package score

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"time"

	"huya-go/internal/huya"
	"huya-go/internal/sniper"
)

const ScoreBaselineFileName = "scores.json"

// BaselineEntry 记录单个账号上一次已知的积分余额及时间戳。
type BaselineEntry struct {
	Score int64 `json:"score"`
	At    int64 `json:"at"` // Unix 秒
}

// BaselineStore 记录每个账号「上次已知的积分余额」，作为抢购结束后刚性核对的基线。
// 借鉴 dygou_go 的 ScoreBaselineStore 设计：在导入账号、手动查积分以及抢购对账后更新。
type BaselineStore struct {
	mu      sync.RWMutex
	path    string
	entries map[int64]BaselineEntry
}

// NewBaselineStore 创建积分基线存储；path 为空时退化为纯内存存储。
func NewBaselineStore(path string) *BaselineStore {
	return &BaselineStore{
		path:    path,
		entries: make(map[int64]BaselineEntry),
	}
}

// Load 从磁盘读取基线文件。文件缺失或损坏均不报错，仅退化为无基线。
func (s *BaselineStore) Load() {
	if s == nil || s.path == "" {
		return
	}
	data, err := os.ReadFile(s.path)
	if err != nil {
		return
	}
	loaded := make(map[int64]BaselineEntry)
	if err := json.Unmarshal(data, &loaded); err != nil {
		return
	}
	s.mu.Lock()
	s.entries = loaded
	s.mu.Unlock()
}

// Get 返回账号已知的基线积分。
func (s *BaselineStore) Get(uid int64) (int64, bool, time.Time) {
	if s == nil {
		return 0, false, time.Time{}
	}
	s.mu.RLock()
	entry, ok := s.entries[uid]
	s.mu.RUnlock()
	if !ok {
		return 0, false, time.Time{}
	}
	return entry.Score, true, time.Unix(entry.At, 0)
}

// Set 记录单账号最新积分余额并落盘。
func (s *BaselineStore) Set(uid int64, score int64) {
	s.SetMany(map[int64]int64{uid: score})
}

// SetMany 批量记录账号最新积分并原子写盘。
func (s *BaselineStore) SetMany(values map[int64]int64) {
	if s == nil || len(values) == 0 {
		return
	}
	now := time.Now().Unix()
	s.mu.Lock()
	for uid, val := range values {
		s.entries[uid] = BaselineEntry{Score: val, At: now}
	}
	snapshot := make(map[int64]BaselineEntry, len(s.entries))
	for uid, entry := range s.entries {
		snapshot[uid] = entry
	}
	s.mu.Unlock()
	s.flush(snapshot)
}

// Snapshot 返回当前基线积分快照。
func (s *BaselineStore) Snapshot() map[int64]int64 {
	if s == nil {
		return nil
	}
	s.mu.RLock()
	defer s.mu.RUnlock()
	out := make(map[int64]int64, len(s.entries))
	for uid, entry := range s.entries {
		out[uid] = entry.Score
	}
	return out
}

// UIDs 返回所有已记录基线的 UID（升序排序）。
func (s *BaselineStore) UIDs() []int64 {
	if s == nil {
		return nil
	}
	s.mu.RLock()
	defer s.mu.RUnlock()
	out := make([]int64, 0, len(s.entries))
	for uid := range s.entries {
		out = append(out, uid)
	}
	sort.Slice(out, func(i, j int) bool { return out[i] < out[j] })
	return out
}

// flush 原子写入磁盘：先写入临时文件再 rename。
func (s *BaselineStore) flush(snapshot map[int64]BaselineEntry) {
	if s == nil || s.path == "" {
		return
	}
	data, err := json.MarshalIndent(snapshot, "", "  ")
	if err != nil {
		return
	}
	dir := filepath.Dir(s.path)
	if dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0700); err != nil {
			return
		}
	}
	tmp, err := os.CreateTemp(dir, "."+filepath.Base(s.path)+".*.tmp")
	if err != nil {
		return
	}
	tmpPath := tmp.Name()
	defer func() { _ = os.Remove(tmpPath) }()
	if _, err := tmp.Write(data); err != nil {
		_ = tmp.Close()
		return
	}
	if err := tmp.Close(); err != nil {
		return
	}
	_ = os.Rename(tmpPath, s.path)
}

