import * as React from "react";

/**
 * Tracks whether a file drag is anywhere over the window. Depth-counted so
 * child enter/leave churn doesn't flicker the flag; resets when disabled.
 */
export function useWindowFileDragOver(enabled: boolean) {
  const [isWindowFileDragOver, setIsWindowFileDragOver] = React.useState(false);

  React.useEffect(() => {
    if (!enabled) {
      setIsWindowFileDragOver(false);
      return;
    }

    let dragDepth = 0;

    function isFileDrag(event: DragEvent): boolean {
      return Array.from(event.dataTransfer?.types ?? []).includes("Files");
    }

    function handleWindowDragEnter(event: DragEvent) {
      if (!isFileDrag(event)) {
        return;
      }
      dragDepth += 1;
      setIsWindowFileDragOver(true);
    }

    function handleWindowDragOver(event: DragEvent) {
      if (!isFileDrag(event)) {
        return;
      }
      event.preventDefault();
      if (event.dataTransfer) {
        event.dataTransfer.dropEffect = "copy";
      }
      setIsWindowFileDragOver(true);
    }

    function handleWindowDragLeave(event: DragEvent) {
      if (!isFileDrag(event)) {
        return;
      }
      dragDepth = Math.max(0, dragDepth - 1);
      if (dragDepth === 0) {
        setIsWindowFileDragOver(false);
      }
    }

    function handleWindowDrop(event: DragEvent) {
      if (!isFileDrag(event)) {
        return;
      }
      event.preventDefault();
      dragDepth = 0;
      setIsWindowFileDragOver(false);
    }

    window.addEventListener("dragenter", handleWindowDragEnter);
    window.addEventListener("dragover", handleWindowDragOver);
    window.addEventListener("dragleave", handleWindowDragLeave);
    window.addEventListener("drop", handleWindowDrop);

    return () => {
      window.removeEventListener("dragenter", handleWindowDragEnter);
      window.removeEventListener("dragover", handleWindowDragOver);
      window.removeEventListener("dragleave", handleWindowDragLeave);
      window.removeEventListener("drop", handleWindowDrop);
    };
  }, [enabled]);

  return isWindowFileDragOver;
}