package services

import (
	"bufio"
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"strings"
	"whatsapp-bot/db"
)

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

// Structs to parse the incoming stream from OpenRouter
type StreamResponse struct {
	Choices []struct {
		Delta struct {
			Content   string `json:"content"`
			ToolCalls []struct {
				ID       string `json:"id"`
				Type     string `json:"type"`
				Function struct {
					Name      string `json:"name"`
					Arguments string `json:"arguments"`
				} `json:"function"`
			} `json:"tool_calls"`
		} `json:"delta"`
		FinishReason string `json:"finish_reason"`
	} `json:"choices"`
}

// StreamAIResponse handles the streaming connection
// onToken: a function that gets called every time we get text (we use this to push to the browser)
// Returns: the full final string (so we can save it to the DB)
func StreamAIResponse(chatHistory []Message, onToken func(string)) (string, error) {
	apiKey := os.Getenv("OPENROUTER_API_KEY")
	url := "https://openrouter.ai/api/v1/chat/completions"

	fullMessages := append([]Message{
		{
			Role:    "system",
			Content: "You are a helpful business assistant. You can book appointments. If the user mentions scheduling an appointment always ask for his phone number and the time and date of the appointment, if the user wants to schedule something before doing it, it is requiered to have a phone number and a date, use the create_appointment tool. Be concise and polite.",
		},
	}, chatHistory...)

	payload := map[string]interface{}{
		"model":    "arcee-ai/trinity-large-preview:free", // arcee-ai/trinity-large-preview:free, stepfun/step-3.5-flash:free
		"messages": fullMessages,
		"stream":   true, // <--- THIS IS KEY
		"tools": []map[string]interface{}{
			{
				"type": "function",
				"function": map[string]interface{}{
					"name":        "create_appointment",
					"description": "Schedules a new appointment",
					"parameters": map[string]interface{}{
						"type": "object",
						"properties": map[string]interface{}{
							"customer_phone": map[string]string{"type": "string"},
							"date":           map[string]string{"type": "string"},
						},
						"required": []string{"customer_phone", "date"},
					},
				},
			},
		},
	}

	jsonData, _ := json.Marshal(payload)
	req, _ := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
	req.Header.Set("Authorization", "Bearer "+apiKey)
	req.Header.Set("Content-Type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	// Prepare to read the stream line by line
	scanner := bufio.NewScanner(resp.Body)

	var fullContentBuffer strings.Builder
	var toolCallBuffer strings.Builder
	var toolName string
	isToolCall := false

	for scanner.Scan() {
		line := scanner.Text()

		// OpenRouter sends "data: {JSON}" lines.
		// Use specific string trimming to handle the format.
		if !strings.HasPrefix(line, "data: ") {
			continue
		}
		jsonStr := strings.TrimPrefix(line, "data: ")

		// The stream ends with "data: [DONE]"
		if jsonStr == "[DONE]" {
			break
		}

		var chunk StreamResponse
		if err := json.Unmarshal([]byte(jsonStr), &chunk); err != nil {
			continue
		}

		if len(chunk.Choices) > 0 {
			delta := chunk.Choices[0].Delta

			// 1. Handle Text Content
			if delta.Content != "" {
				fullContentBuffer.WriteString(delta.Content)
				// Send this chunk to the frontend immediately
				onToken(delta.Content)
			}

			// 2. Handle Tool Calls (Accumulate them, don't stream execution yet)
			if len(delta.ToolCalls) > 0 {
				isToolCall = true
				if delta.ToolCalls[0].Function.Name != "" {
					toolName = delta.ToolCalls[0].Function.Name
				}
				toolCallBuffer.WriteString(delta.ToolCalls[0].Function.Arguments)
			}
		}
	}

	// If it was a tool call, execute it now that the stream is finished
	if isToolCall && toolName == "create_appointment" {
		var args struct {
			Phone string `json:"customer_phone"`
			Date  string `json:"date"`
		}
		// Try to parse the accumulated JSON arguments
		if err := json.Unmarshal([]byte(toolCallBuffer.String()), &args); err == nil {
			err := db.SaveAppointment(args.Phone, args.Date)
			resultMsg := ""
			if err != nil {
				resultMsg = "\n[System: Failed to book appointment.]"
			} else {
				resultMsg = fmt.Sprintf("\n✅ Booked for %s at %s", args.Phone, args.Date)
			}
			// Send the tool result to the frontend
			onToken(resultMsg)
			fullContentBuffer.WriteString(resultMsg)
		}
	}

	return fullContentBuffer.String(), nil
}