/*
 * Copyright (C) 2014-2021 Brian L. Browning
 *
 * This file is part of Beagle
 *
 * Beagle is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Beagle is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package vcf;

import ints.IntArray;
import java.util.Arrays;
import java.util.stream.IntStream;

/**
 * <p>Class {@code LowMafRefGTRec} represent represents phased, non-missing
 * genotypes for a list of reference samples at a single marker.</p>
 *
 * <p>Class {@code LowMafRefGTRec} stores the haplotypes that carry each
 * non-major allele.</p>
 *
 * <p>Instances of class {@code LowMemRefGTRec} are immutable.</p>
 *
 * @author Brian L. Browning {@code <browning@uw.edu>}
 */
public final class LowMafRefGTRec implements RefGTRec {

    private final Marker marker;
    private final Samples samples;
    private final int nHaps;
    private final int majorAllele;
    private final int[][] hapIndices;

    /**
     * Constructs a new {@code LowMafRefGTRec} instance from the specified data.
     *
     * @param rec the phased, non-missing genotype data
     * @throws NullPointerException if {@code rec == null}
     */
    public LowMafRefGTRec(RefGTRec rec) {
        this.hapIndices = rec.hapIndices();
        int majAllele = 0;
        while (hapIndices[majAllele]!=null) {
            ++majAllele;
        }
        this.marker = rec.marker();
        this.samples = rec.samples();
        this.nHaps = rec.size();
        this.majorAllele = majAllele;
    }

    /**
     * Constructs a new {@code LowMafRefGTRc} instance from the specified
     * data.
     *
     * @param gtp a VCF record parser that extracts sample genotypes
     * @throws IllegalArgumentException if the VCF record contains an
     * unphased genotype or missing allele
     * @throws IllegalArgumentException if a format error is detected in the
     * VCF record
     * @throws NullPointerException if {@code gtp == null}
     */
    public LowMafRefGTRec(VcfRecGTParser gtp) {
        this.marker = gtp.marker();
        this.samples = gtp.samples();
        this.nHaps = 2*gtp.nSamples();
        this.hapIndices = gtp.nonMajRefIndices();
        int majAl = -1;
        for (int j=0; j<hapIndices.length; ++j) {
            if (hapIndices[j]==null) {
                majAl = j;
                break;
            }
        }
        this.majorAllele = majAl;
    }

    /**
     * Constructs a new {@code LowMafRefGTRec} instance from the specified data.
     * The specified {@code hapIndices} array is required to contain exactly one
     * {@code null} element. The {@code null} element should be the major
     * allele because this is most memory-efficient, but this requirement is not
     * enforced. A haplotype index should be an element of only one array in
     * {@code hapIndices}. If a haplotype index is an element of more than
     * one array in {@code hapIndices}, it is assigned to the array with
     * smallest index.

     * @param marker the marker
     * @param samples the samples
     * @param hapIndices whose {@code j}-th element is a list of haplotypes
     * sorted in increasing order that carry the {@code j}-th allele, or is
     * {@code null}
     *
     * @throws IllegalArgumentException if the {@code (hapIndices} does
     * not contain exactly one {@code null} element
     * @throws IllegalArgumentException if any non-null element of
     * {@code hapIndices} is not a sorted list of distinct haplotype indices
     * between 0 (inclusive) and {@code 2*samples.size()} (exclusive)
     * @throws IllegalArgumentException if
     * {@code marker.nAlleles() != hapIndices.length}
     * @throws NullPointerException if
     * {@code marker == null || samples == null || hapIndices == null}
     */
    public LowMafRefGTRec(Marker marker, Samples samples, int[][] hapIndices) {
        this.marker = marker;
        this.samples = samples;
        this.nHaps = 2*samples.size();
        this.majorAllele = checkIndicesAndReturnNullIndex(hapIndices, nHaps);
        this.hapIndices = deepCopy(hapIndices);
    }

    static int checkIndicesAndReturnNullIndex(int[][] hapIndices, int nHaps) {
        int majAllele = -1;
        for (int j=0; j<hapIndices.length; ++j) {
            if (hapIndices[j]==null) {
                if (majAllele == -1) {
                    majAllele = j;
                }
                else {
                    throwArrayError();
                }
            }
            else {
                checkSorted(hapIndices[j], nHaps);
            }
        }
        if (majAllele == -1) {
            throwArrayError();
        }
        return majAllele;
    }

    private static void throwArrayError() {
        throw new IllegalArgumentException("invalid array");
    }

    private static void checkSorted(int[] ia, int nHaps) {
        if (ia.length>0 && (ia[0] < 0 || ia[ia.length - 1] >= nHaps)) {
            throwArrayError();
        }
        for (int k=1; k<ia.length; ++k) {
            if (ia[k-1] >= ia[k]) {
                throwArrayError();
            }
        }
    }

    static int[][] deepCopy(int[][] ia) {
        int[][] copy = new int[ia.length][];
        for (int j=0; j<ia.length; ++j) {
            if (ia[j]!=null) {
                copy[j] = ia[j].clone();
            }
        }
        return ia;
    }

