import { ActionQueue } from './actions'
import { el, fmt, icon, labelsFor, num, uiLocaleOf, type Labels } from './labels'

export const LINKS_TAG = 'golem15-seo-links'

/** A page this text could link to. */
export interface LinkOut {
  phrase: string
  title: string
  url: string
}

/** A page that could link here. */
export interface LinkIn {
  phrase: string
  title: string
  adminUrl: string
}

/** The seo_links action's answer (UI-SPEC C19). */
export interface LinksData {
  crawledAt: string | null
  inbound: number | null
  outbound: number | null
  orphan: boolean
  out: LinkOut[]
  in: LinkIn[]
}

interface Payload {
  op: 'links'
  locale: string
}

/** Whether the page can write to the clipboard (a secure context). */
function canCopy(): boolean {
  return typeof navigator !== 'undefined' && !!navigator.clipboard && typeof navigator.clipboard.writeText === 'function'
}

/** A crawl time in the ui-locale. */
export function crawlTime(value: string, locale: string): string {
  const d = new Date(value)
  if (Number.isNaN(d.getTime())) {
    return value
  }
  try {
    return new Intl.DateTimeFormat(locale, { dateStyle: 'medium', timeStyle: 'short' }).format(d)
  } catch {
    return d.toISOString()
  }
}

/**
 * E10 golem15-seo-links (UI-SPEC C19, D-82): the page's inbound and
 * outbound link counts from the last crawl, the orphan warning, up to 10
 * pages this text could link to (with Copy address) and 10 pages that
 * could link here. It asks through summer-action only ({op: links,
 * locale}), on connect and on the ML locale switch, and changes nothing
 * itself.
 */
export class SeoLinksElement extends HTMLElement {
  static observedAttributes = ['busy', 'state', 'ui-locale', 'disabled']

  private data: LinksData | null = null
  private failed = false
  private pending = false
  private shownLocale = ''
  private copied = ''
  private copiedTimer: ReturnType<typeof setTimeout> | undefined
  private connected = false
  private readonly actions = new ActionQueue<Payload>(this, () => this.fail())

  private readonly onResult = (ev: Event): void => {
    const detail = (ev as CustomEvent).detail as { data?: unknown } | undefined
    this.actions.settle()
    const data = detail?.data as LinksData | undefined
    if (data && Array.isArray(data.out) && Array.isArray(data.in)) {
      this.data = data
      this.failed = false
    }
    this.pending = this.actions.current !== null
    this.render()
  }

  private readonly onLocale = (ev: Event): void => {
    const locale = (ev as CustomEvent).detail
    if (typeof locale === 'string' && locale !== '' && locale !== this.shownLocale) {
      this.shownLocale = locale
      this.load()
    }
  }

  connectedCallback(): void {
    this.connected = true
    this.addEventListener('summer-result', this.onResult)
    window.addEventListener('summer:ml-locale', this.onLocale)
    this.render()
    queueMicrotask(() => {
      if (this.connected) {
        this.load()
      }
    })
  }

  disconnectedCallback(): void {
    this.connected = false
    this.removeEventListener('summer-result', this.onResult)
    window.removeEventListener('summer:ml-locale', this.onLocale)
    clearTimeout(this.copiedTimer)
    this.actions.reset()
    this.pending = false
  }

  attributeChangedCallback(name: string, _old: string | null, value: string | null): void {
    if (!this.connected) {
      return
    }
    if (name === 'busy' && value === null) {
      this.actions.flush()
      return
    }
    if (name === 'state' && value === 'error') {
      if (this.actions.settle()) {
        this.fail()
      }
      return
    }
    this.render()
  }

  private labels(): Labels {
    return labelsFor(uiLocaleOf(this))
  }

  /** Asks for the links of the shown locale (one queued request at most). */
  load(): void {
    this.pending = true
    this.actions.request({ op: 'links', locale: this.shownLocale })
    this.render()
  }

  private fail(): void {
    this.failed = true
    this.pending = this.actions.current !== null
    this.render()
  }

