CLIProxyAPI/internal/api/translator/request.go

package translator

import (
	"encoding/json"
	"strings"

	"github.com/luispater/CLIProxyAPI/internal/client"
	log "github.com/sirupsen/logrus"
	"github.com/tidwall/gjson"
)

// PrepareRequest translates a raw JSON request from an OpenAI-compatible format
// to the internal format expected by the backend client. It parses messages,
// roles, content types (text, image, file), and tool calls.
func PrepareRequest(rawJson []byte) (string, *client.Content, []client.Content, []client.ToolDeclaration) {
	// Extract the model name from the request, defaulting to "gemini-2.5-pro".
	modelName := "gemini-2.5-pro"
	modelResult := gjson.GetBytes(rawJson, "model")
	if modelResult.Type == gjson.String {
		modelName = modelResult.String()
	}

	// Process the array of messages.
	contents := make([]client.Content, 0)
	var systemInstruction *client.Content
	messagesResult := gjson.GetBytes(rawJson, "messages")
	if messagesResult.IsArray() {
		messagesResults := messagesResult.Array()
		for i := 0; i < len(messagesResults); i++ {
			messageResult := messagesResults[i]
			roleResult := messageResult.Get("role")
			contentResult := messageResult.Get("content")
			if roleResult.Type != gjson.String {
				continue
			}

			switch roleResult.String() {
			// System messages are converted to a user message followed by a model's acknowledgment.
			case "system":
				if contentResult.Type == gjson.String {
					systemInstruction = &client.Content{Role: "user", Parts: []client.Part{{Text: contentResult.String()}}}
				} else if contentResult.IsObject() {
					// Handle object-based system messages.
					if contentResult.Get("type").String() == "text" {
						systemInstruction = &client.Content{Role: "user", Parts: []client.Part{{Text: contentResult.Get("text").String()}}}
					}
				}
			// User messages can contain simple text or a multi-part body.
			case "user":
				if contentResult.Type == gjson.String {
					contents = append(contents, client.Content{Role: "user", Parts: []client.Part{{Text: contentResult.String()}}})
				} else if contentResult.IsArray() {
					// Handle multi-part user messages (text, images, files).
					contentItemResults := contentResult.Array()
					parts := make([]client.Part, 0)
					for j := 0; j < len(contentItemResults); j++ {
						contentItemResult := contentItemResults[j]
						contentTypeResult := contentItemResult.Get("type")
						switch contentTypeResult.String() {
						case "text":
							parts = append(parts, client.Part{Text: contentItemResult.Get("text").String()})
						case "image_url":
							// Parse data URI for images.
							imageURL := contentItemResult.Get("image_url.url").String()
							if len(imageURL) > 5 {
								imageURLs := strings.SplitN(imageURL[5:], ";", 2)
								if len(imageURLs) == 2 && len(imageURLs[1]) > 7 {
									parts = append(parts, client.Part{InlineData: &client.InlineData{
										MimeType: imageURLs[0],
										Data:     imageURLs[1][7:],
									}})
								}
							}
						case "file":
							// Handle file attachments by determining MIME type from extension.
							filename := contentItemResult.Get("file.filename").String()
							fileData := contentItemResult.Get("file.file_data").String()
							ext := ""
							if split := strings.Split(filename, "."); len(split) > 1 {
								ext = split[len(split)-1]
							}
							if mimeType, ok := MimeTypes[ext]; ok {
								parts = append(parts, client.Part{InlineData: &client.InlineData{
									MimeType: mimeType,
									Data:     fileData,
								}})
							} else {
								log.Warnf("Unknown file name extension '%s' at index %d, skipping file", ext, j)
							}
						}
					}
					contents = append(contents, client.Content{Role: "user", Parts: parts})
				}
			// Assistant messages can contain text or tool calls.
			case "assistant":
				if contentResult.Type == gjson.String {
					contents = append(contents, client.Content{Role: "model", Parts: []client.Part{{Text: contentResult.String()}}})
				} else if !contentResult.Exists() || contentResult.Type == gjson.Null {
					// Handle tool calls made by the assistant.
					toolCallsResult := messageResult.Get("tool_calls")
					if toolCallsResult.IsArray() {
						tcsResult := toolCallsResult.Array()
						for j := 0; j < len(tcsResult); j++ {
							tcResult := tcsResult[j]
							functionName := tcResult.Get("function.name").String()
							functionArgs := tcResult.Get("function.arguments").String()
							var args map[string]any
							if err := json.Unmarshal([]byte(functionArgs), &args); err == nil {
								contents = append(contents, client.Content{
									Role: "model", Parts: []client.Part{{
										FunctionCall: &client.FunctionCall{
											Name: functionName,
											Args: args,
										},
									}},
								})
							}
						}
					}
				}
			// Tool messages contain the output of a tool call.
			case "tool":
				toolCallID := messageResult.Get("tool_call_id").String()
				if toolCallID != "" {
					var responseData string
					if contentResult.Type == gjson.String {
						responseData = contentResult.String()
					} else if contentResult.IsObject() && contentResult.Get("type").String() == "text" {
						responseData = contentResult.Get("text").String()
					}
					functionResponse := client.FunctionResponse{Name: toolCallID, Response: map[string]interface{}{"result": responseData}}
					contents = append(contents, client.Content{Role: "tool", Parts: []client.Part{{FunctionResponse: &functionResponse}}})
				}
			}
		}
	}

	// Translate the tool declarations from the request.
	var tools []client.ToolDeclaration
	toolsResult := gjson.GetBytes(rawJson, "tools")
	if toolsResult.IsArray() {
		tools = make([]client.ToolDeclaration, 1)
		tools[0].FunctionDeclarations = make([]any, 0)
		toolsResults := toolsResult.Array()
		for i := 0; i < len(toolsResults); i++ {
			toolResult := toolsResults[i]
			if toolResult.Get("type").String() == "function" {
				functionTypeResult := toolResult.Get("function")
				if functionTypeResult.Exists() && functionTypeResult.IsObject() {
					var functionDeclaration any
					if err := json.Unmarshal([]byte(functionTypeResult.Raw), &functionDeclaration); err == nil {
						tools[0].FunctionDeclarations = append(tools[0].FunctionDeclarations, functionDeclaration)
					}
				}
			}
		}
	} else {
		tools = make([]client.ToolDeclaration, 0)
	}

	return modelName, systemInstruction, contents, tools
}