class CGI
  # Base module for HTML-generation mixins.
  #
  # Provides methods for code generation for tags following
  # the various DTD element types.
  module TagMaker # :nodoc:

    # Generate code for an element with required start and end tags.
    #
    #   - -
    def nn_element_def(element)
      nOE_element_def(element, <<-END)
          if block_given?
            yield.to_s
          else
            ""
          end +
          "</#{element.upcase}>"
      END
    end

    # Generate code for an empty element.
    #
    #   - O EMPTY
    def nOE_element_def(element, append = nil)
      s = <<-END
          attributes={attributes=>nil} if attributes.kind_of?(String)
          "<#{element.upcase}" + attributes.collect{|name, value|
            next unless value
            " " + CGI::escapeHTML(name.to_s) +
            if true == value
              ""
            else
              '="' + CGI::escapeHTML(value.to_s) + '"'
            end
          }.join + ">"
      END
      s.sub!(/\Z/, " +") << append if append
      s
    end

    # Generate code for an element for which the end (and possibly the
    # start) tag is optional.
    #
    #   O O or - O
    def nO_element_def(element)
      nOE_element_def(element, <<-END)
          if block_given?
            yield.to_s + "</#{element.upcase}>"
          else
            ""
          end
      END
    end

  end # TagMaker


  #
  # Mixin module providing HTML generation methods.
  #
  # For example,
  #   cgi.a("http://www.example.com") { "Example" }
  #     # => "<A HREF=\"http://www.example.com\">Example</A>"
  #
  # Modules Http3, Http4, etc., contain more basic HTML-generation methods
  # (:title, :center, etc.).
  #
  # See class CGI for a detailed example.
  #
  module HtmlExtension


    # Generate an Anchor element as a string.
    #
    # +href+ can either be a string, giving the URL
    # for the HREF attribute, or it can be a hash of
    # the element's attributes.
    #
    # The body of the element is the string returned by the no-argument
    # block passed in.
    #
    #   a("http://www.example.com") { "Example" }
    #     # => "<A HREF=\"http://www.example.com\">Example</A>"
    #
    #   a("HREF" => "http://www.example.com", "TARGET" => "_top") { "Example" }
    #     # => "<A HREF=\"http://www.example.com\" TARGET=\"_top\">Example</A>"
    #
    def a(href = "") # :yield:
      attributes = if href.kind_of?(String)
                     { "HREF" => href }
                   else
                     href
                   end
      if block_given?
        super(attributes){ yield }
      else
        super(attributes)
      end
    end

    # Generate a Document Base URI element as a String.
    #
    # +href+ can either by a string, giving the base URL for the HREF
    # attribute, or it can be a has of the element's attributes.
    #
    # The passed-in no-argument block is ignored.
    #
    #   base("http://www.example.com/cgi")
    #     # => "<BASE HREF=\"http://www.example.com/cgi\">"
    def base(href = "") # :yield:
      attributes = if href.kind_of?(String)
                     { "HREF" => href }
                   else
                     href
                   end
      if block_given?
        super(attributes){ yield }
      else
        super(attributes)
      end
    end

    # Generate a BlockQuote element as a string.
    #
    # +cite+ can either be a string, give the URI for the source of
    # the quoted text, or a hash, giving all attributes of the element,
    # or it can be omitted, in which case the element has no attributes.
    #
    # The body is provided by the passed-in no-argument block
    #
    #   blockquote("http://www.example.com/quotes/foo.html") { "Foo!" }
    #     #=> "<BLOCKQUOTE CITE=\"http://www.example.com/quotes/foo.html\">Foo!</BLOCKQUOTE>
    def blockquote(cite = {})  # :yield:
      attributes = if cite.kind_of?(String)
                     { "CITE" => cite }
                   else
                     cite
                   end
      if block_given?
        super(attributes){ yield }
      else
        super(attributes)
      end
    end


    # Generate a Table Caption element as a string.
    #
    # +align+ can be a string, giving the alignment of the caption
    # (one of top, bottom, left, or right).  It can be a hash of
    # all the attributes of the element.  Or it can be omitted.
    #
    # The body of the element is provided by the passed-in no-argument block.
    #
    #   caption("left") { "Capital Cities" }
    #     # => <CAPTION ALIGN=\"left\">Capital Cities</CAPTION>
    def caption(align = {}) # :yield:
      attributes = if align.kind_of?(String)
                     { "ALIGN" => align }
                   else
                     align
                   end
      if block_given?
        super(attributes){ yield }
      else
        super(attributes)
      end
    end


