'use client';

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

import { Button } from '@/components/ui/button';
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;
}

/**
 * Collapsed-by-default tree. Each row shows a chevron that toggles its
 * children; clicking the row label selects the folder. The "All
 * documents" + "Root" pseudo-rows at the top let reps filter to the
 * full set or to docs without a folder.
 *
 * Designed for unlimited depth — only the top level renders by default
 * so deep trees don't blow out the page; reps drill in by expanding.
 */
export function FolderTreeSidebar({
  selectedFolderId,
  onSelect,
  footer,
}: FolderTreeSidebarProps) {
  const { data: tree = [], isLoading } = useDocumentFolders();

  return (
    <aside className="w-full sm:w-60 shrink-0 border-r bg-muted/40 p-2">
      <div className="mb-2 px-2 text-xs font-medium uppercase tracking-wide text-muted-foreground">
        Folders
      </div>
      <div className="space-y-0.5">
        <PseudoRow
          label="All documents"
          icon={Inbox}
          active={selectedFolderId === undefined}
          onClick={() => onSelect(undefined)}
        />
        <PseudoRow
          label="Root (no folder)"
          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>
        ) : 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}
    </aside>
  );
}

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 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'}
          onClick={() => setOpen((o) => !o)}
          className={cn(
            'flex h-5 w-5 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="flex flex-1 items-center gap-1.5 truncate text-left"
        >
          {open && hasChildren ? (
            <FolderOpen className="h-4 w-4 shrink-0" />
          ) : (
            <Folder className="h-4 w-4 shrink-0" />
          )}
          <span className="truncate">{node.name}</span>
        </button>
      </div>
      {open
        ? node.children.map((child) => (
            <FolderRow
              key={child.id}
              node={child}
              depth={depth + 1}
              selectedFolderId={selectedFolderId}
              onSelect={onSelect}
            />
          ))
        : null}
    </>
  );
}