import Cookies from '@/frame/components/lib/cookies'
import { parseUserAgent } from './user-agent'
import { Router } from 'next/router'
import { isLoggedIn } from '@/frame/components/hooks/useHasAccount'
import { getExperimentVariationForContext } from './experiments/experiment'
import { EventType, EventPropsByType } from '../types'
import { isHeadless } from './is-headless'

const COOKIE_NAME = '_docs-events'

const startVisitTime = Date.now()

const BATCH_INTERVAL = 5000 // 5 seconds

let initialized = false
let cookieValue: string | undefined
let pageEventId: string | undefined

let sentExit = false
let pauseScrolling = false
let scrollPosition = 0
let scrollDirection = 1
let scrollFlipCount = 0
let maxScrollY = 0
let previousPath: string | undefined
let hoveredUrls = new Set()
let eventQueue: any[] = []

function scheduleNextFlush() {
  setTimeout(() => {
    flushQueue()
    scheduleNextFlush()
  }, BATCH_INTERVAL)
}

scheduleNextFlush()

function resetPageParams() {
  sentExit = false
  pauseScrolling = false
  scrollPosition = 0
  scrollDirection = 1
  scrollFlipCount = 0
  maxScrollY = 0
  // Don't reset previousPath
  hoveredUrls = new Set()
}

// Temporary polyfill for crypto.randomUUID()
// Necessary for localhost development (doesn't have https://)
export function uuidv4(): string {
  try {
    return crypto.randomUUID()
  } catch {
    // https://stackoverflow.com/a/2117523
    return (<any>[1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, (c: number) =>
      (c ^ (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (c / 4)))).toString(16),
    )
  }
}

export function getUserEventsId() {
  if (cookieValue) return cookieValue
  cookieValue = Cookies.get(COOKIE_NAME)
  if (cookieValue) return cookieValue
  cookieValue = uuidv4()
  Cookies.set(COOKIE_NAME, cookieValue)
  return cookieValue
}

function getMetaContent(name: string) {
  const metaTag = document.querySelector(`meta[name="${name}"]`) as HTMLMetaElement
  return metaTag?.content
}

export function sendEvent<T extends EventType>({
  type,
  version = '1.0.0',
  eventGroupKey,
  eventGroupId,
  ...props
}: {
  type: T
  version?: string
  eventGroupKey?: string
  eventGroupId?: string
} & EventPropsByType[T]) {
  const body = {
    type,

    context: {
      // Primitives
      event_id: uuidv4(),
      user: getUserEventsId(),
      version,
      created: new Date().toISOString(),
      page_event_id: pageEventId,

      // Content information
      referrer: getReferrer(document.referrer),
      title: document.title,
      href: location.href, // full URL
      hostname: location.hostname, // origin without protocol or port
      path: location.pathname, // path without search or host
      search: location.search, // also known as query string
      hash: location.hash, // also known as anchor
      path_language: getMetaContent('path-language'),
      path_version: getMetaContent('path-version'),
      path_product: getMetaContent('path-product'),
      path_article: getMetaContent('path-article'),
      page_document_type: getMetaContent('page-document-type'),
      page_type: getMetaContent('page-type'),
      content_type: getMetaContent('page-content-type'),
      status: Number(getMetaContent('status') || 0),
      is_logged_in: isLoggedIn(),

      // Device information
      // os, os_version, browser, browser_version:
      ...parseUserAgent(),
      is_headless: isHeadless(),
      viewport_width: document.documentElement.clientWidth,
      viewport_height: document.documentElement.clientHeight,
      screen_width: window.screen.width,
      screen_height: window.screen.height,
      pixel_ratio: window.devicePixelRatio || 1,
      user_agent: navigator.userAgent,

      // Location information
      timezone: new Date().getTimezoneOffset() / -60,
      user_language: navigator.language,

      // Preference information
      application_preference: Cookies.get('toolPreferred'),
      color_mode_preference: getColorModePreference(),
      os_preference: Cookies.get('osPreferred'),
      code_display_preference: Cookies.get('annotate-mode'),

      experiment_variation:
        getExperimentVariationForContext(
          getMetaContent('path-language'),
          getMetaContent('path-version'),
        ) || '',

      // Event grouping
      event_group_key: eventGroupKey,
      event_group_id: eventGroupId,
    },

