Case Sensitive Replacements

I was inspired by the xkcd substitutions commic below to write a simple web server that and mirrors a news site with the substitutions.

However, I ran into a bit of a problem. News sites have varying styles of capitalization. A naive solution is just to globally replace with case insensitive matches.

Global Case-Insensitive

The "g" modifier signifies that a regular expression is global, and the (i) modifier makes it case insensitive.

replacements = {
  'new study': 'tumblr post'
  # ...
}

substitute = (text) ->
  for phrase, replacement of replacements
    regex = new RegExp(phrase.replace(/\ /g, '\\ '), 'gi')
    text = text.replace regex, replacement
  text

If the replaced text was in a title, it comes out awfully:

substitute 'New Study On Teen Health'
# => 'tumblr post On Teen Health'

Case Sensitive Replacement

Here's a quick (read: inefficient) solution to get my silly news mirror up and running.

Case = do ->
  @cases = ['upcase', 'downcase', 'titlecase', 'sentencecase' ]
  
  @upcase = (s) -> 
    s.toUpperCase()
    
  @downcase = (s) -> 
    s.toLowerCase()
  
  @capitalcase = (s) ->
    @upcase(s[0]) + @downcase(s[1..])
  
  @sentencecase = (s) ->
    s.split(/\.\s+/).map(@capitalcase).join('. ')
  
  @titlecase = (s) ->
    s.split(' ').map(@capitalcase).join(' ')
  
  @cases.forEach (type) =>
    @["is_#{type}"] = (s) ->
      s is @[type](s)

  @case_of = (s) ->
    iterator = (prev, type) ->
      prev or @["is_#{type}"](s) and type
    @cases.reduce(iterator, null)

  @match = (mask, s) ->
    type = @case_of mask
    if type then @[type](s) else s
  
  @sensitive = (s) ->
    (mask) => @match(mask, s)
  
  this

I used the design pattern of an immediately called closure to hold onto scope. It allows for grabbing methods by name, which is useful for the meta-programming style way the string is matched against the case mask.

The case matcher is far from useful in the real world, but it outputs reasonable replacements for silly news!

regex = /hello\ world/ig
replacement = Case.sensitive 'greetings planet earth'
for phrase in ['Hello World', 'HELLO WORLD', 'Hello world', 'hello world']
  console.log phrase.replace(regex, replacement)

###
Greetings Planet Earth
GREETINGS PLANET EARTH
Greetings planet earth
greetings planet earth
###