import type { Cursor, Event, Task, Timestamp } from "../../protocol/model";
import type { ActivityAdapter, ActivityScope, ActivitySubscription, ResumeGap, StreamPhase } from "./types";

export class MemoryActivityAdapter implements ActivityAdapter {
  readonly #events: readonly Event[];
  readonly #tasks = new Map<string, Task>();

  constructor(events: readonly Event[] = [], tasks: readonly Task[] = []) {
    this.#events = events;
    tasks.forEach((task) => this.#tasks.set(task.task_id, task));
  }

  subscribe(scope: ActivityScope, cursor: Cursor | undefined, onEvent: (event: Event) => void, onPhase: (phase: StreamPhase, gap?: ResumeGap) => void): ActivitySubscription {
    let closed = false;
    const scoped = this.#events.filter((event) => event.context.server_id === scope.server_id && event.context.project_id === scope.project_id);
    const cursorIndex = cursor ? scoped.findIndex((event) => event.cursor === cursor) : -1;
    const gap = cursor && cursorIndex < 0 ? { requested_cursor: cursor, resumed_cursor: scoped[0]?.cursor, message: "事件游标已失效，期间事件可能缺失。" } : undefined;
    queueMicrotask(() => {
      if (closed) return;
      onPhase("streaming", gap);
      scoped.slice(cursorIndex + 1).forEach((event) => { if (!closed) onEvent(event); });
    });
    return { close: () => { closed = true; } };
  }

  async cancelTask(task: Task): Promise<Task> {
    if (!task.cancellable || ["SUCCEEDED", "FAILED", "CANCELLED"].includes(task.state)) {
      throw new Error("该任务当前不可取消");
    }
    const cancelled = { ...task, state: "CANCELLED" as const, cancellable: false, updated_at: new Date().toISOString() as Timestamp };
    this.#tasks.set(task.task_id, cancelled);
    return cancelled;
  }
}