package config

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"gopkg.in/yaml.v3"
)

// Config 是 YAML 配置结构（只用 YAML，不依赖环境变量）。
type Config struct {
	Server ServerConfig `yaml:"server"`
	JWT    JWTConfig    `yaml:"jwt"`
	DB     DBConfig     `yaml:"db"`
}

type ServerConfig struct {
	Addr                    string `yaml:"addr"`
	GinMode                 string `yaml:"gin_mode"`
	GracefulTimeoutSeconds  int    `yaml:"graceful_timeout_seconds"`
	ReadHeaderTimeoutSeconds int   `yaml:"read_header_timeout_seconds"`
}

type JWTConfig struct {
	Secret        string `yaml:"secret"`
	ExpirySeconds int    `yaml:"expiry_seconds"`
}

type DBConfig struct {
	Driver                 string `yaml:"driver"`
	DSN                    string `yaml:"dsn"`
	MaxOpenConns           int    `yaml:"max_open_conns"`
	MaxIdleConns           int    `yaml:"max_idle_conns"`
	ConnMaxLifetimeSeconds int   `yaml:"conn_max_lifetime_seconds"`
}

// Load 读取 config/config.yaml。
func Load() Config {
	path := filepath.Join("config", "config.yaml")
	raw, err := os.ReadFile(path)
	if err != nil {
		panic(err)
	}

	var cfg Config
	if err := yaml.Unmarshal(raw, &cfg); err != nil {
		panic(err)
	}

	// defaults
	if cfg.Server.Addr == "" {
		cfg.Server.Addr = ":8080"
	}
	if cfg.Server.GinMode == "" {
		cfg.Server.GinMode = gin.ReleaseMode
	}

	ginModeNorm := strings.ToLower(strings.TrimSpace(cfg.Server.GinMode))
	switch ginModeNorm {
	case "debug":
		cfg.Server.GinMode = gin.DebugMode
	case "test":
		cfg.Server.GinMode = gin.TestMode
	case "release":
		cfg.Server.GinMode = gin.ReleaseMode
	default:
		// 若未知，按 release 兜底。
		cfg.Server.GinMode = gin.ReleaseMode
	}

	if cfg.Server.GracefulTimeoutSeconds <= 0 {
		cfg.Server.GracefulTimeoutSeconds = 5
	}
	if cfg.Server.ReadHeaderTimeoutSeconds <= 0 {
		cfg.Server.ReadHeaderTimeoutSeconds = 5
	}

	if cfg.JWT.Secret == "" {
		cfg.JWT.Secret = "dev-secret-change-me"
	}
	if cfg.JWT.ExpirySeconds <= 0 {
		cfg.JWT.ExpirySeconds = 3600
	}

	if cfg.DB.Driver == "" {
		cfg.DB.Driver = "sqlite"
	}
	if cfg.DB.DSN == "" {
		return cfg // 交给 model 层校验并给出更明确错误
	}

	// 连接池 defaults（可选）
	if cfg.DB.MaxOpenConns <= 0 {
		cfg.DB.MaxOpenConns = 10
	}
	if cfg.DB.MaxIdleConns <= 0 {
		cfg.DB.MaxIdleConns = 5
	}
	if cfg.DB.ConnMaxLifetimeSeconds <= 0 {
		cfg.DB.ConnMaxLifetimeSeconds = 3600
	}

	return cfg
}

// ServerDuration 便于下层直接使用 time.Duration。
func (c Config) ServerDuration() (gracefulTimeout time.Duration, readHeaderTimeout time.Duration) {
	if c.Server.GracefulTimeoutSeconds <= 0 {
		return 5 * time.Second, 5 * time.Second
	}
	if c.Server.ReadHeaderTimeoutSeconds <= 0 {
		return time.Duration(c.Server.GracefulTimeoutSeconds) * time.Second, 5 * time.Second
	}
	return time.Duration(c.Server.GracefulTimeoutSeconds) * time.Second, time.Duration(c.Server.ReadHeaderTimeoutSeconds) * time.Second
}

// Validate 校验配置的必填项（用于启动时报错）。
func (c Config) Validate() error {
	if c.DB.DSN == "" {
		return errors.New("db.dsn is empty in config/config.yaml")
	}
	return nil
}