const nestTest = {
  name: 'nest-test',
  level: 'block',
  start(src) {
    return src.match(/:::(info|warn|positive|negative)\n/)?.index;
    },
  tokenizer(src, tokens) {
    const match = src.match(/^:::(info|warn|positive|negative)\n/)
    if (!match) {
      return
    }

    const lines = src.split("\n")
    const replaced = []
    replaced.push(lines.shift()) // ignore opening tag but preserve it for "raw"

    const groups = []
    let group = []
    let indent = 0

    for (let line of lines) {
      if (indent === 0 && line.length === 0) {
        break
      }
      const offset = countIndent(line)
      if (indent > 0 && offset === 0) {
        break
      }
      if (offset !== indent) {
        groups.push(group)
        group = []
        indent = offset
      }
      // we must propagate offset line because we need it to properly work as a block divider in join()
      if (" ".repeat(offset) === line) {
        group.push(line)
      } else {
        group.push(line.slice(offset < 4 ? offset : 4))
      }
      replaced.push(line)
    }

    if (group.length > 0) {
      // avoid appending empty line that won't get rendered anyway
      if (group.length > 1 || group[0].length > 0) {
        groups.push(group)
      }
    }

    const token = {
      type: 'flash',
      raw: replaced.join("\n"),
      kind: match[1],
      tokens: []
    };
    for (let group of groups) {
      this.lexer.blockTokens(group.join("\n"), token.tokens);
    }
    return token;
  }
};

// for some reason using line.search(/[^ ]/) does not yield expected results.
function countIndent(line) {
  let count = 0
  for (let i = 0; i < line.length; i++) {
    if (line.charAt(i) === ' ') {
      count++
    } else {
      break;
    }
  }
  return count
}