package config

import (
	"fmt"
	"os"

	"github.com/spf13/viper"
)

type Config struct {
	Server   ServerConfig
	MySQL    MySQLConfig
	Redis    RedisConfig
	Telegram TelegramConfig
	LLM      LLMConfig
	Serper   SerperConfig
	GitHub   GitHubConfig
	Security SecurityConfig
	App      AppConfig
}

type ServerConfig struct {
	Port         int
	CORSOrigins  []string `mapstructure:"cors_origins"`  // allowed origins, empty = *
	MaxUploadMB  int      `mapstructure:"max_upload_mb"`  // max upload size in MB, default 10
}

type SecurityConfig struct {
	JWTSecret       string `mapstructure:"jwt_secret"`
	PasswordMinLen  int    `mapstructure:"password_min_len"`  // default 8
	WebhookAllowHTTP bool  `mapstructure:"webhook_allow_http"` // allow http:// webhooks
}

type AppConfig struct {
	Name string // display name, default "商户采集系统"
}

type MySQLConfig struct {
	Host     string
	Port     int
	User     string
	Password string
	Database string
}

type RedisConfig struct {
	Host     string
	Port     int
	Password string
	DB       int
}

type TelegramConfig struct {
	AppID       int        `mapstructure:"app_id"`
	AppHash     string     `mapstructure:"app_hash"`
	Accounts    []TGAccount
	SessionsDir string     `mapstructure:"sessions_dir"` // absolute path, e.g. /app/sessions
	SecretKey   string     `mapstructure:"secret_key"`   // base64 32-byte, or literal ${TG_SECRET_KEY}
}

type TGAccount struct {
	Phone       string
	SessionFile string `mapstructure:"session_file"`
}

type LLMConfig struct {
	Provider string
	BaseURL  string `mapstructure:"base_url"`
	APIKey   string `mapstructure:"api_key"`
	Model    string
	Timeout  string
}

type SerperConfig struct {
	APIKey         string `mapstructure:"api_key"`
	ResultsPerPage int    `mapstructure:"results_per_page"`
	MaxPages       int    `mapstructure:"max_pages"`
}

type GitHubConfig struct {
	Token string
}

var global *Config

func Load(path string) (*Config, error) {
	v := viper.New()
	v.SetConfigFile(path)
	v.SetConfigType("yaml")

	if err := v.ReadInConfig(); err != nil {
		return nil, fmt.Errorf("read config file: %w", err)
	}

	cfg := &Config{}
	if err := v.Unmarshal(cfg); err != nil {
		return nil, fmt.Errorf("unmarshal config: %w", err)
	}

	// Apply defaults
	if cfg.Security.JWTSecret == "" {
		cfg.Security.JWTSecret = "spider-jwt-secret-2026"
	}
	if cfg.Security.PasswordMinLen < 6 {
		cfg.Security.PasswordMinLen = 8
	}
	if cfg.Server.MaxUploadMB <= 0 {
		cfg.Server.MaxUploadMB = 10
	}
	if cfg.App.Name == "" {
		cfg.App.Name = "商户采集系统"
	}

	// Resolve ${ENV_VAR} placeholders for secret fields.
	cfg.Telegram.SecretKey = expandEnvPlaceholder(cfg.Telegram.SecretKey)
	cfg.Security.JWTSecret = expandEnvPlaceholder(cfg.Security.JWTSecret)

	if cfg.Telegram.SessionsDir == "" {
		cfg.Telegram.SessionsDir = "/app/sessions"
	}

	global = cfg
	return cfg, nil
}

func Get() *Config {
	return global
}

// expandEnvPlaceholder replaces a value of the form "${VAR}" with os.Getenv("VAR").
// A non-placeholder value is returned unchanged.
func expandEnvPlaceholder(v string) string {
	if len(v) > 3 && v[0] == '$' && v[1] == '{' && v[len(v)-1] == '}' {
		return os.Getenv(v[2 : len(v)-1])
	}
	return v
}