
+      // null input list = null output //
+      ///////////////////////////////////
+      if(list == null)
+      {
+         return (null);
+      }
+
+      int startAt;
+      if(skip == null)
+      {
+         ///////////////////////////////////////////
+         // treat null skip is the same as 0 skip //
+         ///////////////////////////////////////////
+         startAt = 0;
+      }
+      else if(skip > list.size())
+      {
+         ////////////////////////////////////////
+         // if skip is too large, return empty //
+         ////////////////////////////////////////
+         return (new ArrayList<>());
+      }
+      else
+      {
+         startAt = skip;
+      }
+
+      int endAt;
+      if(limit == null)
+      {
+         ////////////////////////////////////////////////////////
+         // treat null limit as request for all after the skip //
+         ////////////////////////////////////////////////////////
+         endAt = list.size();
+      }
+      else if(limit == 0)
+      {
+         /////////////////////////////////////////////
+         // treat limit of zero as request for none //
+         /////////////////////////////////////////////
+         return (new ArrayList<>());
+      }
+      else
+      {
+         endAt = startAt + limit;
+         if (endAt > list.size())
+         {
+            endAt = list.size();
+         }
+      }
+
+      return list.subList(startAt, endAt);
+   }
 }