// GhostLog event bus — mirrors the tiny typed emitter pattern in
// lib/haunting.ts (HauntBus). It exists because <GhostLog/> is mounted once
// at the app-shell level (visible on every screen) while the live WS session
// lives inside <SeanceProvider>, which is only mounted within the séance
// route/page. React context can't cross that boundary (a shell-level
// sibling can't read a provider nested under a route), so SeanceProvider
// publishes the frames GhostLog cares about onto this bus instead — GhostLog
// subscribes for the lifetime of the app and never needs to sit inside the
// séance's own component tree.

export type GhostLogEventMap = {
  /** A new entity is present (or the session cleared it — entity: null). */
  entity: { name: string | null }
  /** One `tell` frame arrived from the server. */
  tell: { text: string }
  /** A `ritual_complete` frame arrived. */
  ritual_complete: { success: boolean; revealed: { alignment: number } | null }
  /** The active séance session ended (page left / socket torn down) —
   * GhostLog should fall back to its idle state. */
  session_end: Record<string, never>
}

type GhostLogHandler<T> = (detail: T) => void

/** Tiny typed emitter — one bad listener never silences the others. */
export class GhostLogBus {
  private handlers = new Map<keyof GhostLogEventMap, Set<GhostLogHandler<never>>>()

  on<K extends keyof GhostLogEventMap>(
    type: K,
    handler: GhostLogHandler<GhostLogEventMap[K]>,
  ): () => void {
    let set = this.handlers.get(type)
    if (!set) {
      set = new Set()
      this.handlers.set(type, set)
    }
    const h = handler as GhostLogHandler<never>
    set.add(h)
    return () => {
      set.delete(h)
    }
  }

  emit<K extends keyof GhostLogEventMap>(type: K, detail: GhostLogEventMap[K]): void {
    const set = this.handlers.get(type)
    if (!set) return
    for (const h of [...set]) (h as GhostLogHandler<GhostLogEventMap[K]>)(detail)
  }
}

/** The shared bus the app-shell GhostLog and the séance provider both use. */
export const ghostLogBus = new GhostLogBus()