package store

import (
	"context"
	"fmt"
	"time"

	"github.com/redis/go-redis/v9"
)

// Redis Key 设计见 doc/backend-architecture.html 第七章。
func KeyQuotaBalance(uid string) string { return "quota:" + uid + ":balance" }
func KeyQuotaTrial(uid string, day string) string {
	return "quota:" + uid + ":trial:" + day
}
func KeyAuthQr(state string) string  { return "authqr:" + state }
func KeyJwtBlock(jti string) string  { return "jwt:block:" + jti }
func KeyRateCnt(did string) string   { return "rate:" + did + ":asr:cnt" }
func KeyRateSecs(did string) string  { return "rate:" + did + ":asr:secs" }
func KeyRateFb(uid, day string) string { return "rate:" + uid + ":fb:" + day }
func KeyActiveSession(did string) string { return "asr:active:" + did }

func OpenRedis(addr string, db int) *redis.Client {
	return redis.NewClient(&redis.Options{Addr: addr, DB: db})
}

// Day 返回服务端时区（Asia/Shanghai）的自然日，作为试用与反馈限频的键。
var cst = time.FixedZone("CST", 8*3600)

func Day(t time.Time) string { return t.In(cst).Format("2006-01-02") }

// ─── 设备 30 分钟滑动窗口限制（ZSET，member 唯一、score 为时间戳秒）───────────────

// slideWindow 原子地：清理过期成员 → 检查阈值 → 通过则记录本次。
// cnt 窗口按"次"记 1；secs 窗口按本次秒数记。
var slideScript = redis.NewScript(`
local key, now, window, limit, val = KEYS[1], tonumber(ARGV[1]), tonumber(ARGV[2]), tonumber(ARGV[3]), tonumber(ARGV[4])
redis.call('ZREMRANGEBYSCORE', key, 0, now - window)
local sum = 0
if ARGV[5] == 'count' then
  sum = redis.call('ZCARD', key)
else
  local members = redis.call('ZRANGE', key, 0, -1)
  for _, m in ipairs(members) do
    local v = string.match(m, ':(%d+)$')
    if v then sum = sum + tonumber(v) end
  end
end
if sum + val > limit then return 0 end
redis.call('ZADD', key, now, now .. '-' .. redis.call('INCR', key .. ':seq') .. ':' .. val)
redis.call('EXPIRE', key, window + 60)
return 1
`)

// AllowSession 设备维度新会话准入：30 分钟内 ≤30 次。
func AllowSession(ctx context.Context, rdb *redis.Client, deviceID string, now time.Time) (bool, error) {
	ok, err := slideScript.Run(ctx, rdb, []string{KeyRateCnt(deviceID)},
		now.Unix(), 30*60, 30, 1, "count").Int()
	return ok == 1, err
}

// AllowAudioSeconds 设备维度时长准入（原子检查并记录）：30 分钟内累计 ≤1800s。
func AllowAudioSeconds(ctx context.Context, rdb *redis.Client, deviceID string, seconds int, now time.Time) (bool, error) {
	ok, err := slideScript.Run(ctx, rdb, []string{KeyRateSecs(deviceID)},
		now.Unix(), 30*60, 30*60, seconds, "sum").Int()
	return ok == 1, err
}

// AudioWindowExhausted 会话 start 时检查时长窗口是否已满（只查不记；本次秒数在结束时
// 经 RecordAudioSeconds 记录——音频已实际消耗，结束时无条件记账）。
func AudioWindowExhausted(ctx context.Context, rdb *redis.Client, deviceID string, now time.Time) (bool, error) {
	ok, err := slideScript.Run(ctx, rdb, []string{KeyRateSecs(deviceID)},
		now.Unix(), 30*60, 30*60, 0, "sum").Int()
	return ok == 0, err
}

// RecordAudioSeconds 会话结束记录本次识别秒数（无条件，limit 取大数）。
func RecordAudioSeconds(ctx context.Context, rdb *redis.Client, deviceID string, seconds int, now time.Time) error {
	return slideScript.Run(ctx, rdb, []string{KeyRateSecs(deviceID)},
		now.Unix(), 30*60, 1<<30, seconds, "sum").Err()
}

// AcquireDeviceSlot 单设备同时仅 1 路识别会话（SET NX + TTL 兜底防泄漏）。
func AcquireDeviceSlot(ctx context.Context, rdb *redis.Client, deviceID, sessionID string) (bool, error) {
	return rdb.SetNX(ctx, KeyActiveSession(deviceID), sessionID, 4*time.Minute).Result()
}

func ReleaseDeviceSlot(ctx context.Context, rdb *redis.Client, deviceID, sessionID string) error {
	// 仅当持有者是自己时释放
	script := redis.NewScript(`
if redis.call('GET', KEYS[1]) == ARGV[1] then return redis.call('DEL', KEYS[1]) end
return 0`)
	return script.Run(ctx, rdb, []string{KeyActiveSession(deviceID)}, sessionID).Err()
}

// IncrDailyCounter 自然日计数器（反馈限频等），返回自增后的值。
func IncrDailyCounter(ctx context.Context, rdb *redis.Client, key string) (int64, error) {
	pipe := rdb.TxPipeline()
	incr := pipe.Incr(ctx, key)
	pipe.Expire(ctx, key, 48*time.Hour)
	if _, err := pipe.Exec(ctx); err != nil {
		return 0, err
	}
	return incr.Val(), nil
}

var _ = fmt.Sprintf // keep fmt for future use