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/**
 * Copyright (C) 2010-2018 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see .
 */
package org.evosuite.graphs.cfg;

import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Set;

import org.evosuite.graphs.EvoSuiteGraph;
import org.jgrapht.graph.DefaultDirectedGraph;
import org.objectweb.asm.Opcodes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * Abstract base class for both forms of CFGs inside EvoSuite
 *
 * One implementation of this is cfg.RawControlFlowGraph, which is also known as
 * the complete CFG The other implementation of this is
 * cfg.ActualControlFlowGraph which is also known as the minimal CFG Look at the
 * respective classes for more detailed information
 *
 * The CFGs can be accessed via the GraphPool which holds for each CUT and each
 * of their methods a complete and a minimal CFG
 *
 * CFGs are created by the CFGGenerator during the analysis of the CUTs'
 * byteCode performed by the BytecodeAnalyzer
 *
 * @author Gordon Fraser, Andre Mis
 */
public abstract class ControlFlowGraph extends
		EvoSuiteGraph {

	private static Logger logger = LoggerFactory
			.getLogger(ControlFlowGraph.class);

	protected String className;
	protected String methodName;
	protected int access;

	private int diameter = -1;

	/**
	 * Creates a fresh and empty CFG for the given class and method
	 *
	 * @param className a {@link java.lang.String} object.
	 * @param methodName a {@link java.lang.String} object.
	 * @param access a int.
	 */
	protected ControlFlowGraph(String className, String methodName, int access) {
		super(ControlFlowEdge.class);

		if (className == null || methodName == null)
			throw new IllegalArgumentException("null given");

		this.className = className;
		this.methodName = methodName;
		this.access = access;
	}

	/**
	 * Creates a CFG determined by the given jGraph for the given class and
	 * method
	 *
	 * @param className a {@link java.lang.String} object.
	 * @param methodName a {@link java.lang.String} object.
	 * @param access a int.
	 * @param jGraph a {@link org.jgrapht.graph.DefaultDirectedGraph} object.
	 */
	protected ControlFlowGraph(String className, String methodName, int access,
			DefaultDirectedGraph jGraph) {
		super(jGraph, ControlFlowEdge.class);

		if (className == null || methodName == null)
			throw new IllegalArgumentException("null given");

		this.className = className;
		this.methodName = methodName;
		this.access = access;
	}

	/**
	 * leadsToNode
	 *
	 * @param e a {@link org.evosuite.graphs.cfg.ControlFlowEdge} object.
	 * @param b a V object.
	 * @return a boolean.
	 */
	public boolean leadsToNode(ControlFlowEdge e, V b) {

		Set handled = new HashSet();

		Queue queue = new LinkedList();
		queue.add(getEdgeTarget(e));
		while (!queue.isEmpty()) {
			V current = queue.poll();
			if (handled.contains(current))
				continue;
			handled.add(current);

			for (V next : getChildren(current))
				if (next.equals(b))
					return true;
				else
					queue.add(next);
		}

		return false;
	}

	// /**
	// * Can be used to retrieve a Branch contained in this CFG identified by
	// it's
	// * branchId
	// *
	// * If no such branch exists in this CFG, null is returned
	// */
	// public abstract BytecodeInstruction getBranch(int branchId);

	/**
	 * Can be used to retrieve an instruction contained in this CFG identified
	 * by it's instructionId
	 *
	 * If no such instruction exists in this CFG, null is returned
	 *
	 * @param instructionId a int.
	 * @return a {@link org.evosuite.graphs.cfg.BytecodeInstruction} object.
	 */
	public abstract BytecodeInstruction getInstruction(int instructionId);

	/**
	 * Determines, whether a given instruction is contained in this CFG
	 *
	 * @param instruction a {@link org.evosuite.graphs.cfg.BytecodeInstruction} object.
	 * @return a boolean.
	 */
	public abstract boolean containsInstruction(BytecodeInstruction instruction);

	/**
	 * Computes the diameter of this CFG and the mutation distances
	 *
	 * Since both takes some time this is not automatically done on each CFG
	 *
	 * GraphPool will automatically call this immediately after the
	 * instantiation of an ActualControlFlowGraph, but not after the creation of
	 * a RawControlFlowGraph
	 */
	public void finalise() {
		computeDiameter();
		// TODO: call this!
		// and sanity check with a flag whenever a call
		// to this method is assumed to have been made
	}

	/**
	 * Returns the Diameter of this CFG
	 *
	 * If the diameter of this graph was not computed previously it is computed
	 * first
	 *
	 * @return a int.
	 */
	public int getDiameter() {
		if (diameter == -1) {
			logger.debug("diameter not computed yet. calling computeDiameter() first!");
			computeDiameter();
		}

		return diameter;
	}
	
	public int getCyclomaticComplexity() {
		// E = the number of edges of the graph.
		// N = the number of nodes of the graph.
		// M = E − N + 2
		int E = this.edgeCount();
		int N = this.vertexCount();
		return E -N + 2;
	}

	/**
	 * computeDiameter
	 */
	protected void computeDiameter() {
		// The diameter is just an upper bound for the approach level
		// Let's try to use something that's easier to compute than
		// FLoydWarshall
		diameter = this.edgeCount();
		/*
		 * FloydWarshall f = new FloydWarshall(graph); diameter = (int) f.getDiameter();
		 */
	}

	/**
	 * determineEntryPoint
	 *
	 * @return a V object.
	 */
	public V determineEntryPoint() {
		Set candidates = determineEntryPoints();

		if (candidates.size() > 1)
			throw new IllegalStateException(
					"expect CFG of a method to contain at most one instruction with no parent in "
							+ methodName);

		for (V instruction : candidates)
			return instruction;

		// there was a back loop to the first instruction within this CFG, so no
		// candidate
		// TODO for now return null and handle in super class
		// RawControlFlowGraph separately by overwriting this method

		// can also happen in empty methods
		return null;
	}

	/**
	 * Getter for the field className.
	 *
	 * @return a {@link java.lang.String} object.
	 */
	public String getClassName() {
		return className;
	}

	/**
	 * Getter for the field methodName.
	 *
	 * @return a {@link java.lang.String} object.
	 */
	public String getMethodName() {
		return methodName;
	}

	/**
	 * getMethodAccess
	 *
	 * @return a int.
	 */
	public int getMethodAccess() {
		return access;
	}

	/**
	 * isPublicMethod
	 *
	 * @return a boolean.
	 */
	public boolean isPublicMethod() {
		return (access & Opcodes.ACC_PUBLIC) == Opcodes.ACC_PUBLIC;
	}

	/**
	 * isStaticMethod
	 *
	 * @return a boolean.
	 */
	public boolean isStaticMethod() {
		return (access & Opcodes.ACC_STATIC) == Opcodes.ACC_STATIC;
	}

	/** {@inheritDoc} */
	@Override
	public String getName() {
		return methodName + " " + getCFGType();
	}

	/** {@inheritDoc} */
	@Override
	protected String dotSubFolder() {
		return toFileString(className) + "/" + getCFGType() + "/";
	}

	/**
	 * getCFGType
	 *
	 * @return a {@link java.lang.String} object.
	 */
	public abstract String getCFGType();
}