create Splitter class and its test

lib/file_manipulator/splitter.rb

@@ -0,0 +1,50 @@
+module FileManipulator
+  class Splitter
+    attr_accessor :file_name, :output_directory, :size
+
+    def initialize(file_name, output_directory, size = 10_485_760)
+      @file_name = file_name
+      @output_directory = output_directory
+      @size = size
+    end
+
+    def run
+      index = 0
+
+      File.open(file_name, 'r') do |input|
+        until input.eof?
+          File.open(File.join(output_directory, output_file_name(index)), 'w') do |output|
+            line = ""
+
+            while output.size <= (size - line.length) && !input.eof?
+              line = input.readline
+              output << line
+            end
+          end
+
+          index += 1
+        end
+      end
+    end
+
+    private
+
+    def basename
+      File.basename(file_name, File.extname(file_name))
+    end
+
+    def extname
+      File.extname(file_name).delete('.')
+    end
+
+    def number_of_digits
+      @number_of_digits ||= Math.log10(File.size(file_name).to_f / size).ceil + 1
+    end
+
+    def output_file_name(index)
+      output_file_name = sprintf("#{basename}_%0#{number_of_digits}d", index)
+
+      "#{output_file_name}.#{extname}" unless extname == ''
+    end
+  end
+end

spec/file_manipulator/splitter_spec.rb

@@ -0,0 +1,93 @@
+require "spec_helper"
+
+module FileManipulator
+  describe Splitter do
+    # one line
+    let(:line) { "123456789\n" } # 10 bytes
+
+    # basename
+    let(:basename) { "foo" } # 10 bytes
+
+    # extname
+    let(:extname) { "txt" } # 10 bytes
+
+    # tempfile
+    let(:tempfile) do
+      name = File.join(Dir.pwd, 'tmp', "#{basename}.#{extname}")
+      File.new(name, 'w')
+    end
+
+    # small_file
+    let(:small_content) { line } # 10 bytes
+    let(:small_file) do
+      tempfile.write(small_content)
+      tempfile.rewind
+      tempfile
+    end
+
+    # large_file
+    let(:large_content) { line * 1_000 } # 10,000 bytes
+    let(:large_file) do
+      tempfile.write(large_content)
+      tempfile.rewind
+      tempfile
+    end
+
+    # output_directory
+    let(:output_directory) { File.join(Dir.pwd, 'tmp') }
+
+    # splitters
+    let(:splitter_small_1) { Splitter.new(small_file.path, output_directory, 1) }
+    let(:splitter_small_2) { Splitter.new(small_file.path, output_directory, 10) }
+    let(:splitter_large_1) { Splitter.new(large_file.path, output_directory, 10) }
+    let(:splitter_large_2) { Splitter.new(large_file.path, output_directory, 100) }
+
+    after do
+      Dir::glob(File.join(output_directory, "*.#{extname}")).each do |_file|
+        File.delete(_file)
+      end
+    end
+
+    it '#new' do
+      expect(splitter_small_2.file_name).to eq(small_file.path)
+      expect(splitter_small_2.output_directory).to eq(output_directory)
+      expect(splitter_small_2.size).to eq(10)
+    end
+
+    describe '#run' do
+      it 'small_1' do
+        splitter_small_1.run
+      end
+
+      it 'small_2' do
+        splitter_small_2.run
+      end
+
+      it 'large_1' do
+        splitter_large_1.run
+      end
+
+      it 'large_2' do
+        splitter_large_2.run
+      end
+    end
+
+    it '#basename' do
+      expect(splitter_small_1.send(:basename)).to eq(basename)
+    end
+
+    it '#extname' do
+      expect(splitter_small_1.send(:extname)).to eq(extname)
+    end
+
+    it '#number_of_digits' do
+      expect(splitter_small_1.send(:number_of_digits)).to eq(2)
+      expect(splitter_large_1.send(:number_of_digits)).to eq(4)
+    end
+
+    it '#output_file_name' do
+      index = 1
+      expect(splitter_small_1.send(:output_file_name, index)).to eq("foo_0#{index}.txt")
+    end
+  end
+end

spec/file_manipulator/version_spec.rb

@@ -0,0 +1,9 @@
+require "spec_helper"
+
+module FileManipulator
+  describe VERSION do
+    it "has a version number" do
+      expect(VERSION).not_to be nil
+    end
+  end
+end

spec/file_manipulator_spec.rb

@@ -4,8 +4,4 @@
   it "has a version number" do
     expect(FileManipulator::VERSION).not_to be nil
   end
-
-  it "does something useful" do
-    expect(false).to eq(true)
-  end
 end

spec/spec_helper.rb

@@ -1,2 +1,3 @@
 $LOAD_PATH.unshift File.expand_path("../../lib", __FILE__)
 require "file_manipulator"
+require 'pry'