/**
 * Copyright 2005-2016 The Kuali Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
 *
 * 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.kuali.rice.core.api.util.collect;

import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

/**
 * This class implements the Map interface for a Properties instance. Exports all properties from the given Properties instance as
 * constants, usable from jstl. Implements the Map interface (by delegating everything to the PropertyTree, which really implements
 * the Map methods directly) so that jstl can translate ${Constants.a} into a call to ConfigConstants.get( "a" ).
 * <p>
 * The contents of this Map cannot be changed once it has been initialized. Any calls to any of the Map methods made before the
 * propertyTree has been initialized (i.e. before setProperties has been called) will throw an IllegalStateException.
 * <p>
 * Jstl converts ${Constants.a.b.c} into get("a").get("b").get("c"), so the properties are stored in a PropertyTree, which converts
 * the initial set( "a.b.c", "value" ) into construction of the necessary tree structure to support get("a").get("b").get("c").
 * <p>
 * Implicitly relies on the assumption that the JSP will be calling toString() on the result of the final <code>get</code>, since
 * <code>get</code> can only return one type, and that type must be the complex one so that further dereferencing will be
 * possible.
 */
//FIXME: use generics, make class threadsafe
public final class PropertiesMap implements Map {
    private PropertyTree propertyTree;

    /**
     * Creates a propertyTree to store the given properties
     * 
     * @param properties
     */
    public void setProperties(Properties properties) {
        propertyTree = new PropertyTree(properties);
    }

    // delegated methods
    @Override
	public Object get(Object key) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.get(key);
    }

    @Override
	public int size() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.size();
    }

    @Override
	public void clear() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        this.propertyTree.clear();
    }

    @Override
	public boolean isEmpty() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.isEmpty();
    }

    @Override
	public boolean containsKey(Object key) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.containsKey(key);
    }

    @Override
	public boolean containsValue(Object value) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.containsValue(value);
    }

    @Override
	public Collection values() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.values();
    }

    @Override
	public void putAll(Map m) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        this.propertyTree.putAll(m);
    }

    @Override
	public Set entrySet() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.entrySet();
    }

    @Override
	public Set keySet() {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.keySet();
    }

    @Override
	public Object remove(Object key) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.remove(key);
    }

    @Override
	public Object put(Object key, Object value) {
        if (propertyTree == null) {
            throw new IllegalStateException("propertyTree has not been initialized");
        }
        return this.propertyTree.put(key, value);
    }

    /**
     * This class is a Recursive container for single- and multi-level key,value pairs. It relies on the assumption that the consumer
     * (presumably a JSP) will (implicitly) call toString at the end of the chain, which will return the String value of the chain's
     * endpoint.
     *
     * It implements Map because that's how we fool jstl into converting "a.b.c" into get("a").get("b").get("c") instead of
     * getA().getB().getC()
     *
     * Uses LinkedHashMap and LinkedHashSet because iteration order is now important.
     *
     *
     */
    static class PropertyTree implements Map {
        private static final Logger LOG = Logger.getLogger(PropertyTree.class);

        final boolean flat;
        final PropertyTree parent;
        String directValue;
        Map children;

        /**
         * Creates an empty instance with no parent
         */
        public PropertyTree() {
            this(false);
        }

        /**
         * Creates an empty instance with no parent. If flat is true, entrySet and size and the iterators will ignore entries in
         * subtrees.
         */
        public PropertyTree(boolean flat) {
            this.parent = null;
            this.children = new LinkedHashMap();
            this.flat = flat;
        }

        /**
         * Creates an empty instance with the given parent. If flat is true, entrySet and size and the iterators will ignore entries in
         * subtrees.
         */
        private PropertyTree(PropertyTree parent) {
            this.parent = parent;
            this.children = new LinkedHashMap();
            this.flat = parent.flat;
        }

        /**
         * Creates an instance pre-loaded with the given Properties
         *
         * @param properties
         */
        public PropertyTree(Properties properties) {
            this();

            setProperties(properties);
        }

        /**
         * Associates the given key with the given value. If the given key has multiple levels (consists of multiple strings separated
         * by '.'), the property value is stored such that it can be retrieved either directly, by calling get() and passing the entire
         * key; or indirectly, by decomposing the key into its separate levels and calling get() successively on the result of the
         * previous level's get. <br>
         * For example, given <br>
         * <code>
         * PropertyTree tree = new PropertyTree();
         * tree.set( "a.b.c", "something" );
         * </code> the following statements are
         * equivalent ways to retrieve the value: <br>
         * <code>
         * Object one = tree.get( "a.b.c" );
         * </code>
         * <code>
         * Object two = tree.get( "a" ).get( "b" ).get( "c" );
         * </code><br>
         * Note: since I can't have the get method return both a PropertyTree and a String, getting an actual String requires calling
         * toString on the PropertyTree returned by get.
         *
         * @param key
         * @param value
         * @throws IllegalArgumentException if the key is null
         * @throws IllegalArgumentException if the value is null
         */
        public void setProperty(String key, String value) {
            validateKey(key);
            validateValue(value);

            if (parent == null) {
                LOG.debug("setting (k,v) (" + key + "," + value + ")");
            }

            if (StringUtils.contains(key, '.')) {
                String prefix = StringUtils.substringBefore(key, ".");
                String suffix = StringUtils.substringAfter(key, ".");

