Chore Support base64 embedding format (#485)

* chore: support base64 embedding format

* fix: add sizeOfFloat32

* chore: refactor base64 decoding

* chore: add tests

* fix linting

* fix test

* fix return error

* fix: use smaller slice for tests

* fix [skip ci]

* chore: refactor test to consider CreateEmbeddings response

* trigger build

* chore: remove named returns

* chore: refactor code to simplify the understanding

* chore: tests have been refactored to match the encoding format passed by request

* chore: fix tests

* fix

* fix

embeddings.go

@@ -2,6 +2,9 @@ package openai
 
 import (
 	"context"
+	"encoding/base64"
+	"encoding/binary"
+	"math"
 	"net/http"
 )
 
@@ -129,15 +132,83 @@ type EmbeddingResponse struct {
 	Usage  Usage          `json:"usage"`
 }
 
+type base64String string
+
+func (b base64String) Decode() ([]float32, error) {
+	decodedData, err := base64.StdEncoding.DecodeString(string(b))
+	if err != nil {
+		return nil, err
+	}
+
+	const sizeOfFloat32 = 4
+	floats := make([]float32, len(decodedData)/sizeOfFloat32)
+	for i := 0; i < len(floats); i++ {
+		floats[i] = math.Float32frombits(binary.LittleEndian.Uint32(decodedData[i*4 : (i+1)*4]))
+	}
+
+	return floats, nil
+}
+
+// Base64Embedding is a container for base64 encoded embeddings.
+type Base64Embedding struct {
+	Object    string       `json:"object"`
+	Embedding base64String `json:"embedding"`
+	Index     int          `json:"index"`
+}
+
+// EmbeddingResponseBase64 is the response from a Create embeddings request with base64 encoding format.
+type EmbeddingResponseBase64 struct {
+	Object string            `json:"object"`
+	Data   []Base64Embedding `json:"data"`
+	Model  EmbeddingModel    `json:"model"`
+	Usage  Usage             `json:"usage"`
+}
+
+// ToEmbeddingResponse converts an embeddingResponseBase64 to an EmbeddingResponse.
+func (r *EmbeddingResponseBase64) ToEmbeddingResponse() (EmbeddingResponse, error) {
+	data := make([]Embedding, len(r.Data))
+
+	for i, base64Embedding := range r.Data {
+		embedding, err := base64Embedding.Embedding.Decode()
+		if err != nil {
+			return EmbeddingResponse{}, err
+		}
+
+		data[i] = Embedding{
+			Object:    base64Embedding.Object,
+			Embedding: embedding,
+			Index:     base64Embedding.Index,
+		}
+	}
+
+	return EmbeddingResponse{
+		Object: r.Object,
+		Model:  r.Model,
+		Data:   data,
+		Usage:  r.Usage,
+	}, nil
+}
+
 type EmbeddingRequestConverter interface {
 	// Needs to be of type EmbeddingRequestStrings or EmbeddingRequestTokens
 	Convert() EmbeddingRequest
 }
 
+// EmbeddingEncodingFormat is the format of the embeddings data.
+// Currently, only "float" and "base64" are supported, however, "base64" is not officially documented.
+// If not specified OpenAI will use "float".
+type EmbeddingEncodingFormat string
+
+const (
+	EmbeddingEncodingFormatFloat  EmbeddingEncodingFormat = "float"
+	EmbeddingEncodingFormatBase64 EmbeddingEncodingFormat = "base64"
+)
+
 type EmbeddingRequest struct {
-	Input any            `json:"input"`
-	Model EmbeddingModel `json:"model"`
-	User  string         `json:"user"`
+	Input          any                     `json:"input"`
+	Model          EmbeddingModel          `json:"model"`
+	User           string                  `json:"user"`
+	EncodingFormat EmbeddingEncodingFormat `json:"encoding_format,omitempty"`
 }
 
 func (r EmbeddingRequest) Convert() EmbeddingRequest {
@@ -158,13 +229,18 @@ type EmbeddingRequestStrings struct {
 	Model EmbeddingModel `json:"model"`
 	// A unique identifier representing your end-user, which will help OpenAI to monitor and detect abuse.
 	User string `json:"user"`
+	// EmbeddingEncodingFormat is the format of the embeddings data.
+	// Currently, only "float" and "base64" are supported, however, "base64" is not officially documented.
+	// If not specified OpenAI will use "float".
+	EncodingFormat EmbeddingEncodingFormat `json:"encoding_format,omitempty"`
 }
 
 func (r EmbeddingRequestStrings) Convert() EmbeddingRequest {
 	return EmbeddingRequest{
-		Input: r.Input,
-		Model: r.Model,
-		User:  r.User,
+		Input:          r.Input,
+		Model:          r.Model,
+		User:           r.User,
+		EncodingFormat: r.EncodingFormat,
 	}
 }
 
@@ -181,13 +257,18 @@ type EmbeddingRequestTokens struct {
 	Model EmbeddingModel `json:"model"`
 	// A unique identifier representing your end-user, which will help OpenAI to monitor and detect abuse.
 	User string `json:"user"`
+	// EmbeddingEncodingFormat is the format of the embeddings data.
+	// Currently, only "float" and "base64" are supported, however, "base64" is not officially documented.
+	// If not specified OpenAI will use "float".
+	EncodingFormat EmbeddingEncodingFormat `json:"encoding_format,omitempty"`
 }
 
 func (r EmbeddingRequestTokens) Convert() EmbeddingRequest {
 	return EmbeddingRequest{
-		Input: r.Input,
-		Model: r.Model,
-		User:  r.User,
+		Input:          r.Input,
+		Model:          r.Model,
+		User:           r.User,
+		EncodingFormat: r.EncodingFormat,
 	}
 }
 
@@ -196,14 +277,27 @@ func (r EmbeddingRequestTokens) Convert() EmbeddingRequest {
 //
 // Body should be of type EmbeddingRequestStrings for embedding strings or EmbeddingRequestTokens
 // for embedding groups of text already converted to tokens.
-func (c *Client) CreateEmbeddings(ctx context.Context, conv EmbeddingRequestConverter) (res EmbeddingResponse, err error) { //nolint:lll
+func (c *Client) CreateEmbeddings(
+	ctx context.Context,
+	conv EmbeddingRequestConverter,
+) (res EmbeddingResponse, err error) {
 	baseReq := conv.Convert()
 	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL("/embeddings", baseReq.Model.String()), withBody(baseReq))
 	if err != nil {
 		return
 	}
 
-	err = c.sendRequest(req, &res)
+	if baseReq.EncodingFormat != EmbeddingEncodingFormatBase64 {
+		err = c.sendRequest(req, &res)
+		return
+	}
 
+	base64Response := &EmbeddingResponseBase64{}
+	err = c.sendRequest(req, base64Response)
+	if err != nil {
+		return
+	}
+
+	res, err = base64Response.ToEmbeddingResponse()
 	return
 }