    ...props,
  }

  queueEvent(body)

  if (type === EventType.exit) {
    flushQueue()
  }

  return body
}

function flushQueue() {
  if (!eventQueue.length) return

  const endpoint = '/api/events'
  const eventsBody = JSON.stringify(eventQueue)
  eventQueue = []

  try {
    navigator.sendBeacon(endpoint, new Blob([eventsBody], { type: 'application/json' }))
  } catch (err) {
    console.warn(`sendBeacon to '${endpoint}' failed.`, err)
  }
}

function queueEvent(eventBody: unknown) {
  eventQueue.push(eventBody)
}

// Sometimes using the back button means the internal referrer path is not there,
// So this fills it in with a JavaScript variable
function getReferrer(documentReferrer: string) {
  if (!previousPath) return documentReferrer
  try {
    // new URL() throws an error if not a valid URL
    const referrerUrl = new URL(documentReferrer)
    if (!referrerUrl.pathname || referrerUrl.pathname === '/') {
      return location.origin + previousPath
    }
  } catch {}
  return documentReferrer
}

function getColorModePreference() {
  // color mode is set as attributes on <html>, we'll use that information
  // along with media query checking rather than parsing the cookie value
  // set by github.com
  let color_mode_preference = document.querySelector('html')?.dataset.colorMode

  if (color_mode_preference === 'auto') {
    if (window.matchMedia('(prefers-color-scheme: light)').matches) {
      color_mode_preference += ':light'
    } else if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
      color_mode_preference += ':dark'
    }
  }

  return color_mode_preference
}

function getPerformance() {
  const paint = performance
    ?.getEntriesByType('paint')
    ?.find(({ name }) => name === 'first-contentful-paint')
  const nav = performance?.getEntriesByType('navigation')?.[0] as
    | PerformanceNavigationTiming
    | undefined
  return {
    firstContentfulPaint: paint ? paint.startTime / 1000 : undefined,
    domInteractive: nav ? nav.domInteractive / 1000 : undefined,
    domComplete: nav ? nav.domComplete / 1000 : undefined,
    render: nav ? (nav.responseEnd - nav.requestStart) / 1000 : undefined,
  }
}

function trackScroll() {
  // Throttle the calculations to no more than five per second
  if (pauseScrolling) return
  pauseScrolling = true
  setTimeout(() => {
    pauseScrolling = false
  }, 200)

  // Calculate where we are on the page
  const scrollPixels = window.scrollY + window.innerHeight
  const newScrollPosition = scrollPixels / document.documentElement.scrollHeight

  // Count scroll flips
  const newScrollDirection = Math.sign(newScrollPosition - scrollPosition)
  if (newScrollDirection !== scrollDirection) scrollFlipCount++

  // Update maximum scroll position reached
  if (newScrollPosition > maxScrollY) maxScrollY = newScrollPosition

  // Update before the next event
  scrollDirection = newScrollDirection
  scrollPosition = newScrollPosition
}

function sendPage() {
  const pageEvent = sendEvent({ type: EventType.page })
  pageEventId = pageEvent?.context?.event_id
}

function sendExit() {
  if (sentExit) return
  sentExit = true
  const { render, firstContentfulPaint, domInteractive, domComplete } = getPerformance()

  const clampedScrollLength = Math.min(maxScrollY, 1)

  return sendEvent({
    type: EventType.exit,
    exit_render_duration: render,
    exit_first_paint: firstContentfulPaint,
    exit_dom_interactive: domInteractive,
    exit_dom_complete: domComplete,
    exit_visit_duration: (Date.now() - startVisitTime) / 1000,
    exit_scroll_length: clampedScrollLength,
    exit_scroll_flip: scrollFlipCount,
  })
}

function initPageAndExitEvent() {
  sendPage() // Initial page hit

  // Regular page exits
  window.addEventListener('scroll', trackScroll)
  document.addEventListener('visibilitychange', () => {
    if (document.visibilityState === 'hidden') {
      sendExit()
    } else {
      flushQueue()
    }
  })

  // Client-side routing
  Router.events.on('routeChangeStart', async (url) => {
    // Don't trigger page events on query string or hash changes
    previousPath = location.pathname // pathname set to "prior" url, arg "upcoming" url
    const newPath = url?.toString().split('?')[0].split('#')[0]
    const shouldSendEvents = newPath !== previousPath
    if (shouldSendEvents) {
      sendExit()
      await waitForPageReady()
      resetPageParams()
      sendPage()
    }
  })
}

