package config

import (
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
	"strconv"

	"douyu_go/internal/activity"
	"douyu_go/internal/constants"
	imgpkg "douyu_go/internal/image"
	"douyu_go/internal/logger"
	"douyu_go/internal/types"
)

// DefaultAppPaths 收集运行时路径，支持环境变量覆盖。
// 默认数据存放在当前用户的应用配置目录，而非工作目录，避免 macOS 应用包目录无写权限。
func DefaultAppPaths() types.AppPaths {
	dataDir := resolvePath(envOrDefault("DOUYU_DATA_DIR", defaultAppDataDir()))
	configFile := filepath.Join(dataDir, constants.DefaultConfigFile)
	accountFile := filepath.Join(dataDir, constants.DefaultAccountFile)
	legacyConfigFile := resolvePath(constants.LegacyDefaultConfigFile)
	legacyAccountFile := resolvePath(constants.LegacyDefaultAccountFile)

	if value := os.Getenv("DOUYU_CONFIG"); value != "" {
		configFile = resolvePath(value)
		legacyConfigFile = ""
	}
	if value := os.Getenv("DOUYU_USERS"); value != "" {
		accountFile = resolvePath(value)
		legacyAccountFile = ""
	}

	return types.AppPaths{
		DataDir:           dataDir,
		ConfigFile:        configFile,
		AccountFile:       accountFile,
		LegacyConfigFile:  legacyConfigFile,
		LegacyAccountFile: legacyAccountFile,
		LogDir:            resolvePath(envOrDefault("DOUYU_LOG_DIR", filepath.Join(dataDir, constants.DefaultLogDir))),
		SuccessDir:        resolvePath(envOrDefault("DOUYU_SUCCESS_DIR", filepath.Join(dataDir, constants.DefaultSuccessDir))),
		FontFiles:         imgpkg.CollectFontCandidates(),
	}
}

func defaultAppDataDir() string {
	if dir, err := os.UserConfigDir(); err == nil && dir != "" {
		return filepath.Join(dir, constants.DefaultAppDataDirName)
	}
	if home, err := os.UserHomeDir(); err == nil && home != "" {
		return filepath.Join(home, "."+constants.DefaultAppDataDirName)
	}
	return "." + constants.DefaultAppDataDirName
}

// resolvePath 将相对路径解析为绝对路径。
func resolvePath(path string) string {
	if filepath.IsAbs(path) {
		return path
	}
	if abs, err := filepath.Abs(path); err == nil {
		return abs
	}
	return path
}

func envOrDefault(key, fallback string) string {
	if value := os.Getenv(key); value != "" {
		return filepath.Clean(value)
	}
	return fallback
}

// MigrateLegacyFile 在目标文件不存在时复制旧版本数据，不删除旧文件。
// 返回值表示是否完成了迁移。
func MigrateLegacyFile(target, legacy string) (bool, error) {
	if target == "" || legacy == "" || samePath(target, legacy) {
		return false, nil
	}
	if _, err := os.Stat(target); err == nil {
		return false, nil
	} else if !errors.Is(err, os.ErrNotExist) {
		return false, err
	}

	content, err := os.ReadFile(legacy)
	if errors.Is(err, os.ErrNotExist) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	if err := os.MkdirAll(filepath.Dir(target), 0700); err != nil {
		return false, err
	}
	if err := os.WriteFile(target, content, 0600); err != nil {
		return false, err
	}
	return true, nil
}

func samePath(left, right string) bool {
	return filepath.Clean(left) == filepath.Clean(right)
}

// LoadTraceConfig 读取 trace 开关；默认关闭，避免保存敏感调试数据。
func LoadTraceConfig() types.TraceConfig {
	return types.TraceConfig{
		Enabled:      isTruthyEnv("DOUYU_TRACE"),
		MaxBodyBytes: envInt("DOUYU_TRACE_MAX_BODY", 0),
	}
}

func isTruthyEnv(key string) bool {
	switch os.Getenv(key) {
	case "1", "true", "TRUE", "yes", "YES", "on", "ON":
		return true
	default:
		return false
	}
}

func envInt(key string, fallback int) int {
	raw := os.Getenv(key)
	if raw == "" {
		return fallback
	}
	value, err := strconv.Atoi(raw)
	if err != nil || value <= 0 {
		return fallback
	}
	return value
}

// defaultConfig 返回内置默认配置。
func defaultConfig() types.Config {
	return types.Config{
		Activity:         activity.DefaultActivityID,
		TimeAPIURL:       constants.DefaultTimeAPI,
		TraceEnabled:     false,
		TraceMaxBody:     0,
		LogLevel:         "info",
		Concurrency:      constants.DefaultConcurrency,
		Attempts:         constants.DefaultAttempts,
		RetryStages:      defaultRetryStages(),
		SeckillMode:      types.SeckillModeAggressive,
		XiaodianPageSize: 200,
	}
}

// defaultRetryStages 返回默认重试间隔阶段配置。
func defaultRetryStages() []types.RetryStage {
	return []types.RetryStage{
		{MaxElapsed: 4, Interval: 120},
		{MaxElapsed: 12, Interval: 200},
		{MaxElapsed: 30, Interval: 500},
		{MaxElapsed: 75, Interval: 1000},
	}
}

// LoadConfig 读取配置文件；缺失时安静使用内置默认配置。
func LoadConfig(path string) types.Config {
	cfg := defaultConfig()
	if path == "" {
		path = constants.DefaultConfigFile
	}

	f, err := os.Open(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			logger.LogEvent("配置", "info", "配置加载完成: 内置默认配置")
		} else {
			logger.LogEvent("配置", "warn", "读取 %s 出错，使用内置默认配置: %v", path, err)
		}
		return cfg
	}
	defer f.Close()

	if err := json.NewDecoder(f).Decode(&cfg); err != nil {
		logger.LogEvent("配置", "warn", "解析 %s 失败，使用内置默认配置: %v", path, err)
		return defaultConfig()
	}
	if cfg.Activity == "" {
		cfg.Activity = activity.DefaultActivityID
	}
	if cfg.TimeAPIURL == "" {
		cfg.TimeAPIURL = constants.DefaultTimeAPI
	}
	if cfg.Concurrency <= 0 {
		cfg.Concurrency = constants.DefaultConcurrency
	}
	if cfg.Attempts <= 0 {
		cfg.Attempts = constants.DefaultAttempts
	}
	if cfg.LogLevel == "" {
		cfg.LogLevel = "info"
	}
	if len(cfg.RetryStages) == 0 {
		cfg.RetryStages = defaultRetryStages()
	}
	normalizeXiaodianConfig(&cfg)
	logger.LogEvent("配置", "success", "配置加载完成: %s", path)
	return cfg
}

// normalizeXiaodianConfig 约束和平小店分页参数，接口单页最大为 200。
func normalizeXiaodianConfig(cfg *types.Config) {
	if cfg.XiaodianPageSize <= 0 || cfg.XiaodianPageSize > 200 {
		cfg.XiaodianPageSize = 200
	}
}

// SaveConfig 将配置写入文件。
func SaveConfig(path string, cfg types.Config) error {
	if path == "" {
		path = constants.DefaultConfigFile
	}
	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
		return err
	}
	return os.WriteFile(path, data, 0600)
}