"use client";
import { useCallback, useRef, useState } from "react";
import { trpc } from "~/lib/trpc/client.js";
import type { AllocationMovedSnapshot } from "./useTimelineDrag.js";

export type { AllocationMovedSnapshot };

const MAX_HISTORY = 20;

export function useAllocationHistory() {
  const [canUndo, setCanUndo] = useState(false);
  const [canRedo, setCanRedo] = useState(false);
  const past = useRef<AllocationMovedSnapshot[]>([]);
  const future = useRef<AllocationMovedSnapshot[]>([]);

  const utils = trpc.useUtils();

  const updateMutation = trpc.timeline.updateAllocationInline.useMutation({
    onSuccess: () => {
      void utils.timeline.getEntries.invalidate();
      void utils.timeline.getEntriesView.invalidate();
      void utils.timeline.getProjectContext.invalidate();
      void utils.timeline.getBudgetStatus.invalidate();
    },
  });

  const push = useCallback((snapshot: AllocationMovedSnapshot) => {
    past.current = [...past.current.slice(-MAX_HISTORY + 1), snapshot];
    future.current = [];
    setCanUndo(true);
    setCanRedo(false);
  }, []);

  const undo = useCallback(async () => {
    const last = past.current[past.current.length - 1];
    if (!last) return;
    past.current = past.current.slice(0, -1);
    future.current = [last, ...future.current];
    setCanUndo(past.current.length > 0);
    setCanRedo(true);
    await updateMutation.mutateAsync({
      allocationId: last.mutationAllocationId,
      startDate: last.before.startDate,
      endDate: last.before.endDate,
    });
  }, [updateMutation]);

  const redo = useCallback(async () => {
    const next = future.current[0];
    if (!next) return;
    future.current = future.current.slice(1);
    past.current = [...past.current, next];
    setCanUndo(true);
    setCanRedo(future.current.length > 0);
    await updateMutation.mutateAsync({
      allocationId: next.mutationAllocationId,
      startDate: next.after.startDate,
      endDate: next.after.endDate,
    });
  }, [updateMutation]);

  return { push, undo, redo, canUndo, canRedo };
}