my solution

lib/cli.ex

@@ -0,0 +1,50 @@
+defmodule Jump.CLI do
+  def main(args \\ []) do
+    parsed_args = parse_args(args)
+
+    parsed_args
+    |> fetch()
+    |> calculate(parsed_args)
+    |> finish()
+  end
+
+  defp parse_args(args) do
+    {opts, _, _} = OptionParser.parse(args, switches: [article: :string, days: :integer])
+    opts
+  end
+
+  defp fetch(args) do
+    the_end = Calendar.strftime(DateTime.utc_now(), "%Y%m%d")
+    {the_end_int, ""} = Integer.parse(the_end)
+
+    start = the_end_int - args[:days]
+
+    Jump.fetch(args[:article], start, the_end)
+  end
+
+  defp calculate(items, args) do
+    total_pageviews = Enum.sum_by(items, &Map.get(&1, "views"))
+    max_views_item = Enum.max_by(items, &Map.get(&1, "views"))
+
+    %{
+      event_name: "campaign_spike_conversion",
+      article: args[:article],
+      window_days: args[:days],
+      total_pageviews: total_pageviews,
+      avg_daily_pageviews: total_pageviews / length(items),
+      top_day: %{
+        date: max_views_item["timestamp"],
+        pageviews: max_views_item["views"]
+      }
+    }
+  end
+
+  defp finish(summary) do
+    Jump.post(summary)
+
+    IO.inspect(summary)
+
+    IO.puts("done.")
+  end
+
+end