const escRegex = /[^a-zA-Z0-9_\u0081-\uffff-]/g
function esc(string: string) {
  return `${string}`.replace(escRegex, (s) => `\\${s}`)
}

const dashCaseRegex = /[A-Z]/g
function dashCase(string: string) {
  return string.replace(dashCaseRegex, (match) => `-${match.toLowerCase()}`)
}

export interface CssVar {
  var: string
  ref: string
}

export interface CssVarOptions {
  fallback?: string | undefined
  prefix?: string | undefined
}

export function cssVar(name: string, options: CssVarOptions = {}): CssVar {
  const { fallback = "", prefix = "" } = options

  const variable = dashCase(["-", prefix, esc(name)].filter(Boolean).join("-"))

  return {
    var: variable,
    ref: `var(${variable}${fallback ? `, ${fallback}` : ""})`,
  }
}