// Package config 加载 IoT Server 的 MQTT、协议密钥和内部接口配置。
package config

import (
	"encoding/hex"
	"fmt"
	"os"
	"strings"

	"gopkg.in/yaml.v3"
)

type MQTT struct {
	Address         string       `yaml:"Address"`
	ListenerID      string       `yaml:"ListenerID"`
	Devices         []MQTTDevice `yaml:"Devices"`
	UpTopic         string       `yaml:"UpTopic"`
	DownTopic       string       `yaml:"DownTopic"`
	AckTopic        string       `yaml:"AckTopic"`
	QoS             byte         `yaml:"QoS"`
	TLS             bool         `yaml:"TLS"`
	CAFile          string       `yaml:"CAFile"`
	CertificateFile string       `yaml:"CertificateFile"`
	PrivateKeyFile  string       `yaml:"PrivateKeyFile"`
}
type MQTTDevice struct {
	ClientID string `yaml:"ClientID"`
	DeviceID string `yaml:"DeviceID"`
	Username string `yaml:"Username"`
	Password string `yaml:"Password"`
}
type HTTP struct {
	Address       string `yaml:"Address"`
	InternalToken string `yaml:"InternalToken"`
	CallbackURL   string `yaml:"CallbackURL"`
}
type Protocol struct {
	Key1 string `yaml:"Key1"`
	Key2 string `yaml:"Key2"`
	Key3 string `yaml:"Key3"`
}
type Config struct {
	Service  string   `yaml:"Service"`
	MQTT     MQTT     `yaml:"MQTT"`
	HTTP     HTTP     `yaml:"HTTP"`
	Protocol Protocol `yaml:"Protocol"`
}

func Load(path string) (Config, error) {
	var cfg Config
	data, err := os.ReadFile(path)
	if err != nil {
		return cfg, err
	}
	if err = yaml.Unmarshal(data, &cfg); err != nil {
		return cfg, err
	}
	if len(cfg.MQTT.Devices) == 1 {
		override(&cfg.MQTT.Devices[0].Password, "HEQI_IOT_MQTT_PASSWORD")
	}
	override(&cfg.HTTP.InternalToken, "HEQI_IOT_INTERNAL_TOKEN")
	override(&cfg.Protocol.Key1, "HEQI_IOT_KEY_1")
	override(&cfg.Protocol.Key2, "HEQI_IOT_KEY_2")
	override(&cfg.Protocol.Key3, "HEQI_IOT_KEY_3")
	if cfg.MQTT.Address == "" || cfg.HTTP.Address == "" || cfg.HTTP.InternalToken == "" {
		return cfg, fmt.Errorf("MQTT.Address、HTTP.Address 和 HTTP.InternalToken 必填")
	}
	if cfg.MQTT.ListenerID == "" {
		cfg.MQTT.ListenerID = "mqtt-tcp"
	}
	if len(cfg.MQTT.Devices) == 0 {
		return cfg, fmt.Errorf("MQTT.Devices 必填，Broker 禁止匿名连接")
	}
	for index, device := range cfg.MQTT.Devices {
		if device.ClientID == "" || device.DeviceID == "" || device.Username == "" || device.Password == "" {
			return cfg, fmt.Errorf("MQTT.Devices[%d] 的 ClientID、DeviceID、Username 和 Password 必填", index)
		}
	}
	return cfg, nil
}

func (cfg Config) Keys() (map[byte][]byte, error) {
	result := map[byte][]byte{}
	for id, value := range map[byte]string{1: cfg.Protocol.Key1, 2: cfg.Protocol.Key2, 3: cfg.Protocol.Key3} {
		if strings.TrimSpace(value) == "" {
			continue
		}
		decoded, err := hex.DecodeString(value)
		if err != nil || len(decoded) != 16 {
			return nil, fmt.Errorf("Protocol.Key%d 必须是 32 位十六进制 AES-128 密钥", id)
		}
		result[id] = decoded
	}
	return result, nil
}

func override(target *string, name string) {
	if value := os.Getenv(name); value != "" {
		*target = value
	}
}