export default {
  extensions: [
    {
      name: 'mfm',
      level: 'inline',
      start (src) { return src.match(/\$\[/)?.index },
      tokenizer (src, tokens) {
        // regex doesn't do well finding MFM tags: it's always either too lazy
        // or too greedy.
        let level = 0
        let walk = 0
        while (level > 0 || walk === 0) {
          if (walk >= src.length) {
            return null
          }
          if (src[walk] + src[walk + 1] === '$[') {
            level++
            walk++
          } else if (src[walk] === ']') {
            level--
          }
          walk++
        }

        // original regex, now definitely on the correct tag
        const rule = /^\$\[(?<tag>[\w\d]+)(?:\.(?<options>\S+))? (?<text>[\S\s]+)\]/
        const match = rule.exec(src.slice(0, walk))
        if (match) {
          const token = {
            type: 'mfm',
            raw: match[0],
            tag: match.groups.tag,
            options: match.groups.options,
            text: match.groups.text,
            tokens: [],
          }
          this.lexer.inline(token.text, token.tokens)
          return token
        }
      },
      renderer (token) {
        const MFM_TAGS = ['tada', 'jelly', 'twitch', 'shake', 'spin', 'jump', 'bounce', 'flip', 'x2', 'x3', 'x4', 'font', 'blur', 'rainbow', 'rotate', 'sparkle']
        if (MFM_TAGS.includes(token.tag)) {
          let options = []
          if (token.options) {
            options = token.options.split(',').map((opt) => (opt.split('=').length === 2 ? `data-${opt.split('=')[0]}="${opt.split('=')[1]}"` : `data-${opt}`))
          }
          return `<span class="mfm _mfm_${token.tag}_" ${options.join(' ')}>${this.parser.parseInline(token.tokens)}</span>`
        }
        return `$[${token.tag} ${this.parser.parseInline(token.tokens)}]`
      },
    },
    {
      name: 'escapedMfm',
      level: 'inline',
      start (src) { return src.match(/\\\$\[/) },
      tokenizer (src, tokens) {
        if (/^\\\$\[/.exec(src)) {
          return { type: 'escapedMfm', raw: '\\$[' }
        }
      },
      renderer (token) {
        return '$['
      },
    },
    {
      name: 'center',
      level: 'block',
      start (src) { return src.match(/<center>/) },
      tokenizer (src, tokens) {
        const rule = /^<center>([\S\s]*)<\/center>/
        const match = rule.exec(src)
        if (match) {
          const token = {
            type: 'center',
            raw: match[0],
            text: match[1],
            tokens: [],
          }
          this.lexer.inline(token.text, token.tokens)
          return token
        }
      },
      renderer (token) {
        return `<center>${this.parser.parseInline(token.tokens)}</center>\n`
      },
    },
  ],
}