CSS selector parsing exercice

CSS_selector_parsing_exercice.fsx

open System

module Domain =
  type ClassName = string
  type TagName = string
  type HtmlId = string
  type Token =
    | TagSelector of TagName
    | ClassSelector of ClassName
    | WhiteSpace
    | IdSelector of HtmlId

module Parsing =
  open Domain

  let (|ExtractClassName|_|) (chars:char list) =
    match chars with
    | '.' :: t -> 
      let name = t |> List.takeWhile Char.IsLetterOrDigit
      if name.Length <> 0
      then Some (String(name |> Seq.toArray),(t |> List.skip name.Length))
      else None
    | _ -> None

  let parseSelector (selector:string) =
    let rec loop (chars:char list) (acc:Token list) : Token list =
      match chars with
      | ExtractClassName (name,t) -> 
        loop t ((TagSelector name) :: acc)
      // TODO: handle other tokens
      | [] -> acc
      | _ :: t -> loop t acc // TODO: fail with invalid tokens
      
    loop (selector |> Seq.toList) []

open Domain

// Tests

let selector1 = "div.toolbox span a#toto"
let parsedTokens = Parsing.parseSelector selector1
let expectedTokens = 
  [ TagSelector "div"
    ClassSelector "toolbox"
    WhiteSpace
    TagSelector "span"
    TagSelector "a" ]

// TODO: assert expectedTokens equals parsedTokens