module Chozo::Mixin
  # Borrowed and modified from: {https://raw.github.com/opscode/chef/11.4.0/lib/chef/mixin/params_validate.rb}
  #
  # Copyright:: Copyright (c) 2008 Opscode, Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  # 
  #     http://www.apache.org/licenses/LICENSE-2.0
  # 
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  module ParamsValidate
    # Takes a hash of options, along with a map to validate them.  Returns the original
    # options hash, plus any changes that might have been made (through things like setting
    # default values in the validation map)
    #
    # For example:
    #
    #   validate({ :one => "neat" }, { :one => { :kind_of => String }})
    # 
    # Would raise an exception if the value of :one above is not a kind_of? string.  Valid
    # map options are:
    #
    # :default:: Sets the default value for this parameter.
    # :callbacks:: Takes a hash of Procs, which should return true if the argument is valid.  
    #              The key will be inserted into the error message if the Proc does not return true:
    #                 "Option #{key}'s value #{value} #{message}!"
    # :kind_of:: Ensure that the value is a kind_of?(Whatever).  If passed an array, it will ensure 
    #            that the value is one of those types.
    # :respond_to:: Ensure that the value has a given method.  Takes one method name or an array of
    #               method names.
    # :required:: Raise an exception if this parameter is missing. Valid values are true or false, 
    #             by default, options are not required.
    # :regex:: Match the value of the paramater against a regular expression.
    # :equal_to:: Match the value of the paramater with ==.  An array means it can be equal to any
    #             of the values.
    def validate(opts, map)
      #--
      # validate works by taking the keys in the validation map, assuming it's a hash, and
      # looking for _pv_:symbol as methods.  Assuming it find them, it calls the right 
      # one.  
      #++
      raise ArgumentError, "Options must be a hash" unless opts.kind_of?(Hash)
      raise ArgumentError, "Validation Map must be a hash" unless map.kind_of?(Hash)   
      
      map.each do |key, validation|
        unless key.kind_of?(Symbol) || key.kind_of?(String)
          raise ArgumentError, "Validation map keys must be symbols or strings!"
        end
        case validation
        when true
          _pv_required(opts, key)
        when false
          true
        when Hash
          validation.each do |check, carg|
            check_method = "_pv_#{check.to_s}"
            if self.respond_to?(check_method, true)
              self.send(check_method, opts, key, carg)
            else
              raise ArgumentError, "Validation map has unknown check: #{check}"
            end
          end
        end
      end
      opts
    end
        
    def set_or_return(symbol, arg, validation)
      iv_symbol = "@#{symbol.to_s}".to_sym
      map = {
        symbol => validation
      }

      if arg == nil && self.instance_variable_defined?(iv_symbol) == true
        self.instance_variable_get(iv_symbol)
      else
        opts = validate({ symbol => arg }, { symbol => validation })
        self.instance_variable_set(iv_symbol, opts[symbol])
      end
    end
          
    private
    
      # Return the value of a parameter, or nil if it doesn't exist.
      def _pv_opts_lookup(opts, key)
        if opts.has_key?(key.to_s)
          opts[key.to_s]
        elsif opts.has_key?(key.to_sym)
          opts[key.to_sym]
        else
          nil
        end
      end
      
      # Raise an exception if the parameter is not found.
      def _pv_required(opts, key, is_required=true)
        if is_required
          if (opts.has_key?(key.to_s) && !opts[key.to_s].nil?) ||
              (opts.has_key?(key.to_sym) && !opts[key.to_sym].nil?)
            true
          else
            raise ValidationFailed, "Required argument #{key} is missing!"
          end
        end
      end
      
      def _pv_equal_to(opts, key, to_be)
        value = _pv_opts_lookup(opts, key)
        unless value.nil?
          passes = false
          Array(to_be).each do |tb|
            passes = true if value == tb
          end
          unless passes
            raise ValidationFailed, "Option #{key} must be equal to one of: #{to_be.join(", ")}!  You passed #{value.inspect}."
          end
        end
      end
      
      # Raise an exception if the parameter is not a kind_of?(to_be)
      def _pv_kind_of(opts, key, to_be)
        value = _pv_opts_lookup(opts, key)
        unless value.nil?
          passes = false
          Array(to_be).each do |tb|
            passes = true if value.kind_of?(tb)
          end
          unless passes
            raise ValidationFailed, "Option #{key} must be a kind of #{to_be}!  You passed #{value.inspect}."
          end
        end
      end
      
      # Raise an exception if the parameter does not respond to a given set of methods.
      def _pv_respond_to(opts, key, method_name_list)
        value = _pv_opts_lookup(opts, key)
        unless value.nil?
          Array(method_name_list).each do |method_name|
            unless value.respond_to?(method_name)
              raise ValidationFailed, "Option #{key} must have a #{method_name} method!"
            end
          end
        end
      end

      # Assert that parameter returns false when passed a predicate method.
      # For example, :cannot_be => :blank will raise a ValidationFailed
      # error value.blank? returns a 'truthy' (not nil or false) value.
      #
      # Note, this will *PASS* if the object doesn't respond to the method.
      # So, to make sure a value is not nil and not blank, you need to do
      # both :cannot_be => :blank *and* :cannot_be => :nil (or :required => true)
      def _pv_cannot_be(opts, key, predicate_method_base_name)
        value = _pv_opts_lookup(opts, key)
        predicate_method = (predicate_method_base_name.to_s + "?").to_sym

        if value.respond_to?(predicate_method)
          if value.send(predicate_method)
            raise ValidationFailed, "Option #{key} cannot be #{predicate_method_base_name}"
          end
        end
      end
    
      # Assign a default value to a parameter.
      def _pv_default(opts, key, default_value)
        value = _pv_opts_lookup(opts, key)
        if value == nil
          opts[key] = default_value
        end
      end
      
      # Check a parameter against a regular expression.
      def _pv_regex(opts, key, regex)
        value = _pv_opts_lookup(opts, key)
        if value != nil
          passes = false
          [ regex ].flatten.each do |r|
            if value != nil
              if r.match(value.to_s)
                passes = true
              end
            end
          end
          unless passes
            raise ValidationFailed, "Option #{key}'s value #{value} does not match regular expression #{regex.inspect}"
          end
        end
      end
      
      # Check a parameter against a hash of proc's.
      def _pv_callbacks(opts, key, callbacks)
        raise ArgumentError, "Callback list must be a hash!" unless callbacks.kind_of?(Hash)
        value = _pv_opts_lookup(opts, key)
        if value != nil
          callbacks.each do |message, zeproc|
            if zeproc.call(value) != true
              raise ValidationFailed, "Option #{key}'s value #{value} #{message}!"
            end
          end
        end
      end

      # Allow a parameter to default to @name
      def _pv_name_attribute(opts, key, is_name_attribute=true)
        if is_name_attribute
          if opts[key] == nil
            opts[key] = self.instance_variable_get("@name")
          end
        end
      end
  end
end