pairtree.rb in pairtree-0.1.0

- old
+ new
@@ -1,7 +1,78 @@
 require 'pairtree/identifier'
 require 'pairtree/path'
 require 'pairtree/obj'
 require 'pairtree/root'
-require 'pairtree/client'
+
+require 'fileutils'
+
 module Pairtree
+  class IdentifierError < Exception; end
+  class PathError < Exception; end
+  class VersionMismatch < Exception; end
+
+  SPEC_VERSION = 0.1
+  
+  ##
+  # Instantiate a pairtree at a given path location
+  # @param [String] path The path in which the pairtree resides
+  # @param [Hash] args Pairtree options
+  # @option args [String] :prefix (nil) the identifier prefix used throughout the pairtree
+  # @option args [String] :version (Pairtree::SPEC_VERSION) the version of the pairtree spec that this tree conforms to
+  # @option args [Boolean] :create (false) if true, create the pairtree and its directory structure if it doesn't already exist
+  def self.at path, args = {}
+    args = { :prefix => nil, :version => nil, :create => false }.merge(args)
+    args[:version] ||= SPEC_VERSION
+    args[:version] = args[:version].to_f
+    
+    root_path = File.join(path, 'pairtree_root')
+    prefix_file = File.join(path, 'pairtree_prefix')
+    version_file = File.join(path, pairtree_version_filename(args[:version]))
+    existing_version_file = Dir[File.join(path, "pairtree_version*")].sort.last
+    
+    if args.delete(:create)
+      if File.exists?(path) and not File.directory?(path)
+        raise PathError, "#{path} exists, but is not a valid pairtree root"
+      end
+      FileUtils.mkdir_p(root_path)
+
+      unless File.exists? prefix_file
+        File.open(prefix_file, 'w') { |f| f.write(args[:prefix].to_s) }
+      end
+      
+      if existing_version_file
+        if existing_version_file != version_file
+          stored_version = existing_version_file.scan(/([0-9]+)_([0-9]+)/).flatten.join('.').to_f
+          raise VersionMismatch, "Version #{args[:version]} specified, but #{stored_version} found."
+        end
+      else
+        args[:version] ||= SPEC_VERSION
+        version_file = File.join(path, pairtree_version_filename(args[:version]))
+        File.open(version_file, 'w') { |f| f.write %{This directory conforms to Pairtree Version #{args[:version]}. Updated spec: http://www.cdlib.org/inside/diglib/pairtree/pairtreespec.html} }
+        existing_version_file = version_file
+      end
+    else
+      unless File.directory? root_path
+        raise PathError, "#{path} does not point to an existing pairtree"
+      end
+    end
+
+    stored_prefix = File.read(prefix_file)
+    unless args[:prefix].nil? or args[:prefix].to_s == stored_prefix
+      raise IdentifierError, "Specified prefix #{args[:prefix].inspect} does not match stored prefix #{stored_prefix.inspect}"
+    end
+    args[:prefix] = stored_prefix
+
+    stored_version = existing_version_file.scan(/([0-9]+)_([0-9]+)/).flatten.join('.').to_f
+    args[:version] ||= stored_version
+    unless args[:version] == stored_version
+      raise VersionMismatch, "Version #{args[:version]} specified, but #{stored_version} found."
+    end
+        
+    Pairtree::Root.new(File.join(path, 'pairtree_root'), args)
+  end
+
+  private
+  def self.pairtree_version_filename(version)
+    "pairtree_version#{version.to_s.gsub(/\./,'_')}"
+  end
 end