* new basis for the save and load system of the index

* the old index will disappear and IndexSearcher will be the interface
  for searching through the index

lib/polecat.rb

@@ -1,4 +1,7 @@
 class Polecat
   require 'polecat/index'
+  require 'polecat/index_writer'
+  require 'polecat/index_reader'
+  require 'polecat/index_searcher'
   require 'polecat/document'
 end

lib/polecat/index_reader.rb

@@ -0,0 +1,46 @@
+class Polecat
+  # reads an index directory
+  #
+  # This class reads the content of an index directory and builds the
+  # necessary structures for the index type.
+  class IndexReader
+    attr_reader :path
+
+    # initialize a new reader
+    #
+    # Create a new reader for the given path. If the directory is empty, you
+    # will get an empty index, else all documents stored in that directory.
+    # @param [String] path the path to the index directory
+    def initialize path
+      @path = path
+      raise ArgumentError, 'no valid directory' unless File.directory? @path
+    end
+
+    # read the content of the directory
+    #
+    # Read all files of the directory and return an index object.
+    # @raise [IOError] raised when the directory is locked
+    # @return [Polecat::Index] the index with all documents
+    def read
+      raise IOError, 'index is locked' if locked?
+      files = Dir[@path + '/*']
+      if files.count > 0
+        documents = []
+        files.each do |file|
+          documents += Marshal.load(File.read(file))
+        end
+      else
+        {}
+      end
+    end
+
+    # checks whether the directory is locked or not
+    def locked?
+      if File.exists? @path + '/index.lock'
+        true
+      else
+        false
+      end
+    end
+  end
+end

lib/polecat/index_searcher.rb

@@ -0,0 +1,32 @@
+class Polecat
+  # interface for searching an index
+  #
+  # Build on top of an Polecat::IndexReader, this class let's you search through
+  # all documents stored in an index.
+  class IndexSearcher
+    attr_reader :reader
+
+    # creates a new Polecat::IndexSearcher
+    #
+    # Create a new Polecat::IndexSearcher to search documents. Either a path
+    # to a directory or a Polecat::IndexReader has to be given, to make this
+    # searcher work.
+    # @example
+    #   # the following has the same meaning
+    #   IndexSearcher.new 'index_dir'
+    #   IndexSearcher.new(IndexReader.new 'index_dir')
+    def initialize *args
+      if args[0].class == Polecat::IndexReader
+        @reader = args[0]
+      elsif args[0].class == String
+        @reader = Polecat::IndexReader.new args[0]
+      end
+    end
+
+    # returns the path of the index directory
+    # @return [String] path of the index directory
+    def path
+      @reader.path
+    end
+  end
+end

lib/polecat/index_writer.rb

@@ -79,5 +79,12 @@ class Polecat
         return true
       end
     end
+
+    # creates an index reader with the writers path
+    #
+    # @returns [Polecat::IndexReader] an IndexReader with the same path
+    def create_reader
+      Polecat::IndexReader.new @path
+    end
   end
 end

spec/index_reader/locked_spec.rb

@@ -0,0 +1,18 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+
+describe "IndexReader#locked?" do
+  before do
+    @path = prepare_index_dir
+  end
+
+  it "returns false when the directory is not locked" do
+    r = Polecat::IndexReader.new @path
+    r.locked?.should == false
+  end
+
+  it "returns true when the directory is locked" do
+    FileUtils.touch @path + '/index.lock'
+    r = Polecat::IndexReader.new @path
+    r.locked?.should == true
+  end
+end

spec/index_reader/new_spec.rb

@@ -0,0 +1,21 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+
+describe "IndexReader#new" do
+  before do
+    @path = prepare_index_dir
+  end
+
+  it "takes a directory path as an argument" do
+    r = Polecat::IndexReader.new @path
+    r.path.should == @path
+  end
+
+  it "raises an error when no path is given" do
+    lambda { Polecat::IndexReader.new }.should raise_error(ArgumentError)
+  end
+
+  it "raises an error when the path is not a directory" do
+    lambda { Polecat::IndexReader.new '/dev/null' }.should(
+      raise_error(ArgumentError))
+  end
+end

spec/index_reader/read_spec.rb

@@ -0,0 +1,40 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+
+describe "IndexReader#read" do
+  before do
+    @path = prepare_index_dir
+  end
+
+  it "returns a hash with all documents" do
+    r = Polecat::IndexReader.new @path
+    r.read.class.should == Hash
+  end
+
+  it "returns an empty hash for a empty directory" do
+    r = Polecat::IndexReader.new @path
+    r.read.count.should == 0
+  end
+
+  it "returns the document count found in the index directory" do
+    w = Polecat::IndexWriter.new @path
+    w.add Spec::FooDocument.new(:id => 23)
+    w.write
+    r = Polecat::IndexReader.new @path
+    r.read.count.should == 1
+  end
+
+  it "merges all documents from different files together" do
+    w = Polecat::IndexWriter.new @path
+    w.add Spec::FooDocument.new(:id => 23)
+    w.write
+    w.add Spec::FooDocument.new(:id => 24)
+    w.write
+    w.create_reader.read.count.should == 2
+  end
+
+  it "raises an error when the directory is locked" do
+    FileUtils.touch @path + '/index.lock'
+    r = Polecat::IndexReader.new @path
+    lambda { r.read }.should raise_error(IOError)
+  end
+end

spec/index_searcher/new_spec.rb

@@ -0,0 +1,17 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+
+describe "IndexSearcher#new" do
+  before do
+    @path = prepare_index_dir
+  end
+
+  it "takes a path as an arugment" do
+    s = Polecat::IndexSearcher.new @path
+    s.path.should == @path
+  end
+
+  it "takes an IndexReader as an argument" do
+    s = Polecat::IndexSearcher.new(Polecat::IndexReader.new @path)
+    s.path.should == @path
+  end
+end

spec/index_writer/create_reader_spec.rb

@@ -0,0 +1,22 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+
+describe "IndexReader#read" do
+  before do
+    @path = prepare_index_dir
+  end
+
+  it "returns a IndexReader" do
+    w = Polecat::IndexWriter.new @path
+    w.create_reader.class.should == Polecat::IndexReader
+  end
+
+  it "returns a different object everytime it is called" do
+    w = Polecat::IndexWriter.new @path
+    w.create_reader.should_not == w.create_reader
+  end
+
+  it "returns an IndexReader with the same path" do
+    w = Polecat::IndexWriter.new @path
+    w.create_reader.path.should == w.path
+  end
+end