package dev.langchain4j.model.embedding;

import dev.langchain4j.model.embedding.onnx.AbstractInProcessEmbeddingModel;
import dev.langchain4j.model.embedding.onnx.OnnxBertBiEncoder;
import dev.langchain4j.model.embedding.onnx.PoolingMode;
import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Objects;
import java.util.concurrent.Executors;

/**
 * An embedding model that runs within your Java application's process. Any BERT-based model (e.g.,
 * from HuggingFace) can be used, as long as it is in ONNX format. Information on how to convert
 * models into ONNX format can be found <a href=
 * "https://huggingface.co/docs/optimum/exporters/onnx/usage_guides/export_a_model">here</a>. Many
 * models already converted to ONNX format are available
 * <a href="https://huggingface.co/Xenova">here</a>. Copy from
 * dev.langchain4j.model.embedding.OnnxEmbeddingModel.
 */
public class S2OnnxEmbeddingModel extends AbstractInProcessEmbeddingModel {
    private static volatile OnnxBertBiEncoder cachedModel;
    private static volatile String cachedModelPath;
    private static volatile String cachedVocabularyPath;

    public S2OnnxEmbeddingModel(String pathToModel, String vocabularyPath) {
        super(Executors.newSingleThreadExecutor());
        if (shouldReloadModel(pathToModel, vocabularyPath)) {
            synchronized (S2OnnxEmbeddingModel.class) {
                if (shouldReloadModel(pathToModel, vocabularyPath)) {
                    URL resource = AbstractInProcessEmbeddingModel.class
                            .getResource("/bert-vocabulary-en.txt");
                    if (StringUtils.isNotBlank(vocabularyPath)) {
                        try {
                            resource = Paths.get(vocabularyPath).toUri().toURL();
                        } catch (MalformedURLException e) {
                            throw new RuntimeException(e);
                        }
                    }
                    cachedModel = loadFromFileSystem(Paths.get(pathToModel), resource);
                    cachedModelPath = pathToModel;
                    cachedVocabularyPath = vocabularyPath;
                }
            }
        }
    }

    public S2OnnxEmbeddingModel(String pathToModel) {
        this(pathToModel, null);
    }

    @Override
    protected OnnxBertBiEncoder model() {
        return cachedModel;
    }

    private static boolean shouldReloadModel(String pathToModel, String vocabularyPath) {
        return cachedModel == null || !Objects.equals(cachedModelPath, pathToModel)
                || !Objects.equals(cachedVocabularyPath, vocabularyPath);
    }

    static OnnxBertBiEncoder loadFromFileSystem(Path pathToModel, URL vocabularyFile) {
        try {
            return new OnnxBertBiEncoder(Files.newInputStream(pathToModel),
                    vocabularyFile.openStream(), PoolingMode.MEAN);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}