module Jekyll::Filters::URLFilters

def absolute_url(input)
  return if input.nil?
  cache = if input.is_a?(String)
            (@context.registers[:site].filter_cache[:absolute_url] ||= {})
          else
            (@context.registers[:cached_absolute_url] ||= {})
          end
  cache[input] ||= compute_absolute_url(input)
  # Duplicate cached string so that the cached value is never mutated by
  # a subsequent filter.
  cache[input].dup
end

def compute_absolute_url(input)
  input = input.url if input.respond_to?(:url)
  return input if Addressable::URI.parse(input.to_s).absolute?
  site = @context.registers[:site]
  site_url = site.config["url"]
  return relative_url(input) if site_url.nil? || site_url == ""
  Addressable::URI.parse(
    site_url.to_s + relative_url(input)
  ).normalize.to_s
end

def compute_relative_url(input)
  input = input.url if input.respond_to?(:url)
  return input if Addressable::URI.parse(input.to_s).absolute?
  parts = [sanitized_baseurl, input]
  Addressable::URI.parse(
    parts.map! { |part| ensure_leading_slash(part.to_s) }.join
  ).normalize.to_s
end

def ensure_leading_slash(input)
  return input if input.nil? || input.empty? || input.start_with?("/")
  "/#{input}"
end

def relative_url(input)
  return if input.nil?
  cache = if input.is_a?(String)
            (@context.registers[:site].filter_cache[:relative_url] ||= {})
          else
            (@context.registers[:cached_relative_url] ||= {})
          end
  cache[input] ||= compute_relative_url(input)
  # Duplicate cached string so that the cached value is never mutated by
  # a subsequent filter.
  cache[input].dup
end

def sanitized_baseurl
  site = @context.registers[:site]
  baseurl = site.config["baseurl"]
  return "" if baseurl.nil?
  baseurl.to_s.chomp("/")
end

def strip_index(input)
  return if input.nil? || input.to_s.empty?
  input.sub(%r!/index\.html?$!, "/")
end