package llm

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

	"github.com/paramah/ai_devs4/s01e02/internal/domain"
)

// LMStudioProvider implements domain.LLMProvider for local LM Studio
type LMStudioProvider struct {
	baseURL string
	model   string
	client  *http.Client
}

// NewLMStudioProvider creates a new LM Studio provider
func NewLMStudioProvider(baseURL, model string) *LMStudioProvider {
	return &LMStudioProvider{
		baseURL: baseURL,
		model:   model,
		client:  &http.Client{},
	}
}

type lmStudioRequest struct {
	Model       string              `json:"model"`
	Messages    []domain.LLMMessage `json:"messages"`
	Tools       []domain.Tool       `json:"tools,omitempty"`
	ToolChoice  interface{}         `json:"tool_choice,omitempty"`
	Temperature float64             `json:"temperature,omitempty"`
}

type lmStudioResponse struct {
	Choices []struct {
		Message      domain.LLMMessage `json:"message"`
		FinishReason string            `json:"finish_reason"`
	} `json:"choices"`
	Error json.RawMessage `json:"error,omitempty"`
}

// Chat sends a chat request with function calling support
func (p *LMStudioProvider) Chat(ctx context.Context, request domain.LLMRequest) (*domain.LLMResponse, error) {
	reqBody := lmStudioRequest{
		Model:       p.model,
		Messages:    request.Messages,
		Tools:       request.Tools,
		Temperature: request.Temperature,
	}

	if request.ToolChoice != "" {
		if request.ToolChoice == "auto" {
			reqBody.ToolChoice = "auto"
		} else {
			reqBody.ToolChoice = map[string]interface{}{
				"type": "function",
				"function": map[string]string{
					"name": request.ToolChoice,
				},
			}
		}
	}

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

	url := p.baseURL + "/v1/chat/completions"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("creating request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")

	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 resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("HTTP %d: %s", resp.StatusCode, string(body))
	}

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

	if len(apiResp.Error) > 0 {
		var errStr string
		if err := json.Unmarshal(apiResp.Error, &errStr); err == nil {
			return nil, fmt.Errorf("API error: %s", errStr)
		}
		var errObj struct {
			Message string `json:"message"`
		}
		if err := json.Unmarshal(apiResp.Error, &errObj); err == nil {
			return nil, fmt.Errorf("API error: %s", errObj.Message)
		}
		return nil, fmt.Errorf("API error: %s", string(apiResp.Error))
	}

	if len(apiResp.Choices) == 0 {
		return nil, fmt.Errorf("no choices in response. Response body: %s", string(body))
	}

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