                PropertyTree node = getChild(prefix);
                node.setProperty(suffix, value);
            }
            else {
                PropertyTree node = getChild(key);
                node.setDirectValue(value);
            }
        }

        /**
         * Inserts all properties from the given Properties instance into this PropertyTree.
         *
         * @param properties
         * @throws IllegalArgumentException if the Properties object is null
         * @throws IllegalArgumentException if a property's key is null
         * @throws IllegalArgumentException if a property's value is null
         */
        public void setProperties(Properties properties) {
            if (properties == null) {
                throw new IllegalArgumentException("invalid (null) Properties object");
            }

            for (Iterator i = properties.entrySet().iterator(); i.hasNext();) {
                Entry e = (Entry) i.next();
                setProperty((String) e.getKey(), (String) e.getValue());
            }
        }

        /**
         * Returns the PropertyTree object with the given key, or null if there is none.
         *
         * @param key
         * @return
         * @throws IllegalArgumentException if the key is null
         */
        private PropertyTree getSubtree(String key) {
            validateKey(key);

            PropertyTree returnValue = null;
            if (StringUtils.contains(key, '.')) {
                String prefix = StringUtils.substringBefore(key, ".");
                String suffix = StringUtils.substringAfter(key, ".");

                PropertyTree child = (PropertyTree) this.children.get(prefix);
                if (child != null) {
                    returnValue = child.getSubtree(suffix);
                }
            }
            else {
                returnValue = (PropertyTree) this.children.get(key);
            }

            return returnValue;
        }


        /**
         * @param key
         * @return the directValue of the PropertyTree associated with the given key, or null if there is none
         */
        public String getProperty(String key) {
            String propertyValue = null;

            PropertyTree subtree = getSubtree(key);
            if (subtree != null) {
                propertyValue = subtree.getDirectValue();
            }

            return propertyValue;
        }


        /**
         * @return an unmodifiable copy of the direct children of this PropertyTree
         */
        public Map getDirectChildren() {
            return Collections.unmodifiableMap(this.children);
        }


        /**
         * Returns the directValue of this PropertyTree, or null if there is none.
         * <p>
         * This is the hack that makes it possible for jstl to get what it needs when trying to retrive the value of a simple key or of
         * a complex (multi-part) key.
         */
        public String toString() {
            return getDirectValue();
        }

        /**
         * Sets the directValue of this PropertyTree to the given value.
         *
         * @param value
         */
        private void setDirectValue(String value) {
            validateValue(value);

            this.directValue = value;
        }

        /**
         * @return directValue of this PropertyTree, or null if there is none
         */
        private String getDirectValue() {
            return this.directValue;
        }

        /**
         * @return true if the directValue of this PropertyTree is not null
         */
        private boolean hasDirectValue() {
            return (this.directValue != null);
        }

        /**
         * @return true if the this PropertyTree has children
         */
        private boolean hasChildren() {
            return (!this.children.isEmpty());
        }

        /**
         * Returns the PropertyTree associated with the given key. If none exists, creates a new PropertyTree associates it with the
         * given key, and returns it.
         *
         * @param key
         * @return PropertyTree associated with the given key
         * @throws IllegalArgumentException if the given key is null
         */
        private PropertyTree getChild(String key) {
            validateKey(key);

            PropertyTree child = (PropertyTree) this.children.get(key);
            if (child == null) {
                child = new PropertyTree(this);
                this.children.put(key, child);
            }

            return child;
        }

        /**
         * @param key
         * @throws IllegalArgumentException if the given key is not a String, or is null
         */
        private void validateKey(Object key) {
            if (!(key instanceof String)) {
                throw new IllegalArgumentException("invalid (non-String) key");
            }
            else if (key == null) {
                throw new IllegalArgumentException("invalid (null) key");
            }
        }

        /**
         * @param value
         * @throws IllegalArgumentException if the given value is not a String, or is null
         */
        private void validateValue(Object value) {
            if (!(value instanceof String)) {
                throw new IllegalArgumentException("invalid (non-String) value");
            }
            else if (value == null) {
                throw new IllegalArgumentException("invalid (null) value");
            }
        }


