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This module holds the core components of the Djenni data generator framework. By itself it provides most of the components to create an efficient end to end data generation framework for a specific domain. It contains the core SupplierBuilder interfaces, implementations for the core Java data types and useful test components. It is intended to be used in conjunction with the source-generator module that will speed up delivery of domain specific data generation and also with common domain modules (TBD) that deliver standard generators for common frameworks such as JAXB.

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package com.robertboothby.djenni.lang;

import com.robertboothby.djenni.SupplierBuilder;
import com.robertboothby.djenni.core.StreamableSupplier;
import com.robertboothby.djenni.core.SupplierHelper;
import com.robertboothby.djenni.distribution.Distribution;
import com.robertboothby.djenni.distribution.simple.SimpleRandomLongDistribution;
import com.robertboothby.djenni.sugar.And;

import java.util.function.Supplier;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.Matchers.is;

/**
 * Builder designed to make it easy and expressive to configure a generator of Long values. Limited to a range
 * defined by the maximum value of a Long.
 * @author robertboothby
 */
public class LongSupplierBuilder implements SupplierBuilder {

    public static final long MIN_INCLUSIVE_VALUE_DEFAULT = 0;
    public static final long MAX_EXCLUSIVE_VALUE_DEFAULT = Long.MAX_VALUE;
    public static final Distribution DISTRIBUTION_DEFAULT = SimpleRandomLongDistribution.UNIFORM;

    private long minInclusiveValue = MIN_INCLUSIVE_VALUE_DEFAULT;
    private long maxExclusiveValue = MAX_EXCLUSIVE_VALUE_DEFAULT;
    private Distribution distribution = DISTRIBUTION_DEFAULT;

    public StreamableSupplier build() {
        if(maxExclusiveValue - minInclusiveValue == 1){
            return SupplierHelper.fix(minInclusiveValue);
        } else {
            Long range = maxExclusiveValue - minInclusiveValue;
            assertThat("Range should be greater than 0 but less than " + Long.MAX_VALUE, range, is(greaterThan(0L)));
            return () -> minInclusiveValue + distribution.generate(range);
        }
    }


    /**
     * Set the minimum and maximum inclusive values.
     * @param minInclusiveValue The minimum inclusive value.
     * @return The And on which to set the maximum exclusive value.
     */
    public And between(Long minInclusiveValue) {
        this.minInclusiveValue = minInclusiveValue;
        return new And() {
            public LongSupplierBuilder and(Long maxExclusiveValue) {
                LongSupplierBuilder.this.maxExclusiveValue = maxExclusiveValue;
                return LongSupplierBuilder.this;
            }
        };
    }

    /**
     * Configure a non-even distribution of values.
     * @param distribution the distribution of values to use.
     * @return this builder for further configuration.
     */
    public LongSupplierBuilder distribution(Distribution distribution) {
        this.distribution = distribution;
        return this;
    }

    /**
     * Configure the integer generator to return a single, exact value;
     * @param onlyValue The only value that the integer generator will return.
     * @return this builder for further configuration.
     */
    public LongSupplierBuilder onlyValue(Long onlyValue){
        this.minInclusiveValue = onlyValue;
        this.maxExclusiveValue = minInclusiveValue + 1;
        return this;
    }
    /**
     * Create an instance of the IntegerSupplierBuilder for configuration - preconfigured to produce uniformly distributed
     * values between 0 and {@link Integer#MAX_VALUE}
     * @return the builder for configuration.
     */
    public static LongSupplierBuilder generateALong() {
        return new LongSupplierBuilder();
    }
}