Add EmbeddingValue union type and Base64 support for embeddings

[yoshioterada]

This implementation adds support for Base64-encoded embeddings as the default response format, while maintaining complete backward compatibility with existing List<Float> usage.

1. Default Behavior Change

• New Default: Embedding requests now default to Base64 encoding format
• Backward Compatibility: Existing code using embedding() method continues to work unchanged
• Performance: Base64 encoding reduces network payload size significantly

Introduces the EmbeddingValue class to support both float list and base64-encoded embedding data, enabling efficient handling and backward compatibility. Embedding, EmbeddingCreateParams, and related classes are updated to use EmbeddingValue, with automatic decoding and encoding between formats. Adds EmbeddingDefaults for global default encoding configuration, and comprehensive tests for new behaviors and compatibility.

Improvement from previous PR

• Overload: Due to the spec of the Kotlin, it was not possible to implement with overload method.
• Immutable: Modified to Immutable class
• Private Constructor: Created the class with private constructor

This PR is the fix of the issue #211
This issue is related to the PR of #303

[yoshioterada]

When verifying the operation in the Azure OpenAI environment, I was able to confirm the operation with the following code:

package com.openai.example;

import com.openai.azure.AzureOpenAIServiceVersion;
import com.openai.azure.credential.AzureApiKeyCredential;
import com.openai.client.OpenAIClient;
import com.openai.client.OpenAIClientAsync;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.client.okhttp.OpenAIOkHttpClientAsync;
import com.openai.models.embeddings.CreateEmbeddingResponse;
import com.openai.models.embeddings.EmbeddingCreateParams;
import com.openai.models.embeddings.EmbeddingModel;
import com.openai.models.embeddings.EmbeddingValue;
import com.openai.services.blocking.EmbeddingService;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;

/**
 * Sample code using Azure OpenAI Embedding API
 * Demonstrates how to retrieve and process embedding data in Base64 and Float formats
 */
public final class EmbeddingsExampleAzure {
    private EmbeddingsExampleAzure() {}

    // Azure OpenAI endpoint and key configuration
    // Please replace with actual values
    private static final String AZURE_OPENAI_ENDPOINT = "https://***********.openai.azure.com";
    private static final String AZURE_OPENAI_KEY = "***********";

    private static OpenAIClient client;

    public static void main(String[] args) {
        // Initialize Azure OpenAI client
        client = OpenAIOkHttpClient.builder()
                .baseUrl(AZURE_OPENAI_ENDPOINT)
                .credential(AzureApiKeyCredential.create(AZURE_OPENAI_KEY))
                .azureServiceVersion(AzureOpenAIServiceVersion.getV2024_02_15_PREVIEW())
                .build();

        EmbeddingsExampleAzure example = new EmbeddingsExampleAzure();
        example.basicSample();
        example.multipleDataSample();
        example.asyncSample();
    }

    /**
     * Basic embedding retrieval sample
     * Demonstrates usage of default format, Float format, and Base64 format
     */
    public void basicSample() {
        EmbeddingService embeddings = client.embeddings();
        String singlePoem = "In the quiet night, stars whisper secrets, dreams take flight.";

        System.out.println("=== Basic Embedding Sample ===");

        // 1. Default format (Base64 is default)
        System.out.println("\n1. Getting embeddings in default format:");
        EmbeddingCreateParams embeddingCreateParams = EmbeddingCreateParams.builder()
                .input(singlePoem)
                .model(EmbeddingModel.TEXT_EMBEDDING_3_SMALL.asString())
                .build();

        embeddings.create(embeddingCreateParams).data().forEach(embedding -> {
            System.out.println("Embedding (default format): " + embedding.toString());

            // Use EmbeddingValue to check the original format
            EmbeddingValue embeddingValue = embedding.embeddingValue();
            if (embeddingValue.isBase64String()) {
                System.out.println(
                        "Received in Base64 format: " + embeddingValue.base64String().substring(0, 50) + "...");
            } else if (embeddingValue.isFloatList()) {
                System.out.println("Received in Float format: " + embeddingValue.floatList().size() + " elements");
            }

            // embedding() method always returns List<Float> (Base64 is automatically decoded)
            List<Float> floats = embedding.embedding();
            System.out.println(
                    "Retrieved as Float array: " + floats.size() + " elements, first 5: " + floats.subList(0, Math.min(5, floats.size())));
        });

        System.out.println("\n------------------------------------------------");

        // 2. Explicitly specify Float format
        System.out.println("\n2. Explicitly specifying Float format:");
        EmbeddingCreateParams embeddingCreateParams2 = EmbeddingCreateParams.builder()
                .input(singlePoem)
                .model(EmbeddingModel.TEXT_EMBEDDING_3_SMALL.asString())
                .encodingFormat(EmbeddingCreateParams.EncodingFormat.FLOAT)
                .build();

        embeddings.create(embeddingCreateParams2).data().forEach(embedding -> {
            EmbeddingValue embeddingValue = embedding.embeddingValue();
            if (embeddingValue.isFloatList()) {
                System.out.println("Received in Float format: " + embeddingValue.floatList().size() + " elements");
                System.out.println("First 5 values: "
                        + embeddingValue
                                .floatList()
                                .subList(
                                        0,
                                        Math.min(5, embeddingValue.floatList().size())));
            }

            // Can also convert to Base64 format
            String base64 = embeddingValue.asBase64String();
            System.out.println("Converted to Base64 format: " + base64.substring(0, 50) + "...");
        });

