--- a/flys-artifacts/ChangeLog	Fri Jan 27 07:53:03 2012 +0000
+++ b/flys-artifacts/ChangeLog	Fri Jan 27 09:42:15 2012 +0000
@@ -1,3 +1,9 @@
+2012-01-27  Raimund Renkert <raimund.renkert@intevation.de>
+
+	* src/main/java/de/intevation/flys/utils/FLYSUtils.java:
+	  New method that creates and returns the chosen differences of w-difference
+	  calculation as string.
+
 2012-01-27  Raimund Renkert <raimund.renkert@intevation.de>
 
 	Issue 138: PDF output for calculations.

--- a/flys-artifacts/src/main/java/de/intevation/flys/utils/FLYSUtils.java	Fri Jan 27 07:53:03 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/utils/FLYSUtils.java	Fri Jan 27 09:42:15 2012 +0000
@@ -29,9 +29,16 @@
 import de.intevation.flys.artifacts.context.FLYSContext;
 import de.intevation.flys.artifacts.FLYSArtifact;
 import de.intevation.flys.artifacts.WINFOArtifact;
+import de.intevation.flys.artifacts.StaticWKmsArtifact;
 import de.intevation.flys.artifacts.model.RiverFactory;
 import de.intevation.flys.artifacts.model.LocationProvider;
 import de.intevation.flys.artifacts.model.WQ;
+import de.intevation.flys.artifacts.model.WKms;
+import de.intevation.flys.artifacts.model.WQKms;
+
+import de.intevation.artifactdatabase.state.State;
+import de.intevation.flys.artifacts.states.WaterlevelSelectState;
+import de.intevation.flys.artifacts.states.WDifferencesState;
 import de.intevation.flys.model.Gauge;
 import de.intevation.flys.model.MainValue;
 import de.intevation.flys.model.River;
@@ -621,5 +628,93 @@
 
         return LocationProvider.getLocation(river, km);
     }
+
+
+    /**
+     * This method returns the differences for a w-differences calculation.
+     *
+     * @param winfo The WINFOArtifact.
+     * @param context The context.
+     *
+     * @return The differences as string separated by semicolon and linebreak.
+     */
+    public static String getWDifferences(
+        WINFOArtifact winfo,
+        CallContext context)
+    {
+        State state = winfo.getCurrentState(context);
+        if(state instanceof WDifferencesState) {
+            String diffids = winfo.getDataAsString("diffids");
+            String datas[] = diffids.split("#");
+
+            // Validate the Data-Strings.
+            for (String s: datas) {
+                if (!WaterlevelSelectState.isValueValid(winfo.getDataAsString("diffids"))) {
+                    return "";
+                }
+            }
+
+            if (datas.length < 2) {
+                return "";
+            }
+
+            String diffs = "";
+            for(int i = 0; i < datas.length; i+=2) {
+                // e.g.:
+                // 42537f1e-3522-42ef-8968-635b03d8e9c6;longitudinal_section.w;1
+                WKms minuendWKms = getWKms(StringUtil.unbracket(datas[i+0]),
+                    context);
+                WKms subtrahendWKms = getWKms(StringUtil.unbracket(datas[i+1]),
+                    context);
+                if (minuendWKms != null && subtrahendWKms != null) {
+                    diffs += StringUtil.wWrap(minuendWKms.getName()) 
+                        + " - " + StringUtil.wWrap(subtrahendWKms.getName());
+                }
+                diffs += ";\n";
+            }
+            return diffs;
+        }
+        else {
+            logger.warn("Not a valid state for differences.");
+            return "";
+        }
+    }
+
+
+    protected static WKms getWKms(String mingle, CallContext context) {
+        String[] def  = mingle.split(";");
+        String   uuid = def[0];
+        String   name = def[1];
+        int      idx  = Integer.parseInt(def[2]);
+
+        if (name.startsWith("staticwkms")) {
+            StaticWKmsArtifact staticWKms =
+                (StaticWKmsArtifact) FLYSUtils.getArtifact(
+                    uuid,
+                    context);
+            WKms wkms = staticWKms.getWKms(idx);
+            if (wkms == null)
+                logger.error("No WKms from artifact.");
+            return wkms;
+        }
+
+        WINFOArtifact flys = (WINFOArtifact) FLYSUtils.getArtifact(
+            uuid,
+            context);
+
+        if (flys == null) {
+            logger.warn("One of the artifacts (1) for diff calculation could not be loaded");
+            return null;
+        }
+        else{
+            WQKms[] wqkms = (WQKms[]) flys.getWaterlevelData().
+                                              getData();
+            if (wqkms == null)
+            logger.warn("not  waterlevels in artifact");
+            else if (wqkms.length < idx)
+            logger.warn("not enough waterlevels in artifact");
+            return wqkms[idx];
+        }
+    }
 }
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