/*
 * @notice
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Modifications copyright (C) 2021 Elasticsearch B.V.
 */
package org.elasticsearch.xpack.lucene.bwc.codecs.index;

import org.apache.lucene.codecs.DocValuesProducer;
import org.apache.lucene.codecs.NormsProducer;
import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.NumericDocValues;
import org.apache.lucene.index.SortedDocValues;
import org.apache.lucene.index.SortedNumericDocValues;
import org.apache.lucene.index.SortedSetDocValues;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.util.BytesRef;

import java.io.IOException;
import java.util.Iterator;

/** Bridge helper methods for legacy codecs to map sorted doc values to iterables. */

public class LegacyDocValuesIterables {

    private LegacyDocValuesIterables() {
        // no
    }

    /** Converts {@link SortedDocValues} into an {@code Iterable&lt;BytesRef&gt;} for all the values.
     *
     * @deprecated Consume {@link SortedDocValues} instead. */
    @Deprecated
    public static Iterable<BytesRef> valuesIterable(final SortedDocValues values) {
        return new Iterable<BytesRef>() {
            @Override
            public Iterator<BytesRef> iterator() {
                return new Iterator<BytesRef>() {
                    private int nextOrd;

                    @Override
                    public boolean hasNext() {
                        return nextOrd < values.getValueCount();
                    }

                    @Override
                    public BytesRef next() {
                        try {
                            return values.lookupOrd(nextOrd++);
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    }
                };
            }
        };
    }

    /** Converts {@link SortedSetDocValues} into an {@code Iterable&lt;BytesRef&gt;} for all the values.
     *
     * @deprecated Consume {@link SortedSetDocValues} instead. */
    @Deprecated
    public static Iterable<BytesRef> valuesIterable(final SortedSetDocValues values) {
        return new Iterable<BytesRef>() {
            @Override
            public Iterator<BytesRef> iterator() {
                return new Iterator<BytesRef>() {
                    private long nextOrd;

                    @Override
                    public boolean hasNext() {
                        return nextOrd < values.getValueCount();
                    }

                    @Override
                    public BytesRef next() {
                        try {
                            return values.lookupOrd(nextOrd++);
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    }
                };
            }
        };
    }

    /** Converts {@link SortedDocValues} into the ord for each document as an {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link SortedDocValues} instead. */
    @Deprecated
    public static Iterable<Number> sortedOrdIterable(final DocValuesProducer valuesProducer, FieldInfo fieldInfo, int maxDoc) {
        return new Iterable<Number>() {
            @Override
            public Iterator<Number> iterator() {

                final SortedDocValues values;
                try {
                    values = valuesProducer.getSorted(fieldInfo);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private int nextDocID;

                    @Override
                    public boolean hasNext() {
                        return nextDocID < maxDoc;
                    }

                    @Override
                    public Number next() {
                        try {
                            if (nextDocID > values.docID()) {
                                values.nextDoc();
                            }
                            int result;
                            if (nextDocID == values.docID()) {
                                result = values.ordValue();
                            } else {
                                result = -1;
                            }
                            nextDocID++;
                            return result;
                        } catch (IOException ioe) {
                            throw new RuntimeException(ioe);
                        }
                    }
                };
            }
        };
    }

    /** Converts number-of-ords per document from {@link SortedSetDocValues} into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link SortedSetDocValues} instead. */
    @Deprecated
    public static Iterable<Number> sortedSetOrdCountIterable(
        final DocValuesProducer valuesProducer,
        final FieldInfo fieldInfo,
        final int maxDoc
    ) {

        return new Iterable<Number>() {

            @Override
            public Iterator<Number> iterator() {

                final SortedSetDocValues values;
                try {
                    values = valuesProducer.getSortedSet(fieldInfo);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private int nextDocID;
                    private int ordCount;

                    @Override
                    public boolean hasNext() {
                        return nextDocID < maxDoc;
                    }

