package llm

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

// OllamaClient implements the LLM interface for Ollama's API.
//
// It communicates with a running Ollama server via its REST API.
// Supports chat, streaming, tool calling (function calling), and
// embedding generation.
type OllamaClient struct {
	baseURL    string
	model      string
	httpClient *http.Client
}

// OllamaOption is a functional option for configuring the OllamaClient.
type OllamaOption func(*OllamaClient)

// WithBaseURL sets the Ollama server base URL.
func WithBaseURL(url string) OllamaOption {
	return func(c *OllamaClient) {
		c.baseURL = strings.TrimRight(url, "/")
	}
}

// WithModel sets the default model name.
func WithModel(model string) OllamaOption {
	return func(c *OllamaClient) {
		c.model = model
	}
}

// WithTimeout sets the HTTP client timeout.
func WithTimeout(timeout time.Duration) OllamaOption {
	return func(c *OllamaClient) {
		c.httpClient.Timeout = timeout
	}
}

// WithHTTPClient sets a custom HTTP client.
func WithHTTPClient(client *http.Client) OllamaOption {
	return func(c *OllamaClient) {
		c.httpClient = client
	}
}

// NewOllamaClient creates a new OllamaClient with the given options.
//
// Default values:
//   - BaseURL: http://localhost:11434
//   - Model: gemma4:e4b
//   - Timeout: 30s
func NewOllamaClient(opts ...OllamaOption) *OllamaClient {
	c := &OllamaClient{
		baseURL: "http://localhost:11434",
		model:   "gemma4:e4b",
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}

	for _, opt := range opts {
		opt(c)
	}

	return c
}

// Chat sends a chat request to Ollama and returns the complete response.
// If the Ollama model returns tool calls, they are parsed and included
// in the Response.
func (c *OllamaClient) Chat(ctx context.Context, messages []Message) (*Response, error) {
	req := OllamaChatRequest{
		Model:    c.model,
		Messages: messages,
		Stream:   false,
	}

	// Build tool definitions if tool package is integrated
	// (tools are added externally via BuildToolDefs)

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

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost,
		c.baseURL+"/api/chat", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("ollama: 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("ollama: request failed: %w", err)
	}
	defer resp.Body.Close()

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

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

	return parseOllamaResponse(rawResp)
}

// parseOllamaResponse attempts to parse the Ollama API response,
// handling both regular text responses and tool call responses.
func parseOllamaResponse(raw json.RawMessage) (*Response, error) {
	// Try as tool call response first (has message.tool_calls)
	var toolResp OllamaToolCallResponse
	if err := json.Unmarshal(raw, &toolResp); err == nil && len(toolResp.Message.ToolCalls) > 0 {
		return &Response{
			Content:   toolResp.Message.Content,
			ToolCalls: toolResp.Message.ToolCalls,
		}, nil
	}

	// Try as regular response
	var chatResp OllamaChatResponse
	if err := json.Unmarshal(raw, &chatResp); err != nil {
		return nil, fmt.Errorf("ollama: failed to parse response: %w", err)
	}

	return &Response{
		Content: chatResp.Message.Content,
	}, nil
}

// Stream sends a chat request to Ollama with streaming enabled.
// The handler receives each content chunk as it arrives.
func (c *OllamaClient) Stream(ctx context.Context, messages []Message, handler StreamHandler) error {
	req := OllamaChatRequest{
		Model:    c.model,
		Messages: messages,
		Stream:   true,
	}

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

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost,
		c.baseURL+"/api/chat", bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("ollama: 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("ollama: stream request failed: %w", err)
	}
	defer resp.Body.Close()

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

	scanner := bufio.NewScanner(resp.Body)
	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			continue
		}

		// Each line is a JSON object: {"model":"...","created_at":"...","message":{"role":"assistant","content":"..."},"done":false}
		var streamResp OllamaChatResponse
		if err := json.Unmarshal([]byte(line), &streamResp); err != nil {
			continue // Skip malformed lines
		}

		if streamResp.Message.Content != "" {
			if err := handler(streamResp.Message.Content); err != nil {
				return err
			}
		}

		if streamResp.Done {
			break
		}
	}

	return scanner.Err()
}

// Embed generates an embedding vector for the given input text.
func (c *OllamaClient) Embed(ctx context.Context, input string) (*EmbeddingResponse, error) {
	req := OllamaEmbedRequest{
		Model: c.model,
		Input: input,
	}

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

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost,
		c.baseURL+"/api/embed", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("ollama: failed to create embed request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")

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

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

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

	return &EmbeddingResponse{
		Embedding: apiResp.Embedding,
	}, nil
}

// BuildToolDefsFromMap converts a generic tool definition map into Ollama ToolDefs.
// This is used to bridge the tool package's Tool interface with Ollama's API format.
func BuildToolDefsFromMap(tools []map[string]interface{}) []ToolDef {
	var defs []ToolDef
	for _, t := range tools {
		name, _ := t["name"].(string)
		desc, _ := t["description"].(string)

		def := ToolDef{
			Type: "function",
			Function: ToolFunction{
				Name:        name,
				Description: desc,
				Parameters: ToolFunctionParameters{
					Type:       "object",
					Properties: make(map[string]ToolProperty),
				},
			},
		}

		if params, ok := t["parameters"].(map[string]interface{}); ok {
			if props, ok := params["properties"].(map[string]interface{}); ok {
				for key, val := range props {
					if p, ok := val.(map[string]interface{}); ok {
						prop := ToolProperty{
							Type:        toString(p["type"]),
							Description: toString(p["description"]),
						}
						def.Function.Parameters.Properties[key] = prop
						if isRequired(p) {
							def.Function.Parameters.Required = append(def.Function.Parameters.Required, key)
						}
					}
				}
			}
		}

		defs = append(defs, def)
	}
	return defs
}

func toString(v interface{}) string {
	if v == nil {
		return ""
	}
	s, _ := v.(string)
	return s
}

func isRequired(p map[string]interface{}) bool {
	req, _ := p["required"].(bool)
	return req
}