package configs

import (
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/spf13/viper"
)

type Config struct {
	Server    ServerConfig    `mapstructure:"server"`
	Redis     RedisConfig     `mapstructure:"redis"`
	RateLimit RateLimitConfig `mapstructure:"rate_limit"`
	Session   SessionConfig   `mapstructure:"session"`
	Log       LogConfig       `mapstructure:"log"`
	CORS      CORSConfig      `mapstructure:"cors"`
}

type ServerConfig struct {
	Host         string        `mapstructure:"host"`
	Port         int           `mapstructure:"port"`
	ReadTimeout  time.Duration `mapstructure:"read_timeout"`
	WriteTimeout time.Duration `mapstructure:"write_timeout"`
	IdleTimeout  time.Duration `mapstructure:"idle_timeout"`
}

type RedisConfig struct {
	Addr     string `mapstructure:"addr"`
	Password string `mapstructure:"password"`
	DB       int    `mapstructure:"db"`
	PoolSize int    `mapstructure:"pool_size"`
}

type RateLimitConfig struct {
	GlobalRPS  float64 `mapstructure:"global_rps"`
	PerIPRPS   float64 `mapstructure:"per_ip_rps"`
	PerIPBurst int     `mapstructure:"burst"`
}

type SessionConfig struct {
	TTL           int `mapstructure:"ttl"`
	MaxTextLength int `mapstructure:"max_text_length"`
}

type LogConfig struct {
	Level  string `mapstructure:"level"`
	Format string `mapstructure:"format"`
}

type CORSConfig struct {
	AllowedOrigins []string `mapstructure:"allowed_origins"`
}

func Load(configPath ...string) (*Config, error) {
	v := viper.New()

	if len(configPath) > 0 && configPath[0] != "" {
		v.SetConfigFile(configPath[0])
	} else {
		v.SetConfigName("config")
		v.SetConfigType("yaml")
		v.AddConfigPath("configs/")
		v.AddConfigPath("./configs/")
		v.AddConfigPath(".")
	}

	v.SetDefault("server.host", "0.0.0.0")
	v.SetDefault("server.port", 8080)
	v.SetDefault("server.read_timeout", "15s")
	v.SetDefault("server.write_timeout", "15s")
	v.SetDefault("server.idle_timeout", "60s")
	v.SetDefault("redis.addr", "localhost:6379")
	v.SetDefault("redis.db", 0)
	v.SetDefault("redis.pool_size", 100)
	v.SetDefault("rate_limit.global_rps", 1000)
	v.SetDefault("rate_limit.per_ip_rps", 50)
	v.SetDefault("rate_limit.burst", 100)
	v.SetDefault("session.ttl", 900)
	v.SetDefault("session.max_text_length", 10000)
	v.SetDefault("log.level", "info")
	v.SetDefault("log.format", "json")

	// 环境变量覆盖（前缀 DUALCHECK_）
	// mapstructure 的 "." 和 "_" 都需要替换成 "_"，并转大写
	v.SetEnvPrefix("DUALCHECK")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_", "-", "_"))
	v.AutomaticEnv()

	// 尝试读取配置文件（文件不存在不报错，用默认值+环境变量）
	if err := v.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			fmt.Fprintf(os.Stderr, "[config] warning: config file error: %v\n", err)
		} else {
			fmt.Fprintf(os.Stderr, "[config] config file not found, using defaults + env vars\n")
		}
	}

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

	return &cfg, nil
}