s01e03/internal/infrastructure/llm/openrouter.go

package llm

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"

	"github.com/paramah/ai_devs4/s01e03/internal/domain"
)

// OpenRouterProvider implements domain.LLMProvider for OpenRouter API
type OpenRouterProvider struct {
	apiKey  string
	model   string
	baseURL string
	client  *http.Client
	verbose bool
}

// NewOpenRouterProvider creates a new OpenRouter provider
func NewOpenRouterProvider(apiKey, model string, verbose bool) *OpenRouterProvider {
	return &OpenRouterProvider{
		apiKey:  apiKey,
		model:   model,
		baseURL: "https://openrouter.ai/api/v1/chat/completions",
		client:  &http.Client{},
		verbose: verbose,
	}
}

type openRouterMessage struct {
	Role       string               `json:"role"`
	Content    string               `json:"content"`
	ToolCallID string               `json:"tool_call_id,omitempty"`
	ToolCalls  []openRouterToolCall `json:"tool_calls,omitempty"`
}

type openRouterToolCall struct {
	ID       string `json:"id"`
	Type     string `json:"type"`
	Function struct {
		Name      string `json:"name"`
		Arguments string `json:"arguments"`
	} `json:"function"`
}

type openRouterRequest struct {
	Model    string               `json:"model"`
	Messages []openRouterMessage  `json:"messages"`
	Tools    []domain.Tool        `json:"tools,omitempty"`
}

type openRouterResponse struct {
	Choices []struct {
		Message struct {
			Content   string               `json:"content"`
			ToolCalls []openRouterToolCall `json:"tool_calls,omitempty"`
		} `json:"message"`
	} `json:"choices"`
	Error *struct {
		Message string `json:"message"`
	} `json:"error,omitempty"`
}

// Complete sends a request to OpenRouter API with function calling support
func (p *OpenRouterProvider) Complete(ctx context.Context, request domain.LLMRequest) (*domain.LLMResponse, error) {
	// Convert domain messages to OpenRouter format
	messages := make([]openRouterMessage, len(request.Messages))
	for i, msg := range request.Messages {
		// Convert tool calls if present
		var toolCalls []openRouterToolCall
		if len(msg.ToolCalls) > 0 {
			toolCalls = make([]openRouterToolCall, len(msg.ToolCalls))
			for j, tc := range msg.ToolCalls {
				toolCalls[j] = openRouterToolCall{
					ID:   tc.ID,
					Type: tc.Type,
					Function: struct {
						Name      string `json:"name"`
						Arguments string `json:"arguments"`
					}{
						Name:      tc.Function.Name,
						Arguments: tc.Function.Arguments,
					},
				}
			}
		}

		messages[i] = openRouterMessage{
			Role:       msg.Role,
			Content:    msg.Content,
			ToolCallID: msg.ToolCallID,
			ToolCalls:  toolCalls,
		}
	}

	reqBody := openRouterRequest{
		Model:    p.model,
		Messages: messages,
		Tools:    request.Tools,
	}

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("marshaling request: %w", err)
	}

	if p.verbose {
		var prettyJSON bytes.Buffer
		if err := json.Indent(&prettyJSON, jsonData, "", "  "); err == nil {
			log.Printf("\n========== LLM REQUEST ==========\nURL: %s\nBody:\n%s\n================================\n", p.baseURL, prettyJSON.String())
		}
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, p.baseURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("creating request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+p.apiKey)

	resp, err := p.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("sending request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("reading response: %w", err)
	}

	if p.verbose {
		var prettyJSON bytes.Buffer
		if err := json.Indent(&prettyJSON, body, "", "  "); err == nil {
			log.Printf("\n========== LLM RESPONSE ==========\nStatus: %d\nBody:\n%s\n==================================\n", resp.StatusCode, prettyJSON.String())
		}
	}

	var apiResp openRouterResponse
	if err := json.Unmarshal(body, &apiResp); err != nil {
		return nil, fmt.Errorf("unmarshaling response: %w", err)
	}

	if apiResp.Error != nil {
		return nil, fmt.Errorf("API error: %s", apiResp.Error.Message)
	}

	if len(apiResp.Choices) == 0 {
		return nil, fmt.Errorf("no choices in response")
	}

	// Convert tool calls to domain format
	toolCalls := make([]domain.ToolCall, len(apiResp.Choices[0].Message.ToolCalls))
	for i, tc := range apiResp.Choices[0].Message.ToolCalls {
		toolCalls[i] = domain.ToolCall{
			ID:   tc.ID,
			Type: tc.Type,
			Function: struct {
				Name      string `json:"name"`
				Arguments string `json:"arguments"`
			}{
				Name:      tc.Function.Name,
				Arguments: tc.Function.Arguments,
			},
		}
	}

	return &domain.LLMResponse{
		Content:   apiResp.Choices[0].Message.Content,
		ToolCalls: toolCalls,
	}, nil
}