                    @Override
                    public Number next() {
                        try {
                            if (nextDocID > values.docID()) {
                                if (values.nextDoc() != DocIdSetIterator.NO_MORE_DOCS) {
                                    ordCount = 0;
                                    while (values.nextOrd() != SortedSetDocValues.NO_MORE_ORDS) {
                                        ordCount++;
                                    }
                                }
                            }
                            int result;
                            if (nextDocID == values.docID()) {
                                result = ordCount;
                            } else {
                                result = 0;
                            }
                            nextDocID++;
                            return result;
                        } catch (IOException ioe) {
                            throw new RuntimeException(ioe);
                        }
                    }
                };
            }
        };
    }

    /** Converts all concatenated ords (in docID order) from {@link SortedSetDocValues} into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link SortedSetDocValues} instead. */
    @Deprecated
    public static Iterable<Number> sortedSetOrdsIterable(final DocValuesProducer valuesProducer, final FieldInfo fieldInfo) {

        return new Iterable<Number>() {

            @Override
            public Iterator<Number> iterator() {

                final SortedSetDocValues values;
                try {
                    values = valuesProducer.getSortedSet(fieldInfo);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private boolean nextIsSet;
                    private long nextOrd;

                    private void setNext() {
                        try {
                            if (nextIsSet == false) {
                                if (values.docID() == -1) {
                                    values.nextDoc();
                                }
                                while (true) {
                                    if (values.docID() == DocIdSetIterator.NO_MORE_DOCS) {
                                        nextOrd = -1;
                                        break;
                                    }
                                    nextOrd = values.nextOrd();
                                    if (nextOrd != -1) {
                                        break;
                                    }
                                    values.nextDoc();
                                }
                                nextIsSet = true;
                            }
                        } catch (IOException ioe) {
                            throw new RuntimeException(ioe);
                        }
                    }

                    @Override
                    public boolean hasNext() {
                        setNext();
                        return nextOrd != -1;
                    }

                    @Override
                    public Number next() {
                        setNext();
                        assert nextOrd != -1;
                        nextIsSet = false;
                        return nextOrd;
                    }
                };
            }
        };
    }

    /** Converts number-of-values per document from {@link SortedNumericDocValues} into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link SortedDocValues} instead. */
    @Deprecated
    public static Iterable<Number> sortedNumericToDocCount(final DocValuesProducer valuesProducer, final FieldInfo fieldInfo, int maxDoc) {
        return new Iterable<Number>() {

            @Override
            public Iterator<Number> iterator() {

                final SortedNumericDocValues values;
                try {
                    values = valuesProducer.getSortedNumeric(fieldInfo);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private int nextDocID;

                    @Override
                    public boolean hasNext() {
                        return nextDocID < maxDoc;
                    }

                    @Override
                    public Number next() {
                        try {
                            if (nextDocID > values.docID()) {
                                values.nextDoc();
                            }
                            int result;
                            if (nextDocID == values.docID()) {
                                result = values.docValueCount();
                            } else {
                                result = 0;
                            }
                            nextDocID++;
                            return result;
                        } catch (IOException ioe) {
                            throw new RuntimeException(ioe);
                        }
                    }
                };
            }
        };
    }

    /** Converts all concatenated values (in docID order) from {@link SortedNumericDocValues} into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link SortedDocValues} instead. */
    @Deprecated
    public static Iterable<Number> sortedNumericToValues(final DocValuesProducer valuesProducer, final FieldInfo fieldInfo) {
        return new Iterable<Number>() {

            @Override
            public Iterator<Number> iterator() {

                final SortedNumericDocValues values;
                try {
                    values = valuesProducer.getSortedNumeric(fieldInfo);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private boolean nextIsSet;
                    private int nextCount;
                    private int upto;
                    private long nextValue;

                    private void setNext() {
                        try {
                            if (nextIsSet == false) {
                                if (upto == nextCount) {
                                    values.nextDoc();
                                    if (values.docID() == DocIdSetIterator.NO_MORE_DOCS) {
                                        nextCount = 0;
                                        nextIsSet = false;
                                        return;
                                    } else {
                                        nextCount = values.docValueCount();
                                    }
                                    upto = 0;
                                }
                                nextValue = values.nextValue();
                                upto++;
                                nextIsSet = true;
                            }
                        } catch (IOException ioe) {
                            throw new RuntimeException(ioe);
                        }
                    }

