/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.index.mapper.vectors;

import org.apache.lucene.index.ByteVectorValues;
import org.apache.lucene.index.FloatVectorValues;
import org.apache.lucene.search.VectorScorer;
import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.ElementType;
import org.elasticsearch.script.field.vectors.ByteKnnDenseVectorDocValuesField;
import org.elasticsearch.script.field.vectors.DenseVector;
import org.elasticsearch.script.field.vectors.DenseVectorDocValuesField;
import org.elasticsearch.script.field.vectors.KnnDenseVectorDocValuesField;
import org.elasticsearch.test.ESTestCase;

import java.io.IOException;

import static org.hamcrest.Matchers.containsString;

public class KnnDenseVectorScriptDocValuesTests extends ESTestCase {

    public void testFloatGetVectorValueAndGetMagnitude() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        float[] expectedMagnitudes = { 1.7320f, 2.4495f, 3.3166f };

        DenseVectorDocValuesField field = new KnnDenseVectorDocValuesField(wrap(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();
        for (int i = 0; i < vectors.length; i++) {
            field.setNextDocId(i);
            assertEquals(1, field.size());
            assertEquals(dims, scriptDocValues.dims());
            assertArrayEquals(vectors[i], scriptDocValues.getVectorValue(), 0.0001f);
            assertEquals(expectedMagnitudes[i], scriptDocValues.getMagnitude(), 0.0001f);
        }
    }

    public void testByteGetVectorValueAndGetMagnitude() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        float[] expectedMagnitudes = { 1.7320f, 2.4495f, 3.3166f };

        DenseVectorDocValuesField field = new ByteKnnDenseVectorDocValuesField(wrapBytes(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();
        for (int i = 0; i < vectors.length; i++) {
            field.setNextDocId(i);
            assertEquals(1, field.size());
            assertEquals(dims, scriptDocValues.dims());
            assertArrayEquals(vectors[i], scriptDocValues.getVectorValue(), 0.0001f);
            assertEquals(expectedMagnitudes[i], scriptDocValues.getMagnitude(), 0.0001f);
        }
    }

    public void testFloatMetadataAndIterator() throws IOException {
        int dims = 3;
        float[][] vectors = fill(new float[randomIntBetween(1, 5)][dims], ElementType.FLOAT);
        DenseVectorDocValuesField field = new KnnDenseVectorDocValuesField(wrap(vectors), "test", dims);
        for (int i = 0; i < vectors.length; i++) {
            field.setNextDocId(i);
            DenseVector dv = field.get();
            assertEquals(1, dv.size());
            assertFalse(dv.isEmpty());
            assertEquals(dims, dv.getDims());
            UnsupportedOperationException e = expectThrows(UnsupportedOperationException.class, field::iterator);
            assertEquals("Cannot iterate over single valued dense_vector field, use get() instead", e.getMessage());
        }
        assertEquals(1, field.size());
        field.setNextDocId(vectors.length);
        DenseVector dv = field.get();
        assertEquals(dv, DenseVector.EMPTY);
    }

    public void testByteMetadataAndIterator() throws IOException {
        int dims = 3;
        float[][] vectors = fill(new float[randomIntBetween(1, 5)][dims], ElementType.BYTE);
        DenseVectorDocValuesField field = new ByteKnnDenseVectorDocValuesField(wrapBytes(vectors), "test", dims);
        for (int i = 0; i < vectors.length; i++) {
            field.setNextDocId(i);
            DenseVector dv = field.get();
            assertEquals(1, dv.size());
            assertFalse(dv.isEmpty());
            assertEquals(dims, dv.getDims());
            UnsupportedOperationException e = expectThrows(UnsupportedOperationException.class, field::iterator);
            assertEquals("Cannot iterate over single valued dense_vector field, use get() instead", e.getMessage());
        }
        assertEquals(1, field.size());
        field.setNextDocId(vectors.length);
        DenseVector dv = field.get();
        assertEquals(dv, DenseVector.EMPTY);
    }

    protected float[][] fill(float[][] vectors, ElementType elementType) {
        for (float[] vector : vectors) {
            for (int i = 0; i < vector.length; i++) {
                vector[i] = elementType == ElementType.FLOAT ? randomFloat() : randomByte();
            }
        }
        return vectors;
    }

    public void testFloatMissingValues() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        DenseVectorDocValuesField field = new KnnDenseVectorDocValuesField(wrap(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();

        field.setNextDocId(3);
        Exception e = expectThrows(IllegalArgumentException.class, scriptDocValues::getVectorValue);
        assertEquals("A document doesn't have a value for a vector field!", e.getMessage());

        e = expectThrows(IllegalArgumentException.class, scriptDocValues::getMagnitude);
        assertEquals("A document doesn't have a value for a vector field!", e.getMessage());
    }

    public void testByteMissingValues() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        DenseVectorDocValuesField field = new ByteKnnDenseVectorDocValuesField(wrapBytes(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();

        field.setNextDocId(3);
        Exception e = expectThrows(IllegalArgumentException.class, scriptDocValues::getVectorValue);
        assertEquals("A document doesn't have a value for a vector field!", e.getMessage());

        e = expectThrows(IllegalArgumentException.class, scriptDocValues::getMagnitude);
        assertEquals("A document doesn't have a value for a vector field!", e.getMessage());
    }

