// The schema.org FAQPage node of a FAQ (D-43): one Question per item with its
// acceptedAnswer as plain text (the answer's HTML without markup), @id
// <page URL>#faq. FaqBlock adds it to the page's one JSON-LD @graph through
// vue-seo-layer's useSchemaNode (prop schema, default true), so a page keeps
// one JSON-LD script; a second block on the page with the same @id merges
// into the first (the first one's questions stay). Pure, so `node --test`
// drives it.

import type { Faq } from './types.ts'

export interface FaqPageNode {
  '@type': 'FAQPage'
  '@id': string
  url: string
  mainEntity: Array<{ '@type': 'Question'; name: string; acceptedAnswer: { '@type': 'Answer'; text: string } }>
  [key: string]: unknown
}

const NAMED: Record<string, string> = { amp: '&', lt: '<', gt: '>', quot: '"', apos: "'", nbsp: ' ' }

/** Plain text of an answer: tags dropped (script and style with their content), entities decoded, whitespace collapsed. */
export function faqAnswerText(html: string | null | undefined): string {
  if (!html) return ''
  return html
    .replace(/<(script|style)\b[\s\S]*?<\/\1\s*>/gi, ' ')
    .replace(/<[^>]*>/g, ' ')
    .replace(/&(#x[0-9a-f]+|#[0-9]+|[a-z]+);/gi, (m, code: string) => {
      if (code[0] === '#') {
        const n = code[1] === 'x' || code[1] === 'X' ? Number.parseInt(code.slice(2), 16) : Number.parseInt(code.slice(1), 10)
        return Number.isFinite(n) && n > 0 && n <= 0x10ffff ? String.fromCodePoint(n) : m
      }
      return NAMED[code.toLowerCase()] ?? m
    })
    .replace(/\s+/g, ' ')
    .trim()
}

/** The FAQPage node of `faq` on the page at `pageUrl`, or null without questions. */
export function faqSchema(faq: Faq | null | undefined, pageUrl: string): FaqPageNode | null {
  const items = (faq?.content ?? []).filter((item) => item && typeof item.question === 'string' && item.question.trim() !== '')
  if (items.length === 0) return null
  const url = pageUrl.split('#')[0] ?? pageUrl
  return {
    '@type': 'FAQPage',
    '@id': `${url}#faq`,
    url,
    mainEntity: items.map((item) => ({
      '@type': 'Question',
      name: item.question.trim(),
      acceptedAnswer: { '@type': 'Answer', text: faqAnswerText(item.answer) },
    })),
  }
}