export interface ExtractedBlock {
  blockId: string
  content: string
}

export function extractBlocksFromHtml(html: string): ExtractedBlock[] {
  const blocks: ExtractedBlock[] = []
  const regex = /<(?:p|h[1-6]|blockquote|li)[^>]*data-id="([^"]+)"[^>]*>([\s\S]*?)<\/(?:p|h[1-6]|blockquote|li)>/gi
  let match
  while ((match = regex.exec(html)) !== null) {
    const blockId = match[1]
    const content = match[2].replace(/<[^>]+>/g, ' ').replace(/\s+/g, ' ').trim()
    if (content.length >= 10) {
      blocks.push({ blockId, content })
    }
  }
  return blocks
}

export function jaccardSimilarity(a: string, b: string): number {
  const tokenize = (s: string) =>
    new Set(
      s
        .toLowerCase()
        .replace(/[^\w\s]/g, '')
        .split(/\s+/)
        .filter(w => w.length > 3)
    )
  const A = tokenize(a)
  const B = tokenize(b)
  if (A.size === 0 || B.size === 0) return 0
  let intersection = 0
  A.forEach(w => { if (B.has(w)) intersection++ })
  return intersection / (A.size + B.size - intersection)
}

function extractPlainBlocksFromHtml(html: string): ExtractedBlock[] {
  const blocks: ExtractedBlock[] = []
  const regex = /<(?:p|h[1-6]|blockquote|li|td|th|div)[^>]*>([\s\S]*?)<\/(?:p|h[1-6]|blockquote|li|td|th|div)>/gi
  let match
  while ((match = regex.exec(html)) !== null) {
    const content = match[1].replace(/<[^>]+>/g, ' ').replace(/\s+/g, ' ').trim()
    if (content.length >= 10) {
      blocks.push({ blockId: '', content })
    }
  }
  return blocks
}

function pickBestFromBlocks(blocks: ExtractedBlock[], hint: string): ExtractedBlock | null {
  if (blocks.length === 0) return null
  if (!hint.trim()) return blocks[0]

  let best = blocks[0]
  let bestScore = jaccardSimilarity(hint, best.content)
  for (const block of blocks.slice(1)) {
    const score = jaccardSimilarity(hint, block.content)
    if (score > bestScore) {
      best = block
      bestScore = score
    }
  }
  return best
}

export function pickBestBlockForHint(html: string, hint: string): ExtractedBlock | null {
  return pickBestFromBlocks(extractBlocksFromHtml(html), hint)
}

/** Fallback when notes have no data-id yet (citation statique, pas de bloc vivant). */
export function pickBestPlainPassageForHint(html: string, hint: string): ExtractedBlock | null {
  return pickBestFromBlocks(extractPlainBlocksFromHtml(html), hint)
}