// ReconcileItem 是单个账号刚性对账的结果。
type ReconcileItem struct {
	UID          int64  `json:"uid"`
	BeforeScore  int64  `json:"beforeScore"`
	CurrentScore int64  `json:"currentScore"`
	DiffScore    int64  `json:"diffScore"`
	TargetPrice  int64  `json:"targetPrice"`
	HasBaseline  bool   `json:"hasBaseline"`
	Confirmed    bool   `json:"confirmed"` // 是否刚性确认扣分成功
	Message      string `json:"message"`
}

// ReconcileAccounts 对指定账号进行全量积分拉取与基线差值比对。
// 若 diff == targetPrice（或 diff > 0 满足商品售价），则刚性确认为成功兑换。
func ReconcileAccounts(ctx context.Context, client huya.ActivityClient, store *BaselineStore, sid int32, targetPrice int64, accounts []sniper.Account, concurrency int) ([]ReconcileItem, error) {
	if client == nil {
		return nil, fmt.Errorf("client 不能为空")
	}
	if concurrency <= 0 {
		concurrency = 10
	}
	if concurrency > 20 {
		concurrency = 20
	}

	results := make([]ReconcileItem, len(accounts))
	sem := make(chan struct{}, concurrency)
	var wg sync.WaitGroup

	updatedScores := make(map[int64]int64)
	var updateMu sync.Mutex

	for i, acc := range accounts {
		i, acc := i, acc
		wg.Add(1)
		go func() {
			defer wg.Done()
			select {
			case sem <- struct{}{}:
				defer func() { <-sem }()
			case <-ctx.Done():
				results[i] = ReconcileItem{
					UID:     acc.UID,
					Message: "对账已取消",
				}
				return
			}

			beforeScore, hasBaseline, _ := store.Get(acc.UID)
			resp, err := client.QueryUserScore(ctx, acc.UID, acc.Cookie, sid)
			if err != nil || resp == nil || resp.Status != 200 {
				errMsg := "查询当前积分失败"
				if err != nil {
					errMsg = err.Error()
				} else if resp != nil {
					errMsg = resp.Msg
				}
				results[i] = ReconcileItem{
					UID:         acc.UID,
					BeforeScore: beforeScore,
					HasBaseline: hasBaseline,
					Message:     errMsg,
				}
				return
			}

			currScore := resp.AvailableScore()
			updateMu.Lock()
			updatedScores[acc.UID] = currScore
			updateMu.Unlock()

			if !hasBaseline {
				results[i] = ReconcileItem{
					UID:          acc.UID,
					BeforeScore:  currScore,
					CurrentScore: currScore,
					HasBaseline:  false,
					Confirmed:    false,
					Message:      "无初始基线（已将当前积分记录为新基线）",
				}
				return
			}

			diff := beforeScore - currScore
			confirmed := false
			msg := ""

			if diff > 0 {
				if targetPrice > 0 && diff == targetPrice {
					confirmed = true
					msg = fmt.Sprintf("刚性扣分确认成功: -%d 分 (当前剩余 %d)", diff, currScore)
				} else if targetPrice > 0 && diff >= targetPrice {
					confirmed = true
					msg = fmt.Sprintf("刚性扣分确认成功(含多件或多扣): -%d 分 (当前剩余 %d)", diff, currScore)
				} else {
					confirmed = true
					msg = fmt.Sprintf("积分发生扣除: -%d 分 (当前剩余 %d)", diff, currScore)
				}
			} else if diff == 0 {
				msg = fmt.Sprintf("积分未变动 (当前 %d)", currScore)
			} else {
				msg = fmt.Sprintf("积分增加 +%d 分 (当前 %d)", -diff, currScore)
			}

			results[i] = ReconcileItem{
				UID:          acc.UID,
				BeforeScore:  beforeScore,
				CurrentScore: currScore,
				DiffScore:    diff,
				TargetPrice:  targetPrice,
				HasBaseline:  true,
				Confirmed:    confirmed,
				Message:      msg,
			}
		}()
	}

	wg.Wait()

	// 对账拉取到的最新积分批量写回基线，使下一次抢购可基于最新值比对
	if len(updatedScores) > 0 && store != nil {
		store.SetMany(updatedScores)
	}

	return results, ctx.Err()
}