export type FxKind = 'spark' | 'mist' | 'ripple' | 'blade' | 'pulse' | 'seasonShift' | 'drift'

export type FxMode = 'soft' | 'std' | 'full'

export interface FxEmit {
  kind: FxKind
  payload?: Record<string, number | string>
  at: number
}

export interface FxBus {
  emit(e: FxEmit): void
}

/** 竞态安全发射闸：单循环、队列不覆盖、档位过滤、reduced-motion 降级 */
export class FxGate {
  private queue: FxEmit[] = []
  private draining = false
  mode: FxMode = 'std'
  preferReduced = false

  constructor(private bus: FxBus) {}

  setMode(m: FxMode): void {
    this.mode = m
  }

  setReduced(r: boolean): void {
    this.preferReduced = r
  }

  allowed(kind: FxKind): boolean {
    if (this.mode === 'soft') return kind === 'ripple' || kind === 'pulse' || kind === 'drift'
    if (this.mode === 'full') return true
    return kind !== 'blade' // std：火花/雾/涟漪/脉动，刀光仅 full
  }

  emit(kind: FxKind, payload?: FxEmit['payload']): void {
    if (!this.allowed(kind) || this.preferReduced || this.draining) return
    this.queue.push({ kind, payload, at: Date.now() })
    this.drain()
  }

  private drain(): void {
    if (this.draining) return
    this.draining = true
    // 单帧集中派发（不逐个 setTimeout，防止栈深+竞态覆盖）
    const batch = this.queue
    this.queue = []
    try {
      for (const e of batch) this.bus.emit(e)
    } finally {
      this.draining = false
    }
  }

  pending(): number {
    return this.queue.length + (this.draining ? 1 : 0)
  }

  /** 纯逻辑：资源差量（防负值与 NaN，供漂字用） */
  static deltas(prev: Record<string, number>, next: Record<string, number>): Record<string, number> {
    const out: Record<string, number> = {}
    const keys = new Set([...Object.keys(prev), ...Object.keys(next)])
    for (const k of keys) {
      const a = prev[k] ?? 0
      const b = next[k] ?? 0
      if (Number.isFinite(a) && Number.isFinite(b) && b !== a) out[k] = b - a
    }
    return out
  }
}