// We want to wait for the DOM to mutate the <meta> tags
// as well as finish routeChangeComplete (location.pathname)
// before sending the page event in order to get accurate data
async function waitForPageReady() {
  const route = new Promise((resolve) => {
    const handler = () => {
      Router.events.off('routeChangeComplete', handler)
      setTimeout(() => resolve(true))
    }
    Router.events.on('routeChangeComplete', handler)
  })
  const mutate = new Promise((resolve) => {
    const observer = new MutationObserver((mutations) => {
      const metaMutated = mutations.find(
        (mutation) =>
          mutation.target?.nodeName === 'META' ||
          Array.from(mutation.addedNodes).find((node) => node.nodeName === 'META') ||
          Array.from(mutation.removedNodes).find((node) => node.nodeName === 'META'),
      )
      if (metaMutated) {
        observer.disconnect()
        setTimeout(() => resolve(true))
      }
    })
    observer.observe(document.getElementsByTagName('head')[0], {
      subtree: true,
      childList: true,
      attributes: true,
    })
  })
  return Promise.all([route, mutate])
}

function initClipboardEvent() {
  for (const verb of ['copy', 'cut', 'paste']) {
    document.documentElement.addEventListener(verb, () => {
      sendEvent({ type: EventType.clipboard, clipboard_operation: verb })
    })
  }
}

function initCopyButtonEvent() {
  document.documentElement.addEventListener('click', (evt) => {
    const target = evt.target as HTMLElement
    const button = target.closest('.js-btn-copy') as HTMLButtonElement
    if (!button) return

    sendEvent({
      type: EventType.clipboard,
      clipboard_operation: 'copy',
      clipboard_target: '.js-btn-copy',
    })
  })
}

function initLinkEvent() {
  document.documentElement.addEventListener('click', (evt) => {
    const target = evt.target as HTMLElement
    const link = target.closest('a[href]') as HTMLAnchorElement
    if (!link) return
    const sameSite = link.origin === location.origin
    const container = target.closest(`[data-container]`) as HTMLElement | null

    // We can attach `data-group-key` and `data-group-id` to any anchor element to include them in the event
    const eventGroupKey = link?.dataset?.groupKey || undefined
    const eventGroupId = link?.dataset?.groupId || undefined

    sendEvent({
      type: EventType.link,
      link_url: link.href,
      link_samesite: sameSite,
      link_samepage: sameSite && link.pathname === location.pathname,
      link_container: container?.dataset.container,
      eventGroupKey,
      eventGroupId,
    })
  })

  // Add tracking for scroll to top button
  document.documentElement.addEventListener('click', (evt) => {
    const target = evt.target as HTMLElement
    if (!target.closest('.ghd-scroll-to-top')) return
    const url = window.location.href.split('#')[0] // Remove hash
    sendEvent({
      type: EventType.link,
      link_url: `${url}#scroll-to-top`,
      link_samesite: true,
      link_samepage: true,
      link_container: 'static',
    })
  })
}

function initHoverEvent() {
  let timer: number | null = null
  document.documentElement.addEventListener('mouseover', (evt) => {
    const target = evt.target as HTMLElement
    const link = target.closest('a[href]') as HTMLAnchorElement | null

    if (!link) return

    // For hover events, we only want to record them for links inside the
    // content area.
    const mainContent = document.querySelector('#main-content') as HTMLElement | null
    if (!mainContent || !mainContent.contains(link)) return

    if (hoveredUrls.has(link.href)) return // Otherwise this is a flood of events

    if (timer) {
      window.clearTimeout(timer)
    }
    timer = window.setTimeout(() => {
      const sameSite = link.origin === location.origin
      hoveredUrls.add(link.href)
      sendEvent({
        type: EventType.hover,
        hover_url: link.href,
        hover_samesite: sameSite,
      })
    }, 500)
  })

  // Doesn't matter which link you hovered on that triggered a timer,
  // you're clearly not hovering over it anymore.
  document.documentElement.addEventListener('mouseout', () => {
    if (timer) {
      window.clearTimeout(timer)
    }
  })
}

function initPrintEvent() {
  window.addEventListener('beforeprint', () => {
    sendEvent({ type: EventType.print })
  })
}

export function initializeEvents() {
  if (initialized) return
  initialized = true
  initPageAndExitEvent() // must come first
  initLinkEvent()
  initHoverEvent()
  initClipboardEvent()
  initCopyButtonEvent()
  initPrintEvent()
}