//   Copyright 2012 Georg-August-Universität Göttingen, Germany
//
//   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 de.ugoe.cs.autoquest.tasktrees.taskequality;

import de.ugoe.cs.autoquest.tasktrees.treeifc.IOptional;
import de.ugoe.cs.autoquest.tasktrees.treeifc.IOptionalInstance;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITask;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskInstance;

/**
 * <p>
 * This class is capable of comparing any task which is not an optional with an
 * optional. This is needed, because optionals may mark exactly that task as optional. In this
 * case, the optional would be equal to that task if it was executed. The rule
 * returns lexically equal, it the child of the optional is lexically equal to the task
 * or if the child of the optional is a selection and this selections contains a lexically equal
 * task. The same applies for syntactical and semantical equality.
 * </p>

 * @author Patrick Harms
 */
public class TaskAndOptionalComparisonRule implements TaskComparisonRule {
    
    /* (non-Javadoc)
     * @see TaskComparisonRule#isApplicable(ITask, ITask)
     */
    @Override
    public boolean isApplicable(ITask task1, ITask task2) {
        return ((task1 instanceof IOptional) && (!(task2 instanceof IOptional))) ||
               ((task2 instanceof IOptional) && (!(task1 instanceof IOptional)));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areLexicallyEqual(ITask, ITask)
     */
    @Override
    public boolean areLexicallyEqual(ITask task1, ITask task2) {
        TaskEquality equality = getEquality(task1, task2, TaskEquality.LEXICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.LEXICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areSyntacticallyEqual(ITask, ITask)
     */
    @Override
    public boolean areSyntacticallyEqual(ITask task1, ITask task2) {
        TaskEquality equality = getEquality(task1, task2, TaskEquality.SYNTACTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.SYNTACTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areSemanticallyEqual(ITask, ITask)
     */
    @Override
    public boolean areSemanticallyEqual(ITask task1, ITask task2) {
        TaskEquality equality = getEquality(task1, task2, TaskEquality.SEMANTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.SEMANTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#compare(ITask, ITask)
     */
    @Override
    public TaskEquality compare(ITask task1, ITask task2) {
        return getEquality(task1, task2, null);
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#isApplicable(ITaskInstance, ITaskInstance)
     */
    @Override
    public boolean isApplicable(ITaskInstance instance1, ITaskInstance instance2) {
        return isApplicable(instance1.getTask(), instance2.getTask());
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areLexicallyEqual(ITaskInstance, ITaskInstance)
     */
    @Override
    public boolean areLexicallyEqual(ITaskInstance instance1, ITaskInstance instance2) {
        TaskEquality equality = getEquality(instance1, instance2, TaskEquality.LEXICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.LEXICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areSyntacticallyEqual(ITaskInstance, ITaskInstance)
     */
    @Override
    public boolean areSyntacticallyEqual(ITaskInstance instance1, ITaskInstance instance2) {
        TaskEquality equality = getEquality(instance1, instance2, TaskEquality.SYNTACTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.SYNTACTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#areSemanticallyEqual(ITaskInstance, ITaskInstance)
     */
    @Override
    public boolean areSemanticallyEqual(ITaskInstance instance1, ITaskInstance instance2) {
        TaskEquality equality = getEquality(instance1, instance2, TaskEquality.SEMANTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(TaskEquality.SEMANTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see TaskComparisonRule#compare(ITaskInstance, ITaskInstance)
     */
    @Override
    public TaskEquality compare(ITaskInstance instance1, ITaskInstance instance2) {
        return getEquality(instance1, instance2, null);
    }

    /**
     * <p>
     * compares two tasks with each other checking for the provided required level of
     * equality. One of the tasks must be an optional, the other one not. If this is not the
     * case, the method returns null. The returned equality level is at most lexical equality
     * as the optional can not be identical to something not being an optional.
     * </p>
     * 
     * @param task1                 the first task to be compared
     * @param task2                 the second task to be compared
     * @param requiredEqualityLevel the equality level to be checked for
     * 
     * @return the determined equality.
     */
    private TaskEquality getEquality(ITask task1, ITask task2, TaskEquality requiredEqualityLevel) {
        IOptional optional = null;
        ITask task = null;
        
        if (task1 instanceof IOptional) {
            if (task2 instanceof IOptional) {
                // the rule is not responsible for two optionals
                return null;
            }
            
            optional = (IOptional) task1;
            task = task2;
        }
        else if (task2 instanceof IOptional) {
            if (task1 instanceof IOptional) {
                // the rule is not responsible for two optionals
                return null;
            }
            
            optional = (IOptional) task2;
            task = task1;
        }
        else {
            return null;
        }

