package jcgp.tests;

import static org.junit.Assert.*;

import java.util.Random;

import jcgp.Parameters;
import jcgp.Utilities;
import jcgp.function.Arithmetic;
import jcgp.function.FunctionSet;
import jcgp.population.Chromosome;
import jcgp.population.Population;

import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

/**
 * 
 * Tests which cover the behaviour specified for a population.
 * 
 *  - A population should be able to return parents and offspring separately. 
 *  - It should be possible to iterate through all the chromosomes in a population
 *    with one indexing system - parents then offspring.
 *  - When constructed with no arguments, it should generate populationSize
 *    random chromosomes, distributed according to the EA parameters.
 *  - If one or more chromosomes are passed into the constructor, it should use them
 *    as parents to create the rest of the population.
 *  
 * 
 * @author Eduardo Pedroni
 *
 */
public class PopulationTests {

	private Population population;

	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
		// initialise function set
		FunctionSet functionSet = new FunctionSet(new Arithmetic.Addition(), new Arithmetic.Subtraction());

		// initialise utilities
		Utilities.setResources(new Random(1234), functionSet);

		// initialise parameters
		Parameters.setColumns(20);
		Parameters.setRows(20);
		Parameters.setInputs(2);
		Parameters.setOutputs(4);
		Parameters.setLevelsBack(1);
		Parameters.setMutationRate(10);
		Parameters.setTotalGenerations(100);
		Parameters.setTotalRuns(5);
		Parameters.setPopulationSize(1, 4);
		Parameters.setMaxArity(functionSet.getMaxArity());
	}

	@Before
	public void setUp() throws Exception {
		population = new Population();
	}

	@Test
	public void defaultPopulationTest() {
		// check that the constructor really generates populationSize chromosomes when none is given
		int offspring = 0, parent = 0;
		while (true) {
			try {
				population.getOffspring(offspring);
			} catch (IndexOutOfBoundsException e) {
				break;
			}
			offspring++;
		}
		while (true) {
			try {
				population.getParent(parent);
			} catch (IndexOutOfBoundsException e) {
				break;
			}
			parent++;
		}
		assertTrue("Incorrect number of chromosomes generated.", offspring + parent == Parameters.getPopulationSize());
	}
	
	@Test
	public void offspringParentTest() {
		// the first parent should not be the same as the first offspring
		assertTrue("Same chromosome returned as parent and offspring", population.getOffspring(0) != population.getParent(0));
	}
	
	@Test
	public void singleIndexTest() {
		// assuming 1+4
		// the first chromosome should be the first (and only) parent
		assertTrue("Incorrect chromosome returned.", population.getChromosome(0) == population.getParent(0));
		// the next 4 chromosomes should be the offspring, in order
		for (int i = 0; i < Parameters.getOffspringCount(); i++) {
			assertTrue("Incorrect chromosome returned.", population.getChromosome(i + 1) == population.getOffspring(i));
		}
	}

	@Test
	public void preinitialisedChromosomeTest() {
		// the original chromosome that will be cloned
		Chromosome oc = new Chromosome();

		// initialise a population with a copy of it
		population = new Population(oc);
		// check that the first parent chromosome is identical to, but not the same instance as, the one given
		assertTrue("Incorrect chromosome in population.", population.getParent(0).compareTo(oc) && population.getParent(0) != oc);
	}
}