import { useCallback, useEffect, useRef, useState } from "react";
import { createPortal } from "react-dom";
import type { Editor } from "@tiptap/react";
import { Sparkles } from "lucide-react";
import { cn } from "@/lib/utils";
import { useCanvasUIContext } from "../../contexts/CanvasUIContext";

const REWRITABLE_TYPES = new Set(["paragraph", "heading", "blockquote"]);

const BTN_SIZE = 24;
const BTN_GAP = 6;   // gap between button right edge and text left edge
// Extra zone around the button that still counts as "near" (bridges the gap)
const HOVER_MARGIN = BTN_GAP + 8;
// Delay before hiding the button (ms) — long enough to cross the gap at slow speed
const HIDE_DELAY = 380;

interface HoverState {
  top: number;
  left: number;
  height: number;
  nodeFrom: number;
  nodeTo: number;
  text: string;
}

interface WritingParagraphMenuProps {
  editor: Editor;
  onAiRewrite: () => void;
}

export function WritingParagraphMenu({ editor, onAiRewrite }: WritingParagraphMenuProps) {
  const { setWritingSelection } = useCanvasUIContext();
  const [hover, setHover] = useState<HoverState | null>(null);
  const hideTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
  // Keep a ref in sync so the document-level handler always reads fresh state
  const hoverRef = useRef<HoverState | null>(null);
  hoverRef.current = hover;

  const clearHideTimer = useCallback(() => {
    if (hideTimerRef.current) {
      clearTimeout(hideTimerRef.current);
      hideTimerRef.current = null;
    }
  }, []);

  const scheduleHide = useCallback(() => {
    clearHideTimer();
    hideTimerRef.current = setTimeout(() => setHover(null), HIDE_DELAY);
  }, [clearHideTimer]);

  // Document-level mousemove: cancel hide when cursor is in the button's vicinity.
  // This bridges the gap between the editor's text edge and the button.
  useEffect(() => {
    const handleDocMove = (e: MouseEvent) => {
      const h = hoverRef.current;
      if (!h) return;

      const btnLeft = h.left - BTN_SIZE - BTN_GAP;
      const btnTop  = h.top + h.height / 2 - BTN_SIZE / 2;

      const inZone =
        e.clientX >= btnLeft - HOVER_MARGIN &&
        e.clientX <= h.left + HOVER_MARGIN &&  // extend slightly into text side
        e.clientY >= btnTop  - HOVER_MARGIN &&
        e.clientY <= btnTop  + BTN_SIZE + HOVER_MARGIN;

      if (inZone) clearHideTimer();
    };

    document.addEventListener("mousemove", handleDocMove);
    return () => document.removeEventListener("mousemove", handleDocMove);
  }, [clearHideTimer]);

  useEffect(() => {
    const editorDom = editor.view.dom as HTMLElement;

    const handleMouseMove = (e: MouseEvent) => {
      const pos = editor.view.posAtCoords({ left: e.clientX, top: e.clientY });
      if (!pos) { scheduleHide(); return; }

      const $pos = editor.state.doc.resolve(pos.pos);
      const depth = Math.min(1, $pos.depth);
      if (depth === 0) { scheduleHide(); return; }

      const nodeStart = $pos.before(depth);
      const node = editor.state.doc.nodeAt(nodeStart);
      if (!node || !REWRITABLE_TYPES.has(node.type.name)) {
        scheduleHide();
        return;
      }

      const text = node.textContent.trim();
      if (!text) { scheduleHide(); return; }

      const domNode = editor.view.nodeDOM(nodeStart);
      if (!domNode || !(domNode instanceof HTMLElement)) {
        scheduleHide();
        return;
      }

      const rect = domNode.getBoundingClientRect();
      clearHideTimer();
      setHover({
        top:      rect.top,
        left:     rect.left,
        height:   rect.height,
        nodeFrom: nodeStart + 1,
        nodeTo:   nodeStart + node.nodeSize - 1,
        text,
      });
    };

    editorDom.addEventListener("mousemove", handleMouseMove);
    editorDom.addEventListener("mouseleave", scheduleHide);

    return () => {
      editorDom.removeEventListener("mousemove", handleMouseMove);
      editorDom.removeEventListener("mouseleave", scheduleHide);
      clearHideTimer();
    };
  }, [editor, clearHideTimer, scheduleHide]);

  const handleClick = useCallback(() => {
    if (!hover) return;
    editor.chain().focus().setTextSelection({ from: hover.nodeFrom, to: hover.nodeTo }).run();
    editor.commands.setAiHighlight(hover.nodeFrom, hover.nodeTo);
    setWritingSelection({ from: hover.nodeFrom, to: hover.nodeTo, text: hover.text });
    onAiRewrite();
  }, [hover, editor, setWritingSelection, onAiRewrite]);

  if (!hover) return null;

  const btnTop  = hover.top  + hover.height / 2 - BTN_SIZE / 2;
  const btnLeft = Math.max(4, hover.left - BTN_SIZE - BTN_GAP);

  return createPortal(
    <button
      type="button"
      style={{
        position: "fixed",
        top:    btnTop,
        left:   btnLeft,
        width:  BTN_SIZE,
        height: BTN_SIZE,
        zIndex: 9998,
      }}
      onMouseEnter={clearHideTimer}
      onMouseLeave={scheduleHide}
      onClick={handleClick}
      className={cn(
        "inline-flex items-center justify-center rounded-md",
        "bg-background border border-border shadow-sm",
        "text-muted-foreground hover:text-amber-500 hover:border-amber-400 hover:bg-amber-50 dark:hover:bg-amber-950/30",
        "transition-all duration-150",
        "animate-in fade-in zoom-in-90 duration-100",
      )}
      title="AI 改写此段落"
    >
      <Sparkles className="h-3.5 w-3.5" />
    </button>,
    document.body,
  );
}