package handler

import (
	"encoding/json"
	"log"
	"star-cloud-gateway/internal/bridge"
	"strings"

	mqtt "github.com/eclipse/paho.mqtt.golang"
)

type MqttHandler struct {
	pusher *bridge.RedisPusher
}

func NewMqttHandler(pusher *bridge.RedisPusher) *MqttHandler {
	return &MqttHandler{pusher: pusher}
}

func (h *MqttHandler) HandleMessage(client mqtt.Client, msg mqtt.Message) {
	topic := msg.Topic()
	payload := msg.Payload()

	log.Printf("Received message on topic: %s", topic)

	var serialNo, msgType string
	var jsonPayload interface{}

	// 檢查是否為系統主題 ($SYS)
	if strings.HasPrefix(topic, "$SYS/") {
		parts := strings.Split(topic, "/")
		
		// 尋找事件類型 (connected 或 disconnected)
		var event string
		for _, p := range parts {
			if p == "connected" || p == "disconnected" {
				event = p
				break
			}
		}

		// 尋找 Client ID (通常位於 "clients" 的下一層)
		for i, p := range parts {
			if p == "clients" && i+1 < len(parts) {
				serialNo = parts[i+1]
				break
			}
		}

		
		if event != "" && serialNo != "" {
			// 解析系統 JSON Payload (補強：有些版本會把 ClientID 放在 Payload 裡)
			var sysData map[string]interface{}
			if err := json.Unmarshal(payload, &sysData); err == nil {
				if cid, ok := sysData["clientid"].(string); ok {
					serialNo = cid
				}
			}

			msgType = "status"
			statusValue := "online"
			if event == "disconnected" {
				statusValue = "offline"
			}
			jsonPayload = map[string]string{"status": statusValue}

			log.Printf("Detected system event: Client [%s] is now [%s]", serialNo, statusValue)
		} else {
			return
		}
	} else {
		// 一般業務主題 (machine/{serialNo}/{type})
		parts := strings.Split(topic, "/")
		if len(parts) < 3 {
			return
		}
		serialNo = parts[1]
		msgType = parts[2]

		err := json.Unmarshal(payload, &jsonPayload)
		if err != nil {
			// 如果不是有效的 JSON，則視為純文字/數值 (Raw Value)
			jsonPayload = string(payload)
		}
	}

	bridgePayload := bridge.BridgePayload{
		Type:     msgType,
		SerialNo: cleanSerialNo(serialNo),
		Payload:  jsonPayload,
	}

	h.pusher.Push(bridgePayload)
}

// cleanSerialNo 處理 Client ID 格式，將 SC_M0408_pndk 轉為 M0408
func cleanSerialNo(clientID string) string {
	if clientID == "" {
		return ""
	}

	// 1. 移除已知前綴 SC_
	cleaned := strings.TrimPrefix(clientID, "SC_")

	// 2. 如果中間還有底線，通常代表隨機碼，只取前面部分
	// 例如 M0408_test -> M0408
	if idx := strings.Index(cleaned, "_"); idx != -1 {
		return cleaned[:idx]
	}

	return cleaned
}