"use client";

import clsx from "clsx";
import { AnimatePresence, motion, useIsPresent } from "framer-motion";
import Link from "next/link";
import { usePathname } from "next/navigation";
import { type ComponentPropsWithoutRef, type ReactNode, useRef } from "react";

import { remToPx } from "../lib/remToPx";
import { Button } from "./Button";
import { useIsInsideMobileNavigation } from "./MobileNavigation";
import { useSectionStore } from "./SectionProvider";
import { Tag } from "./Tag";

interface NavGroup {
    title: string;
    links: Array<{
        title: string;
        href: string;
    }>;
}

function useInitialValue<T>(value: T, condition = true) {
    const initialValue = useRef(value).current;
    return condition ? initialValue : value;
}

function TopLevelNavItem({
    href,
    children,
}: {
    href: string;
    children: ReactNode;
}) {
    return (
        <li className="md:hidden">
            <Link
                href={href}
                className="block py-1 text-sm text-zinc-600 transition hover:text-zinc-900 dark:text-zinc-400 dark:hover:text-white"
            >
                {children}
            </Link>
        </li>
    );
}

function NavLink({
    href,
    children,
    tag,
    active = false,
    isAnchorLink = false,
}: {
    href: string;
    children: ReactNode;
    tag?: string;
    active?: boolean;
    isAnchorLink?: boolean;
}) {
    return (
        <Link
            href={href}
            aria-current={active ? "page" : undefined}
            className={clsx(
                "flex justify-between gap-2 py-1 pr-3 text-sm transition",
                isAnchorLink ? "pl-7" : "pl-4",
                active
                    ? "text-zinc-900 dark:text-white"
                    : "text-zinc-600 hover:text-zinc-900 dark:text-zinc-400 dark:hover:text-white",
            )}
        >
            <span className="truncate">{children}</span>
            {tag && (
                <Tag variant="small" color="zinc">
                    {tag}
                </Tag>
            )}
        </Link>
    );
}

function VisibleSectionHighlight({
    group,
    pathname,
}: {
    group: NavGroup;
    pathname: string;
}) {
    const [sections, visibleSections] = useInitialValue(
        [
            useSectionStore((s) => s.sections),
            useSectionStore((s) => s.visibleSections),
        ],
        useIsInsideMobileNavigation(),
    );

    const isPresent = useIsPresent();
    const firstVisibleSectionIndex = Math.max(
        0,
        [{ id: "_top" }, ...sections].findIndex(
            (section) => section.id === visibleSections[0],
        ),
    );
    const itemHeight = remToPx(2);
    const height = isPresent
        ? Math.max(1, visibleSections.length) * itemHeight
        : itemHeight;
    const top =
        group.links.findIndex((link) => link.href === pathname) * itemHeight +
        firstVisibleSectionIndex * itemHeight;

    return (
        <motion.div
            layout={true}
            initial={{ opacity: 0 }}
            animate={{ opacity: 1, transition: { delay: 0.2 } }}
            exit={{ opacity: 0 }}
            className="absolute inset-x-0 top-0 bg-zinc-800/2.5 will-change-transform dark:bg-white/2.5"
            style={{ borderRadius: 8, height, top }}
        />
    );
}

function ActivePageMarker({
    group,
    pathname,
}: {
    group: NavGroup;
    pathname: string;
}) {
    const itemHeight = remToPx(2);
    const offset = remToPx(0.25);
    const activePageIndex = group.links.findIndex(
        (link) => link.href === pathname,
    );
    const top = offset + activePageIndex * itemHeight;

    return (
        <motion.div
            layout={true}
            className="absolute left-2 h-6 w-px bg-brand-500"
            initial={{ opacity: 0 }}
            animate={{ opacity: 1, transition: { delay: 0.2 } }}
            exit={{ opacity: 0 }}
            style={{ top }}
        />
    );
}

function NavigationGroup({
    group,
    className,
}: {
    group: NavGroup;
    className?: string;
}) {
    // If this is the mobile navigation then we always render the initial
    // state, so that the state does not change during the close animation.
    // The state will still update when we re-open (re-render) the navigation.
    const isInsideMobileNavigation = useIsInsideMobileNavigation();
    const [pathname, sections] = useInitialValue(
        [usePathname(), useSectionStore((s) => s.sections)],
        isInsideMobileNavigation,
    );

    const isActiveGroup =
        group.links.findIndex((link) => link.href === pathname) !== -1;