        ITask child = optional.getMarkedTask();
        
        // now, that we found the optional and the task, lets compare the child of the optional
        // with the task.
        if (child == null) {
            return null;
        }

        TaskEquality taskEquality = callRuleManager(child, task, requiredEqualityLevel);

        // although the subtask may be identical to the task, we can not return identical, as
        // the optional is not identical to the task, but at most lexically equal
        if (taskEquality == TaskEquality.IDENTICAL) {
            return TaskEquality.LEXICALLY_EQUAL;
        }
        else {
            return taskEquality;
        }

    }
    
    /**
     * <p>
     * used to to call the task equality rule manager for the comparison of the two provided
     * children. If no required equality level is provided, than the most concrete equality is
     * returned. Otherwise, the required equality is returned as long as the children are equal
     * on that level.
     * </p> 
     * 
     * @param child1                the first task to be compared
     * @param child2                the second task to be compared
     * @param requiredEqualityLevel the equality level to be checked for
     * 
     * @return the determined equality
     */
    private TaskEquality callRuleManager(ITask        child1,
                                         ITask        child2,
                                         TaskEquality requiredEqualityLevel)
    {
        if (requiredEqualityLevel == null) {
            return TaskEqualityRuleManager.getInstance().compare(child1, child2);
        }
        else if (TaskEqualityRuleManager.getInstance().areAtLeastEqual
                     (child1, child2, requiredEqualityLevel))
        {
            return requiredEqualityLevel;
        }
        else {
            return TaskEquality.UNEQUAL;
        }
    }

    /**
     * <p>
     * compares two task instances with each other checking for the provided required level of
     * equality. One of the task instances must be an optional, the other one not. If this is not
     * the case, the method returns null. The returned equality level is at most lexical equality
     * as the optional can not be identical to something not being a optional.
     * </p>
     * 
     * @param taskInstance1         the first task instance to be compared
     * @param taskInstance2         the second task instance to be compared
     * @param requiredEqualityLevel the equality level to be checked for
     * 
     * @return the determined equality.
     */
    private TaskEquality getEquality(ITaskInstance taskInstance1,
                                     ITaskInstance taskInstance2,
                                     TaskEquality  requiredEqualityLevel)
    {
        IOptionalInstance optional = null;
        ITaskInstance task = null;
        
        if (taskInstance1 instanceof IOptionalInstance) {
            if (taskInstance2 instanceof IOptionalInstance) {
                // the rule is not responsible for two iterations
                return null;
            }
            
            optional = (IOptionalInstance) taskInstance1;
            task = taskInstance2;
        }
        else if (taskInstance2 instanceof IOptionalInstance) {
            if (taskInstance1 instanceof IOptionalInstance) {
                // the rule is not responsible for two iterations
                return null;
            }
            
            optional = (IOptionalInstance) taskInstance2;
            task = taskInstance1;
        }
        else {
            return null;
        }

        // now, that we found the optional and the task, lets compare the children of the optional
        // with the task.
        
        if (optional.getChild() == null) {
            return null;
        }

        TaskEquality taskEquality =
            callRuleManager(optional.getChild(), task, requiredEqualityLevel);
            
        // although the subtask may be identical to the task, we can not return identical, as
        // the optional is not identical to the task, but at most lexically equal
        if (taskEquality == TaskEquality.IDENTICAL) {
            return TaskEquality.LEXICALLY_EQUAL;
        }
        else {
            return taskEquality;
        }

    }
    
    /**
     * <p>
     * used to to call the task equality rule manager for the comparison of the two provided
     * children. If no required equality level is provided, than the most concrete equality is
     * returned. Otherwise, the required equality is returned as long as the children are equal
     * on that level.
     * </p> 
     * 
     * @param taskInstance1         the first task instance to be compared
     * @param taskInstance2         the second task instance to be compared
     * @param requiredEqualityLevel the equality level to be checked for
     * 
     * @return the determined equality
     */
    private TaskEquality callRuleManager(ITaskInstance taskInstance1,
                                         ITaskInstance taskInstance2,
                                         TaskEquality  requiredEqualityLevel)
    {
        if (requiredEqualityLevel == null) {
            return TaskEqualityRuleManager.getInstance().compare(taskInstance1, taskInstance2);
        }
        else if (TaskEqualityRuleManager.getInstance().areAtLeastEqual
                     (taskInstance1, taskInstance2, requiredEqualityLevel))
        {
            return requiredEqualityLevel;
        }
        else {
            return TaskEquality.UNEQUAL;
        }
    }
}