import type { Locale } from '#shared/utils/locale'

interface SeoOptions {
  locale: Locale
  /** The bare, unprefixed path, e.g. `/blog/mio-slug` — never `/en/...`. */
  path: string
  title: string
  description: string
  type?: 'website' | 'article'
  image?: string
  /** False when no translation exists at all for this content — omits the alternate link. */
  hasAlternate?: boolean
  jsonLd?: Record<string, unknown>
}

/**
 * Centralises canonical/hreflang/OG/JSON-LD head tags so IT and EN pages for
 * the same content always agree on each other's URL — duplicating this per
 * page, doubled for two locales, is exactly how hreflang correctness drifts.
 */
export function useSeo(options: SeoOptions) {
  const { public: config } = useRuntimeConfig()
  const bare = options.path === '/' ? '' : options.path
  const itUrl = `${config.siteUrl}${bare}`
  const enUrl = `${config.siteUrl}/en${bare}`
  const canonical = options.locale === 'en' ? enUrl : itUrl

  useSeoMeta({
    title: options.title,
    description: options.description,
    ogTitle: options.title,
    ogDescription: options.description,
    ogType: options.type ?? 'website',
    ogUrl: canonical,
    ogImage: options.image,
    twitterCard: options.image ? 'summary_large_image' : undefined,
  })

  const link: Array<{ rel: 'canonical' | 'alternate'; href: string; hreflang?: string }> = [
    { rel: 'canonical', href: canonical },
  ]
  if (options.hasAlternate !== false) {
    link.push(
      { rel: 'alternate', hreflang: 'it', href: itUrl },
      { rel: 'alternate', hreflang: 'en', href: enUrl },
      { rel: 'alternate', hreflang: 'x-default', href: itUrl }
    )
  }

  useHead({
    htmlAttrs: { lang: options.locale },
    // unhead's Link type narrows required keys per literal `rel` value in a
    // way a plain canonical/alternate/hreflang link doesn't fit — the shape
    // itself is valid HTML, so this is a type-only escape hatch.
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    link: link as any,
    script: options.jsonLd
      ? [{ type: 'application/ld+json', innerHTML: JSON.stringify(options.jsonLd) }]
      : undefined,
  })
}