        // Map methods
        /**
         * Returns an unmodifiable Set containing all key,value pairs in this PropertyTree and its children.
         *
         * @see java.util.Map#entrySet()
         */
        public Set entrySet() {
            return Collections.unmodifiableSet(collectEntries(null, this.flat).entrySet());
        }

        /**
         * Builds a HashMap containing all of the key,value pairs stored in this PropertyTree
         *
         * @return
         */
        private Map collectEntries(String prefix, boolean flattenEntries) {
            LinkedHashMap entryMap = new LinkedHashMap();

            for (Iterator i = this.children.entrySet().iterator(); i.hasNext();) {
                Entry e = (Entry) i.next();
                PropertyTree child = (PropertyTree) e.getValue();
                String childKey = (String) e.getKey();

                // handle children with values
                if (child.hasDirectValue()) {
                    String entryKey = (prefix == null) ? childKey : prefix + "." + childKey;
                    String entryValue = child.getDirectValue();

                    entryMap.put(entryKey, entryValue);
                }

                // handle children with children
                if (!flattenEntries && child.hasChildren()) {
                    String childPrefix = (prefix == null) ? childKey : prefix + "." + childKey;

                    entryMap.putAll(child.collectEntries(childPrefix, flattenEntries));
                }
            }

            return entryMap;
        }

        /**
         * @return the number of keys contained, directly or indirectly, in this PropertyTree
         */
        public int size() {
            return entrySet().size();
        }

        /**
         * @see java.util.Map#isEmpty()
         */
        public boolean isEmpty() {
            return entrySet().isEmpty();
        }

        /**
         * Returns an unmodifiable Collection containing the values of all of the entries of this PropertyTree.
         *
         * @see java.util.Map#values()
         */
        public Collection values() {
            ArrayList values = new ArrayList();

            Set entrySet = entrySet();
            for (Iterator i = entrySet.iterator(); i.hasNext();) {
                Entry e = (Entry) i.next();

                values.add(e.getValue());
            }

            return Collections.unmodifiableList(values);
        }

        /**
         * Returns an unmodifiable Set containing the keys of all of the entries of this PropertyTree.
         *
         * @see java.util.Map#keySet()
         */
        public Set keySet() {
            LinkedHashSet keys = new LinkedHashSet();

            Set entrySet = entrySet();
            for (Iterator i = entrySet.iterator(); i.hasNext();) {
                Entry e = (Entry) i.next();

                keys.add(e.getKey());
            }

            return Collections.unmodifiableSet(keys);
        }

        /**
         * @see java.util.Map#containsKey(Object)
         */
        public boolean containsKey(Object key) {
            validateKey(key);

            boolean containsKey = false;

            Set entrySet = entrySet();
            for (Iterator i = entrySet.iterator(); !containsKey && i.hasNext();) {
                Entry e = (Entry) i.next();

                Object entryKey = e.getKey();
                containsKey = (entryKey != null) && entryKey.equals(key);
            }

            return containsKey;
        }

        /**
         * @see java.util.Map#containsValue(Object)
         */
        public boolean containsValue(Object value) {
            validateValue(value);

            boolean containsValue = false;

            Set entrySet = entrySet();
            for (Iterator i = entrySet.iterator(); !containsValue && i.hasNext();) {
                Entry e = (Entry) i.next();

                Object entryValue = e.getValue();
                containsValue = (entryValue != null) && entryValue.equals(value);
            }

            return containsValue;
        }

        /**
         * Traverses the tree structure until it finds the PropertyTree pointed to by the given key, and returns that PropertyTree
         * instance.
         * <p>
         * Only returns PropertyTree instances; if you want the String value pointed to by a given key, you must call toString() on the
         * returned PropertyTree (after verifying that it isn't null, of course).
         *
         * @see java.util.Map#get(Object)
         */
        public Object get(Object key) {
            validateKey(key);

            return getSubtree((String) key);
        }


        // unsupported operations
        /**
         * Unsupported, since you can't change the contents of a PropertyTree once it has been initialized.
         */
        public void clear() {
            throw new UnsupportedOperationException();
        }

        /**
         * Unsupported, since you can't change the contents of a PropertyTree once it has been initialized.
         */
        public void putAll(Map t) {
            throw new UnsupportedOperationException();
        }

        /**
         * Unsupported, since you can't change the contents of a PropertyTree once it has been initialized.
         */
        public Object remove(Object key) {
            throw new UnsupportedOperationException();
        }

        /**
         * Unsupported, since you can't change the contents of a PropertyTree once it has been initialized.
         */
        public Object put(Object key, Object value) {
            throw new UnsupportedOperationException();
        }
    }
}
