import { useCallback, useEffect, useState } from 'react'
import Link from 'next/link'
import { useRouter } from 'next/router'
import clsx from 'clsx'

import { Logo } from '@/components/Logo'
import { Prose } from '@/components/Prose'
import {HeroPattern} from "@/components/HeroPattern";
import {NavigationDocs} from "@/components/NavigationDocs";
import {Header} from "@/components/Header";
import {NavigationAPI} from "@/components/NavigationAPI";
import {motion} from "framer-motion";
import {Footer} from "@/components/Footer";

const navigation = [
  {
    title: 'Introduction',
    links: [
      { title: 'Getting started', href: '/' },
      { title: 'Installation', href: '/installation' },
    ],
  },
  {
    title: 'Core concepts',
    links: [
      { title: 'Understanding caching', href: '/understanding-caching' },
      {
        title: 'Predicting user behavior',
        href: '/predicting-user-behavior',
      },
      { title: 'Basics of time-travel', href: '/basics-of-time-travel' },
      {
        title: 'Introduction to string theory',
        href: '/introduction-to-string-theory',
      },
      { title: 'The butterfly effect', href: '/the-butterfly-effect' },
    ],
  },
  {
    title: 'Advanced guides',
    links: [
      { title: 'Writing plugins', href: '/writing-plugins' },
      { title: 'Neuralink integration', href: '/neuralink-integration' },
      { title: 'Temporal paradoxes', href: '/temporal-paradoxes' },
      { title: 'Testing', href: '/testing' },
      { title: 'Compile-time caching', href: '/compile-time-caching' },
      {
        title: 'Predictive data generation',
        href: '/predictive-data-generation',
      },
    ],
  },
  {
    title: 'API reference',
    links: [
      { title: 'CacheAdvance.predict()', href: '/cacheadvance-predict' },
      { title: 'CacheAdvance.flush()', href: '/cacheadvance-flush' },
      { title: 'CacheAdvance.revert()', href: '/cacheadvance-revert' },
      { title: 'CacheAdvance.regret()', href: '/cacheadvance-regret' },
    ],
  },
  {
    title: 'Contributing',
    links: [
      { title: 'How to contribute', href: '/how-to-contribute' },
      { title: 'Architecture guide', href: '/architecture-guide' },
      { title: 'Design principles', href: '/design-principles' },
    ],
  },
]

function GitHubIcon(props) {
  return (
    <svg aria-hidden="true" viewBox="0 0 16 16" {...props}>
      <path d="M8 0C3.58 0 0 3.58 0 8C0 11.54 2.29 14.53 5.47 15.59C5.87 15.66 6.02 15.42 6.02 15.21C6.02 15.02 6.01 14.39 6.01 13.72C4 14.09 3.48 13.23 3.32 12.78C3.23 12.55 2.84 11.84 2.5 11.65C2.22 11.5 1.82 11.13 2.49 11.12C3.12 11.11 3.57 11.7 3.72 11.94C4.44 13.15 5.59 12.81 6.05 12.6C6.12 12.08 6.33 11.73 6.56 11.53C4.78 11.33 2.92 10.64 2.92 7.58C2.92 6.71 3.23 5.99 3.74 5.43C3.66 5.23 3.38 4.41 3.82 3.31C3.82 3.31 4.49 3.1 6.02 4.13C6.66 3.95 7.34 3.86 8.02 3.86C8.7 3.86 9.38 3.95 10.02 4.13C11.55 3.09 12.22 3.31 12.22 3.31C12.66 4.41 12.38 5.23 12.3 5.43C12.81 5.99 13.12 6.7 13.12 7.58C13.12 10.65 11.25 11.33 9.47 11.53C9.76 11.78 10.01 12.26 10.01 13.01C10.01 14.08 10 14.94 10 15.21C10 15.42 10.15 15.67 10.55 15.59C13.71 14.53 16 11.53 16 8C16 3.58 12.42 0 8 0Z" />
    </svg>
  )
}

function useTableOfContents(tableOfContents) {
  let [currentSection, setCurrentSection] = useState(tableOfContents[0]?.id)

  let getHeadings = useCallback((tableOfContents) => {
    return tableOfContents
      .flatMap((node) => [node.id, ...node.children.map((child) => child.id)])
      .map((id) => {
        let el = document.getElementById(id)
        if (!el) return

        let style = window.getComputedStyle(el)
        let scrollMt = parseFloat(style.scrollMarginTop)

