orchestrate download and printing

thank you @ pspdfkit to show me how to use XM(ER)L-stuff from erlang :-) Feels like using Swift in combination with ObjC

weather/lib/weather/cli.ex

@@ -1,10 +1,12 @@
 defmodule Weather.CLI do
-  
   def run(argv) do
-    # get shortname of airport from argv
-    # use Weather.Gov to fetch XML data
-    # parse XML using :xmler_scan, see: https://medium.com/@blogscot/parsing-xml-using-elixir-mostly-f1368593b0ca
-    # pring 
+    argv
+    |> process()
   end
-  
-end
+
+  def process(airport) when is_binary(airport) do
+    airport
+    |> Weather.Gov.current_observations()
+    |> Weather.NiceXMLFormatter.format_observation_nicely()
+  end
+end

weather/lib/weather/gov_weather.ex

@@ -1,21 +1,25 @@
 defmodule Weather.Gov do
-  
   def url(airport) do
     "https://w1.weather.gov/xml/current_obs/#{airport}.xml"
   end
-  
-  def current_observerations(airport) do
+
+  def current_observations(airport) do
     url(airport)
-    |> HTTPoison.get(["Accept": "application/xml"])
+    |> HTTPoison.get(Accept: "application/xml")
     |> process_result()
   end
-  
+
   def process_result({:ok, %HTTPoison.Response{status_code: 200, body: body}}) do
     body
   end
 
+  def process_result({:ok, %HTTPoison.Response{status_code: 404}}) do
+    IO.puts("Location wasn't found")
+    System.halt(404)
+  end
+
   def process_result({:ok, %HTTPoison.Response{status_code: status_code}}) do
-    IO.puts("Wrong status code: #{status_code}")
+    IO.puts("Another error occured, code: #{status_code}")
     System.halt(status_code)
   end
 
@@ -23,4 +27,4 @@ defmodule Weather.Gov do
     IO.inspect(reason)
     System.halt(2)
   end
-end
+end

weather/lib/weather/nice_formatter.ex

@@ -0,0 +1,23 @@
+defmodule Weather.NiceXMLFormatter do
+  require Weather.XML
+
+  def format_observation_nicely(xml_string) when is_binary(xml_string) do
+    {doc, []} =
+      xml_string
+      |> to_charlist()
+      |> :xmerl_scan.string()
+
+    location = get_child("location", doc)
+    weather = get_child("weather", doc)
+    observation_time = get_child("observation_time", doc)
+    
+    IO.puts "Location: #{location}"
+    IO.puts "Weather: #{weather}"
+    IO.puts observation_time
+  end
+
+  defp get_child(node_name, doc) do
+    :xmerl_xpath.string('/current_observation/#{node_name}/text()', doc)
+    |> Enum.map(&Weather.XML.xmlText(&1, :value))
+  end
+end

weather/lib/weather/xml.ex

@@ -0,0 +1,9 @@
+# thank you PSPDFKit-people: https://pspdfkit.com/blog/2018/how-to-parse-xml-documents-in-elixir/
+
+defmodule Weather.XML do
+  import Record
+  
+  defrecord(:xmlElement, extract(:xmlElement, from_lib: "xmerl/include/xmerl.hrl"))
+  defrecord(:xmlAttribute, extract(:xmlAttribute, from_lib: "xmerl/include/xmerl.hrl"))
+  defrecord(:xmlText, extract(:xmlText, from_lib: "xmerl/include/xmerl.hrl"))
+end

weather/mix.exs

@@ -14,7 +14,7 @@ defmodule Weather.MixProject do
   # Run "mix help compile.app" to learn about applications.
   def application do
     [
-      extra_applications: [:logger, :httpoison]
+      extra_applications: [:logger, :httpoison, :xmerl]
     ]
   end