package config

import (
	"bytes"
	"fmt"
	"net"
	"os"
	"time"

	"gopkg.in/yaml.v3"
)

const DefaultPath = "config/local.yaml"

// Config 汇总用户服务的运行配置。
type Config struct {
	App      AppConfig      `yaml:"app"`
	Registry RegistryConfig `yaml:"registry"`
}

// AppConfig 描述用户服务自身监听参数。
type AppConfig struct {
	Name            string        `yaml:"name"`
	Env             string        `yaml:"env"`
	HTTPAddr        string        `yaml:"http_addr"`
	GRPCAddr        string        `yaml:"grpc_addr"`
	ShutdownTimeout time.Duration `yaml:"shutdown_timeout"`
}

// RegistryConfig 预留服务注册中心接入参数，当前只保留注销钩子扩展点。
type RegistryConfig struct {
	Enabled           bool          `yaml:"enabled"`
	Provider          string        `yaml:"provider"`
	Endpoint          string        `yaml:"endpoint"`
	ServiceName       string        `yaml:"service_name"`
	InstanceID        string        `yaml:"instance_id"`
	RegisterTimeout   time.Duration `yaml:"register_timeout"`
	DeregisterTimeout time.Duration `yaml:"deregister_timeout"`
}

// Load 从 YAML 文件加载配置并校验。
func Load(path string) (Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return Config{}, fmt.Errorf("read config file %s: %w", path, err)
	}

	cfg := defaultConfig()
	decoder := yaml.NewDecoder(bytes.NewReader(data))
	decoder.KnownFields(true)
	if err := decoder.Decode(&cfg); err != nil {
		return Config{}, fmt.Errorf("decode config file %s: %w", path, err)
	}

	if err := validate(cfg); err != nil {
		return Config{}, err
	}
	return cfg, nil
}

func defaultConfig() Config {
	return Config{
		App: AppConfig{
			Name:            "chatappuser",
			Env:             "local",
			HTTPAddr:        ":8081",
			GRPCAddr:        ":9001",
			ShutdownTimeout: 10 * time.Second,
		},
		Registry: RegistryConfig{
			RegisterTimeout:   3 * time.Second,
			DeregisterTimeout: 5 * time.Second,
		},
	}
}

func validate(cfg Config) error {
	if cfg.App.Name == "" {
		return fmt.Errorf("app.name is required")
	}
	if _, err := net.ResolveTCPAddr("tcp", cfg.App.HTTPAddr); err != nil {
		return fmt.Errorf("app.http_addr is invalid: %w", err)
	}
	if _, err := net.ResolveTCPAddr("tcp", cfg.App.GRPCAddr); err != nil {
		return fmt.Errorf("app.grpc_addr is invalid: %w", err)
	}
	if cfg.App.ShutdownTimeout <= 0 {
		return fmt.Errorf("app.shutdown_timeout must be greater than 0")
	}
	if cfg.Registry.RegisterTimeout <= 0 {
		return fmt.Errorf("registry.register_timeout must be greater than 0")
	}
	if cfg.Registry.DeregisterTimeout <= 0 {
		return fmt.Errorf("registry.deregister_timeout must be greater than 0")
	}
	return nil
}