/**
 * Scheduler — Serial inbound queue with priority ordering
 *
 * Mention-containing deltas are pushed to the front of the queue.
 * Processing is serial to avoid concurrent agent turns.
 */

import { logger } from '../util/logger.js';
import type { ChannelDelta } from './types.js';
import type { ActionExecutor } from './executor.js';

export class Scheduler {
  private executor: ActionExecutor;
  private queue: ChannelDelta[] = [];
  private _processing = false;

  constructor(executor: ActionExecutor) {
    this.executor = executor;
  }

  enqueue(delta: ChannelDelta): void {
    if (delta.hasMention) {
      this.queue.unshift(delta);
    } else {
      this.queue.push(delta);
    }

    logger.debug(
      `[scheduler] ENQUEUE ch=${delta.channelId} pos=${delta.hasMention ? 'FRONT' : 'BACK'} queue=${this.queue.length}`,
    );
    void this._processNext();
  }

  private async _processNext(): Promise<void> {
    if (this._processing || this.queue.length === 0) return;
    this._processing = true;

    try {
      const delta = this.queue.shift()!;
      logger.debug(`[scheduler] PROCESS ch=${delta.channelId} msgs=${delta.messageCount} remaining=${this.queue.length}`);
      await this.executor.handleDelta(delta);
    } catch (err) {
      logger.error(`[scheduler] ERROR processing delta: ${(err as Error).message}`);
    } finally {
      this._processing = false;
      if (this.queue.length > 0) {
        setTimeout(() => void this._processNext(), 0);
      }
    }
  }

  get queueSize(): number {
    return this.queue.length;
  }
}