    return (
        <li className={clsx("relative mt-6", className)}>
            <motion.h2
                layout="position"
                className="text-sm font-semibold text-zinc-900 dark:text-white"
            >
                {group.title}
            </motion.h2>
            <div className="relative mt-3 pl-2">
                <AnimatePresence initial={!isInsideMobileNavigation}>
                    {isActiveGroup && (
                        <VisibleSectionHighlight
                            group={group}
                            pathname={pathname}
                        />
                    )}
                </AnimatePresence>
                <motion.div
                    layout={true}
                    className="absolute inset-y-0 left-2 w-px bg-zinc-900/10 dark:bg-white/5"
                />
                <AnimatePresence initial={false}>
                    {isActiveGroup && (
                        <ActivePageMarker group={group} pathname={pathname} />
                    )}
                </AnimatePresence>
                <ul className="border-l border-transparent">
                    {group.links.map((link) => (
                        <motion.li
                            key={link.href}
                            layout="position"
                            className="relative"
                        >
                            <NavLink
                                href={link.href}
                                active={link.href === pathname}
                            >
                                {link.title}
                            </NavLink>
                            <AnimatePresence mode="popLayout" initial={false}>
                                {link.href === pathname &&
                                    sections.length > 0 && (
                                        <motion.ul
                                            role="list"
                                            initial={{ opacity: 0 }}
                                            animate={{
                                                opacity: 1,
                                                transition: { delay: 0.1 },
                                            }}
                                            exit={{
                                                opacity: 0,
                                                transition: { duration: 0.15 },
                                            }}
                                        >
                                            {sections.map((section) => (
                                                <li key={section.id}>
                                                    <NavLink
                                                        href={`${link.href}#${section.id}`}
                                                        tag={section.tag}
                                                        isAnchorLink={true}
                                                    >
                                                        {section.title}
                                                    </NavLink>
                                                </li>
                                            ))}
                                        </motion.ul>
                                    )}
                            </AnimatePresence>
                        </motion.li>
                    ))}
                </ul>
            </div>
        </li>
    );
}

export const navigation: NavGroup[] = [
    {
        title: "Guides",
        links: [
            { title: "Introduction", href: "/introduction" },
            { title: "SDKs", href: "/sdks" },
            { title: "Entities", href: "/entities" },
            { title: "Signatures", href: "/signatures" },
            { title: "Federation", href: "/federation" },
            { title: "Extensions", href: "/extensions" },
        ],
    },
    {
        title: "Federation",
        links: [
            { title: "HTTP", href: "/federation/http" },
            { title: "Validation", href: "/federation/validation" },
            { title: "Discovery", href: "/federation/discovery" },
            { title: "Delegation", href: "/federation/delegation" },
        ],
    },
    {
        title: "Structures",
        links: [
            { title: "ContentFormat", href: "/structures/content-format" },
            { title: "Collection", href: "/structures/collection" },
        ],
    },
    {
        title: "Entities",
        links: [
            { title: "Delete", href: "/entities/delete" },
            { title: "Follow", href: "/entities/follow" },
            { title: "FollowAccept", href: "/entities/follow-accept" },
            { title: "FollowReject", href: "/entities/follow-reject" },
            { title: "Group", href: "/entities/group" },
            { title: "Notes", href: "/entities/note" },
            { title: "InstanceMetadata", href: "/entities/instance-metadata" },
            { title: "Unfollow", href: "/entities/unfollow" },
            { title: "Users", href: "/entities/user" },
        ],
    },
    {
        title: "Extensions",
        links: [
            { title: "Custom Emojis", href: "/extensions/custom-emojis" },
            { title: "Likes", href: "/extensions/likes" },
            { title: "Migration", href: "/extensions/migration" },
            { title: "Polls", href: "/extensions/polls" },
            { title: "Reactions", href: "/extensions/reactions" },
            { title: "Reports", href: "/extensions/reports" },
            { title: "Share", href: "/extensions/share" },
            { title: "Vanity", href: "/extensions/vanity" },
            { title: "WebSockets", href: "/extensions/websockets" },
        ],
    },
];

export function Navigation(props: ComponentPropsWithoutRef<"nav">) {
    return (
        <nav {...props} aria-label="Side navigation">
            <ul>
                <TopLevelNavItem href="/">API</TopLevelNavItem>
                {navigation.map((group, groupIndex) => (
                    <NavigationGroup
                        key={group.title}
                        group={group}
                        className={groupIndex === 0 ? "md:mt-0" : ""}
                    />
                ))}
                <li className="sticky bottom-0 z-10 mt-6 min-[416px]:hidden">
                    <Button
                        href="/changelog"
                        variant="filled"
                        className="w-full"
                    >
                        Working Draft 4
                    </Button>
                </li>
            </ul>
        </nav>
    );
}