  /** Writes url to the clipboard and says so for 2 s. */
  private copy(url: string): void {
    if (!canCopy()) {
      return
    }
    void navigator.clipboard.writeText(url).then(() => {
      this.copied = url
      clearTimeout(this.copiedTimer)
      this.copiedTimer = setTimeout(() => {
        this.copied = ''
        this.render()
      }, 2000)
      this.render()
    }, () => undefined)
  }

  /** The suggestion line “:phrase” → :title with the title as a link (or text). */
  private line(labels: Labels, phrase: string, title: string, href: string): HTMLElement {
    const line = el('span', 'seo-links__line')
    const [before, after = ''] = labels.linksPhrase.split(':title')
    line.append(fmt(before ?? '', { phrase }))
    if (href) {
      const a = el('a', 'seo-links__title', title)
      a.href = href
      a.target = '_blank'
      a.rel = 'noopener'
      line.append(a)
    } else {
      line.append(el('span', 'seo-links__title', title))
    }
    line.append(fmt(after, { phrase }))
    return line
  }

  private render(): void {
    if (!this.connected) {
      return
    }
    const labels = this.labels()
    const locale = uiLocaleOf(this)
    const sections: HTMLElement[] = []
    this.setAttribute('aria-busy', String(this.pending))
    if (this.pending) {
      const line = el('p', 'seo-links__meta seo-links__checking', labels.linksChecking)
      line.setAttribute('role', 'status')
      sections.push(line)
    }
    const data = this.data
    if (data) {
      const counts = el('div', 'seo-links__counts')
      if (data.crawledAt !== null && data.inbound !== null && data.outbound !== null) {
        const stats = el('div', 'summer-stats')
        for (const [value, label] of [
          [data.inbound, labels.linksInbound],
          [data.outbound, labels.linksOutbound],
        ] as Array<[number, string]>) {
          const stat = el('div', 'summer-stat')
          stat.append(el('span', 'summer-stat__value', num(value, locale)), el('span', 'summer-stat__label', label))
          stats.append(stat)
        }
        counts.append(stats, el('p', 'seo-links__meta', fmt(labels.linksCrawled, { time: crawlTime(data.crawledAt, locale) })))
      } else {
        counts.append(el('p', 'seo-links__meta seo-links__not-crawled', labels.linksNotCrawled))
      }
      sections.push(counts)
      if (data.orphan) {
        const callout = el('div', 'summer-callout summer-callout--warning seo-links__orphan')
        callout.append(el('p', 'summer-callout__title', labels.linksOrphanTitle), el('p', 'summer-callout__text', labels.linksOrphanText))
        sections.push(callout)
      }
      const copyable = canCopy()
      const out = el('div', 'seo-links__list seo-links__list--out')
      out.append(el('p', 'seo-links__heading', labels.linksOut))
      for (const s of data.out.slice(0, 10)) {
        const row = el('div', 'seo-links__row')
        row.append(this.line(labels, s.phrase, s.title, s.url))
        if (copyable && !this.hasAttribute('disabled')) {
          const button = el('button', 'seo-links__copy', labels.linksCopy)
          button.type = 'button'
          button.addEventListener('click', () => this.copy(s.url))
          row.append(button)
        } else {
          row.append(el('code', 'seo-links__url', s.url))
        }
        out.append(row)
      }
      if (data.out.length === 0) {
        out.append(el('p', 'seo-links__meta seo-links__none', labels.linksNone))
      }
      sections.push(out)
      const inbound = el('div', 'seo-links__list seo-links__list--in')
      inbound.append(el('p', 'seo-links__heading', labels.linksIn))
      for (const s of data.in.slice(0, 10)) {
        const row = el('div', 'seo-links__row')
        row.append(this.line(labels, s.phrase, s.title, s.adminUrl))
        inbound.append(row)
      }
      if (data.in.length === 0) {
        inbound.append(el('p', 'seo-links__meta seo-links__none', labels.linksNone))
      }
      sections.push(inbound)
    }
    if (this.failed) {
      const line = el('p', 'seo-links__error')
      line.setAttribute('role', 'status')
      line.append(icon('circle-alert'), el('span', '', labels.linksFailed))
      sections.push(line)
    }
    const status = el('p', 'seo-links__status', this.copied ? labels.linksCopied : '')
    status.setAttribute('role', 'status')
    sections.push(status)
    this.replaceChildren(...sections)
  }
}