;Generates a new article page.
""        :ident
""        :title
""        :subtitle
time.stamp :ts
false     :valid-id

(
  (str) expect first :ident
  ident "^[a-z0-9-]+$" match? :valid-regexp
  (sys.pwd "contents" "articles") => "/" join sys.ls :filelist
  filelist (fs.filename "(.+)\\..+$" search 1 get) map ident in? not :valid-file
  valid-regexp valid-file and
) ^validate

(valid-id not) (
  "ID" io.ask @ident
  ident validate @valid-id
  (valid-id not) 
    ("ID must not be already used and it must contain only lowercase letters, numbers, or -" io.warn) 
  when
) while

"Title" io.ask @title
"Subtitle" io.ask @subtitle

"-----\nid: $1\ntitle: \"$2\"\nsubtitle: \"$3\"\ncontent-type: article\ntimestamp: $4\n-----\n\n" (ident title subtitle ts) =% :metadata

("Create article?" io.confirm) 
  (
    (ident ".md") => "" join :fn 
    (sys.pwd "contents" "articles" fn) => "/" join :path
    metadata path fs.write
  ) 
when