Add support for keyword lists (Issue aerosol#12)

lib/tabula.ex

@@ -26,6 +26,10 @@ defmodule Tabula do
   ]
 
   @default_sheet :org_mode
+  @access_functions [
+    default:  [access_functions: [get: &Map.get/3, keys: &Map.keys/1]],
+    keywords: [access_functions: [get: &Keyword.get/3, keys: &Keyword.keys/1]]
+  ]
 
   defmacro __using__(opts) do
     quote do
@@ -51,27 +55,33 @@ defmodule Tabula do
     |> IO.puts
   end
 
-  def render_table(rows, opts \\ []) do
+  def render_table([h|_] = rows, opts \\ []) do
+    opts = set_access_functions(opts, h)
     cols = extract_cols(rows, opts)
     _render_table(rows, cols, opts)
     |> :erlang.list_to_binary
   end
 
-  def max_widths(cols, rows) do
-    max_index = rows
-    |> length
-    |> strlen
-    cols
-    |> map(fn k ->
+  defp set_access_functions(opts, a_row) do
+    opts
+    |> Keyword.merge(@access_functions[:default])
+    |> (fn (opts) ->
+      is_list(a_row) && Keyword.merge(opts, @access_functions[:keywords]) || opts
+    end).()
+  end
+
+  def max_widths(cols, rows, opts \\ @access_functions[:default]) do
+    extraction_function = opts[:access_functions][:get]
+    max_index = rows |> length |> strlen
+    cols |> map(fn k ->
       max([
-        strlen(k), max_index
-        | map(rows, &(Map.get(&1, k) |> strlen))
+        strlen(k), max_index | map(rows, &(extraction_function.(&1, k, nil) |> strlen))
       ])
     end)
   end
 
   defp _render_table(rows, [_|_]=cols, opts) do
-    widths     = max_widths(cols, rows)
+    widths     = max_widths(cols, rows, opts)
     formatters = widths |> formatters(opts)
     spacers    = widths |> spacers(opts)
 
@@ -87,12 +97,10 @@ defmodule Tabula do
 
   end
 
-  defp extract_cols([first|_]=_rows, opts) do
+  defp extract_cols([first|_] = _rows, opts) do
     case opts[:only] do
-      nil ->
-        first |> Map.keys
-      cols when is_list(cols) ->
-        cols
+      nil -> opts[:access_functions][:keys].(first)
+      cols when is_list(cols) -> cols
     end
   end
 
@@ -142,11 +150,11 @@ defmodule Tabula do
 
   defp strlen(x), do: render_cell(x) |> String.length()
 
-  defp values(cols, {row, index}, _opts) do
+  defp values(cols, {row, index}, opts) do
     cols
     |> map(fn (@index) -> index+1
-              (col)    -> Map.get(row, col)
-           end)
+      (col) -> opts[:access_functions][:get].(row, col, nil)
+    end)
   end
 
   defp style(style, opts) do

test/tabula_test.exs

@@ -145,4 +145,19 @@ defmodule TabulaTest do
     assert table == expect
   end
 
+  test "Support keyword lists and preserve ordering of columns" do
+    rows = [
+      [name: "ecto", point: %Point{x: 0, y: 0}, version: Version.parse!("2.0.4")],
+      [name: "phoenix", point: %Point{x: 1, y: 0}, version: Version.parse!("1.2.0")]
+    ]
+    table = Tabula.render_table(rows)
+
+    expect = """
+    :name   | :point                        | :version
+    --------+-------------------------------+---------
+    ecto    | %TabulaTest.Point{x: 0, y: 0} | 2.0.4   
+    phoenix | %TabulaTest.Point{x: 1, y: 0} | 1.2.0   
+    """
+    assert table == expect
+  end
 end