Adding an initial API for the DomTree data structure.

Change-Id: I55da78c11f49c1e5843cfefbe0a5eed02c59498b

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.primitives;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.Sets;
+import org.onosproject.store.service.DocumentPath;
+
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.Objects;
+import java.util.TreeSet;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A tree node made for {@code DocumentTree}
+ * implementations that keeps records of its parent and children.
+ */
+public class DocumentTreeNode<V> {
+    private final DocumentPath key;
+    private V value;
+    private final TreeSet<DocumentTreeNode<V>> children =
+            Sets.newTreeSet(new Comparator<DocumentTreeNode<V>>() {
+                @Override
+                public int compare(DocumentTreeNode<V> o1,
+                                   DocumentTreeNode<V> o2) {
+                    return o1.getKey().compareTo(o2.getKey());
+                }
+            });
+    private DocumentTreeNode parent;
+
+    public DocumentTreeNode(DocumentPath key, V value,
+                            DocumentTreeNode parent) {
+        this.key = checkNotNull(key);
+        this.value = checkNotNull(value);
+        this.parent = parent;
+    }
+
+    /**
+     * Returns this objects key.
+     *
+     * @return the key
+     */
+    public DocumentPath getKey() {
+        return key;
+    }
+
+    /**
+     * Returns this objects value.
+     *
+     * @return the value
+     */
+    public V getValue() {
+        return value;
+    }
+
+    /**
+     * Sets this objects value.
+     *
+     * @param value the value to be set
+     */
+    public void setValue(V value) {
+        this.value = value;
+    }
+
+    /**
+     * Returns a collection of the children of this node.
+     *
+     * @return a sorted iterator for the children of this node.
+     */
+    public Iterator<DocumentTreeNode<V>> getChildren() {
+        return children.iterator();
+    }
+
+    /**
+     * Adds a child to this node.
+     *
+     * @param child the child node to be added
+     * @return true if the child set was modified as a result of this call,
+     * false otherwise
+     */
+    public boolean addChild(DocumentTreeNode<V> child) {
+        return children.add(child);
+    }
+
+    /**
+     * Removes a child from the children of this node.
+     *
+     * @param child the child node to be removed
+     * @return true if the child set was modified as a result of this call,
+     * false otherwise
+     */
+    public boolean removeChild(String child) {
+        return children.remove(child);
+    }
+
+    /**
+     * Returns the parent of this node.
+     *
+     * @return the parent node of this node, which may be null
+     */
+    public DocumentTreeNode<V> getParent() {
+        return parent;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(this.key);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof DocumentTreeNode) {
+            DocumentTreeNode that = (DocumentTreeNode) obj;
+            if (this.parent.equals(that.parent)) {
+                if (this.children.size() == that.children.size()) {
+                    for (DocumentTreeNode child : this.children) {
+                        if (!that.children.contains(child)) {
+                            return false;
+                        }
+                    }
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        MoreObjects.ToStringHelper helper =
+                MoreObjects.toStringHelper(getClass())
+                .add("parent", this.parent)
+                .add("key", this.key)
+                .add("value", this.value);
+        for (DocumentTreeNode child : children) {
+            helper = helper.add("child", child.key);
+        }
+        return helper.toString();
+    }
+
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+/**
+ * Exceptions for use by the {@code DocumentTree} and {@code DocumentPath}.
+ */
+public class DocumentException extends RuntimeException {
+    public DocumentException() {
+        super();
+    }
+
+    public DocumentException(String message) {
+        super(message);
+    }
+
+    public DocumentException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public DocumentException(Throwable cause) {
+        super(cause);
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * A path class for identifying nodes within the {@code DocumentTree}.
+ *
+ * Note: indexing is ONE based so the root is the 1st level, to retrieve the
+ * root one should query level 1.
+ */
+public class DocumentPath implements Comparable {
+
+    private final ArrayList<String> tokens = Lists.newArrayList();
+
+    /**
+     * Private utility constructor for internal generation of partial paths only.
+     *
+     * @param path
+     */
+    private DocumentPath(List<String> path) {
+        Preconditions.checkNotNull(path);
+        this.tokens.addAll(path);
+    }
+
+    /**
+     * Constructor to generate new {@DocumentPath}, new paths must contain at
+     * least one name and string names may NOT contain any '.'s. If one field
+     * is null that field will be ignored.
+     *
+     * @throws IllegalDocumentNameException if both parameters are null or the string
+     * name contains an illegal character ('.')
+     * @param nodeName the name of the last level of this path
+     * @param parentPath the path representing the parents leading up to this
+     *                   node, in the case of the root this should be null
+     */
+    public DocumentPath(String nodeName, DocumentPath parentPath) {
+        if (nodeName.contains(".")) {
+            throw new IllegalDocumentNameException(
+                    "Periods are not allowed in names.");
+        }
+        if (parentPath != null) {
+            tokens.addAll(parentPath.path());
+        }
+        if (nodeName != null) {
+            tokens.add(nodeName);
+        }
+        if (tokens.isEmpty()) {
+            throw new IllegalDocumentNameException("A document path must contain at" +
+                                                   "least one non-null" +
+                                                   "element.");
+        }
+    }
+
+    /**
+     * Returns a path from the root to the parent of this node, if this node is
+     * the root this call returns null.
+     *
+     * @return a {@code DocumentPath} representing a path to this paths parent,
+     * null if this a root path
+     */
+    public DocumentPath parent() {
+        if (tokens.size() <= 1) {
+            return null;
+        }
+        return new DocumentPath(this.tokens.subList(0, tokens.size() - 1));
+    }
+
+    /**
+     * Returns the complete list of tokens representing this path in correct
+     * order.
