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package com.enterprisemath.math.nn;

import com.enterprisemath.utils.ValidationUtils;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.commons.lang3.builder.ToStringBuilder;

/**
 * Definition of synapse. This is connection between 2 neurons.
 *
 * @author radek.hecl
 */
public class Synapse {

    /**
     * Builder object.
     */
    public static class Builder {

        /**
         * Id of neuron where synapse starts.
         */
        private String startId;

        /**
         * Id of neuron where synapse ends.
         */
        private String endId;

        /**
         * Weight.
         */
        private double weight;

        /**
         * Sets id of the neuron where synapse starts.
         *
         * @param startId start neuron id
         * @return this instance
         */
        public Builder setStartId(String startId) {
            this.startId = startId;
            return this;
        }

        /**
         * Sets id of the neuron where synapse end.
         *
         * @param endId end neuron id
         * @return this instance
         */
        public Builder setEndId(String endId) {
            this.endId = endId;
            return this;
        }

        /**
         * Sets weight.
         *
         * @param weight weight
         * @return this instance
         */
        public Builder setWeight(double weight) {
            this.weight = weight;
            return this;
        }

        /**
         * Builds the result object.
         *
         * @return created object
         */
        public Synapse build() {
            return new Synapse(this);
        }
    }

    /**
     * Id of neuron where synapse starts.
     */
    private String startId;

    /**
     * Id of neuron where synapse ends.
     */
    private String endId;

    /**
     * Weight.
     */
    private double weight;

    /**
     * Creates new instance.
     *
     * @param builder builder object
     */
    public Synapse(Builder builder) {
        this.startId = builder.startId;
        this.endId = builder.endId;
        this.weight = builder.weight;
        guardInvariants();
    }

    /**
     * Guards this object to be consistent. Throws exception if this is not the case.
     */
    private void guardInvariants() {
        ValidationUtils.guardNotEmpty(startId, "startId cannot be empty");
        ValidationUtils.guardNotEmpty(endId, "endId cannot be empty");
    }

    /**
     * Returns neuron id where synapse starts.
     *
     * @return neuron id where synapse starts
     */
    public String getStartId() {
        return startId;
    }

    /**
     * Returns neuron id where synapse ends.
     *
     * @return neuron id where synapse ends
     */
    public String getEndId() {
        return endId;
    }

    /**
     * Returns wheight.
     *
     * @return weight
     */
    public double getWeight() {
        return weight;
    }

    @Override
    public int hashCode() {
        return HashCodeBuilder.reflectionHashCode(this);
    }

    @Override
    public boolean equals(Object obj) {
        return EqualsBuilder.reflectionEquals(this, obj);
    }

    @Override
    public String toString() {
        return ToStringBuilder.reflectionToString(this);
    }

    /**
     * Creates new instance.
     *
     * @param startId identification of start neuron
     * @param endId identification of end neuron
     * @param weight weight
     * @return created instance
     */
    public static Synapse create(String startId, String endId, double weight) {
        return new Synapse.Builder().
                setStartId(startId).
                setEndId(endId).
                setWeight(weight).
                build();
    }
}