package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

type Config struct {
	Host             string `json:"host"`
	Port             int    `json:"port"`
	DLLDir           string `json:"dll_dir"`
	CORSOrigin       string `json:"cors_origin"`
	LogDir           string `json:"log_dir"`
	LogRetentionDays int    `json:"log_retention_days"`
	LogMaxFileMB     int    `json:"log_max_file_mb"`
	LogMaxTotalMB    int    `json:"log_max_total_mb"`
	RestartDelayMS   int    `json:"restart_delay_ms"`
	MaxRapidRestarts int    `json:"max_rapid_restarts"`
	AppRoot          string `json:"-"`
}

func defaultConfig(appRoot string) Config {
	return Config{
		Host:             "127.0.0.1",
		Port:             17880,
		DLLDir:           "package/DWCardReaderDLL",
		CORSOrigin:       "*",
		LogDir:           "logs",
		LogRetentionDays: 30,
		LogMaxFileMB:     20,
		LogMaxTotalMB:    200,
		RestartDelayMS:   1500,
		MaxRapidRestarts: 5,
		AppRoot:          appRoot,
	}
}

func resolveAppRoot() (string, error) {
	if root := strings.TrimSpace(os.Getenv("CARD_APP_ROOT")); root != "" {
		return filepath.Abs(root)
	}

	cwd, cwdErr := os.Getwd()
	if cwdErr == nil && fileExists(filepath.Join(cwd, "config.json")) {
		return filepath.Abs(cwd)
	}

	exe, exeErr := os.Executable()
	if exeErr == nil {
		return filepath.Abs(filepath.Dir(exe))
	}
	if cwdErr != nil {
		return "", fmt.Errorf("无法确定程序目录: cwd=%v, executable=%v", cwdErr, exeErr)
	}
	return filepath.Abs(cwd)
}

func loadConfig() (Config, error) {
	root, err := resolveAppRoot()
	if err != nil {
		return Config{}, err
	}
	return loadConfigAt(root)
}

func loadConfigAt(root string) (Config, error) {
	root, err := filepath.Abs(root)
	if err != nil {
		return Config{}, fmt.Errorf("解析程序目录失败: %w", err)
	}
	cfg := defaultConfig(root)
	path := filepath.Join(root, "config.json")
	if data, readErr := os.ReadFile(path); readErr == nil {
		if err = json.Unmarshal(data, &cfg); err != nil {
			return Config{}, fmt.Errorf("配置文件格式错误 %s: %w", path, err)
		}
	} else if !errors.Is(readErr, os.ErrNotExist) {
		return Config{}, fmt.Errorf("读取配置文件失败 %s: %w", path, readErr)
	}
	cfg.AppRoot = root

	if value := strings.TrimSpace(os.Getenv("CARD_HOST")); value != "" {
		cfg.Host = value
	}
	if value := strings.TrimSpace(os.Getenv("CARD_PORT")); value != "" {
		cfg.Port, err = strconv.Atoi(value)
		if err != nil {
			return Config{}, fmt.Errorf("CARD_PORT 不是有效端口: %q", value)
		}
	}
	if value := strings.TrimSpace(os.Getenv("CARD_DLL_DIR")); value != "" {
		cfg.DLLDir = value
	}
	if value := os.Getenv("CARD_CORS_ORIGIN"); value != "" {
		cfg.CORSOrigin = value
	}
	if value := strings.TrimSpace(os.Getenv("CARD_LOG_DIR")); value != "" {
		cfg.LogDir = value
	}
	if value := strings.TrimSpace(os.Getenv("CARD_LOG_MAX_FILE_MB")); value != "" {
		cfg.LogMaxFileMB, err = strconv.Atoi(value)
		if err != nil {
			return Config{}, fmt.Errorf("CARD_LOG_MAX_FILE_MB 不是有效整数: %q", value)
		}
	}
	if value := strings.TrimSpace(os.Getenv("CARD_LOG_MAX_TOTAL_MB")); value != "" {
		cfg.LogMaxTotalMB, err = strconv.Atoi(value)
		if err != nil {
			return Config{}, fmt.Errorf("CARD_LOG_MAX_TOTAL_MB 不是有效整数: %q", value)
		}
	}

	if strings.TrimSpace(cfg.Host) == "" {
		return Config{}, errors.New("host 不能为空")
	}
	if cfg.Port < 1 || cfg.Port > 65535 {
		return Config{}, fmt.Errorf("port 超出范围: %d", cfg.Port)
	}
	if strings.TrimSpace(cfg.DLLDir) == "" {
		return Config{}, errors.New("dll_dir 不能为空")
	}
	if strings.TrimSpace(cfg.CORSOrigin) == "" {
		cfg.CORSOrigin = "*"
	}
	if strings.TrimSpace(cfg.LogDir) == "" {
		cfg.LogDir = "logs"
	}
	if cfg.LogRetentionDays <= 0 {
		cfg.LogRetentionDays = 30
	}
	if cfg.LogMaxFileMB <= 0 {
		cfg.LogMaxFileMB = 20
	}
	if cfg.LogMaxTotalMB <= 0 {
		cfg.LogMaxTotalMB = 200
	}
	if cfg.LogMaxTotalMB < cfg.LogMaxFileMB*3 {
		return Config{}, fmt.Errorf("log_max_total_mb 至少应为 log_max_file_mb 的 3 倍（当前 %d < %d）", cfg.LogMaxTotalMB, cfg.LogMaxFileMB*3)
	}
	if cfg.RestartDelayMS < 100 {
		cfg.RestartDelayMS = 1500
	}
	if cfg.MaxRapidRestarts <= 0 {
		cfg.MaxRapidRestarts = 5
	}
	if !filepath.IsAbs(cfg.LogDir) {
		cfg.LogDir = filepath.Join(cfg.AppRoot, cfg.LogDir)
	}
	return cfg, nil
}

func fileExists(path string) bool {
	info, err := os.Stat(path)
	return err == nil && !info.IsDir()
}