        System.out.println("\n------------------------------------------------");

        // 3. Explicitly specify Base64 format
        System.out.println("\n3. Explicitly specifying Base64 format:");
        EmbeddingCreateParams embeddingCreateParams3 = EmbeddingCreateParams.builder()
                .input(singlePoem)
                .model(EmbeddingModel.TEXT_EMBEDDING_3_SMALL.asString())
                .encodingFormat(EmbeddingCreateParams.EncodingFormat.BASE64)
                .build();

        embeddings.create(embeddingCreateParams3).data().forEach(embedding -> {
            EmbeddingValue embeddingValue = embedding.embeddingValue();
            if (embeddingValue.isBase64String()) {
                System.out.println(
                        "Received in Base64 format: " + embeddingValue.base64String().substring(0, 50) + "...");
            }

            // Automatically convert to Float array
            List<Float> floats = embeddingValue.asFloatList();
            System.out.println(
                    "Auto-converted to Float array: " + floats.size() + " elements, first 5: " + floats.subList(0, Math.min(5, floats.size())));
        });

        System.out.println("\n================================================");
    }

    /**
     * Multiple data embedding retrieval sample
     */
    public void multipleDataSample() {
        EmbeddingService embeddings = client.embeddings();

        System.out.println("\n=== Multiple Data Embedding Sample ===");

        getPoems().forEach(poem -> {
            System.out.println("\nPoem (start): " + poem);

            EmbeddingCreateParams embeddingCreateParams = EmbeddingCreateParams.builder()
                    .input(poem)
                    .model(EmbeddingModel.TEXT_EMBEDDING_3_SMALL.asString())
                    .build(); // Use default format (Base64)

            embeddings.create(embeddingCreateParams).data().forEach(embedding -> {
                List<Float> floats = embedding.embedding();
                System.out.println("Embedding (default): " + floats.size() + " dimensions");

                // Check original format
                EmbeddingValue embeddingValue = embedding.embeddingValue();
                if (embeddingValue.isBase64String()) {
                    System.out.println("Original format: Base64");
                } else {
                    System.out.println("Original format: Float array");
                }
            });
            System.out.println("Poem (end)");
        });

        System.out.println("\n================================================");
    }

    /**
     * Asynchronous embedding retrieval sample
     */
    public void asyncSample() {
        System.out.println("\n=== Asynchronous Embedding Sample ===");

        CountDownLatch latch = new CountDownLatch(1);
        try {
            OpenAIClientAsync asyncClient = OpenAIOkHttpClientAsync.builder()
                    .baseUrl(AZURE_OPENAI_ENDPOINT)
                    .credential(AzureApiKeyCredential.create(AZURE_OPENAI_KEY))
                    .azureServiceVersion(AzureOpenAIServiceVersion.getV2024_02_15_PREVIEW())
                    .build();

            CompletableFuture<CreateEmbeddingResponse> completableFuture = asyncClient
                    .embeddings()
                    .create(EmbeddingCreateParams.builder()
                            .input("The quick brown fox jumped over the lazy dog")
                            .model(EmbeddingModel.TEXT_EMBEDDING_3_SMALL)
                            .encodingFormat(EmbeddingCreateParams.EncodingFormat.FLOAT)
                            .user("user-1234")
                            .build());

            completableFuture
                    .thenAccept(response -> {
                        response.validate();
                        response.data().forEach(embedding -> {
                            System.out.println("Asynchronous embedding retrieval completed:");
                            System.out.println("Embedding info: " + embedding.toString());

                            EmbeddingValue embeddingValue = embedding.embeddingValue();
                            if (embeddingValue.isFloatList()) {
                                System.out.println(
                                        "Float format: " + embeddingValue.floatList().size() + " dimensions");
                            }

                            // Visitor pattern usage example
                            String result = embeddingValue.accept(new EmbeddingValue.Visitor<String>() {
                                @Override
                                public String visitFloatList(List<Float> floatList) {
                                    return "Processing Float array: " + floatList.size() + " elements";
                                }

                                @Override
                                public String visitBase64String(String base64String) {
                                    return "Processing Base64 string: " + base64String.length() + " characters";
                                }
                            });
                            System.out.println("Visitor pattern result: " + result);

                            latch.countDown();
                        });
                    })
                    .exceptionally(ex -> {
                        System.err.println("Error: " + ex.getMessage());
                        latch.countDown();
                        return null;
                    });

            latch.await();
            System.out.println("Asynchronous processing completed");

        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            System.err.println("Processing was interrupted");
        }

        System.out.println("\n================================================");
        System.out.println("All samples execution completed");
    }

    /**
     * Get sample poems list
     */
    private List<String> getPoems() {
        List<String> poems = new ArrayList<>();
        poems.add("In the quiet night, stars whisper secrets, dreams take flight.");
        poems.add("Beneath the moon's glow, shadows dance, hearts begin to know.");
        poems.add("Waves crash on the shore, time stands still, love forevermore.");
        poems.add("Autumn leaves fall, painting the ground, nature's final call.");
        poems.add("Morning dew glistens, a new day dawns, hope always listens.");
        poems.add("Mountains stand tall, silent guardians, witnessing it all.");
        poems.add("In a field of green, flowers bloom bright, a serene scene.");
        poems.add("Winter's chill bites, fireside warmth, cozy, long nights.");
        poems.add("Spring's gentle breeze, life awakens, hearts find ease.");
        poems.add("Sunset hues blend, day meets night, a perfect end.");
        return poems;
    }
}