1 files changed, 132 insertions, 0 deletions
diff --git a/predicate-search-core/src/main/java/com/yahoo/search/predicate/PredicateQueryParser.java b/predicate-search-core/src/main/java/com/yahoo/search/predicate/PredicateQueryParser.java
new file mode 100644
index 00000000000..6f5fac54354
--- /dev/null
+++ b/predicate-search-core/src/main/java/com/yahoo/search/predicate/PredicateQueryParser.java
@@ -0,0 +1,132 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.search.predicate;
+
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonToken;
+import org.apache.commons.lang.ArrayUtils;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * Parses predicate queries from JSON.
+ *
+ * Input JSON is assumed to have the following format:
+ * {
+ *      "features": [
+ *          {"k": "key-name", "v":"value", "s":"0xDEADBEEFDEADBEEF"}
+ *      ],
+ *      "rangeFeatures": [
+ *          {"k": "key-name", "v":42, "s":"0xDEADBEEFDEADBEEF"}
+ *      ]
+ *  }
+ *
+ * @author bjorncs
+ */
+public class PredicateQueryParser {
+    private final JsonFactory factory = new JsonFactory();
+
+    @FunctionalInterface
+    public interface FeatureHandler<V> {
+        void accept(String key, V value, long subqueryBitmap);
+    }
+
+    /**
+     * Parses predicate query from JSON.
+     * @param json JSON input.
+     * @param featureHandler The handler is invoked when a feature is parsed.
+     * @param rangeFeatureHandler The handler is invoked when a range feature is parsed.
+     * @throws IllegalArgumentException If JSON is invalid.
+     */
+    public void parseJsonQuery(
+            String json, FeatureHandler<String> featureHandler, FeatureHandler<Long> rangeFeatureHandler)
+    throws IllegalArgumentException {
+
+        try (JsonParser parser = factory.createParser(json)) {
+            skipToken(parser, JsonToken.START_OBJECT);
+            while (parser.nextToken() != JsonToken.END_OBJECT) {
+                String fieldName = parser.getCurrentName();
+                switch (fieldName) {
+                    case "features":
+                        parseFeatures(parser, JsonParser::getText, featureHandler);
+                        break;
+                    case "rangeFeatures":
+                        parseFeatures(parser, JsonParser::getLongValue, rangeFeatureHandler);
+                        break;
+                    default:
+                        throw new IllegalArgumentException("Invalid field name: " + fieldName);
+                }
+            }
+        } catch (IllegalArgumentException e) {
+            throw e;
+        } catch (IOException e) {
+            throw new AssertionError("This should never happen when parsing from a String", e);
+        } catch (Exception e) {
+            throw new IllegalArgumentException(String.format("Parsing query from JSON failed: '%s'", json), e);
+        }
+    }
+
+    private static <V> void parseFeatures(
+            JsonParser parser, ValueParser<V> valueParser, FeatureHandler<V> featureHandler) throws IOException {
+        skipToken(parser, JsonToken.START_ARRAY);
+        while (parser.nextToken() != JsonToken.END_ARRAY) {
+            parseFeature(parser, valueParser, featureHandler);
+        }
+    }
+
+    private static <V> void parseFeature(
+            JsonParser parser, ValueParser<V> valueParser, FeatureHandler<V> featureHandler) throws IOException {
+        String key = null;
+        V value = null;
+        long subqueryBitmap = SubqueryBitmap.DEFAULT_VALUE; // Specifying subquery bitmap is optional.
+
+        while (parser.nextToken() != JsonToken.END_OBJECT) {
+            String fieldName = parser.getCurrentName();
+            skipToken(parser, JsonToken.VALUE_STRING, JsonToken.VALUE_NUMBER_INT);
+            switch (fieldName) {
+                case "k":
+                    key = parser.getText();
+                    break;
+                case "v":
+                    value = valueParser.parse(parser);
+                    break;
+                case "s":
+                    subqueryBitmap = fromHexString(parser.getText());
+                    break;
+                default:
+                    throw new IllegalArgumentException("Invalid field name: " + fieldName);
+            }
+        }
+        if (key == null) {
+            throw new IllegalArgumentException(
+                    String.format("Feature key is missing! (%s)", parser.getCurrentLocation()));
+        }
+        if (value == null) {
+            throw new IllegalArgumentException(
+                    String.format("Feature value is missing! (%s)", parser.getCurrentLocation()));
+        }
+        featureHandler.accept(key, value, subqueryBitmap);
+    }
+
+    private static void skipToken(JsonParser parser, JsonToken... expected) throws IOException {
+        JsonToken actual = parser.nextToken();
+        if (!ArrayUtils.contains(expected, actual)) {
+            throw new IllegalArgumentException(
+                    String.format("Expected a token in %s, got %s (%s).",
+                            Arrays.toString(expected), actual, parser.getTokenLocation()));
+        }
+    }
+
+    private static long fromHexString(String subqueryBitmap) {
+        if (!subqueryBitmap.startsWith("0x")) {
+            throw new IllegalArgumentException("Not a valid subquery bitmap ('0x' prefix missing): " + subqueryBitmap);
+        }
+        return Long.parseUnsignedLong(subqueryBitmap.substring(2), 16);
+    }
+
+    @FunctionalInterface
+    private interface ValueParser<V> {
+        V parse(JsonParser parser) throws IOException;
+    }
+}