require 'support/class_options'

class TextFilters
  
  define_option :default_processor, :liquid
  define_option :default_filter,    'Textile'
  define_option :logger,            nil
  
  @registered_filters = {}

  # The default create_link method...
  # Override for your specific filter, if needed, in the #define block
  def create_link(title, url)
    %Q|<a href="#{url}">#{title}</a>|
  end
  
  # Process the text with using the specified context
  def process_text(text, context, processor=nil)
    case (processor || TextFilters.default_processor)
    when :erb then process_with_erb(text, context)
    when :liquid then process_with_liquid(text, context)
    else raise "Unknown Text Processor '#{processor.to_s}'"
    end
  end
  
  class << self
    attr_reader :registered_filters
    private :new

    # Use this to create and register your TextFilters
    def define(name, &block)
      begin
        p = new
        p.instance_eval(&block)
        if p.respond_to? :render_text
          registered_filters[name] = p
        else
          raise "#render_text isn't implemented in this class"
        end
      rescue LoadError
        TextFilters.logger.debug "Filter '#{name}' was not included: #{$!}" unless TextFilters.logger.nil?
      rescue
        TextFilters.logger.debug "Filter '#{name}' was not included: #{$!}" unless TextFilters.logger.nil?
      end
    end

    def [](name)
      registered_filters[name || TextFilters.default_filter]
    end
    
    def all
      registered_filters
    end

    def render_text(text, name=nil)
      registered_filters[name].render_text(text)
    end

    def process_text(text, context=nil, name=nil, processor=nil)
      registered_filters[name].process_text(text, context, processor)
    end

    # Call
    def transform(text, context=nil, name=nil, processor=nil)
      render_text( process_text(text, context, name, processor), name )
    end
  end
  
private

  # This is an instance method so that it won't puke on requiring
  # a non-existant library until it's being registered -- the only
  # place I can really capture the LoadError
  def require(name)
    Kernel.require name
  end

  # Use ERB to process text...
  def process_with_erb(text, context)
    begin
      ERB.new( text ).result( context.get_binding )
    rescue
      raise "ERB Error: #{$!}"
    end
  end

  # Use Liquid to process text...
  def process_with_liquid(text, context={})
    begin
      context = context.stringify_keys if context.respond_to? :stringify_keys
      Liquid::Template.parse(text).render(context)
    rescue
      raise "Liquid Error: #{$!}"
    end
  end
  
end

class Hash
  # Having the method_missing catchall in conjunction with get_binding 
  # allows us to use the hash as a Context for ERB
  def method_missing(meth, *arg)
    if self.has_key? meth.to_s
      self[meth.to_s]
    else
      super
    end
  end
  # Gets the binding object for use with ERB
  def get_binding
    binding
  end
end