        let top = window.scrollY + el.getBoundingClientRect().top - scrollMt
        return { id, top }
      })
  }, [])

  useEffect(() => {
    if (tableOfContents.length === 0) return
    let headings = getHeadings(tableOfContents)
    function onScroll() {
      let top = window.scrollY
      let current = headings[0]?.id
      for (let heading of headings) {
        if (top >= heading?.top) {
          current = heading?.id
        } else {
          break
        }
      }
      setCurrentSection(current)
    }
    window.addEventListener('scroll', onScroll, { passive: true })
    onScroll()
    return () => {
      window.removeEventListener('scroll', onScroll)
    }
  }, [getHeadings, tableOfContents])

  return currentSection
}

export function Layout({ children, title, tableOfContents }) {
  let router = useRouter()
  let isHomePage = router.pathname === '/'
  let allLinks = navigation.flatMap((section) => section.links)
  let linkIndex = allLinks.findIndex((link) => link.href === router.pathname)
  let previousPage = allLinks[linkIndex - 1]
  let nextPage = allLinks[linkIndex + 1]
  let section = navigation.find((section) =>
    section.links.find((link) => link.href === router.pathname)
  )

  let currentSection = useTableOfContents(tableOfContents)

  function isActive(section) {
    if (section.id === currentSection) {
      return true
    }
    if (!section.children) {
      return false
    }
    return section.children.findIndex(isActive) > -1
  }

  return (
    <>
      <HeroPattern/>
      <div className="relative mx-auto flex max-w-8xl sm:px-2 lg:px-8 xl:px-12 lg:ml-72 xl:ml-80">
        <motion.header
            layoutScroll
            className="contents lg:pointer-events-none lg:fixed lg:inset-0 lg:z-40 lg:flex"
        >
          <div className="contents lg:pointer-events-auto lg:block lg:w-72 lg:overflow-y-auto lg:border-r lg:border-zinc-900/10 lg:px-6 lg:pb-8 lg:pt-4 lg:dark:border-white/10 xl:w-80">
            <div className="hidden lg:flex">
              <Link href="/" aria-label="Home">
                <Logo className="h-6" />
              </Link>
            </div>
            <Header />
            {router.route.startsWith("/ipa") ? <NavigationAPI className="hidden lg:mt-10 lg:block" tableOfContents={tableOfContents} /> : <NavigationDocs className="hidden lg:mt-10 lg:block" />}
          </div>
        </motion.header>
        <div className="min-w-0 max-w-2xl flex-auto px-4 py-16 lg:max-w-none lg:pl-8 lg:pr-0 xl:px-5">
          <main className="py-16">
            <Prose as="article">{children}</Prose>
          </main>
          <Footer />
        </div>
        {!router.route.startsWith("/ipa/resources") && <div className="hidden xl:sticky xl:top-[4.5rem] xl:-mr-6 xl:block xl:h-[calc(100vh-4.5rem)] xl:flex-none xl:overflow-y-auto xl:py-16 xl:pr-6 pl-12">
          <nav aria-labelledby="on-this-page-title" className="w-80">
            {tableOfContents.length > 0 && (
              <>
                <h2
                  id="on-this-page-title"
                  className="font-display text-sm font-medium text-slate-900 dark:text-white"
                >
                  On this page
                </h2>
                <ol role="list" className="mt-4 space-y-3 text-sm">
                  {tableOfContents.map((section) => (
                    <li key={section.id}>
                      <h3>
                        <Link
                          href={`#${section.id}`}
                          className={clsx(
                            isActive(section)
                              ? 'text-orange-500'
                              : 'font-normal text-slate-500 hover:text-slate-700 dark:text-slate-400 dark:hover:text-slate-300'
                          )}
                        >
                          {section.title}
                        </Link>
                      </h3>
                      {section.children.length > 0 && (
                        <ol
                          role="list"
                          className="mt-2 space-y-3 pl-5 text-slate-500 dark:text-slate-400"
                        >
                          {section.children.map((subSection) => (
                            <li key={subSection.id}>
                              <Link
                                href={`#${subSection.id}`}
                                className={
                                  isActive(subSection)
                                    ? 'text-orange-500'
                                    : 'hover:text-slate-600 dark:hover:text-slate-300'
                                }
                              >
                                {subSection.title}
                              </Link>
                            </li>
                          ))}
                        </ol>
                      )}
                    </li>
                  ))}
                </ol>
              </>
            )}
          </nav>
        </div>}
      </div>
    </>
  )
}