import MarkdownIt from 'markdown-it'

const markdown = new MarkdownIt({
  html: false,
  linkify: true,
  breaks: true
})

const defaultTableOpen = markdown.renderer.rules.table_open
const defaultTableClose = markdown.renderer.rules.table_close

markdown.renderer.rules.table_open = (tokens, idx, options, env, self) => (
  `<div class="markdown-table-wrap">${defaultTableOpen ? defaultTableOpen(tokens, idx, options, env, self) : '<table>'}`
)

markdown.renderer.rules.table_close = (tokens, idx, options, env, self) => (
  `${defaultTableClose ? defaultTableClose(tokens, idx, options, env, self) : '</table>'}</div>`
)

const ALLOWED_COLON_HEADING_TITLES = new Set([
  '基础信息识别结果',
  '报销测算参考',
  '补充信息'
])

function splitColonHeadingLine(line) {
  const rawLine = String(line || '')
  const trimmed = rawLine.trim()
  if (!trimmed || trimmed.startsWith('|') || /^#{1,6}\s/.test(trimmed)) {
    return [rawLine]
  }

  const chineseColonIndex = trimmed.indexOf('：')
  const asciiColonIndex = trimmed.indexOf(':')
  const colonIndexes = [chineseColonIndex, asciiColonIndex].filter((index) => index > 0)
  if (!colonIndexes.length) {
    return [rawLine]
  }

  const colonIndex = Math.min(...colonIndexes)
  const title = trimmed.slice(0, colonIndex + 1)
  const titleText = title.slice(0, -1)
  const body = trimmed.slice(colonIndex + 1).trim()
  if (!ALLOWED_COLON_HEADING_TITLES.has(titleText)) {
    return [rawLine]
  }

  return body ? [`### ${title}`, '', body] : [`### ${title}`]
}

function normalizeColonHeadings(text) {
  const lines = String(text || '').replace(/\r\n?/g, '\n').split('\n')
  const normalizedLines = []
  let inFence = false

  lines.forEach((line) => {
    if (/^\s*(```|~~~)/.test(line)) {
      inFence = !inFence
      normalizedLines.push(line)
      return
    }
    if (inFence) {
      normalizedLines.push(line)
      return
    }

    const nextLines = splitColonHeadingLine(line)
    if (nextLines[0]?.startsWith('### ') && normalizedLines.length) {
      const previousLine = normalizedLines[normalizedLines.length - 1]
      if (String(previousLine || '').trim()) {
        normalizedLines.push('')
      }
    }
    normalizedLines.push(...nextLines)
  })

  return normalizedLines.join('\n').replace(/\n{3,}/g, '\n\n')
}

export function renderMarkdown(text = '') {
  const normalized = normalizeColonHeadings(text).trim()
  return normalized ? markdown.render(normalized) : ''
}