import { marked } from 'marked'
import { markedHighlight } from 'marked-highlight'
import katex from 'katex'
import hljs from 'highlight.js'

function renderMath(text, displayMode) {
  try {
    return katex.renderToString(text, {
      displayMode,
      throwOnError: false,
      strict: false,
    })
  } catch {
    return text
  }
}

// marked extension for inline math $...$
const mathExtension = {
  name: 'math',
  level: 'inline',
  start(src) {
    const idx = src.search(/(?<!\$)\$(?!\$)/)
    return idx === -1 ? undefined : idx
  },
  tokenizer(src) {
    const match = src.match(/^\$\s*([^\$\n]+?)\s*\$/)
    if (match) {
      return { type: 'math', raw: match[0], text: match[1].trim(), displayMode: false }
    }
  },
  renderer(token) {
    return renderMath(token.text, token.displayMode)
  },
}

// marked extension for block math $$...$$
const blockMathExtension = {
  name: 'blockMath',
  level: 'block',
  start(src) {
    const idx = src.indexOf('$$')
    return idx === -1 ? undefined : idx
  },
  tokenizer(src) {
    const match = src.match(/^\$\$\s*([\s\S]+?)\s*\$\$\n?/)
    if (match) {
      return { type: 'blockMath', raw: match[0], text: match[1].trim() }
    }
  },
  renderer(token) {
    return `<div class="math-block">${renderMath(token.text, true)}</div>`
  },
}

// 配置 marked 支持代码高亮
marked.use(markedHighlight({
  langPrefix: 'hljs language-',
  highlight(code, lang) {
    const language = hljs.getLanguage(lang) ? lang : 'plaintext'
    return hljs.highlight(code, { language }).value
  }
}))

marked.use({
  gfm: true,
  breaks: true,
  extensions: [blockMathExtension, mathExtension]
})

export function renderMarkdown(text) {
  return marked.parse(text)
}