New SchemaWalker, KeywordWalker

The general idea seems to be there.

Based on the code of SyntaxProcessor and SyntaxChecker. Both of these already
have all the logic to correctly walk schemas, and only schemas. Now all that is
needed is a more generic implementation.

Spawned from the discussion in issue #41.

Signed-off-by: Francis Galiegue <[email protected]>

Author: fge

src/main/java/com/github/fge/jsonschema/processors/walk/KeywordWalker.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2013, Francis Galiegue <[email protected]>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the Lesser GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * Lesser GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.github.fge.jsonschema.processors.walk;
+
+import com.github.fge.jsonschema.exceptions.ProcessingException;
+import com.github.fge.jsonschema.jsonpointer.JsonPointer;
+import com.github.fge.jsonschema.report.ProcessingReport;
+import com.github.fge.jsonschema.tree.SchemaTree;
+
+import java.util.Collection;
+
+public interface KeywordWalker
+{
+    void walk(final Collection<JsonPointer> pointers,
+        final ProcessingReport report, final SchemaTree tree)
+        throws ProcessingException;
+}

src/main/java/com/github/fge/jsonschema/processors/walk/SchemaWalker.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2013, Francis Galiegue <[email protected]>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the Lesser GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * Lesser GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.github.fge.jsonschema.processors.walk;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.fge.jsonschema.exceptions.ProcessingException;
+import com.github.fge.jsonschema.jsonpointer.JsonPointer;
+import com.github.fge.jsonschema.library.Dictionary;
+import com.github.fge.jsonschema.processing.Processor;
+import com.github.fge.jsonschema.processors.data.SchemaHolder;
+import com.github.fge.jsonschema.report.ProcessingMessage;
+import com.github.fge.jsonschema.report.ProcessingReport;
+import com.github.fge.jsonschema.tree.SchemaTree;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Ordering;
+import com.google.common.collect.Sets;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static com.github.fge.jsonschema.messages.SyntaxMessages.*;
+
+/*
+ * NOTE NOTE NOTE: the schema MUST be valid at this point
+ */
+public final class SchemaWalker
+    implements Processor<SchemaHolder, SchemaHolder>
+{
+    private final Map<String, KeywordWalker> walkers;
+
+    public SchemaWalker(final Dictionary<KeywordWalker> dict)
+    {
+        walkers = dict.entries();
+    }
+
+    @Override
+    public SchemaHolder process(final ProcessingReport report,
+        final SchemaHolder input)
+        throws ProcessingException
+    {
+        walk(report, input.getValue());
+        return input;
+    }
+
+    private void walk(final ProcessingReport report, final SchemaTree tree)
+        throws ProcessingException
+    {
+        final JsonNode node = tree.getNode();
+
+        /*
+         * Grab all walkers and object member names. Retain walkers only for
+         * registered keywords, and remove from the member names set what is in
+         * the walkers' key set: if non empty, some walkers are missing (on
+         * purpose or not), report them.
+         */
+        final Map<String, KeywordWalker> map = Maps.newTreeMap();
+        map.putAll(walkers);
+
+        final Set<String> fieldNames = Sets.newHashSet(node.fieldNames());
+        map.keySet().retainAll(fieldNames);
+        fieldNames.removeAll(map.keySet());
+
+        if (!fieldNames.isEmpty())
+            report.warn(newMsg(tree).message(UNKNOWN_KEYWORDS)
+                .put("ignored", Ordering.natural().sortedCopy(fieldNames)));
+
+        /*
+         * Now, walk each keyword, and collect pointers for further processing.
+         */
+        final List<JsonPointer> pointers = Lists.newArrayList();
+        for (final KeywordWalker walker: map.values())
+            walker.walk(pointers, report, tree);
+
+        /*
+         * Operate on these pointers.
+         */
+        for (final JsonPointer pointer: pointers)
+            walk(report, tree.append(pointer));
+    }
+
+    private static ProcessingMessage newMsg(final SchemaTree tree)
+    {
+        return new ProcessingMessage().put("schema", tree);
+    }
+
+    @Override
+    public String toString()
+    {
+        return "schema waler";
+    }
+}