1 files changed, 100 insertions, 0 deletions
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingExpression.java b/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingExpression.java
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+++ b/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingExpression.java
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+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.search.grouping.request;
+
+import com.yahoo.javacc.UnicodeUtilities;
+
+import java.util.List;
+
+/**
+ * This class represents an expression in a {@link GroupingOperation}. You may manually construct this expression, or
+ * you may use the {@link com.yahoo.search.grouping.request.parser.GroupingParser} to generate one from a query-string.
+ *
+ * @author <a href="mailto:simon@yahoo-inc.com">Simon Thoresen</a>
+ */
+public abstract class GroupingExpression extends GroupingNode {
+
+    private Integer level = null;
+
+    protected GroupingExpression(String image) {
+        super(image);
+    }
+
+    /**
+     * Resolves the conceptual level of this expression. This level represents the type of data that is consumed by this
+     * expression, where level 0 is a single hit, level 1 is a group, level 2 is a list of groups, and so forth. This
+     * method verifies the input level against the expression type, and recursively resolves the level of all argument
+     * expressions.
+     *
+     * @param level The level of the input data.
+     * @throws IllegalArgumentException Thrown if the level of this expression could not be resolved.
+     * @throws IllegalStateException    Thrown if type failed to accept the number of arguments provided.
+     */
+    public void resolveLevel(int level) {
+        if (level < 0) {
+            throw new IllegalArgumentException("Expression '" + this + "' recurses through a single hit.");
+        }
+        this.level = level;
+    }
+
+    /**
+     * Returns the conceptual level of this expression.
+     *
+     * @return The level.
+     * @throws IllegalArgumentException Thrown if the level of this expression has not been resolved.
+     * @see #resolveLevel(int)
+     */
+    public int getLevel() {
+        if (level == null) {
+            throw new IllegalStateException("Level for expression '" + this + "' has not been resolved.");
+        }
+        return level;
+    }
+
+    /**
+     * Recursively calls {@link ExpressionVisitor#visitExpression(GroupingExpression)} for this expression and all of
+     * its argument expressions.
+     *
+     * @param visitor The visitor to call.
+     */
+    public void visit(ExpressionVisitor visitor) {
+        visitor.visitExpression(this);
+    }
+
+    /**
+     * Returns a string description of the given list of expressions. This is a comma-separated list of the expressions
+     * own {@link GroupingExpression#toString()} output.
+     *
+     * @param lst The list of expressions to output.
+     * @return The string description.
+     */
+    public static String asString(List<GroupingExpression> lst) {
+        StringBuilder ret = new StringBuilder();
+        for (int i = 0, len = lst.size(); i < len; ++i) {
+            ret.append(lst.get(i));
+            if (i < len - 1) {
+                ret.append(", ");
+            }
+        }
+        return ret.toString();
+    }
+
+    /**
+     * Returns a string representation of an object that can be used in the 'image' constructor argument of {@link
+     * GroupingNode}. This method ensures that strings are quoted, and that all complex characters are escaped.
+     *
+     * @param obj The object to output.
+     * @return The string representation.
+     */
+    public static String asImage(Object obj) {
+        if (!(obj instanceof String)) {
+            return obj.toString();
+        }
+        return UnicodeUtilities.quote((String)obj, '"');
+    }
+
+    @Override
+    public GroupingExpression setLabel(String label) {
+        super.setLabel(label);
+        return this;
+    }
+}