    public void testFloatGetFunctionIsNotAccessible() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        DenseVectorDocValuesField field = new KnnDenseVectorDocValuesField(wrap(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();

        field.setNextDocId(0);
        Exception e = expectThrows(UnsupportedOperationException.class, () -> scriptDocValues.get(0));
        assertThat(
            e.getMessage(),
            containsString(
                "accessing a vector field's value through 'get' or 'value' is not supported, use 'vectorValue' or 'magnitude' instead."
            )
        );
    }

    public void testByteGetFunctionIsNotAccessible() throws IOException {
        int dims = 3;
        float[][] vectors = { { 1, 1, 1 }, { 1, 1, 2 }, { 1, 1, 3 } };
        DenseVectorDocValuesField field = new ByteKnnDenseVectorDocValuesField(wrapBytes(vectors), "test", dims);
        DenseVectorScriptDocValues scriptDocValues = field.toScriptDocValues();

        field.setNextDocId(0);
        Exception e = expectThrows(UnsupportedOperationException.class, () -> scriptDocValues.get(0));
        assertThat(
            e.getMessage(),
            containsString(
                "accessing a vector field's value through 'get' or 'value' is not supported, use 'vectorValue' or 'magnitude' instead."
            )
        );
    }

    public void testFloatMissingVectorValues() throws IOException {
        int dims = 7;
        DenseVectorDocValuesField emptyKnn = new KnnDenseVectorDocValuesField(null, "test", dims);

        emptyKnn.setNextDocId(0);
        assertEquals(0, emptyKnn.toScriptDocValues().size());
        assertTrue(emptyKnn.toScriptDocValues().isEmpty());
        assertEquals(DenseVector.EMPTY, emptyKnn.get());
        assertNull(emptyKnn.get(null));
        assertNull(emptyKnn.getInternal());
        UnsupportedOperationException e = expectThrows(UnsupportedOperationException.class, emptyKnn::iterator);
        assertEquals("Cannot iterate over single valued dense_vector field, use get() instead", e.getMessage());
    }

    public void testByteMissingVectorValues() throws IOException {
        int dims = 7;
        DenseVectorDocValuesField emptyKnn = new ByteKnnDenseVectorDocValuesField(null, "test", dims);

        emptyKnn.setNextDocId(0);
        assertEquals(0, emptyKnn.toScriptDocValues().size());
        assertTrue(emptyKnn.toScriptDocValues().isEmpty());
        assertEquals(DenseVector.EMPTY, emptyKnn.get());
        assertNull(emptyKnn.get(null));
        assertNull(emptyKnn.getInternal());
        UnsupportedOperationException e = expectThrows(UnsupportedOperationException.class, emptyKnn::iterator);
        assertEquals("Cannot iterate over single valued dense_vector field, use get() instead", e.getMessage());
    }

    public static ByteVectorValues wrapBytes(float[][] vectors) {
        return new ByteVectorValues() {
            int index = 0;
            byte[] byteVector = new byte[vectors[0].length];

            @Override
            public int dimension() {
                return 0;
            }

            @Override
            public int size() {
                return vectors.length;
            }

            @Override
            public DocIndexIterator iterator() {
                return new DocIndexIterator() {
                    @Override
                    public int index() {
                        return index;
                    }

                    @Override
                    public int docID() {
                        return index;
                    }

                    @Override
                    public int nextDoc() {
                        throw new UnsupportedOperationException();
                    }

                    @Override
                    public int advance(int target) {
                        if (target >= size()) {
                            return NO_MORE_DOCS;
                        }
                        return index = target;
                    }

                    @Override
                    public long cost() {
                        return 0;
                    }
                };
            }

            @Override
            public byte[] vectorValue(int ord) {
                assert ord == index;
                for (int i = 0; i < byteVector.length; i++) {
                    byteVector[i] = (byte) vectors[index][i];
                }
                return byteVector;
            }

            @Override
            public ByteVectorValues copy() {
                throw new UnsupportedOperationException();
            }

            @Override
            public VectorScorer scorer(byte[] floats) {
                throw new UnsupportedOperationException();
            }
        };
    }

    public static FloatVectorValues wrap(float[][] vectors) {
        int dim = vectors.length > 0 ? vectors[0].length : 0;
        return new FloatVectorValues() {
            int index = -1;

            @Override
            public int dimension() {
                return dim;
            }

            @Override
            public int size() {
                return vectors.length;
            }

            @Override
            public DocIndexIterator iterator() {
                return new DocIndexIterator() {
                    @Override
                    public int index() {
                        return index;
                    }

                    @Override
                    public int docID() {
                        return index;
                    }

                    @Override
                    public int nextDoc() throws IOException {
                        return advance(index + 1);
                    }

                    @Override
                    public int advance(int target) throws IOException {
                        if (target >= size()) {
                            return NO_MORE_DOCS;
                        }
                        return index = target;
                    }

                    @Override
                    public long cost() {
                        return 0;
                    }
                };
            }

            @Override
            public float[] vectorValue(int ord) {
                assert ord == index;
                return vectors[index];
            }

            @Override
            public FloatVectorValues copy() {
                throw new UnsupportedOperationException();
            }

            @Override
            public VectorScorer scorer(float[] floats) {
                throw new UnsupportedOperationException();
            }
        };
    }
}