/*
 * 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; you may not use this file except in compliance with the Elastic License
 * 2.0.
 *
 * This Java port of CLD3 was derived from Google's CLD3 project at https://github.com/google/cld3
 */
package org.elasticsearch.xpack.core.ml.inference.trainedmodel.langident;

import org.apache.lucene.util.RamUsageEstimator;
import org.elasticsearch.common.ParseField;
import org.elasticsearch.common.collect.Tuple;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.xcontent.ConstructingObjectParser;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentParser;
import org.elasticsearch.xpack.core.ml.inference.results.ClassificationInferenceResults;
import org.elasticsearch.xpack.core.ml.inference.results.InferenceResults;
import org.elasticsearch.xpack.core.ml.inference.results.TopClassEntry;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.ClassificationConfig;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.InferenceConfig;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.InferenceHelpers;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.LenientlyParsedTrainedModel;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.PredictionFieldType;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.StrictlyParsedTrainedModel;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TargetType;
import org.elasticsearch.xpack.core.ml.inference.trainedmodel.inference.InferenceModel;
import org.elasticsearch.xpack.core.ml.utils.ExceptionsHelper;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
import static org.elasticsearch.xpack.core.ml.inference.utils.Statistics.softMax;

public class LangIdentNeuralNetwork implements StrictlyParsedTrainedModel, LenientlyParsedTrainedModel, InferenceModel {

    public static final ParseField NAME = new ParseField("lang_ident_neural_network");
    public static final ParseField EMBEDDED_VECTOR_FEATURE_NAME = new ParseField("embedded_vector_feature_name");
    public static final ParseField HIDDEN_LAYER = new ParseField("hidden_layer");
    public static final ParseField SOFTMAX_LAYER = new ParseField("softmax_layer");
    public static final ConstructingObjectParser<LangIdentNeuralNetwork, Void> STRICT_PARSER = createParser(false);
    public static final ConstructingObjectParser<LangIdentNeuralNetwork, Void> LENIENT_PARSER = createParser(true);

    private static final List<String> LANGUAGE_NAMES = Arrays.asList(
        "eo", "co", "eu", "ta", "de", "mt", "ps", "te", "su", "uz", "zh-Latn", "ne",
        "nl", "sw", "sq", "hmn", "ja", "no", "mn", "so", "ko", "kk", "sl", "ig",
        "mr", "th", "zu", "ml", "hr", "bs", "lo", "sd", "cy", "hy", "uk", "pt",
        "lv", "iw", "cs", "vi", "jv", "be", "km", "mk", "tr", "fy", "am", "zh",
        "da", "sv", "fi", "ht", "af", "la", "id", "fil", "sm", "ca", "el", "ka",
        "sr", "it", "sk", "ru", "ru-Latn", "bg", "ny", "fa", "haw", "gl", "et",
        "ms", "gd", "bg-Latn", "ha", "is", "ur", "mi", "hi", "bn", "hi-Latn", "fr",
        "yi", "hu", "xh", "my", "tg", "ro", "ar", "lb", "el-Latn", "st", "ceb",
        "kn", "az", "si", "ky", "mg", "en", "gu", "es", "pl", "ja-Latn", "ga", "lt",
        "sn", "yo", "pa", "ku");

    private static final long SHALLOW_SIZE = RamUsageEstimator.shallowSizeOfInstance(LangIdentNeuralNetwork.class);

    private static final int EMBEDDING_VECTOR_LENGTH = 80;

    @SuppressWarnings("unchecked")
    private static ConstructingObjectParser<LangIdentNeuralNetwork, Void> createParser(boolean lenient) {
        ConstructingObjectParser<LangIdentNeuralNetwork, Void> parser = new ConstructingObjectParser<>(
            NAME.getPreferredName(),
            lenient,
            a -> new LangIdentNeuralNetwork((String) a[0],
                (LangNetLayer) a[1],
                (LangNetLayer) a[2]));
        parser.declareString(constructorArg(), EMBEDDED_VECTOR_FEATURE_NAME);
        parser.declareObject(constructorArg(),
            (p, c) -> lenient ? LangNetLayer.LENIENT_PARSER.apply(p, c) : LangNetLayer.STRICT_PARSER.apply(p, c),
            HIDDEN_LAYER);
        parser.declareObject(constructorArg(),
            (p, c) -> lenient ? LangNetLayer.LENIENT_PARSER.apply(p, c) : LangNetLayer.STRICT_PARSER.apply(p, c),
            SOFTMAX_LAYER);
        return parser;
    }

    public static LangIdentNeuralNetwork fromXContentStrict(XContentParser parser) {
        return STRICT_PARSER.apply(parser, null);
    }

    public static LangIdentNeuralNetwork fromXContentLenient(XContentParser parser) {
        return LENIENT_PARSER.apply(parser, null);
    }

    private final LangNetLayer hiddenLayer;
    private final LangNetLayer softmaxLayer;
    private final String embeddedVectorFeatureName;

    public LangIdentNeuralNetwork(String embeddedVectorFeatureName,
                                  LangNetLayer hiddenLayer,
                                  LangNetLayer softmaxLayer) {
        this.embeddedVectorFeatureName = ExceptionsHelper.requireNonNull(embeddedVectorFeatureName, EMBEDDED_VECTOR_FEATURE_NAME);
        this.hiddenLayer = ExceptionsHelper.requireNonNull(hiddenLayer, HIDDEN_LAYER);
        this.softmaxLayer = ExceptionsHelper.requireNonNull(softmaxLayer, SOFTMAX_LAYER);
    }

    public LangIdentNeuralNetwork(StreamInput in) throws IOException {
        this.embeddedVectorFeatureName = in.readString();
        this.hiddenLayer = new LangNetLayer(in);
        this.softmaxLayer = new LangNetLayer(in);
    }

