open String
open Str


let is_url url =
  let regexp = regexp "\\(https?\\://\\)?\\(www\\.\\)?.+\\..+" in
  string_match regexp url 0

let is_imgur_url url =
  let regexp = regexp "\\(https?\\://\\)?i\\.imgur\\.com/.+\\..+" in
  string_match regexp url 0

let get_imgur_gallery_url url =
  if not (is_imgur_url url) then
    None
  else begin
    (* Remove i. from the beginning *)
    let prefix = regexp "i\\.imgur\\.com" in
    let s = replace_first prefix "imgur.com" url in

    (* Remove image extension *)
    let len = length s in
    let ext = regexp "\\.[^\\.]+$" in
    let ext_pos = search_backward ext s (len - 1) in
    Some (string_before s ext_pos)
  end

let is_youtube_url url =
  let regexp = regexp "\\(https?\\://\\)?\\(www\\.\\)?\\(youtube\\.com\\)\\|\\(youtu\\.be\\)/.+" in
  string_match regexp url 0


let remove_spaces str =
  match str with
  | Some s ->
    let spaces = regexp "\\( *\\\n\\)+ *" in
    Some (global_replace spaces "" s)
  | None -> None

let format_title str =
  "[ " ^ str ^ " ]"


(* Maybe have a list of functions and
 * iter on all the items in the list *)
let evaluate str =
  match str with
  | str when is_imgur_url str ->
    begin
      match get_imgur_gallery_url str with
      | None -> None
      | Some url ->
        begin
          let title = SimpleHttp.get_http_title (SimpleHttp.get_body url) |> remove_spaces in
          match title with
          | Some t -> Some (format_title t)
          | None -> None
        end
    end
  | str when is_url str ->
    (let title = SimpleHttp.get_http_title (SimpleHttp.get_body str) |> remove_spaces in
    match title with
    | Some t -> Some (format_title t)
    | None -> None)
  | "o/" -> Some "o/"
  | _ -> None