/**
 * 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.krms.api.engine;

import java.io.Serializable;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;

import org.springframework.util.CollectionUtils;

/**
 * Identifies a (hopefully) resolvable {@link Term}.  For resolution in the {@link TermResolutionEngine}, The
 * appropriate {@link TermResolver} will be selected by matching the name and parameters of the {@link Term} with
 * the output and parameter names of the {@link TermResolver}. 
 *
 * @author Kuali Rice Team (rice.collab@kuali.org)
 */
public final class Term implements Comparable<Term> {

        private final String name;
        
        private final Map<String, String> parameters;
        
        private static final TreeMapComparator<String,String> treeMapComparator = new TreeMapComparator<String, String>();

    /**
     * Constructor
     * @param name of the term
     */
        public Term(String name) {
                this(name, null);
        }       
        
        /**
         * This constructs a Term, which is a named piece of data that is usually obtainable
         * through the {@link TermResolutionEngine}
         *
     * @param name the term name
     * @param parameters an optional map of properties that may be used to allow a single TermResolver to resolve multiple Terms
     */
        public Term(String name, Map<String, String> parameters) {
                this.name = name;
                if (parameters == null) {
                        this.parameters = Collections.emptyMap();
                } else {
                        // using TreeMap for ordered iteration since we're comparable
                        this.parameters = Collections.unmodifiableMap(new TreeMap<String, String>(parameters));
                }
        }

    /**
     * Return the name of the term
     * @return name of the term
     */
        public String getName() { return this.name; }
        public Map<String, String> getProperties() { return parameters; }

        /* (non-Javadoc)
         * @see java.lang.Object#hashCode()
         */
        @Override
        public int hashCode() {
                final int prime = 31;
                int result = 1;
                result = prime * result + ((name == null) ? 0 : name.hashCode());
                result = prime * result + ((parameters == null) ? 0 : parameters.hashCode());
                return result;
        }

        /* (non-Javadoc)
         * @see java.lang.Object#equals(java.lang.Object)
         */
        @Override
        public boolean equals(Object obj) {
                if (this == obj)
                        return true;
                if (obj == null)
                        return false;
                if (getClass() != obj.getClass())
                        return false;
                Term other = (Term) obj;
                return this.compareTo(other) == 0;
        }

        @Override
        public int compareTo(Term o) {
                if (o == null) return 1;
                if (this == o) return 0;
                return (treeMapComparator.compare(this.parameters, o.parameters));
        }
        
        /**
     * Return an unmodifiable Map of parameters specified on this Term.
         * @return an unmodifiable Map of parameters specified on this Term.  Guaranteed non-null.
         */
        public Map<String, String> getParameters() {
                return Collections.unmodifiableMap(parameters);
        }

        @Override
        public String toString() {
                // TODO make this pretty
                StringBuilder sb = new StringBuilder();
                if (parameters != null) for (Entry<String,String> parameter : parameters.entrySet()) {
                        sb.append(", ");
                        sb.append(parameter.getKey());
                        sb.append("=");
                        sb.append(parameter.getValue());
                }
                return getClass().getSimpleName()+"(["+ name + "]" +  sb.toString() + ")";
        }

        @SuppressWarnings("rawtypes")
        private static class TreeMapComparator<T extends Comparable, V extends Comparable> implements Comparator<Map<T,V>>, Serializable {
                
                private static final long serialVersionUID = 1L;

                /**
                 * This overridden method compares two {@link TreeMap}s whose keys and elements are both {@link Comparable}
                 * 
                 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
                 */
                @SuppressWarnings("unchecked")
        @Override
                public int compare(Map<T,V> o1, Map<T,V> o2) {
                        if (CollectionUtils.isEmpty(o1)) {
                                if (CollectionUtils.isEmpty(o2)) return 0;
                                return -1;
                        } else if (CollectionUtils.isEmpty(o2)) {
                                return 1;
                        }
                        
                        // neither one is empty.  Iterate through both.

                        Iterator<Entry<T,V>> o1Iter = o1.entrySet().iterator();
                        Iterator<Entry<T,V>> o2Iter = o2.entrySet().iterator();
                        
                        while (o1Iter.hasNext() && o2Iter.hasNext()) {
                                Entry<T,V> o1Elem = o1Iter.next(); 
                                Entry<T,V> o2Elem = o2Iter.next();
                                if (o1Elem == null) {
                                        if (o2Elem == null) continue;
                                        return -1;
                                } 
                                
                                T o1ElemKey = o1Elem.getKey();
                                T o2ElemKey = o2Elem.getKey();
                                if (o1ElemKey == null) {
                                        if (o2ElemKey != null) return -1;
                                        // if they're both null, fall through
                                } else {
                                        int elemKeyCompare = o1ElemKey.compareTo(o2ElemKey);
                                        if (elemKeyCompare != 0) return elemKeyCompare;
                                }
                                
                                V o1ElemValue = o1Elem.getValue();
                                V o2ElemValue = o2Elem.getValue();
                                if (o1ElemValue == null) {
                                        if (o2ElemValue != null) return -1;
                                        // if they're both null, fall through
                                } else {
                                        int elemValueCompare = o1ElemValue.compareTo(o2ElemValue);
                                        if (elemValueCompare != 0) return elemValueCompare;
                                }
                        }
                        
                        if (o1Iter.hasNext()) return 1;
                        if (o2Iter.hasNext()) return -1;
                        return 0;
                }

        }

        
}