package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sync"
)

// -----------------------------------------------------------------------------
// 配额 (总目录字节数限制, 默认 10GB, 0=不限)
// -----------------------------------------------------------------------------

var (
	quotaMu   sync.Mutex
	quotaUsed int64 // 当前目录已用字节数
)

// initQuota 启动时扫描目录, 初始化配额计数
func initQuota() {
	if *quota <= 0 {
		log.Printf("[quota] disabled")
		return
	}
	rescanQuota()
	log.Printf("[quota] %s / %s", formatSize(quotaUsed), formatSize(*quota))
}

// rescanQuota 重新扫描目录并重置计数. 调用频率低 (启动 + 清理器每次跑完), 用来修正漂移.
func rescanQuota() {
	quotaMu.Lock()
	defer quotaMu.Unlock()
	var total int64
	_ = filepath.Walk(*uploadDir, func(_ string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() {
			return nil
		}
		total += info.Size()
		return nil
	})
	quotaUsed = total
}

// quotaSnapshot 原子返回 used/cap
func quotaSnapshot() (used, cap_ int64) {
	quotaMu.Lock()
	defer quotaMu.Unlock()
	return quotaUsed, *quota
}

// quotaRemaining 返回剩余可上传字节数. quota<=0 时返回 math.MaxInt64.
func quotaRemaining() int64 {
	quotaMu.Lock()
	defer quotaMu.Unlock()
	if *quota <= 0 {
		return 1 << 62
	}
	return *quota - quotaUsed
}

// quotaReserve 原子地预留 n 字节配额: 超限返回 false, 否则扣减并返回 true.
func quotaReserve(n int64) bool {
	quotaMu.Lock()
	defer quotaMu.Unlock()
	if *quota > 0 && quotaUsed+n > *quota {
		return false
	}
	quotaUsed += n
	return true
}

func quotaSub(n int64) {
	if n <= 0 {
		return
	}
	quotaMu.Lock()
	quotaUsed -= n
	if quotaUsed < 0 { // 漂移防护
		quotaUsed = 0
	}
	quotaMu.Unlock()
}

// formatSize 字节 → 人类可读
func formatSize(b int64) string {
	const (
		KB = 1 << 10
		MB = 1 << 20
		GB = 1 << 30
		TB = 1 << 40
	)
	switch {
	case b >= TB:
		return fmt.Sprintf("%.2f TB", float64(b)/TB)
	case b >= GB:
		return fmt.Sprintf("%.2f GB", float64(b)/GB)
	case b >= MB:
		return fmt.Sprintf("%.2f MB", float64(b)/MB)
	case b >= KB:
		return fmt.Sprintf("%.2f KB", float64(b)/KB)
	default:
		return fmt.Sprintf("%d B", b)
	}
}

// quotaUsedSnapshot 不持锁读, 仅用于 cleaner 自身的日志 (允许轻微漂移)
func quotaUsedSnapshot() int64 {
	quotaMu.Lock()
	defer quotaMu.Unlock()
	return quotaUsed
}