const VAR_RE = /\{\{([a-zA-Z_][a-zA-Z0-9_]*)\}\}/g

export function parseVars(template) {
  const seen = new Set()
  const vars = []
  let m
  VAR_RE.lastIndex = 0
  while ((m = VAR_RE.exec(template)) !== null) {
    if (!seen.has(m[1])) {
      seen.add(m[1])
      vars.push(m[1])
    }
  }
  return vars
}

export function fillTemplate(template, values) {
  return template.replace(/\{\{([a-zA-Z_][a-zA-Z0-9_]*)\}\}/g, (_, k) => values[k] ?? `{{${k}}}`)
}