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//               The Next Generation Logic Library                       //
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//  Copyright 2015-20xx Christoph Zengler                                //
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package org.logicng.transformations.cnf;

import org.logicng.configurations.Configuration;
import org.logicng.configurations.ConfigurationType;

/**
 * The configuration object for the CNF encoding.
 * @version 1.2
 * @since 1.1
 */
public final class CNFConfig extends Configuration {

    /**
     * The algorithm for the CNF encoding.
     */
    public enum Algorithm {
        FACTORIZATION, TSEITIN, PLAISTED_GREENBAUM, ADVANCED, BDD
    }

    final Algorithm algorithm;
    final Algorithm fallbackAlgorithmForAdvancedEncoding;
    final int distributionBoundary;
    final int createdClauseBoundary;
    final int atomBoundary;

    /**
     * Constructs a new configuration with a given type.
     * @param builder the builder
     */
    private CNFConfig(final Builder builder) {
        super(ConfigurationType.CNF);
        this.algorithm = builder.algorithm;
        this.fallbackAlgorithmForAdvancedEncoding = builder.fallbackAlgorithmForAdvancedEncoding;
        this.distributionBoundary = builder.distributionBoundary;
        this.createdClauseBoundary = builder.createdClauseBoundary;
        this.atomBoundary = builder.atomBoundary;
    }

    /**
     * Returns a new builder for the configuration.
     * @return the builder
     */
    public static Builder builder() {
        return new Builder();
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder(String.format("CNFConfig{%n"));
        sb.append("algorithm=").append(this.algorithm).append(System.lineSeparator());
        sb.append("fallbackAlgorithmForAdvancedEncoding=").append(this.fallbackAlgorithmForAdvancedEncoding).append(System.lineSeparator());
        sb.append("distributedBoundary=").append(this.distributionBoundary).append(System.lineSeparator());
        sb.append("createdClauseBoundary=").append(this.createdClauseBoundary).append(System.lineSeparator());
        sb.append("atomBoundary=").append(this.atomBoundary).append(System.lineSeparator());
        sb.append("}").append(System.lineSeparator());
        return sb.toString();
    }

    /**
     * The builder for a CNF configuration.
     */
    public static class Builder {

        private Algorithm algorithm = Algorithm.ADVANCED;
        private Algorithm fallbackAlgorithmForAdvancedEncoding = Algorithm.TSEITIN;
        private int distributionBoundary = -1;
        private int createdClauseBoundary = 1000;
        private int atomBoundary = 12;

        private Builder() {
            // Initialize only via factory
        }

        /**
         * Sets the algorithm for the CNF encoding. The default value is {@code ADVANCED}.
         * @param algorithm the algorithm for the CNF encoding
         * @return the builder
         */
        public Builder algorithm(final Algorithm algorithm) {
            this.algorithm = algorithm;
            return this;
        }

        /**
         * Sets the fallback algorithm for the advanced CNF encoding.  When the boundaries for the factorization are met, the
         * encoding switches to this algorithm.  The default value is {@code TSEITIN}.
         * @param fallbackAlgorithmForAdvancedEncoding the fallback algorithm for the advanced CNF encoding
         * @return the builder
         */
        public Builder fallbackAlgorithmForAdvancedEncoding(final Algorithm fallbackAlgorithmForAdvancedEncoding) {
            if (fallbackAlgorithmForAdvancedEncoding != Algorithm.TSEITIN
                    && fallbackAlgorithmForAdvancedEncoding != Algorithm.PLAISTED_GREENBAUM) {
                throw new IllegalArgumentException("Fallback algorithm for advanced CNF encoding must be one of Tseitin or " +
                        "Plaisted & Greenbaum");
            }
            this.fallbackAlgorithmForAdvancedEncoding = fallbackAlgorithmForAdvancedEncoding;
            return this;
        }

        /**
         * Sets the boundary how many distributions should be performed in the factorization before the method is switched
         * (in the {@code ADVANCED} encoding).  Disable this boundary by setting it to -1. The default value is -1.
         * @param distributionBoundary the distribution boundary
         * @return the builder
         */
        public Builder distributionBoundary(final int distributionBoundary) {
            this.distributionBoundary = distributionBoundary;
            return this;
        }

        /**
         * Sets the boundary how many clauses should be created in the factorization before the method is switched
         * (in the {@code ADVANCED} encoding).  Disable this boundary by setting it to -1. The default value is 1000.
         * @param createdClauseBoundary the clause creation boundary
         * @return the builder
         */
        public Builder createdClauseBoundary(final int createdClauseBoundary) {
            this.createdClauseBoundary = createdClauseBoundary;
            return this;
        }

        /**
         * Sets the boundary for how many atoms in a formula factorization is performed in Tseitin and Plaisted & Greenbaum.
         * The default value is 12.
         * @param atomBoundary the atom boundary
         * @return the builder
         */
        public Builder atomBoundary(final int atomBoundary) {
            this.atomBoundary = atomBoundary;
            return this;
        }

        /**
         * Builds the configuration.
         * @return the configuration.
         */
        public CNFConfig build() {
            return new CNFConfig(this);
        }
    }
}