fuck_404s.rb

class Redirector
  FALLBACK = '/'

  def self.url(a)
    match(a)[:key]
  end

  def self.handle(url)
    RedirectTable::MAP[url] || url(url) || FALLBACK
  end

private

  def self.distance(a, b)
    [(0..a.size).to_a].tap { |mx|
      (1..b.size).each do |j|
        mx << [j] + [0] * (a.size)
      end
      (1..b.size).each do |i|
        (1..a.size).each do |j|
          mx[i][j] = if a[j - 1] == b[i - 1]
            mx[i-1][j-1]
          else
            [mx[i-1][j], mx[i][j-1], mx[i-1][j-1]].min + 1
          end
        end
      end
    }[-1][-1]
  end

  def self.keys
    @client ||= Client.new cache: true
    @sidebar ||= Sidebar.new @client
    @sidebar.links.map(&:href)
  end

  def self.match(a)
    keys.map { |key| { key: key, distance: distance(a, key) } }.min_by { |hsh| hsh[:distance] }
  end
end