chore(growth): fetch extended data for indicators

Also, improve module doc.

lib/growth/indicators/download.ex

@@ -1,6 +1,13 @@
 defmodule Growth.Indicators.Download do
   @moduledoc """
-  Download, extract, and load indicators to construct z-score for:
+  To calculate z-scores for the different growth measurements, the system must:
+
+  1. Fetch indicators from World Health Organization
+  2. Extract data from excel sheets
+  3. Convert the data into proper format, specially, handle with decimal values
+  3. Add metadata to make search for the parameters possible
+
+  The following indicators to construct z-scores are fetched:
 
   * [height for age 0 to 5 years](https://www.who.int/tools/child-growth-standards/standards/length-height-for-age)
   * [height for age 5 to 19 years](https://www.who.int/tools/growth-reference-data-for-5to19-years/indicators/height-for-age)
@@ -201,11 +208,16 @@ defmodule Growth.Indicators.Download do
   def process_measure(
         {measure,
          %{
-           female: %{age_tables: female_urls, expanded_tables: _},
-           male: %{age_tables: male_urls, expanded_tables: _}
+           female: %{age_tables: female_urls, expanded_tables: e_female_urls},
+           male: %{age_tables: male_urls, expanded_tables: e_male_urls}
          }}
       ) do
-    [{:female, female_urls}, {:male, male_urls}]
+    [
+      {:female, :age, female_urls},
+      {:male, :age, male_urls},
+      {:female, :expanded, e_female_urls},
+      {:male, :expanded, e_male_urls}
+    ]
     |> Enum.map(&Task.async(__MODULE__, :process_gender, [&1]))
     |> Task.await_many()
     |> merge()
@@ -213,18 +225,18 @@ defmodule Growth.Indicators.Download do
     |> save(measure)
   end
 
-  def process_gender({gender, urls}) do
+  def process_gender({gender, category, urls}) do
     urls
-    |> Enum.map(&Task.async(__MODULE__, :process, [gender, &1]))
+    |> Enum.map(&Task.async(__MODULE__, :process, [gender, category, &1]))
     |> Task.await_many()
     |> merge()
   end
 
-  def process(gender, url) do
+  def process(gender, category, url) do
     url
     |> fetch!()
     |> extract!(url)
-    |> convert(gender, url)
+    |> convert(gender, category, url)
   end
 
   def fetch!(url) do
@@ -247,15 +259,15 @@ defmodule Growth.Indicators.Download do
     end
   end
 
-  @common_header ~w(source gender age_unit age l m s sd3neg sd2neg sd1neg sd0 sd1 sd2 sd3)
+  @common_header ~w(source category gender age_unit age l m s sd3neg sd2neg sd1neg sd0 sd1 sd2 sd3)
 
   # FIX: (jpd) weight for lenght/height does not have an age in the header row
-  def convert([header | rows], gender, url) do
+  def convert([header | rows], gender, category, url) do
     age_unit = header |> hd() |> String.downcase()
 
     fixed_header = header |> tl() |> Enum.map(&String.downcase/1) |> Enum.map(&String.trim/1)
 
-    parsed_header = ["source" | ["gender" | ["age_unit" | ["age" | fixed_header]]]]
+    parsed_header = ["source" | ["category" | ["gender" | ["age_unit" | ["age" | fixed_header]]]]]
 
     # NOTE: (jpd): parsing the rows consist in:
     # 1. convert row values to decimal
@@ -267,7 +279,7 @@ defmodule Growth.Indicators.Download do
     parsed_rows =
       rows
       |> Stream.map(fn row -> Enum.map(row, &Decimal.new/1) end)
-      |> Stream.map(&[url | [gender | [age_unit | &1]]])
+      |> Stream.map(&[url | [category | [gender | [age_unit | &1]]]])
       |> Stream.map(&Enum.zip(parsed_header, &1))
       |> Stream.map(&Map.new/1)
       |> Stream.map(&Map.take(&1, @common_header))