--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/flys-artifacts/src/main/java/org/dive4elements/river/artifacts/datacage/templating/StackFrames.java	Thu Apr 25 12:06:39 2013 +0200
@@ -0,0 +1,168 @@
+package org.dive4elements.river.artifacts.datacage.templating;
+
+import java.util.ArrayList;
+import java.util.Map;
+import java.util.List;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Set;
+
+import javax.xml.xpath.XPathVariableResolver;
+
+import javax.xml.namespace.QName;
+
+import org.apache.log4j.Logger;
+
+
+/**
+ * Maintains stack of 'frames' which are maps from string to object.
+ * Used for variables in datacage/meta-data system.
+ */
+public class StackFrames
+implements   XPathVariableResolver
+{
+    private static Logger log = Logger.getLogger(StackFrames.class);
+
+    public static final Object NULL = new Object();
+
+    /** The frames (used like a stack). */
+    protected List<Map<String, Object>> frames;
+
+    public StackFrames() {
+        frames = new ArrayList<Map<String, Object>>();
+    }
+
+    public StackFrames(Map<String, Object> initialFrame) {
+        this();
+        if (initialFrame != null) {
+            frames.add(new HashMap<String, Object>(initialFrame));
+        }
+    }
+
+    /** Push a new String->Object map. */
+    public void enter() {
+        frames.add(new HashMap<String, Object>());
+    }
+
+    /** Pop/Remove last String->Object map. */
+    public void leave() {
+        frames.remove(frames.size()-1);
+    }
+
+    /** Put Key/Value in last String->Object map. */
+    public void put(String key, Object value) {
+        int N = frames.size();
+        if (N > 0) {
+            frames.get(N-1).put(key, value);
+        }
+    }
+
+    /** Put multiple Key/Values in last String->Object map. */
+    public void put(String [] keys, Object [] values) {
+        Map<String, Object> top = frames.get(frames.size()-1);
+        for (int i = 0; i < keys.length; ++i) {
+            top.put(keys[i], values[i]);
+        }
+    }
+
+    /** Check last frame (string->object map) for key. */
+    public boolean containsKey(String key) {
+        key = key.toUpperCase();
+        for (int i = frames.size()-1; i >= 0; --i) {
+            if (frames.get(i).containsKey(key)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Get element (variable) key.
+     * Returns null if not found.
+     * @param key name to resolve
+     * @return resolution, null if not found.
+     */
+    public Object get(String key) {
+        return get(key, null);
+    }
+
+    /** result[0] is modified with value when true returned.
+     * @return false if key not found in any frame. */
+    public boolean getStore(String key, Object [] result) {
+
+        key = key.toUpperCase();
+
+        for (int i = frames.size()-1; i >= 0; --i) {
+            Map<String, Object> frame = frames.get(i);
+            if (frame.containsKey(key)) {
+                result[0] = frame.get(key);
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public Object get(String key, Object def) {
+
+        key = key.toUpperCase();
+
+        for (int i = frames.size()-1; i >= 0; --i) {
+            Map<String, Object> frame = frames.get(i);
+            if (frame.containsKey(key)) {
+                return frame.get(key);
+            }
+        }
+
+        return def;
+    }
+
+    public Object getNull(String key) {
+        return getNull(key, null);
+    }
+
+    public Object getNull(String key, Object def) {
+
+        key = key.toUpperCase();
+
+        for (int i = frames.size()-1; i >= 0; --i) {
+            Map<String, Object> frame = frames.get(i);
+            if (frame.containsKey(key)) {
+                Object value = frame.get(key);
+                return value != null ? value : NULL;
+            }
+        }
+
+        return def;
+    }
+
+    @Override
+    public Object resolveVariable(QName variableName) {
+        if (log.isDebugEnabled()) {
+            log.debug("resolve var: " + variableName);
+        }
+
+        return getNull(variableName.getLocalPart());
+    }
+
+    public String dump() {
+        StringBuilder sb = new StringBuilder("[");
+        Set<String> already = new HashSet<String>();
+
+        boolean first = true;
+
+        for (int i = frames.size()-1; i >= 0; --i) {
+            Map<String, Object> frame = frames.get(i);
+            for (Map.Entry<String, Object> entry: frame.entrySet()) {
+                if (already.add(entry.getKey())) {
+                    if (first) { first = false;   }
+                    else       { sb.append(", "); }
+                    sb.append('\'').append(entry.getKey())
+                      .append("'='").append(entry.getValue()).append('\'');
+                }
+            }
+        }
+        return sb.append(']').toString();
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :