"use client";

import { ChevronDown, ChevronUp, PanelRight, MoreVertical, FileText } from "lucide-react";
import { Sheet, SheetClose, SheetContent, SheetHeader, SheetTrigger } from "@/components/ui/sheet";
import DocsMenu from "@/components/DocsMenu";
import { ModeToggle } from "@/components/ThemeToggle";
import { DialogTitle, DialogDescription } from "@/components/ui/dialog";
import ContextPopover from "@/components/ContextPopover";
import TocObserver from "./TocObserver";
import * as React from "react";
import { useRef, useMemo } from "react";
import { usePathname } from "next/navigation";
import { Button } from "./ui/button";
import { useActiveSection } from "@/hooks";
import { TocItem } from "@/lib/toc";
import Search from "@/components/SearchBox";
import GitHubButton from "@/components/Github";
import { NavMenu } from "@/components/navbar";
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuTrigger,
} from "@/components/ui/dropdown-menu";

interface MobTocProps {
  tocs: TocItem[];
  title?: string;
}

const subscribe = () => () => undefined;
const getMountedSnapshot = () => true;
const getServerSnapshot = () => false;

const useClickOutside = (ref: React.RefObject<HTMLElement | null>, callback: () => void) => {
  const callbackRef = useRef(callback);

  React.useEffect(() => {
    callbackRef.current = callback;
  });

  React.useEffect(() => {
    const handleClick = (event: MouseEvent) => {
      if (ref.current && !ref.current.contains(event.target as Node)) {
        callbackRef.current();
      }
    };
    document.addEventListener("mousedown", handleClick);
    return () => document.removeEventListener("mousedown", handleClick);
  }, [ref]);
};

export default function MobToc({ tocs, title }: MobTocProps) {
  const pathname = usePathname();
  const [isExpanded, setIsExpanded] = React.useState(false);
  const tocRef = useRef<HTMLDivElement>(null);
  const contentRef = useRef<HTMLDivElement>(null);

  // Use custom hooks
  const { activeId, setActiveId } = useActiveSection(tocs);

  // Only show on /docs pages
  const isDocsPage = useMemo(() => pathname?.startsWith("/docs"), [pathname]);

  // Get title from active section if available, otherwise document title
  const activeSection = useMemo(() => {
    return tocs.find((toc) => toc.href.slice(1) === activeId);
  }, [tocs, activeId]);

  const displayTitle = activeSection?.text || title || "On this page";

  const mounted = React.useSyncExternalStore(subscribe, getMountedSnapshot, getServerSnapshot);

  // Toggle expanded state
  const toggleExpanded = React.useCallback((e: React.MouseEvent) => {
    e.stopPropagation();
    setIsExpanded((prev) => !prev);
  }, []);

  // Close TOC when clicking outside
  useClickOutside(tocRef, () => {
    if (isExpanded) {
      setIsExpanded(false);
    }
  });

  // Don't render anything if not on docs page
  if (!isDocsPage || !mounted) return null;

  const chevronIcon = isExpanded ? (
    <ChevronUp className="text-muted-foreground h-4 w-4 shrink-0" />
  ) : (
    <ChevronDown className="text-muted-foreground h-4 w-4 shrink-0" />
  );

  return (
    <div ref={tocRef} className="sticky top-0 z-50 -mx-4 -mt-4 mb-4 lg:hidden">
      <div className="bg-background/95 border-muted dark:border-foreground/10 dark:bg-background w-full border-b shadow-sm backdrop-blur-sm">
        <div className="p-2">
          <div className="flex items-center gap-2">
            <DropdownMenu>
              <DropdownMenuTrigger asChild>
                <Button
                  variant="ghost"
                  size="icon"
                  className="h-8 w-8 shrink-0"
                  aria-label="Navigation menu"
                >
                  <MoreVertical className="text-muted-foreground h-5 w-5" />
                </Button>
              </DropdownMenuTrigger>
              <DropdownMenuContent align="start" className="flex min-w-40 flex-col gap-1 p-2">
                <NavMenu />
              </DropdownMenuContent>
            </DropdownMenu>
            <Button
              variant="ghost"
              size="sm"
              className="-mx-1 h-auto min-w-0 flex-1 justify-between rounded-md px-2 py-2 hover:bg-transparent hover:text-inherit"
              onClick={toggleExpanded}
              aria-label={isExpanded ? "Collapse table of contents" : "Expand table of contents"}
            >
              <div className="flex min-w-0 items-center gap-2">
                <span className="line-clamp-1 truncate text-sm font-medium capitalize">
                  {displayTitle}
                </span>
              </div>
              {chevronIcon}
            </Button>
            <Search />
            <Sheet>
              <SheetTrigger asChild>
                <Button variant="ghost" size="icon" className="hidden max-lg:flex">
                  <PanelRight className="text-muted-foreground h-6 w-6 shrink-0" />
                </Button>
              </SheetTrigger>
              <SheetContent className="flex w-full flex-col gap-4 px-0 lg:w-auto" side="right">
                <DialogTitle className="sr-only">Navigation Menu</DialogTitle>
                <DialogDescription className="sr-only">
                  Main navigation menu with links to different sections
                </DialogDescription>
                <SheetHeader>
                  <SheetClose className="px-4" asChild>
                    <div className="flex items-center justify-between">
                      <GitHubButton />
                      <div className="mr-8">
                        <ModeToggle />
                      </div>
                    </div>
                  </SheetClose>
                </SheetHeader>
                <div className="flex flex-col gap-4 overflow-y-auto">
                  <div className="mx-2 space-y-2 px-5">
                    <ContextPopover />
                    <DocsMenu isSheet />
                  </div>
                </div>
              </SheetContent>
            </Sheet>
          </div>

          <div
            className="grid transition-[grid-template-rows,opacity] duration-200 ease-in-out"
            style={{
              gridTemplateRows: isExpanded ? "1fr" : "0fr",
              opacity: isExpanded ? 1 : 0,
            }}
          >
            <div ref={contentRef} className="overflow-hidden">
              <div className="mt-2 max-h-[60vh] overflow-y-auto px-4 pb-2">
                {tocs?.length ? (
                  <TocObserver data={tocs} activeId={activeId} onActiveIdChange={setActiveId} />
                ) : (
                  <div className="flex flex-col items-center justify-center px-2 py-8 text-center">
                    <FileText className="text-muted-foreground/40 mb-3 h-8 w-8" />
                    <p className="text-muted-foreground mb-1 text-sm font-medium">No headings</p>
                    <p className="text-muted-foreground/70 text-xs leading-relaxed">
                      {`This page doesn't have section headings yet.`}
                    </p>
                  </div>
                )}
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  );
}