                    @Override
                    public boolean hasNext() {
                        setNext();
                        return nextCount != 0;
                    }

                    @Override
                    public Number next() {
                        setNext();
                        assert nextCount != 0;
                        nextIsSet = false;
                        return nextValue;
                    }
                };
            }
        };
    }

    /** Converts norms into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link NumericDocValues} instead. */
    @Deprecated
    public static Iterable<Number> normsIterable(final FieldInfo field, final NormsProducer normsProducer, final int maxDoc) {

        return new Iterable<Number>() {

            @Override
            public Iterator<Number> iterator() {

                final NumericDocValues values;
                try {
                    values = normsProducer.getNorms(field);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private int docIDUpto = -1;

                    @Override
                    public boolean hasNext() {
                        return docIDUpto + 1 < maxDoc;
                    }

                    @Override
                    public Number next() {
                        docIDUpto++;
                        if (docIDUpto > values.docID()) {
                            try {
                                values.nextDoc();
                            } catch (IOException ioe) {
                                throw new RuntimeException(ioe);
                            }
                        }
                        Number result;
                        if (docIDUpto == values.docID()) {
                            try {
                                result = values.longValue();
                            } catch (IOException ioe) {
                                throw new RuntimeException(ioe);
                            }
                        } else {
                            // Unlike NumericDocValues, norms used to return 0 for missing values:
                            result = 0;
                        }
                        return result;
                    }
                };
            }
        };
    }

    /** Converts values from {@link BinaryDocValues} into {@code Iterable&lt;BytesRef&gt;}.
     *
     * @deprecated Consume {@link BinaryDocValues} instead. */
    @Deprecated
    public static Iterable<BytesRef> binaryIterable(final FieldInfo field, final DocValuesProducer valuesProducer, final int maxDoc) {
        return new Iterable<BytesRef>() {
            @Override
            public Iterator<BytesRef> iterator() {

                final BinaryDocValues values;
                try {
                    values = valuesProducer.getBinary(field);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<BytesRef>() {
                    private int docIDUpto = -1;

                    @Override
                    public boolean hasNext() {
                        return docIDUpto + 1 < maxDoc;
                    }

                    @Override
                    public BytesRef next() {
                        docIDUpto++;
                        if (docIDUpto > values.docID()) {
                            try {
                                values.nextDoc();
                            } catch (IOException ioe) {
                                throw new RuntimeException(ioe);
                            }
                        }
                        BytesRef result;
                        if (docIDUpto == values.docID()) {
                            try {
                                result = values.binaryValue();
                            } catch (IOException e) {
                                throw new RuntimeException(e);
                            }
                        } else {
                            result = null;
                        }
                        return result;
                    }
                };
            }
        };
    }

    /** Converts values from {@link NumericDocValues} into {@code Iterable&lt;Number&gt;}.
     *
     * @deprecated Consume {@link NumericDocValues} instead. */
    @Deprecated
    public static Iterable<Number> numericIterable(final FieldInfo field, final DocValuesProducer valuesProducer, final int maxDoc) {
        return new Iterable<Number>() {
            @Override
            public Iterator<Number> iterator() {

                final NumericDocValues values;
                try {
                    values = valuesProducer.getNumeric(field);
                } catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }

                return new Iterator<Number>() {
                    private int docIDUpto = -1;

                    @Override
                    public boolean hasNext() {
                        return docIDUpto + 1 < maxDoc;
                    }

                    @Override
                    public Number next() {
                        docIDUpto++;
                        if (docIDUpto > values.docID()) {
                            try {
                                values.nextDoc();
                            } catch (IOException ioe) {
                                throw new RuntimeException(ioe);
                            }
                        }
                        Number result;
                        if (docIDUpto == values.docID()) {
                            try {
                                result = values.longValue();
                            } catch (IOException ioe) {
                                throw new RuntimeException(ioe);
                            }
                        } else {
                            result = null;
                        }
                        return result;
                    }
                };
            }
        };
    }
}
