"use client";

import Link from "next/link";
import { usePathname } from "next/navigation";
import { curriculum } from "@/lib/curriculum";
import { cn } from "@/lib/utils";
import { useState } from "react";

const unitColorMap = {
  "unit-1": "text-unit-1-dark",
  "unit-2": "text-unit-2-dark",
  "unit-3": "text-unit-3-dark",
  "unit-4": "text-unit-4-dark",
  "unit-5": "text-unit-5-dark",
};

const unitDotColor = {
  "unit-1": "bg-unit-1",
  "unit-2": "bg-unit-2",
  "unit-3": "bg-unit-3",
  "unit-4": "bg-unit-4",
  "unit-5": "bg-unit-5",
};

export function MobileNav() {
  const pathname = usePathname();
  const [isOpen, setIsOpen] = useState(false);

  return (
    <div className="lg:hidden">
      <button
        onClick={() => setIsOpen(!isOpen)}
        className="flex items-center gap-2 rounded-xl border border-border/60 bg-surface px-3.5 py-2 text-sm font-medium shadow-[var(--shadow-sm)] transition-all hover:shadow-[var(--shadow-md)]"
        aria-label="Toggle navigation"
      >
        <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
          {isOpen ? (
            <path strokeLinecap="round" strokeLinejoin="round" d="M6 18L18 6M6 6l12 12" />
          ) : (
            <path strokeLinecap="round" strokeLinejoin="round" d="M4 6h16M4 12h16M4 18h16" />
          )}
        </svg>
        Topics
      </button>

      {isOpen && (
        <div className="absolute left-0 right-0 top-full z-40 max-h-[70vh] overflow-y-auto border-b border-border/60 bg-surface p-4 shadow-[var(--shadow-lg)]">
          <Link
            href="/lessons"
            onClick={() => setIsOpen(false)}
            className="mb-4 flex items-center gap-2 rounded-xl px-3 py-2 text-sm font-medium text-muted transition-colors hover:bg-background hover:text-foreground"
          >
            <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
              <path strokeLinecap="round" strokeLinejoin="round" d="M4 6h16M4 10h16M4 14h16M4 18h16" />
            </svg>
            All Topics
          </Link>
          <div className="mb-3 h-px bg-border/60" />
          {curriculum.map((unit) => (
            <div key={unit.slug} className="mb-4">
              <p className={cn("mb-1.5 flex items-center gap-2 px-3 text-xs font-bold uppercase tracking-wider", unitColorMap[unit.color])}>
                <span className={cn("h-2 w-2 rounded-full", unitDotColor[unit.color])} />
                Unit {unit.number}: {unit.title}
              </p>
              <div className="space-y-0.5">
                {unit.topics.map((topic) => {
                  const href = `/lessons/${unit.slug}/${topic.slug}`;
                  return (
                    <Link
                      key={topic.slug}
                      href={href}
                      onClick={() => setIsOpen(false)}
                      className={cn(
                        "block rounded-lg px-3 py-1.5 text-sm transition-colors",
                        pathname === href
                          ? "bg-foreground text-background font-medium"
                          : "text-muted hover:bg-background hover:text-foreground",
                      )}
                    >
                      {topic.shortTitle}
                    </Link>
                  );
                })}
              </div>
            </div>
          ))}
        </div>
      )}
    </div>
  );
}
