response_caching_middleware.lua

return function (request, next_middleware)
  -- initialize cache store

  local threshold = 86400 -- 1 day
  local key = 'cache=' .. request.uri_full
  
  
  -- flush cache
  if request.method == "DELETE" then
    bucket.middleware.delete(key)
    local body, status, headers = http.simple(request.uri_full)
    return { body = body, status = status, headers = headers }
  end

  if request.method == "GET" then
    -- request new one
    if request.args.new and request.args.hits < "3" then
      console.log("new one!")
      key = 'new=http://' .. request.host .. request.uri
      console.log(key)
      local response = next_middleware()      
      bucket.middleware.set(key, response)
      send.event({channel = "cache", msg = "new content demanded", level = "debug", content = response })
      
      return response
    end
    
    local stored = bucket.middleware.get(key)
    if stored ~= nil then
      console.log("stored")
      console.log(stored)
      local expires = stored.headers['X-Expires']
      if expires and expires > time.now() then -- not expired yet
        --send.event({channel = "cache", msg = "returned cached content", level = "debug", key = key, content = stored, expires = expires, now = time.now() })
        stored.headers['Expires'] = time.http(expires)
      end
      console.log(key)
      return stored
    end
     --send.event({channel = "cache", msg = "NOT  cached content", level = "debug", key = key, content = stored, expires = expires, now = time.now() })
  end

  -- if content is not cached, do the real request & get response
  local response = next_middleware()

  if request.method == 'GET' then
    local expires = time.now() + threshold
    response.headers['X-Expires'] = expires
    bucket.middleware.set(key, response, expires)
    send.event({channel = "cache", msg = "stored cached content", level = "debug", content = response })
  end

  return response
end