Add exercise 9 from chapter 14

Author: Bernard Pietraga

.gitignore

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+.DS_Store

chapter_14/working_with_multiple_processes_9.ex

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+defmodule CatCount do
+  def run do
+    { _, wd } = File.cwd
+    File.cd!("./")
+    IO.puts "Start word count"
+    Scheduler.schedule(CatCount, :count, File.ls!)
+    |> Enum.map(fn({file, count}) ->
+      :io.format "~-30s ~10B~n", [file, count]
+    end)
+    IO.puts "End word count"
+    File.cd! wd
+  end
+
+  def count(scheduler, file) do
+    send scheduler, {self(), {file, count_words(file)}}
+  end
+
+  def count_words(file),
+    do: _count_words(Regex.compile("cat"), file)
+  defp _count_words({:ok, regex}, file),
+    do: Regex.scan(regex, File.read!(file)) |> length
+  defp _count_words({:error, _reason}, _file),
+    do: -1
+end
+
+defmodule Scheduler do
+  def schedule(module, function, data) do
+    data
+    |> Enum.map(fn(x) -> spawn(module, function, [self(), x]) end)
+    |> collect_results([])
+  end
+
+  def collect_results(processes, results) do
+    receive do
+      { child, result } when length(processes) > 1 ->
+        collect_results(List.delete(processes, child), [result | results])
+      { _child, result } ->
+        [result | results]
+    end
+  end
+end
+
+CatCount.run

chapter_14/working_with_multiple_processes_9/cat_1.txt

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+My cat ate sandwich.

chapter_14/working_with_multiple_processes_9/cat_2.txt

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+cat in shell!
+cat on the tree!

chapter_14/working_with_multiple_processes_9/cat_3.txt

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+cat
+cat
+
+cat

chapter_14/working_with_multiple_processes_9/working_with_multiple_processes_9.ex

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+defmodule CatDirCount do
+  def run do
+    File.cd!("./")
+    IO.puts "START CAT COUNTER"
+    Scheduler.schedule(CatDirCount, :count, File.ls!)
+    |> Enum.map(fn({file, count}) ->
+      :io.format("~-40s\s|~2b~n", [file, count])
+    end)
+    IO.puts "END CAT COUNTER"
+  end
+
+  def count(scheduler, file) do
+    send scheduler, {self(), {file, count_words(file)}}
+  end
+
+  def count_words(file),
+    do: _count_words(Regex.compile("cat"), file)
+  defp _count_words({:ok, regex}, file),
+    do: Regex.scan(regex, File.read!(file)) |> length
+  defp _count_words({:error, _reason}, _file),
+    do: 0
+end
+
+defmodule Scheduler do
+  def schedule(module, function, data) do
+    data
+    |> Enum.map(fn(x) -> spawn(module, function, [self(), x]) end)
+    |> collect_results([])
+  end
+
+  def collect_results(processes, results) do
+    receive do
+      {child, result} when length(processes) > 1 ->
+        collect_results(List.delete(processes, child), [result | results])
+      {_child, result} ->
+        [result | results]
+    end
+  end
+end
+
+ExUnit.start
+
+defmodule CatDirCountTest do
+  use ExUnit.Case
+  import ExUnit.CaptureIO
+
+  test "run returns list of files with cats" do
+    terminal_string = """
+      START CAT COUNTER
+      working_with_multiple_processes_9.ex     | 5
+      cat_3.txt                                | 3
+      cat_2.txt                                | 2
+      cat_1.txt                                | 1
+      END CAT COUNTER
+      """
+    expected = capture_io fn ->
+      CatDirCount.run
+    end
+
+    assert expected == terminal_string
+  end
+end