1 files changed, 70 insertions, 0 deletions

diff --git a/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java b/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java
new file mode 100644
index 0000000..937c2c4
--- /dev/null
+++ b/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java
@@ -0,0 +1,70 @@
+package uk.ac.ox.cs.pagoda.util;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.LinkedList;
+
+public class ConjunctiveQueryHelper {
+        
+        public static String[][] getAnswerVariables(String queryText) {
+                Collection<String> disVars = new LinkedList<String>(), undisVars = new LinkedList<String>(); 
+                for (String var: getAllVariables(queryText))
+                        if (var.startsWith("?")) disVars.add(var.substring(1)); 
+                        else undisVars.add(var.substring(2));
+                
+                String[] distinguishedVariables = disVars.toArray(new String[0]); 
+                String[] undistinguishedVariables = undisVars.toArray(new String[0]); 
+                String[] answerVariables = null;
+                
+                String uppercase = queryText.toUpperCase(); 
+                int selectIndex = uppercase.indexOf("SELECT");
+                int whereIndex = uppercase.indexOf("WHERE"); 
+                String selectClause = queryText.substring(selectIndex + 6, whereIndex); 
+                if (selectClause.contains("*")) answerVariables = distinguishedVariables;
+                else {
+                        String[] terms = selectClause.split(" ");
+                        int num = 0; 
+                        for (int i = 0; i < terms.length; ++i)
+                                if (terms[i].startsWith("?")) ++num;
+                        answerVariables = new String[num]; 
+                        for (int i = 0, j = 0; i < terms.length; ++i)
+                                if (terms[i].startsWith("?"))
+                                        answerVariables[j++] = terms[i].substring(1);
+                }
+        
+                if (answerVariables != distinguishedVariables) {
+                        int index = 0; 
+                        for (; index < answerVariables.length; ++index) {
+                                distinguishedVariables[index] = answerVariables[index]; 
+                                disVars.remove(answerVariables[index]); 
+                        }
+                        for (String var: disVars)
+                                distinguishedVariables[index++] = var; 
+                }
+                
+                return new String[][] { answerVariables, distinguishedVariables, undistinguishedVariables };
+        }
+
+        private static Collection<String> getAllVariables(String queryText) {
+                Collection<String> vars = new HashSet<String>(); 
+                int start, end = 0; 
+                char ch; 
+                while ((start = queryText.indexOf("?", end)) != -1) {
+                        end = start + 1; 
+                        while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ') 
+                                ++end;
+                        vars.add(queryText.substring(start, end + 1)); 
+                }
+                
+                end = 0; 
+                while ((start = queryText.indexOf("_:", end)) != -1) {
+                        end = start + 1; 
+                        while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ') 
+                                ++end;
+                        vars.add(queryText.substring(start, end + 1)); 
+                }
+
+                return vars; 
+        }
+
+}