package com.lagodiuk.gp.symbolic;

import java.util.LinkedList;
import java.util.List;

import com.lagodiuk.gp.symbolic.SymbolicRegressionEngine;
import com.lagodiuk.gp.symbolic.SymbolicRegressionIterationListener;
import com.lagodiuk.gp.symbolic.TabulatedFunctionFitness;
import com.lagodiuk.gp.symbolic.Target;
import com.lagodiuk.gp.symbolic.interpreter.Expression;
import com.lagodiuk.gp.symbolic.interpreter.Functions;

/**
 * f(x) - ? 

 * 
 * f(0) = 0 

 * f(1) = 11 

 * f(2) = 24 

 * f(3) = 39 

 * f(4) = 56 

 * f(5) = 75 

 * f(6) = 96 

 * 
 * (target function is f(x) = x^2 + 10*x)
 */
public class HelloSymbolicRegression {

    public static void main(String[] args) {

        // define training set
        TabulatedFunctionFitness fitness =
                new TabulatedFunctionFitness(
                        new Target().when("x", 0).targetIs(0),
                        new Target().when("x", 1).targetIs(11),
                        new Target().when("x", 2).targetIs(24),
                        new Target().when("x", 3).targetIs(39),
                        new Target().when("x", 4).targetIs(56),
                        new Target().when("x", 5).targetIs(75),
                        new Target().when("x", 6).targetIs(96));

        SymbolicRegressionEngine engine =
                new SymbolicRegressionEngine(
                        fitness,
                        // define variables
                        list("x"),
                        // define base functions
                        list(Functions.ADD, Functions.SUB, Functions.MUL, Functions.VARIABLE, Functions.CONSTANT));

        addListener(engine);

        // 200 iterations
        engine.evolve(200);
    }

    /**
     * Track each iteration
     */
    private static void addListener(SymbolicRegressionEngine engine) {
        engine.addIterationListener(new SymbolicRegressionIterationListener() {
            @Override
            public void update(SymbolicRegressionEngine engine) {

                Expression bestSyntaxTree = engine.getBestSyntaxTree();

                double currFitValue = engine.fitness(bestSyntaxTree);

                // log to console
                System.out.println(
                        String.format("iter = %s \t fit = %s \t func = %s",
                                engine.getIteration(), currFitValue, bestSyntaxTree.print()));

                // halt condition
                if (currFitValue < 5) {
                    engine.terminate();
                }
            }
        });
    }

    private static  List list(T... items) {
        List list = new LinkedList();
        for (T item : items) {
            list.add(item);
        }
        return list;
    }
}