require 'glue/flexob'
require 'glue/configuration'

module Glue

# A template is a text file with embeded Ruby code. The template
# processor converts the original text file to ruby code and
# then evaluates this code to produce the result of the 
# template transformation.

module TemplateMixin

  # Convert a template to actual Ruby code, ready to be 
  # evaluated.
  #
  # [+template+] 
  #    The template as a String.
  #
  # [+buffer+]
  #    The variable to act as a buffer where the ruby code
  #    for this template will be generated. Passed as a
  #    String.
  #
  #  [+base_dir+]
  #    The base directory where the templates reside.
  
  def compile_template(template, buffer = '@out', base_dir = Dir.pwd)
    text = template.dup

    # Strip the xml header! (interracts with the following gsub!)
    text.gsub!(/<\?xml.*\?>/, "")

    # Statically include sub-template files.
    # The target file is included at compile time.
    #
    # gmosx: must be xformed before the <?r pi.
    #
    # Example:    
    # <?include href="root/myfile.sx" ?>

    text.gsub!(/<\?include href=["|'](.*?)["|'](.*)\?>/) do |match|
      itext = File.read("#{base_dir}/#$1")
      itext.gsub!(/<\?xml.*\?>/, '')
      itext.gsub!(/<\/?root(.*?)>/m, ' ');
      itext
    end

    # Transform include instructions <include href="xxx" />
    # must be transformed before the processinc instructions.
    # Useful to include fragments cached on disk
    #
    # gmosx, FIXME: NOT TESTED! test and add caching.
    # add load_statically_included fixes.

    text.gsub!(/<include href=["|'](.*?)["|'](.*)(.?)\/>/) do |match|
      "<?r File.read( '\#{@dispatcher.root}/#$1' ?>"
    end
    
    # xform render/inject instructions <render href="xxx" />
    # must be transformed before the processinc instructions.

    text.gsub!(/<(render|inject) href=["|'](.*?)["|'](.*)(.?)\/>/) do |match|
      "<?r render '#$2' ?>"
    end

    # Remove <root> elements. typically removed by xslt but lets
    # play it safe. The <root> element is typically added to
    # template files to make them XHTML valid.
    
    text.gsub!(/<(\/)?root>/, '')
    
    # Transform the processing instructions, use <?r as
    # a marker.
    
    text.gsub!(/\?>/, "; #{buffer} << %^")
    text.gsub!(/<\?r(\s?)/, "^; ")
    
    # Transform alternative code tags. 
    # (very useful in xsl stylesheets)
    
    text.gsub!(/<\/ruby>/, "; #{buffer} << %^")
    text.gsub!(/<ruby>/, "^; ")

    # Also handle erb/asp/jsp style tags. Those tags
    # *cannot* be used with an xslt stylesheet.

    text.gsub!(/%>/, "; #{buffer} << %^")
    text.gsub!(/<%/, "^; ")

    # Alterative versions of interpolation.
    # (very useful in xsl stylesheets)
    # Example: #\my_val\
    
    text.gsub!(/\#\\(.*?)\\/, '#{\1}')

    # Alternative for entities.
    # (useful in xsl stylesheets)
    # Examples: %nbsp;, %rquo;

    text.gsub!(/%(\S*?);/, '&\1;')

    # Compile time ruby code. This code is evaluated when
    # compiling the template and the result injected directly
    # into the result. Usefull for example to prevaluate
    # localization. Just use the #[] marker instead of #{}.
    
    text.gsub!(/\#\[(.*?)\]/) do |match|
      eval($1)
    end
    
    text =  "#{buffer} << %^" + text + "^"

    return text
  end

  # Evaluate the template.
  #
  # [+ruby+]
  #    A String containing the compiled template
  #    code.
  #
  #  [+binding+]
  #    The evaluation binding for the rendering.

  def evaluate_template(ruby, the_binding = nil)
    eval(ruby, the_binding)
  end

  # Compile and render the template.
  
  def process_template(template, buffer = '@out', the_binding = nil)
    evaluate_template(compile_template(template, buffer), the_binding)
  end

end

# A helper class that provides access to the Template methods
# as singleton methods.

class Template
  
  # The default root directory where template files reside.

  if File.exist?('template')
    default_root = 'template'
  elsif File.exist?('src/template')
    default_root = 'src/template'
  else
    default_root = 'public'
  end
  
  setting :root, :default => default_root, :doc => 'The default root directory where template files reside'

  # The default template name.
  
  setting :default, :default => 'index', :doc => 'The default template name'
  
  # The default template file extension.
  
  setting :extension, :default => 'xhtml', :doc => 'The default template file extension'

  # Strip xml comments from templates?
  
  setting :strip_xml_comments, :default => false, :doc => 'Strip xml comments from templates?'

  class << self
    include TemplateMixin
    alias_method :compile, :compile_template
    alias_method :transform, :compile_template
    alias_method :evaluate, :evaluate_template
    alias_method :process, :process_template
  end
  
  include TemplateMixin
  
  # Helper.
  
  def render(template)
    str = ''
    process_template(template, 'str', binding)
    return str
  end
end

# A Template that reads from files and also 
# provides a simple but effective caching scheme.
# An intuitive binding mechanism provides the
# expansion environment.

class FileTemplate < Flexob
  include TemplateMixin

  @@compiled_template_cache = {}

  attr_accessor :template_filename

  def initialize(filename = nil)
    super
    @template_filename = filename
  end
  
  def process
    __out__ = ''
    
    unless compiled = @@compiled_template_cache[@template_filename]
      template = File.read(@template_filename)
      compiled = compile_template(template, '__out__')
      @@compiled_template_cache[@template_filename] = compiled
    end
    
    evaluate_template(compiled, binding)  
    
    return __out__
  end
end

end

# * George Moschovitis <gm@navel.gr>