'use client';

import { useState } from 'react';
import { ChevronRight, Folder, FolderOpen, FolderTree, Inbox, Lock } from 'lucide-react';

import { Button } from '@/components/ui/button';
import { Sheet, SheetContent, SheetHeader, SheetTitle, SheetTrigger } from '@/components/ui/sheet';
import { cn } from '@/lib/utils';
import { useDocumentFolders, type FolderNode } from '@/hooks/use-document-folders';

interface FolderTreeSidebarProps {
  /** Currently-selected folder id, or `null` for root, or `undefined`
   *  for "All documents" (no folder filter). */
  selectedFolderId: string | null | undefined;
  onSelect: (folderId: string | null | undefined) => void;
  /** Slot below the tree for a "New folder" affordance from the parent. */
  footer?: React.ReactNode;
}

/**
 * Mobile-only Sheet trigger that opens the folder tree in a drawer.
 *
 * Desktop rendering lives in `documents-hub.tsx` as one panel of a
 * `<ResizablePanelGroup>` so power users on wide monitors can drag the
 * split. Both surfaces render the same `<FolderTreeBody>` underneath.
 */
export function FolderTreeSidebar({ selectedFolderId, onSelect, footer }: FolderTreeSidebarProps) {
  const [mobileOpen, setMobileOpen] = useState(false);

  const handleMobileSelect = (id: string | null | undefined) => {
    onSelect(id);
    setMobileOpen(false);
  };

  return (
    <div className="sm:hidden px-3 pt-3">
      <Sheet open={mobileOpen} onOpenChange={setMobileOpen}>
        <SheetTrigger asChild>
          <Button variant="outline" size="sm" className="min-h-[44px]">
            <FolderTree className="mr-2 h-4 w-4" />
            Show folders
          </Button>
        </SheetTrigger>
        <SheetContent side="left" className="w-3/4 max-w-xs p-0">
          <SheetHeader className="border-b px-3 py-3">
            <SheetTitle className="text-sm">Folders</SheetTitle>
          </SheetHeader>
          <div className="p-2 overflow-y-auto">
            <FolderTreeBody
              selectedFolderId={selectedFolderId}
              onSelect={handleMobileSelect}
              footer={footer}
            />
          </div>
        </SheetContent>
      </Sheet>
    </div>
  );
}

export function FolderTreeBody({
  selectedFolderId,
  onSelect,
  footer,
}: {
  selectedFolderId: string | null | undefined;
  onSelect: (folderId: string | null | undefined) => void;
  footer?: React.ReactNode;
}) {
  const { data: tree = [], isLoading, isError } = useDocumentFolders();

  return (
    <>
      <div className="space-y-0.5">
        <PseudoRow
          label="All documents"
          icon={Inbox}
          active={selectedFolderId === undefined}
          onClick={() => onSelect(undefined)}
        />
        <PseudoRow
          label="Root"
          icon={Folder}
          active={selectedFolderId === null}
          onClick={() => onSelect(null)}
        />
      </div>
      <div className="mt-3 space-y-0.5">
        {isLoading ? (
          <p className="px-2 text-xs text-muted-foreground">Loading...</p>
        ) : isError ? (
          <p className="px-2 text-xs text-destructive">Failed to load folders.</p>
        ) : tree.length === 0 ? (
          <p className="px-2 text-xs text-muted-foreground">No folders yet.</p>
        ) : (
          tree.map((node) => (
            <FolderRow
              key={node.id}
              node={node}
              depth={0}
              selectedFolderId={selectedFolderId}
              onSelect={onSelect}
            />
          ))
        )}
      </div>
      {footer ? <div className="mt-4 border-t pt-3">{footer}</div> : null}
    </>
  );
}

function PseudoRow({
  label,
  icon: Icon,
  active,
  onClick,
}: {
  label: string;
  icon: typeof Inbox;
  active: boolean;
  onClick: () => void;
}) {
  return (
    <Button
      variant="ghost"
      size="sm"
      className={cn(
        'w-full min-h-[44px] justify-start font-normal',
        active && 'bg-accent text-foreground',
      )}
      onClick={onClick}
    >
      <Icon className="mr-2 h-4 w-4" />
      {label}
    </Button>
  );
}

function FolderRow({
  node,
  depth,
  selectedFolderId,
  onSelect,
}: {
  node: FolderNode;
  depth: number;
  selectedFolderId: string | null | undefined;
  onSelect: (folderId: string | null) => void;
}) {
  const [open, setOpen] = useState(false);
  const hasChildren = node.children.length > 0;
  const isActive = selectedFolderId === node.id;

  return (
    <>
      <div
        className={cn(
          'group flex items-center gap-0.5 rounded-md px-1 py-0.5 text-sm',
          isActive && 'bg-accent text-foreground',
        )}
        style={{ paddingLeft: `${depth * 12 + 4}px` }}
      >
        <button
          type="button"
          aria-label={`${open ? 'Collapse' : 'Expand'} ${node.name}`}
          aria-expanded={hasChildren ? open : undefined}
          aria-hidden={!hasChildren}
          tabIndex={hasChildren ? 0 : -1}
          onClick={() => setOpen((o) => !o)}
          className={cn(
            'flex min-h-[44px] min-w-[44px] items-center justify-center text-muted-foreground hover:text-foreground',
            !hasChildren && 'invisible',
          )}
        >
          <ChevronRight className={cn('h-3.5 w-3.5 transition-transform', open && 'rotate-90')} />
        </button>
        <button
          type="button"
          onClick={() => onSelect(node.id)}
          className={cn(
            'flex min-h-[44px] flex-1 items-center gap-1.5 truncate py-2 text-left',
            node.archivedAt != null && 'text-muted-foreground',
          )}
        >
          {open && hasChildren ? (
            <FolderOpen className="h-4 w-4 shrink-0" />
          ) : (
            <Folder className="h-4 w-4 shrink-0" />
          )}
          <span className="truncate">
            {node.name}
            {node.systemManaged ? <span className="sr-only"> (system folder)</span> : null}
          </span>
          {node.systemManaged ? (
            <Lock className="ml-1 h-3 w-3 shrink-0 text-muted-foreground" aria-hidden="true" />
          ) : null}
        </button>
      </div>
      {open
        ? node.children.map((child) => (
            <FolderRow
              key={child.id}
              node={child}
              depth={depth + 1}
              selectedFolderId={selectedFolderId}
              onSelect={onSelect}
            />
          ))
        : null}
    </>
  );
}