    @Override
    public int[][] hapIndices() {
        return deepCopy(hapIndices);
    }

    @Override
    public boolean isPhased(int sample) {
        if (sample < 0 || sample >= this.samples().size()) {
            throw new IndexOutOfBoundsException(String.valueOf(sample));
        }
        return true;
    }

    /**
     * Returns {@code true}.
     * @return {@code true}
     */
    @Override
    public boolean isPhased() {
        return true;
    }

    @Override
    public Samples samples() {
        return samples;
    }


    @Override
    public int size() {
        return nHaps;
    }

    @Override
    public Marker marker() {
        return marker;
    }


    @Override
    public int allele1(int sample) {
        return get(sample<<1);
    }

    @Override
    public int allele2(int sample) {
        return get((sample<<1) | 0b1);
    }

    @Override
    public int get(int hap) {
        if (hap < 0 || hap >= nHaps) {
            throw new IndexOutOfBoundsException(String.valueOf(hap));
        }
        for (int j=0; j<hapIndices.length; ++j) {
            if (j != majorAllele) {
                if (Arrays.binarySearch(hapIndices[j], hap) >= 0) {
                    return j;
                }
            }
        }
        return majorAllele;
    }

    @Override
    public int[] alleles() {
        int[] ia = IntStream.range(0, nHaps)
                .map(h -> majorAllele)
                .toArray();
        for (int al=0; al<hapIndices.length; ++al) {
            if (al != majorAllele) {
                for (int h : hapIndices[al]) {
                    ia[h] = al;
                }
            }
        }
        return ia;
    }


    @Override
    public boolean isAlleleCoded() {
        return true;
    }

    @Override
    public int majorAllele() {
        return majorAllele;
    }

    @Override
    public int[] alleleCounts() {
        int[] alCnts = new int[marker.nAlleles()];
        alCnts[majorAllele] = nHaps;
        for (int j=0; j<alCnts.length; ++j) {
            if (j!=majorAllele) {
                int alCnt = hapIndices[j].length;
                alCnts[j] = alCnt;
                alCnts[majorAllele] -= alCnt;
            }
        }
        return alCnts;
    }

    @Override
    public int alleleCount(int allele) {
        if (hapIndices[allele]==null) {
            throw new IllegalArgumentException("major allele");
        }
        else {
            return hapIndices[allele].length;
        }
    }

    @Override
    public int hapIndex(int allele, int copy) {
        if (hapIndices[allele]==null) {
            throw new IllegalArgumentException("major allele");
        }
        else {
            return hapIndices[allele][copy];
        }
    }

    @Override
    public boolean isCarrier(int allele, int hap) {
        return get(hap)==allele;
    }

    /**
     * Returns the data represented by {@code this} as a VCF
     * record with a GT format field. The returned VCF record
     * will have missing QUAL and INFO fields, will have "PASS"
     * in the filter field, and will have a GT format field.
     * @return the data represented by {@code this} as a VCF
     * record with a GT format field
     */
    @Override
    public String toString() {
        return GTRec.toVcfRec(this);
    }

    @Override
    public int nMaps() {
        return 1;
    }

    @Override
    public IntArray[] maps() {
        return new IntArray[] {toIntArray()};
    }

    @Override
    public IntArray map(int index) {
        if (index!=0) {
            throw new IndexOutOfBoundsException(String.valueOf(index));
        }
        return toIntArray();
    }

    private IntArray toIntArray() {
        int[] ia = IntStream.range(0, nHaps)
                .map(i -> majorAllele)
                .toArray();
        for (int al=0; al<hapIndices.length; ++al) {
            if (hapIndices[al]!=null) {
                for (int i : hapIndices[al]) {
                    ia[i] = al;
                }
            }
        }
        return IntArray.packedCreate(ia, hapIndices.length);
    }
}