import { useState, useCallback, useRef, useEffect } from "react";
import type {
  AssistantTransportCommand,
  CommandQueueState,
  QueuedCommand,
} from "./types";

export const createInitialQueueState = (): CommandQueueState => ({
  queued: [],
  inTransit: [],
});

export const useCommandQueue = (opts: { onQueue: () => void }) => {
  const onQueueRef = useRef(opts.onQueue);
  useEffect(() => {
    onQueueRef.current = opts.onQueue;
  });

  const [, rerender] = useState(0);
  const queueStateRef = useRef<CommandQueueState>(createInitialQueueState());

  const enqueue = (command: AssistantTransportCommand) => {
    queueStateRef.current = {
      queued: [...queueStateRef.current.queued, command],
      inTransit: queueStateRef.current.inTransit,
    };
    rerender((prev) => prev + 1);

    onQueueRef.current();
  };

  const flush = (): QueuedCommand[] => {
    if (queueStateRef.current.queued.length === 0) return [];

    const queued = queueStateRef.current.queued;
    queueStateRef.current = {
      queued: [],
      inTransit: [...queueStateRef.current.inTransit, ...queued],
    };
    rerender((prev) => prev + 1);

    return queued;
  };

  const markDelivered = () => {
    queueStateRef.current = { ...queueStateRef.current, inTransit: [] };
    rerender((prev) => prev + 1);
  };

  const reset = useCallback(() => {
    queueStateRef.current = createInitialQueueState();
    rerender((prev) => prev + 1);
  }, []);

  return {
    state: queueStateRef.current,
    enqueue,
    flush,
    markDelivered,
    reset,
  };
};