package llm

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

type OllamaClient struct {
	baseClient
	httpClient *http.Client
	baseURL    string
}

type OllamaConfig struct {
	BaseURL  string
	ModelKey string
}

func NewOllamaClient(cfg OllamaConfig) (*OllamaClient, error) {
	baseURL := cfg.BaseURL
	if baseURL == "" {
		baseURL = "http://ollama:11434"
	}

	modelKey := cfg.ModelKey
	if modelKey == "" {
		modelKey = "llama3.2"
	}

	return &OllamaClient{
		baseClient: baseClient{
			providerID: "ollama",
			modelKey:   modelKey,
		},
		httpClient: &http.Client{
			Timeout: 300 * time.Second,
		},
		baseURL: baseURL,
	}, nil
}

type ollamaChatRequest struct {
	Model    string          `json:"model"`
	Messages []ollamaMessage `json:"messages"`
	Stream   bool            `json:"stream"`
	Options  *ollamaOptions  `json:"options,omitempty"`
}

type ollamaMessage struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type ollamaOptions struct {
	Temperature float64  `json:"temperature,omitempty"`
	NumPredict  int      `json:"num_predict,omitempty"`
	TopP        float64  `json:"top_p,omitempty"`
	Stop        []string `json:"stop,omitempty"`
}

type ollamaChatResponse struct {
	Model     string        `json:"model"`
	CreatedAt string        `json:"created_at"`
	Message   ollamaMessage `json:"message"`
	Done      bool          `json:"done"`
}

func (c *OllamaClient) StreamText(ctx context.Context, req StreamRequest) (<-chan StreamChunk, error) {
	messages := make([]ollamaMessage, 0, len(req.Messages))
	for _, m := range req.Messages {
		messages = append(messages, ollamaMessage{
			Role:    string(m.Role),
			Content: m.Content,
		})
	}

	chatReq := ollamaChatRequest{
		Model:    c.modelKey,
		Messages: messages,
		Stream:   true,
	}

	if req.Options.MaxTokens > 0 || req.Options.Temperature > 0 || req.Options.TopP > 0 || len(req.Options.StopWords) > 0 {
		chatReq.Options = &ollamaOptions{}
		if req.Options.MaxTokens > 0 {
			chatReq.Options.NumPredict = req.Options.MaxTokens
		}
		if req.Options.Temperature > 0 {
			chatReq.Options.Temperature = req.Options.Temperature
		}
		if req.Options.TopP > 0 {
			chatReq.Options.TopP = req.Options.TopP
		}
		if len(req.Options.StopWords) > 0 {
			chatReq.Options.Stop = req.Options.StopWords
		}
	}

	body, err := json.Marshal(chatReq)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	url := fmt.Sprintf("%s/api/chat", c.baseURL)
	httpReq, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

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

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		defer resp.Body.Close()
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("Ollama API error: status %d, body: %s", resp.StatusCode, string(body))
	}

	ch := make(chan StreamChunk, 100)
	go func() {
		defer close(ch)
		defer resp.Body.Close()

		reader := bufio.NewReader(resp.Body)

		for {
			line, err := reader.ReadString('\n')
			if err != nil {
				if err != io.EOF {
					return
				}
				return
			}

			line = strings.TrimSpace(line)
			if line == "" {
				continue
			}

			var streamResp ollamaChatResponse
			if err := json.Unmarshal([]byte(line), &streamResp); err != nil {
				continue
			}

			if streamResp.Message.Content != "" {
				ch <- StreamChunk{ContentChunk: streamResp.Message.Content}
			}

			if streamResp.Done {
				ch <- StreamChunk{FinishReason: "stop"}
				return
			}
		}
	}()

	return ch, nil
}

func (c *OllamaClient) GenerateText(ctx context.Context, req StreamRequest) (string, error) {
	messages := make([]ollamaMessage, 0, len(req.Messages))
	for _, m := range req.Messages {
		messages = append(messages, ollamaMessage{
			Role:    string(m.Role),
			Content: m.Content,
		})
	}

	chatReq := ollamaChatRequest{
		Model:    c.modelKey,
		Messages: messages,
		Stream:   false,
	}

	if req.Options.MaxTokens > 0 || req.Options.Temperature > 0 || req.Options.TopP > 0 {
		chatReq.Options = &ollamaOptions{}
		if req.Options.MaxTokens > 0 {
			chatReq.Options.NumPredict = req.Options.MaxTokens
		}
		if req.Options.Temperature > 0 {
			chatReq.Options.Temperature = req.Options.Temperature
		}
		if req.Options.TopP > 0 {
			chatReq.Options.TopP = req.Options.TopP
		}
	}

	body, err := json.Marshal(chatReq)
	if err != nil {
		return "", fmt.Errorf("failed to marshal request: %w", err)
	}

	url := fmt.Sprintf("%s/api/chat", c.baseURL)
	httpReq, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(body))
	if err != nil {
		return "", fmt.Errorf("failed to create request: %w", err)
	}

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

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return "", fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return "", fmt.Errorf("Ollama API error: status %d, body: %s", resp.StatusCode, string(body))
	}

	var chatResp ollamaChatResponse
	if err := json.NewDecoder(resp.Body).Decode(&chatResp); err != nil {
		return "", fmt.Errorf("failed to decode response: %w", err)
	}

	if chatResp.Message.Content == "" {
		return "", errors.New("empty response from Ollama")
	}

	return chatResp.Message.Content, nil
}