package services

// 14 天 Pro 试用:首次启动落一个安装时间戳,窗口内等效 Pro(无需授权码)。
// 滥用防护(多层,删库重装只能重置最外层):
//  1. DATA_DIR/.trial-start(0600)——用户可删,快但易防
//  2. 库内 settings.trial_started_at——随 lokistack.json 走,删库重装会重置
//  3. 主机指纹(机器级):/etc/machine-id 优先(容器内不稳定)、回退 os.Hostname+CPU 数+
//     DATA_DIR 所在磁盘标识——重装容器/换目录仍命中同一指纹则不重发试用
// 指纹哈希只存本地(与远端无关),换机器必然新试用(接受:试用成本有限,Pro 功能
// 本身零边际成本,追杀到 BIOS 级指纹得不偿失)。
import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"os"
	"runtime"
	"strconv"
	"strings"
	"time"

	"lokistack/config"
	"lokistack/models"
	"lokistack/repository"
)

const trialDays = 14

// TrialRemainingDays 剩余试用天数(0=无试用;>0=试用中)。trialStart==0 表示从未启动过计时。
func TrialRemainingDays() int {
	start := trialStartAt()
	if start == 0 {
		return trialDays // 尚未计时:首查即激活,调用方应先 ensureTrialStarted
	}
	days := int((trialStartExpiry(start) - time.Now().Unix()) / 86400)
	if days < 0 {
		days = 0
	}
	return days
}

// TrialActive 试用是否生效(Pro 等效)
func TrialActive() bool {
	start := trialStartAt()
	if start == 0 {
		return true // 未计时视为可用(首次调用会落时间戳)
	}
	return time.Now().Unix() < trialStartExpiry(start)
}

func trialStartExpiry(start int64) int64 { return start + int64(trialDays)*86400 }

// EnsureTrialStarted 首次启动时落试用起点(幂等)。三层防线:文件 > 库 > 指纹。
// 指纹命中"该机器已用过试用"则不重发(防删库重装刷试用)。
func EnsureTrialStarted() {
	if trialStartAt() != 0 {
		return
	}
	now := time.Now().Unix()
	// 库内 + 文件双写(任一存在即以最早的为准——防先删文件再删库分次续命)
	if start := earliestKnownStart(now); start < now {
		persistTrialStart(start)
		return
	}
	// 本机指纹库:命中则这台机器已消费过试用,直接落一个已过期起点(不重发)
	fp := hostTrialFingerprint()
	if fp != "" && fingerprintConsumed(fp) {
		persistTrialStart(now - int64(trialDays)*86400 - 1)
		return
	}
	persistTrialStart(now)
	if fp != "" {
		recordFingerprint(fp)
	}
}

func trialStartAt() int64 {
	if start := trialStartFromFile(); start > 0 {
		return start
	}
	return trialStartFromDB()
}

func trialStartFromFile() int64 {
	cfg := trialDataDir()
	raw, err := os.ReadFile(cfg + "/.trial-start")
	if err != nil {
		return 0
	}
	v, err := strconv.ParseInt(strings.TrimSpace(string(raw)), 10, 64)
	if err != nil || v <= 0 {
		return 0
	}
	return v
}

func trialStartFromDB() int64 {
	db := repository.GetDB()
	if db == nil {
		return 0
	}
	db.RLock()
	defer db.RUnlock()
	for _, s := range db.Settings {
		if s.Key == "trial_started_at" {
			v, err := strconv.ParseInt(s.Value, 10, 64)
			if err == nil && v > 0 {
				return v
			}
		}
	}
	return 0
}

// earliestKnownStart 文件与库中较早的起点(都无则返回 now)
func earliestKnownStart(now int64) int64 {
	file := trialStartFromFile()
	dbv := trialStartFromDB()
	switch {
	case file > 0 && dbv > 0:
		return min64(file, dbv)
	case file > 0:
		return file
	case dbv > 0:
		return dbv
	default:
		return now
	}
}

func persistTrialStart(start int64) {
	// 库
	db := repository.GetDB()
	if db != nil {
		db.Lock()
		exists := false
		for i := range db.Settings {
			if db.Settings[i].Key == "trial_started_at" {
				v, _ := strconv.ParseInt(db.Settings[i].Value, 10, 64)
				if v == 0 || start < v {
					db.Settings[i].Value = strconv.FormatInt(start, 10)
				}
				exists = true
				break
			}
		}
		if !exists {
			db.Settings = append(db.Settings, newSetting("trial_started_at", strconv.FormatInt(start, 10)))
		}
		db.RequestSave()
		db.Unlock()
	}
	// 文件(0600)
	dir := trialDataDir()
	_ = os.MkdirAll(dir, 0o700)
	_ = os.WriteFile(dir+"/.trial-start", []byte(strconv.FormatInt(start, 10)), 0o600)
}

// hostTrialFingerprint 机器级指纹(与 DATA_DIR 完全无关,删目录/换挂载不变):
// machine-id > hostname+cpu。故意不含任何 DATA_DIR 特征——目录 mtime 会因删除/重建漂移,
// 含它等于给刷试用留后门。
func hostTrialFingerprint() string {
	if raw, err := os.ReadFile("/etc/machine-id"); err == nil {
		if id := strings.TrimSpace(string(raw)); len(id) >= 8 {
			return hashPart(id, "mid")
		}
	}
	host, err := os.Hostname()
	if err != nil || host == "" {
		return ""
	}
	return hashPart(fmt.Sprintf("%s|%d", host, runtime.NumCPU()), "host")
}

func hashPart(seed, prefix string) string {
	sum := sha256.Sum256([]byte("lokistack-trial|" + seed))
	return prefix + "-" + hex.EncodeToString(sum[:10])
}

// 指纹记录:库内 settings.trial_fp_<hash> = 1
func fingerprintConsumed(fp string) bool {
	db := repository.GetDB()
	if db == nil {
		return false
	}
	key := "trial_fp_" + fp
	db.RLock()
	defer db.RUnlock()
	for _, s := range db.Settings {
		if s.Key == key && s.Value == "1" {
			return true
		}
	}
	return false
}

func recordFingerprint(fp string) {
	db := repository.GetDB()
	if db == nil {
		return
	}
	key := "trial_fp_" + fp
	db.Lock()
	defer db.Unlock()
	for _, s := range db.Settings {
		if s.Key == key {
			return
		}
	}
	db.Settings = append(db.Settings, newSetting(key, "1"))
	db.RequestSave()
}

func trialDataDir() string {
	if trialDataDirOverride != "" {
		return trialDataDirOverride
	}
	return config.GetConfig().DataDir
}

// trialDataDirOverride 测试注入(空=用 config.DataDir)
var trialDataDirOverride string

func newSetting(key, value string) models.SystemSetting {
	db := repository.GetDB()
	id := uint(0)
	if db != nil {
		id = db.NextID("settings")
	}
	return models.SystemSetting{ID: id, Key: key, Value: value}
}

func min64(a, b int64) int64 {
	if a < b {
		return a
	}
	return b
}