import { type MouseEvent, type ReactNode, useEffect, useMemo, useState } from "react";
import clsx from "clsx";
import { ChevronDown } from "lucide-react";

export interface SidebarItem {
  label: string;
  href: string;
  icon?: ReactNode;
  children?: SidebarItem[];
}

export interface SidebarProps {
  title?: string;
  items: SidebarItem[];
  activeHref?: string;
  onNavigate?: (href: string) => void;
  headerExtra?: ReactNode;
}

/**
 * Brand palette
 *   #10B981 — dominant dark green   → brand mark, active state, hover text
 *   #10B981 — secondary green       → hover background tint
 *   #10B981 — muted green tone      → sidebar canvas
 */
const Sidebar = ({
  title,
  items,
  activeHref,
  onNavigate,
  headerExtra,
}: SidebarProps) => {
  const activePath = activeHref?.toLowerCase() ?? "";
  const defaultExpanded = useMemo(
    () =>
      items.reduce<Record<string, boolean>>((acc, item) => {
        if (item.children?.length) {
          acc[item.href] =
            activePath === item.href.toLowerCase() ||
            activePath.startsWith(`${item.href.toLowerCase()}/`) ||
            item.children.some((child) =>
              activePath.startsWith(child.href.toLowerCase()),
            );
        }
        return acc;
      }, {}),
    [activePath, items],
  );
  const [expanded, setExpanded] = useState<Record<string, boolean>>(defaultExpanded);

  useEffect(() => {
    setExpanded((current) => ({ ...defaultExpanded, ...current }));
  }, [defaultExpanded]);

  const navigateTo = (event: MouseEvent<HTMLAnchorElement>, href: string) => {
    if (onNavigate) {
      event.preventDefault();
      onNavigate(href);
    }
  };

  return (
    <aside className="flex w-64 flex-col gap-1 border-r border-sidebar-border bg-sidebar px-3 py-5 ">
      {title ? (
        <div className="flex items-center justify-between gap-2 px-3 pb-4">
          <div className="flex items-center gap-2">
            <div className="flex h-9 w-9 items-center justify-center rounded-xl bg-sidebar-primary text-sm font-bold text-white">
              {title.charAt(0)}
            </div>
            <div className="text-base font-semibold text-slate-800 dark:text-slate-100">
              {title}
            </div>
          </div>
          {headerExtra}
        </div>
      ) : null}

      <nav className="flex flex-col gap-1">
        {items.map((item) => {
          const hasChildren = Boolean(item.children?.length);
          const itemHref = item.href.toLowerCase();
          const childActive =
            item.children?.some((child) =>
              activePath.startsWith(child.href.toLowerCase()),
            ) ?? false;
          const isCurrentItem = hasChildren
            ? activePath === itemHref
            : activePath === itemHref || activePath.startsWith(`${itemHref}/`);
          const isSectionActive = childActive && !isCurrentItem;

          return (
            <div key={item.href} className="flex flex-col gap-1">
              <div
                className={clsx(
                  "group flex items-center gap-2 rounded-md transition",
                  isCurrentItem
                    ? "bg-sidebar-primary text-sidebar-primary-foreground shadow-sm"
                    : isSectionActive
                      ? "bg-sidebar-accent/70 text-sidebar-accent-foreground"
                      : "text-sidebar-foreground hover:bg-sidebar-accent/60 hover:text-sidebar-accent-foreground",
                )}
              >
                <a
                  href={item.href}
                  onClick={(event) => navigateTo(event, item.href)}
                  aria-current={isCurrentItem ? "page" : undefined}
                  className="flex min-w-0 flex-1 items-center gap-3 px-3 py-2.5 text-sm font-medium"
                >
                  {item.icon ? (
                    <span
                      className={clsx(
                        "flex h-5 w-5 items-center justify-center [&_svg]:h-5 [&_svg]:w-5",
                        isCurrentItem
                          ? "text-white"
                          : isSectionActive
                            ? "text-[#10B981] dark:text-emerald-300"
                            : "text-slate-500 group-hover:text-[#10B981] dark:text-slate-400 dark:group-hover:text-white",
                      )}
                    >
                      {item.icon}
                    </span>
                  ) : null}
                  <span className="truncate">{item.label}</span>
                </a>
                {hasChildren ? (
                  <button
                    type="button"
                    aria-label={`Toggle ${item.label}`}
                    aria-expanded={expanded[item.href] ?? false}
                    onClick={() =>
                      setExpanded((current) => ({
                        ...current,
                        [item.href]: !current[item.href],
                      }))
                    }
                    className={clsx(
                      "mr-2 inline-flex h-8 w-8 items-center justify-center rounded-md transition",
                      isCurrentItem
                        ? "text-white/90 hover:bg-white/10"
                        : isSectionActive
                          ? "text-[#10B981] hover:bg-sidebar-accent/80 dark:text-emerald-300"
                          : "text-slate-500 hover:bg-sidebar-accent/60 dark:text-slate-400",
                    )}
                  >
                    <ChevronDown
                      className={clsx(
                        "h-4 w-4 transition-transform",
                        expanded[item.href] ? "rotate-180" : "rotate-0",
                      )}
                    />
                  </button>
                ) : null}
              </div>

              {hasChildren && expanded[item.href] ? (
                <div className="ml-4 flex flex-col gap-1 border-l border-sidebar-border/60 pl-3">
                  {item.children!.map((child) => {
                    const childActiveHref = activePath === child.href.toLowerCase();

                    return (
                      <a
                        key={child.href}
                        href={child.href}
                        onClick={(event) => navigateTo(event, child.href)}
                        aria-current={childActiveHref ? "page" : undefined}
                        className={clsx(
                          "rounded-md px-3 py-2 text-sm transition",
                          childActiveHref
                            ? "bg-sidebar-primary text-sidebar-primary-foreground shadow-sm"
                            : "text-sidebar-foreground hover:bg-sidebar-accent/60 hover:text-sidebar-accent-foreground",
                        )}
                      >
                        {child.label}
                      </a>
                    );
                  })}
                </div>
              ) : null}
            </div>
          );
        })}
      </nav>
    </aside>
  );
};

export default Sidebar;