class ReverseMarkdown::Cleaner

def clean_punctuation_characters(string)
  string.gsub(/(\*\*|~~|__)\s([\.!\?'"])/, "\\1".strip + "\\2")
end

def clean_tag_borders(string)
  result = string.gsub(/\s?\*{2,}.*?\*{2,}\s?/) do |match|
    preserve_border_whitespaces(match, default_border: ReverseMarkdown.config.tag_border) do
      match.strip.sub('** ', '**').sub(' **', '**')
    end
  end
  result = result.gsub(/\s?\_{2,}.*?\_{2,}\s?/) do |match|
    preserve_border_whitespaces(match, default_border: ReverseMarkdown.config.tag_border) do
      match.strip.sub('__ ', '__').sub(' __', '__')
    end
  end
  result = result.gsub(/\s?~{2,}.*?~{2,}\s?/) do |match|
    preserve_border_whitespaces(match, default_border: ReverseMarkdown.config.tag_border) do
      match.strip.sub('~~ ', '~~').sub(' ~~', '~~')
    end
  end
  result.gsub(/\s?\[.*?\]\s?/) do |match|
    preserve_border_whitespaces(match) do
      match.strip.sub('[ ', '[').sub(' ]', ']')
    end
  end
end

def force_encoding(string)
  ReverseMarkdown.config.force_encoding or return string
  string.encode('UTF-8', 'binary', invalid: :replace, undef: :replace, replace: '')
end

def present_or_default(string, default)
  if string.nil? || string.empty?
    default
  else
    string
  end
end

def preserve_border_whitespaces(string, options = {}, &block)
  return string if string =~ /\A\s*\Z/
  default_border = options.fetch(:default_border, '')
  # If the string contains part of a link so the characters [,],(,)
  # then don't add any extra spaces
  default_border = '' if string =~ /[\[\(\]\)]/
  string_start   = present_or_default(string[/\A\s*/], default_border)
  string_end     = present_or_default(string[/\s*\Z/], default_border)
  result         = yield
  string_start + result + string_end
end

def remove_inner_whitespaces(string)
  string.each_line.inject("") do |memo, line|
    memo + preserve_border_whitespaces(line) do
      line.strip.gsub(/[ \t]{2,}/, ' ')
    end
  end
end

def remove_leading_newlines(string)
  string.gsub(/\A\n+/, '')
end

def remove_newlines(string)
  string.gsub(/\n{3,}/, "\n\n")
end

def tidy(string)
  result = remove_inner_whitespaces(string)
  result = remove_newlines(result)
  result = remove_leading_newlines(result)
  result = clean_tag_borders(result)
  clean_punctuation_characters(result)
end