/**
 * Sanitizer für Übungs-Rich-HTML inkl. §11 Platzhalter (span data-shinkan-exercise-media).
 * DOMPurify mit fester Allowlist.
 */

import DOMPurify from 'dompurify'
import { sanitizeInlineMediaCaption } from './inlineMediaCaption'

const ALLOWED_TAGS = ['p', 'div', 'br', 'ul', 'ol', 'li', 'h3', 'b', 'strong', 'i', 'em', 'u', 'span', 'a']
const ALLOWED_ATTR = [
  'href',
  'class',
  'data-shinkan-exercise-media',
  'data-shinkan-exercise-media-size',
  'data-shinkan-exercise-media-caption',
]
const SIZE_OK = new Set(['small', 'medium', 'full'])

function hookAttribute(_node, data) {
  const name = data.attrName
  if (name === 'href') {
    const href = String(data.attrValue || '').trim()
    if (!/^https?:\/\//i.test(href)) data.keepAttr = false
    else data.attrValue = href
    return
  }
  if (name === 'class') {
    const keep = String(data.attrValue || '')
      .split(/\s+/)
      .filter((c) => c === 'shinkan-inline-media')
    if (!keep.length) data.keepAttr = false
    else data.attrValue = keep.join(' ')
    return
  }
  if (name === 'data-shinkan-exercise-media') {
    if (!/^\d+$/.test(String(data.attrValue || '').trim())) data.keepAttr = false
    return
  }
  if (name === 'data-shinkan-exercise-media-size') {
    const size = String(data.attrValue || '').trim().toLowerCase()
    if (!SIZE_OK.has(size)) data.keepAttr = false
    else data.attrValue = size
    return
  }
  if (name === 'data-shinkan-exercise-media-caption') {
    const caption = sanitizeInlineMediaCaption(String(data.attrValue || ''))
    if (!caption) data.keepAttr = false
    else data.attrValue = caption
  }
}

const instances = new WeakMap()

function purifyFor(win) {
  const existing = instances.get(win)
  if (existing) return existing
  const purify = DOMPurify(win)
  purify.addHook('uponSanitizeAttribute', hookAttribute)
  instances.set(win, purify)
  return purify
}

/**
 * @param {string|null|undefined} html
 * @param {Window=} win
 * @returns {string}
 */
export function sanitizeExerciseRichDisplayHtml(html, win) {
  if (html == null || typeof html !== 'string') return ''
  const trimmed = html.trim()
  if (!trimmed) return ''
  const target = win || (typeof window !== 'undefined' ? window : null)
  if (!target) return ''
  return purifyFor(target).sanitize(trimmed, {
    ALLOWED_TAGS,
    ALLOWED_ATTR,
    ALLOW_DATA_ATTR: false,
  })
}