+     *
+     * @return a list of strings representing this path
+     */
+    public List<String> path() {
+        return ImmutableList.copyOf(tokens);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(tokens);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof DocumentPath) {
+            DocumentPath that = (DocumentPath) obj;
+            return this.tokens.equals(that.tokens);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder stringBuilder = new StringBuilder();
+        Iterator<String> iter = tokens.iterator();
+        while (iter.hasNext()) {
+            stringBuilder.append(iter.next());
+            if (iter.hasNext()) {
+                stringBuilder.append(".");
+            }
+        }
+        return stringBuilder.toString();
+    }
+
+    @Override
+    public int compareTo(Object o) {
+        if (o instanceof DocumentPath) {
+            DocumentPath that = (DocumentPath) o;
+            int shorterLength = this.tokens.size() > that.tokens.size() ?
+                    that.tokens.size() : this.tokens.size();
+            for (int i = 0; i < shorterLength; i++) {
+                if (this.tokens.get(i).compareTo(that.tokens.get(i)) != 0) {
+                    return this.tokens.get(i).compareTo(that.tokens.get(i));
+                }
+            }
+
+            if (this.tokens.size() > that.tokens.size()) {
+                return 1;
+            } else if (that.tokens.size() > this.tokens.size()) {
+                return -1;
+            } else {
+                return 0;
+            }
+        }
+        throw new IllegalArgumentException("Compare can only compare objects" +
+                                                   "of the same type.");
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+import org.onosproject.store.primitives.DocumentTreeNode;
+
+import java.util.Iterator;
+
+/**
+ * Interface for a tree with structure wherein keys hold information
+ * about the hierarchical structure of the tree (name of parent,
+ * grandparent etc.).
+ */
+public interface DocumentTree<V> {
+
+    /**
+     * Returns the root of the tree. This will be the first part of any fully
+     * qualified path and will enable discovery of the entire tree.
+     *
+     * @return a string that is the name of the root of the tree.
+     */
+    DocumentPath root();
+
+    /**
+     * Returns a sorted list containing all key value pairs that are direct
+     * descendants of the supplied parent. The returned list will be immutable.
+     * If the specified parent does not exist this method will fail with an
+     * exception.
+     *
+     * @throws NoSuchDocumentPathException if the parent does not exist
+     * @param parentPath the path to the parent of the desired nodes
+     * @return an iterator of the children of the specified parent
+     */
+    Iterator<DocumentTreeNode<V>> getChildren(DocumentPath parentPath);
+
+    /**
+     * Returns the value associated with the supplied key or null if no such
+     * node exists.
+     *
+     * @param key the key to query
+     * @return a value or null
+     */
+    DocumentTreeNode<V> getNode(DocumentPath key);
+
+    /**
+     * Takes a string that specifies the complete path to the mapping to be
+     * added or updated and creates the key value mapping or updates the value.
+     * If the specified parent cannot be found the operation fails with an
+     * error.
+     *
+     * @throws NoSuchDocumentPathException if the specified parent does not
+     * exist.
+     * @param key the fully qualified key of the entry to be added or updated
+     * @param value the non-null value to be associated with the key
+     * @return the previous mapping or null if there was no previous mapping
+     */
+    V putNode(DocumentPath key, V value);
+
+    /**
+     * Takes the fully qualified  name of the node to be added along with
+     * the value to be added. If the specified key already exists it doesnot
+     * update anything & returns false. If the parent does not exist the
+     * operation fails with an exception.
+     *
+     * @throws NoSuchDocumentPathException if the specified parent does not
+     * exist.
+     * @param key the fully qualified key of the entry to be added or updated
+     * @param value the non-null value to be associated with the key
+     * @return returns true if the mapping could be added successfully
+     */
+    boolean createNode(DocumentPath key, V value);
+
+    /**
+     * Removes the node with the specified fully qualified key. Returns null if
+     * the node did not exist. This method will throw an exception if called on
+     * a non-leaf node.
+     *
+     * @throws IllegalDocumentModificationException if the node had children.
+     * @param key the fully qualified key of the node to be removed
+     * @return the previous value of the node or null if it did not exist
+     */
+    V removeNode(DocumentPath key);
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+/**
+ * An exception to be thrown when a node cannot be removed normally because
+ * it does not exist or because it is not a leaf node.
+ */
+public class IllegalDocumentModificationException extends DocumentException {
+    public IllegalDocumentModificationException() {
+    }
+
+    public IllegalDocumentModificationException(String message) {
+        super(message);
+    }
+
+    public IllegalDocumentModificationException(String message,
+                                                Throwable cause) {
+        super(message, cause);
+    }
+
+    public IllegalDocumentModificationException(Throwable cause) {
+        super(cause);
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+/**
+ * An exception thrown when an illegally named node is submitted.
+ */
+public class IllegalDocumentNameException extends DocumentException {
+    public IllegalDocumentNameException() {
+    }
+
+    public IllegalDocumentNameException(String message) {
+        super(message);
+    }
+
+    public IllegalDocumentNameException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public IllegalDocumentNameException(Throwable cause) {
+        super(cause);
+    }
+}
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.service;
+
+/**
+ * An exception to be thrown when an invalid path is passed to the
+ * {@code DocumentTree}.
+ */
+public class NoSuchDocumentPathException extends DocumentException {
+    public NoSuchDocumentPathException() {
+    }
+
+    public NoSuchDocumentPathException(String message) {
+        super(message);
+    }
+
+    public NoSuchDocumentPathException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public NoSuchDocumentPathException(Throwable cause) {
+        super(cause);
+    }
+}