proxx/converter.go

package main

import (
	"encoding/json"
	"strings"
)

// ConvertOpenAIRequest converts an OpenAI ChatCompletionRequest to Anthropic format
func ConvertOpenAIRequest(req *ChatCompletionRequest) *AnthropicRequest {
	system, remainingMessages := extractSystemMessage(req.Messages)

	anthropicReq := &AnthropicRequest{
		Model:     req.Model,
		Messages:  convertMessages(remainingMessages),
		System:    system,
		MaxTokens: 32000,
		Thinking: &AnthropicThinking{
			Type:         "enabled",
			BudgetTokens: 10000,
		},
	}

	if req.MaxTokens != nil {
		anthropicReq.MaxTokens = *req.MaxTokens
	}
	if req.Stream != nil {
		anthropicReq.Stream = *req.Stream
	}
	if req.Temperature != nil {
		anthropicReq.Temperature = req.Temperature
	}
	if req.TopP != nil {
		anthropicReq.TopP = req.TopP
	}
	if len(req.Stop) > 0 {
		anthropicReq.StopSequences = req.Stop
	}
	if len(req.Tools) > 0 {
		anthropicReq.Tools = convertTools(req.Tools)
	}
	if req.ToolChoices != nil {
		anthropicReq.ToolChoice = convertToolChoice(req.ToolChoices)
	}

	return anthropicReq
}

// extractSystemMessage pulls role="system" messages and joins them
func extractSystemMessage(messages []Message) (string, []Message) {
	var systemParts []string
	var rest []Message

	for _, msg := range messages {
		if msg.Role == "system" {
			if content, ok := msg.Content.(string); ok {
				systemParts = append(systemParts, content)
			}
		} else {
			rest = append(rest, msg)
		}
	}

	return strings.Join(systemParts, "\n"), rest
}

// convertMessages converts OpenAI messages to Anthropic content blocks
func convertMessages(messages []Message) []AnthropicMessage {
	var result []AnthropicMessage

	for _, msg := range messages {
		anthropicMsg := AnthropicMessage{
			Role: msg.Role,
		}

		switch content := msg.Content.(type) {
		case string:
			anthropicMsg.Content = content
		case []interface{}:
			var blocks []ContentBlock
			for _, part := range content {
				partMap, ok := part.(map[string]interface{})
				if !ok {
					continue
				}
				partType, _ := partMap["type"].(string)
				if partType == "text" {
					text, _ := partMap["text"].(string)
					blocks = append(blocks, ContentBlock{Type: "text", Text: text})
				}
				// Image parts: skip for now, Anthropic uses different format
			}
			anthropicMsg.Content = blocks
		}

		result = append(result, anthropicMsg)
	}

	return result
}

// convertTools converts OpenAI function tools to Anthropic tool format
func convertTools(tools []Tool) []AnthropicTool {
	var result []AnthropicTool
	for _, tool := range tools {
		anthropicTool := AnthropicTool{
			Name:        tool.Function.Name,
			Description: tool.Function.Description,
			InputSchema: tool.Function.Parameters,
		}
		result = append(result, anthropicTool)
	}
	return result
}

// convertToolChoice converts OpenAI tool_choice to Anthropic format
func convertToolChoice(tc *ToolChoice) *AnthropicToolChoice {
	if tc == nil {
		return nil
	}
	result := &AnthropicToolChoice{}
	if tc.Type != "" {
		if tc.Type == "required" {
			result.Type = "any"
		} else {
			result.Type = tc.Type
		}
	}
	if tc.Function != nil {
		result.Name = tc.Function.Name
	}
	return result
}

// ConvertAnthropicResponse converts an Anthropic response to OpenAI format
func ConvertAnthropicResponse(resp *AnthropicResponse, model string) *ChatCompletionResponse {
	response := &ChatCompletionResponse{
		ID:      resp.Id,
		Object:  "chat.completion",
		Created: 1234567890,
		Model:   model,
		Choices: make([]Choice, 0),
		Usage: Usage{
			PromptTokens:     resp.Usage.InputTokens,
			CompletionTokens: resp.Usage.OutputTokens,
			TotalTokens:      resp.Usage.InputTokens + resp.Usage.OutputTokens,
		},
	}

	if len(resp.Content) == 0 {
		response.Choices = append(response.Choices, Choice{
			Index:        0,
			Message:      Message{Role: "assistant", Content: ""},
			FinishReason: mapStopReason(resp.StopReason),
		})
		return response
	}

	// First pass: collect text and tool calls
	var textContent string
	var toolCalls []ToolCall

	for _, block := range resp.Content {
		if block.Type == "text" {
			textContent += block.Text
		} else if block.Type == "tool_use" {
			// Serialize the input back to JSON
			inputJSON, _ := json.Marshal(block.Input)
			toolCalls = append(toolCalls, ToolCall{
				ID:   block.Id,
				Type: "function",
				Function: FunctionCall{
					Name:      block.Name,
					Arguments: string(inputJSON),
				},
			})
		}
	}

	if len(toolCalls) > 0 {
		response.Choices = append(response.Choices, Choice{
			Index: 0,
			Message: Message{
				Role:      "assistant",
				Content:   textContent,
				ToolCalls: toolCalls,
			},
			FinishReason: mapStopReason(resp.StopReason),
		})
	} else {
		response.Choices = append(response.Choices, Choice{
			Index:        0,
			Message:      Message{Role: "assistant", Content: textContent},
			FinishReason: mapStopReason(resp.StopReason),
		})
	}

	return response
}

// mapStopReason maps Anthropic stop reasons to OpenAI finish reasons
func mapStopReason(reason string) string {
	switch reason {
	case "end_turn":
		return "stop"
	case "tool_use":
		return "tool_calls"
	case "max_tokens":
		return "length"
	default:
		return "stop"
	}
}

// buildToolCalls builds OpenAI ToolCall slice from Anthropic ContentBlocks
func buildToolCalls(content []ContentBlock) []ToolCall {
	var toolCalls []ToolCall
	for _, block := range content {
		if block.Type == "tool_use" {
			inputJSON, _ := json.Marshal(block.Input)
			toolCalls = append(toolCalls, ToolCall{
				ID:   block.Id,
				Type: "function",
				Function: FunctionCall{
					Name:      block.Name,
					Arguments: string(inputJSON),
				},
			})
		}
	}
	return toolCalls
}