package config

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

type Config struct {
	Addr           string
	DatabaseURL    string
	RedisURL       string
	JWTSecret      []byte
	AdminUser      string
	AdminPassword  string
	BooksDir       string
	CacheDir       string
	ScanInterval   time.Duration
	UploadMaxMB    int64
	TrustedProxies []string
}

func Load() (*Config, error) {
	env := func(k, def string) string {
		if v := os.Getenv(k); v != "" {
			return v
		}
		return def
	}
	envList := func(k, def string) []string {
		v := env(k, def)
		out := make([]string, 0, len(strings.Split(v, ",")))
		for _, s := range strings.Split(v, ",") {
			if s = strings.TrimSpace(s); s != "" {
				out = append(out, s)
			}
		}
		return out
	}
	scanSec, err := strconv.Atoi(env("SCAN_INTERVAL_SEC", "60"))
	if err != nil {
		return nil, fmt.Errorf("SCAN_INTERVAL_SEC: %w", err)
	}
	uploadMB, err := strconv.ParseInt(env("UPLOAD_MAX_MB", "200"), 10, 64)
	if err != nil {
		return nil, fmt.Errorf("UPLOAD_MAX_MB: %w", err)
	}
	secret := os.Getenv("JWT_SECRET")
	if secret == "" {
		return nil, fmt.Errorf("JWT_SECRET required")
	}
	// Validate required fields.
	dbURL := env("DATABASE_URL", "")
	if dbURL == "" {
		return nil, fmt.Errorf("DATABASE_URL is required")
	}
	if _, perr := pgxpool.ParseConfig(dbURL); perr != nil {
		return nil, fmt.Errorf("DATABASE_URL: %w", perr)
	}
	if env("REDIS_URL", "") == "" {
		log.Printf("redis disabled: rate-limit/scan-lock/page-cache off")
	}

	// resolveDir: macOS 开发机上 /var、/tmp 是指向 /private 的软链,
	// 启动时解析一次才能让 root_path 前缀校验对上真实路径;目录不存在/出错则保留原值(Docker 路径不受影响)
	resolveDir := func(dir string) string {
		if r, e := filepath.EvalSymlinks(dir); e == nil {
			return r
		}
		return dir
	}
	return &Config{
		Addr:           env("ADDR", ":8080"),
		DatabaseURL:    env("DATABASE_URL", ""),
		RedisURL:       env("REDIS_URL", ""),
		JWTSecret:      []byte(secret),
		AdminUser:      env("ADMIN_USER", ""),
		AdminPassword:  env("ADMIN_PASSWORD", ""),
		BooksDir:       resolveDir(env("BOOKS_DIR", "/data/books")),
		CacheDir:       resolveDir(env("CACHE_DIR", "/data/cache")),
		ScanInterval:   time.Duration(scanSec) * time.Second,
		UploadMaxMB:    uploadMB,
		TrustedProxies: envList("TRUSTED_PROXY_CIDRS", "172.16.0.0/12"),
	}, nil
}