package sniper

import (
	"time"
)

// sessionLostLimit 返回「连续会话失效多少次后停止该账号」的阈值。
func sessionLostLimit(cfg Config) int {
	if cfg.SessionLostLimit > 0 {
		return cfg.SessionLostLimit
	}
	return defaultSessionLostLimit
}

// completeRound 每个账号每轮只更新一次连续失败/会话失效计数。
// 多目标一轮同时失败不会被放大成多次失败；任意可信业务回包都会清零会话失效。
func (s *runState) completeRound(uid int64, categories []string, sessionLimit int) {
	s.mu.Lock()
	defer s.mu.Unlock()
	account := s.accounts[uid]
	if account == nil {
		return
	}

	hasSuccess := false
	hasRetry := false
	hasSessionLost := false
	hasSessionAlive := false
	for _, category := range categories {
		switch category {
		case CategorySuccess:
			hasSuccess = true
			hasSessionAlive = true
		case CategorySessionLost:
			hasSessionLost = true
		default:
			if sessionAliveCategory(category) {
				hasSessionAlive = true
			}
			if backoffCategory(category) {
				hasRetry = true
			}
		}
	}

	if hasSuccess {
		account.failStreak = 0
		account.sessionStreak = 0
		return
	}
	if hasRetry {
		account.failStreak++
	}
	if hasSessionAlive {
		account.sessionStreak = 0
	} else if hasSessionLost {
		account.sessionStreak++
	}
	if sessionLimit > 0 && account.sessionStreak >= sessionLimit {
		account.done = true
	}
}

// roundDelay 返回本轮结束后该账号的统一等待时间：取本轮所有失败分类里
// 最长的退避值，不再为每个 target 单独维护下一次重试时间。
func (s *runState) roundDelay(uid int64, cfg Config, categories []string) time.Duration {
	delay := cfg.Delay
	if delay <= 0 {
		delay = 100 * time.Millisecond
	}
	seen := make(map[string]bool, len(categories))
	for _, category := range categories {
		if category == "" || seen[category] || !backoffCategory(category) {
			continue
		}
		seen[category] = true
		if candidate := s.retryDelay(uid, cfg, category); candidate > delay {
			delay = candidate
		}
	}
	return delay
}

// retryDelay 计算当前账号在某个结局后的退避时间。
func (s *runState) retryDelay(uid int64, cfg Config, category string) time.Duration {
	s.mu.Lock()
	streak := 0
	if account := s.accounts[uid]; account != nil {
		streak = account.failStreak
	}
	s.mu.Unlock()
	return computeRetryDelay(s.elapsed(), streak, cfg, category)
}

// computeRetryDelay 使用与 dygou_go 相同的简单阶梯：
// 分类基础值 × 时间阶段 × 连续失败倍率，最后叠加抖动并封顶 1.5 秒。
func computeRetryDelay(elapsed time.Duration, failStreak int, cfg Config, category string) time.Duration {
	base := cfg.ErrorBackoff
	switch category {
	case CategoryTooFrequent:
		base = cfg.TooFrequentBackoff
	case CategoryNotOpen:
		base = maxDuration(cfg.Delay, 50*time.Millisecond)
	}
	if base <= 0 {
		base = defaultRetryBackoff
	}
	delay := time.Duration(stageMultiplier(elapsed, category)) * base
	if mult := streakMultiplier(failStreak); mult > 1 {
		delay *= time.Duration(mult)
	}
	if delay > maxRetryDelay {
		delay = maxRetryDelay
	}
	delay = jitterDuration(delay)
	if delay > maxRetryDelay {
		delay = maxRetryDelay
	}
	return delay
}

// elapsed 返回相对开抢时刻的已用时，用于按阶段取退避节奏。
func (s *runState) elapsed() time.Duration {
	if !s.openAt.IsZero() {
		elapsed := time.Since(s.openAt)
		if elapsed < 0 {
			return 0
		}
		return elapsed
	}
	if s.startedAt.IsZero() {
		return 0
	}
	return time.Since(s.startedAt)
}

// stageMultiplier 按已抢购时长返回退避倍率：开抢头 2 秒最激进，5 秒后放慢到 3 倍。
func stageMultiplier(elapsed time.Duration, category string) int {
	if backoffCategory(category) {
		switch {
		case elapsed < 2*time.Second:
			return 1
		case elapsed < 5*time.Second:
			return 2
		default:
			return 3
		}
	}
	if elapsed >= 5*time.Second {
		return 2
	}
	return 1
}

// backoffCategory 返回该结局是否需要账号级退避。
func backoffCategory(category string) bool {
	switch category {
	case "", CategorySuccess, CategoryNotEnough, CategoryAlreadyDone, CategoryOffShelf:
		return false
	default:
		return true
	}
}

// streakMultiplier 把连续失败次数换算成翻倍系数：第 3 次起 ×2，第 4 次起 ×4。
func streakMultiplier(streak int) int {
	if streak <= 2 {
		return 1
	}
	mult := 1
	for i := 2; i < streak && mult < 4; i++ {
		mult <<= 1
	}
	return mult
}

// sessionAliveCategory 返回该结局是否能证明当前账号的登录态仍然有效。
// 网络错误、协议异常和限流都不算。
func sessionAliveCategory(category string) bool {
	switch category {
	case CategorySuccess, CategoryNotOpen, CategorySoldOut, CategoryNotEnough,
		CategoryAlreadyDone, CategoryOffShelf, CategoryCondition, CategoryFailed:
		return true
	default:
		return false
	}
}