lib/aladdin/config.rb in aladdin-0.0.5 vs lib/aladdin/config.rb in aladdin-0.0.6

@@ -1,14 +1,15 @@
 # ~*~ encoding: utf-8 ~*~
-
 module Aladdin
 
   # Raised when there is a configuration error.
   class ConfigError < StandardError; end
 
-  # Configuration options for Aladdin.
-  class Config
+  # Configuration options for Aladdin. Gets all of its values from {FILE}.
+  # Values in this file should not be trusted because they are given by the
+  # user.
+  class Config < Hash
 
     # Name of configuration file.
     FILE = 'manifest.json'
 
     # Default configuration options.
@@ -17,35 +18,65 @@
         'bin' => 'make',
         'arg_prefix' => ''
        },
       'title' => 'Lesson X',
       'description' => 'This is a placeholder description. You should provide your own',
-      'categories' => []
+      'categories' => [],
+      'static_paths' => %w(images)
     }
 
     # Creates a new configuration from the file at the given path. Merges the
     # configuration hash parsed from the file with {DEFAULTS}. Raises
     # {ConfigError} if the file could not be read or parsed.
     # @param [String] root            path to lesson root
     def initialize(root)
-      path = File.expand_path FILE, root
-      case
-      when (not File.exist? path)
-        ConfigError.new("We couldn't find a manifest file at #{path}")
-      when (not File.readable? path)
-        ConfigError.new("We found a manifest file at #{path}, but couldn't " +
-          "read it. Please ensure that the permissions are set correctly.")
-      else
-        config = ::JSON.parse(File.read path)
-        @config = DEFAULTS.deep_merge config
-      end
+      @path = File.expand_path FILE, root
+      ensure_readable
+      super nil
+      merge! DEFAULTS.deep_merge ::JSON.parse File.read @path
+      ensure_valid
     rescue ::JSON::JSONError => e
       raise ConfigError.new e.message
     end
 
-    # @return [Hash] a hash copy of the configuration options
-    def to_hash
-      @config.clone
+    private
+
+    # Raises {ConfigError} unless the configuration file exists and is
+    # readable.
+    def ensure_readable
+      missing unless File.exist? @path
+      not_readable unless File.readable? @path
+    end
+
+    # Raises {ConfigError} unless the all of the values in the supplied
+    # configuration have the same type as those in {DEFAULTS}.
+    def ensure_valid(defaults=DEFAULTS, supplied=self)
+      supplied.each do |key, value|
+        bad_type(key, defaults[key], value) unless value.is_a? defaults[key].class
+        ensure_valid(defaults[key], value) if Hash === value
+      end
+    end
+
+    def missing
+      raise ConfigError.new <<-eos.squish
+        We expected a manifest file at #{@path}, but couldn't find it. Please
+        ensure that you have a file named #{Aladdin::Config::File} at the root
+        of your lesson directory.
+      eos
+    end
+
+    def not_readable
+      raise ConfigError.new <<-eos.squish
+        We found a manifest file at #{@path}, but couldn't open it for reading.
+        Please ensure that you have the permissions to read the file.
+      eos
+    end
+
+    def bad_type(key, expected, actual)
+      raise ConfigError.new <<-eos.squish
+        The #{key} option in the manifest file should be a #{expected.class.name}
+        instead of a #{actual.class.name}.
+      eos
     end
 
   end
 
 end