    @Override
    public InferenceResults infer(Map<String, Object> fields, InferenceConfig config, Map<String, String> featureDecoderMap) {
        if (config.requestingImportance()) {
            throw ExceptionsHelper.badRequestException("[{}] model does not supports feature importance",
                NAME.getPreferredName());
        }
        if (config instanceof ClassificationConfig == false) {
            throw ExceptionsHelper.badRequestException("[{}] model only supports classification",
                NAME.getPreferredName());
        }
        Object vector = fields.get(embeddedVectorFeatureName);
        if (vector instanceof double[] == false) {
            throw ExceptionsHelper.badRequestException("[{}] model could not find non-null numerical array named [{}]",
                NAME.getPreferredName(),
                embeddedVectorFeatureName);
        }
        double[] embeddedVector = (double[]) vector;
        if (embeddedVector.length != EMBEDDING_VECTOR_LENGTH) {
            throw ExceptionsHelper.badRequestException("[{}] model is expecting embedding vector of length [{}] but got [{}]",
                NAME.getPreferredName(),
                EMBEDDING_VECTOR_LENGTH,
                embeddedVector.length);
        }
        double[] h0 = hiddenLayer.productPlusBias(false, embeddedVector);
        double[] scores = softmaxLayer.productPlusBias(true, h0);

        double[] probabilities = softMax(scores);

        ClassificationConfig classificationConfig = (ClassificationConfig) config;
        Tuple<InferenceHelpers.TopClassificationValue, List<TopClassEntry>> topClasses = InferenceHelpers.topClasses(
            probabilities,
            LANGUAGE_NAMES,
            null,
            classificationConfig.getNumTopClasses(),
            PredictionFieldType.STRING);
        final InferenceHelpers.TopClassificationValue classificationValue = topClasses.v1();
        assert classificationValue.getValue() >= 0 && classificationValue.getValue() < LANGUAGE_NAMES.size() :
            "Invalid language predicted. Predicted language index " + topClasses.v1();
        return new ClassificationInferenceResults(classificationValue.getValue(),
            LANGUAGE_NAMES.get(classificationValue.getValue()),
            topClasses.v2(),
            Collections.emptyList(),
            classificationConfig,
            classificationValue.getProbability(),
            classificationValue.getScore());
    }

    @Override
    public InferenceResults infer(double[] embeddedVector, InferenceConfig config) {
        throw new UnsupportedOperationException("[lang_ident] does not support nested inference");
    }

    @Override
    public void rewriteFeatureIndices(Map<String, Integer> newFeatureIndexMapping) {
        if (newFeatureIndexMapping != null && newFeatureIndexMapping.isEmpty() == false) {
            throw new UnsupportedOperationException("[lang_ident] does not support nested inference");
        }
    }

    @Override
    public String[] getFeatureNames() {
        return new String[] {embeddedVectorFeatureName};
    }

    @Override
    public TargetType targetType() {
        return TargetType.CLASSIFICATION;
    }

    @Override
    public void validate() {
    }

    @Override
    public long estimatedNumOperations() {
        long numOps = hiddenLayer.getBias().length; // adding bias
        numOps += hiddenLayer.getWeights().length; // multiplying weights
        numOps += softmaxLayer.getBias().length; // adding bias
        numOps += softmaxLayer.getWeights().length; // multiplying softmax weights
        return numOps;
    }

    @Override
    public boolean supportsFeatureImportance() {
        return false;
    }

    @Override
    public long ramBytesUsed() {
        long size = SHALLOW_SIZE;
        size += RamUsageEstimator.sizeOf(hiddenLayer);
        size += RamUsageEstimator.sizeOf(softmaxLayer);
        return size;
    }

    @Override
    public String getWriteableName() {
        return NAME.getPreferredName();
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        out.writeString(embeddedVectorFeatureName);
        this.hiddenLayer.writeTo(out);
        this.softmaxLayer.writeTo(out);
    }

    @Override
    public String getName() {
        return NAME.getPreferredName();
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject();
        builder.field(EMBEDDED_VECTOR_FEATURE_NAME.getPreferredName(), embeddedVectorFeatureName);
        builder.field(HIDDEN_LAYER.getPreferredName(), hiddenLayer);
        builder.field(SOFTMAX_LAYER.getPreferredName(), softmaxLayer);
        builder.endObject();
        return builder;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        LangIdentNeuralNetwork that = (LangIdentNeuralNetwork) o;
        return Objects.equals(embeddedVectorFeatureName, that.embeddedVectorFeatureName)
            && Objects.equals(hiddenLayer, that.hiddenLayer)
            && Objects.equals(softmaxLayer, that.softmaxLayer);
    }

    @Override
    public int hashCode() {
        return Objects.hash(embeddedVectorFeatureName, hiddenLayer, softmaxLayer);
    }

}
