package edu.neu.ccs.evergreen.model;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import edu.neu.ccs.evergreen.exception.ContradictionException;

/**
 * Tracks all of the assignments that have been made.
 */
public class Assignments {
	/**
	 * The weight unsatisfied by this assignment.
	 */
	public int unsatisfiedWeight;
	
	private Map<Integer, Assignment> assignments = new HashMap<Integer, Assignment>();

	private LinkedList<Assignment> assignmentOrder = new LinkedList<Assignment>();

	private LinkedList<Assignment> decisions = new LinkedList<Assignment>();

	/**
	 * @see java.lang.Object#clone()
	 */
	public Assignments clone() {
		Assignments newAssignments = new Assignments();
		newAssignments.assignments.putAll(assignments);
		newAssignments.decisions.addAll(decisions);
		newAssignments.assignmentOrder.addAll(assignmentOrder);
		newAssignments.unsatisfiedWeight = unsatisfiedWeight;
		return newAssignments;
	}

	/**
	 * Add a new assignment.
	 * 
	 * @param assignment
	 *            Assignment to add
	 * @return True if assignment was new; false otherwise
	 */
	public boolean addAssignment(Assignment assignment) {
		Assignment oldAssignment = assignments.put(assignment.getVariable(),
				assignment);
		if (oldAssignment != null) {
			assignments.put(assignment.getVariable(), oldAssignment);
			if (oldAssignment.getValue() != assignment.getValue()) {
				throw new ContradictionException(assignment.getVariable()
						+ " caused a contradiction", assignment
						.getForcingConstraint());
			}
			return true;
		}
		if (assignment.getDecision()) {
			decisions.add(assignment);
			// TODO: Convert to aspect
			Stats.decide++;
		} else {
			// TODO: Convert to aspect
			Stats.unitPropagate++;
		}
		assignmentOrder.add(assignment);
		return true;
	}

	/**
	 * Add all of the assignments from another assignment instance to this one.
	 * 
	 * @param assignments
	 *            Assignments to add
	 */
	public void addAssignments(Assignments assignments) {
		for (Assignment assignment : assignments.assignments.values()) {
			addAssignment(assignment);
		}
	}

	/**
	 * Does the given variable have an assignment?
	 * 
	 * @param variable
	 *            Variable to check
	 * @return True if it is assigned.
	 */
	public boolean assigned(int variable) {
		return assignments.containsKey(variable);
	}

	/**
	 * How many variables have been given an assignment.
	 * 
	 * @return # of variables assigned
	 */
	public int size() {
		return assignments.size();
	}

	/**
	 * Remove an assignment from the system.
	 * 
	 * @return Removed assignment
	 */
	public Assignment removeAnAssignment() {
		Integer variable = assignments.keySet().iterator().next();
		return assignments.remove(variable);
	}

	/**
	 * Return an ordered list of decisions that were made.
	 * 
	 * @return Decision assignments
	 */
	public List<Assignment> getDecisions() {
		return Collections.unmodifiableList(decisions);
	}

	/**
	 * Return the last decision that was made.
	 * 
	 * @return Last decision assignment
	 */
	public Assignment getLastDecision() {
		return decisions.getLast();
	}

	/**
	 * Return assignment for a variable.
	 * 
	 * @param variable
	 *            Variable
	 * @return Assignment to variable
	 */
	public Assignment getAssignment(int variable) {
		return assignments.get(variable);
	}

	/**
	 * Generate the assignment this instance represents in the standard output
	 * format.
	 * 
	 * @param maxVariable
	 *            Maximum variable to include in output
	 * @return Assignment string
	 */
	public String solutionString(int maxVariable) {
		StringBuffer result = new StringBuffer();
		for (int variable = 1; variable <= maxVariable; variable++) {
			Assignment assignment = getAssignment(variable);
			if ((variable % 10) != 1) {
				result.append(" ");
			}
			if (assignment.getValue() == 0)
			{
				result.append("!");
			}
			result.append("v");
			result.append(assignment.getVariable());
			if ((variable % 10) == 0) {
				result.append("\n");
			}
		}
		if ((maxVariable % 10) != 0) {
			result.append("\n");
		}
		return result.toString();
	}

	/**
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		StringBuffer result = new StringBuffer();
		for (Assignment assignment : assignments.values()) {
			if (result.length() > 0) {
				result.append(", ");
			}
			result.append(assignment.toString());
		}
		return result.toString();
	}
	
	/**
	 * Return all of the assignments made.
	 * @return List of assignment
	 */
	public List<Assignment> getAssignments() {
		return assignmentOrder;
	}
}