    # Generate a Checkbox Input element as a string.
    #
    # The attributes of the element can be specified as three arguments,
    # +name+, +value+, and +checked+.  +checked+ is a boolean value;
    # if true, the CHECKED attribute will be included in the element.
    #
    # Alternatively, the attributes can be specified as a hash.
    #
    #   checkbox("name")
    #     # = checkbox("NAME" => "name")
    #
    #   checkbox("name", "value")
    #     # = checkbox("NAME" => "name", "VALUE" => "value")
    #
    #   checkbox("name", "value", true)
    #     # = checkbox("NAME" => "name", "VALUE" => "value", "CHECKED" => true)
    def checkbox(name = "", value = nil, checked = nil)
      attributes = if name.kind_of?(String)
                     { "TYPE" => "checkbox", "NAME" => name,
                       "VALUE" => value, "CHECKED" => checked }
                   else
                     name["TYPE"] = "checkbox"
                     name
                   end
      input(attributes)
    end

    # Generate a sequence of checkbox elements, as a String.
    #
    # The checkboxes will all have the same +name+ attribute.
    # Each checkbox is followed by a label.
    # There will be one checkbox for each value.  Each value
    # can be specified as a String, which will be used both
    # as the value of the VALUE attribute and as the label
    # for that checkbox.  A single-element array has the
    # same effect.
    #
    # Each value can also be specified as a three-element array.
    # The first element is the VALUE attribute; the second is the
    # label; and the third is a boolean specifying whether this
    # checkbox is CHECKED.
    #
    # Each value can also be specified as a two-element
    # array, by omitting either the value element (defaults
    # to the same as the label), or the boolean checked element
    # (defaults to false).
    #
    #   checkbox_group("name", "foo", "bar", "baz")
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="foo">foo
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="bar">bar
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="baz">baz
    #
    #   checkbox_group("name", ["foo"], ["bar", true], "baz")
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="foo">foo
    #     # <INPUT TYPE="checkbox" CHECKED NAME="name" VALUE="bar">bar
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="baz">baz
    #
    #   checkbox_group("name", ["1", "Foo"], ["2", "Bar", true], "Baz")
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="1">Foo
    #     # <INPUT TYPE="checkbox" CHECKED NAME="name" VALUE="2">Bar
    #     # <INPUT TYPE="checkbox" NAME="name" VALUE="Baz">Baz
    #
    #   checkbox_group("NAME" => "name",
    #                    "VALUES" => ["foo", "bar", "baz"])
    #
    #   checkbox_group("NAME" => "name",
    #                    "VALUES" => [["foo"], ["bar", true], "baz"])
    #
    #   checkbox_group("NAME" => "name",
    #                    "VALUES" => [["1", "Foo"], ["2", "Bar", true], "Baz"])
    def checkbox_group(name = "", *values)
      if name.kind_of?(Hash)
        values = name["VALUES"]
        name = name["NAME"]
      end
      values.collect{|value|
        if value.kind_of?(String)
          checkbox(name, value) + value
        else
          if value[-1] == true || value[-1] == false
            checkbox(name, value[0],  value[-1]) +
            value[-2]
          else
            checkbox(name, value[0]) +
            value[-1]
          end
        end
      }.join
    end


    # Generate an File Upload Input element as a string.
    #
    # The attributes of the element can be specified as three arguments,
    # +name+, +size+, and +maxlength+.  +maxlength+ is the maximum length
    # of the file's _name_, not of the file's _contents_.
    #
    # Alternatively, the attributes can be specified as a hash.
    #
    # See #multipart_form() for forms that include file uploads.
    #
    #   file_field("name")
    #     # <INPUT TYPE="file" NAME="name" SIZE="20">
    #
    #   file_field("name", 40)
    #     # <INPUT TYPE="file" NAME="name" SIZE="40">
    #
    #   file_field("name", 40, 100)
    #     # <INPUT TYPE="file" NAME="name" SIZE="40" MAXLENGTH="100">
    #
    #   file_field("NAME" => "name", "SIZE" => 40)
    #     # <INPUT TYPE="file" NAME="name" SIZE="40">
    def file_field(name = "", size = 20, maxlength = nil)
      attributes = if name.kind_of?(String)
                     { "TYPE" => "file", "NAME" => name,
                       "SIZE" => size.to_s }
                   else
                     name["TYPE"] = "file"
                     name
                   end
      attributes["MAXLENGTH"] = maxlength.to_s if maxlength
      input(attributes)
    end


    # Generate a Form element as a string.
    #
    # +method+ should be either "get" or "post", and defaults to the latter.
    # +action+ defaults to the current CGI script name.  +enctype+
    # defaults to "application/x-www-form-urlencoded".
    #
    # Alternatively, the attributes can be specified as a hash.
    #
    # See also #multipart_form() for forms that include file uploads.
    #
    #   form{ "string" }
    #     # <FORM METHOD="post" ENCTYPE="application/x-www-form-urlencoded">string</FORM>
    #
    #   form("get") { "string" }
    #     # <FORM METHOD="get" ENCTYPE="application/x-www-form-urlencoded">string</FORM>
    #
    #   form("get", "url") { "string" }
    #     # <FORM METHOD="get" ACTION="url" ENCTYPE="application/x-www-form-urlencoded">string</FORM>
    #
    #   form("METHOD" => "post", "ENCTYPE" => "enctype") { "string" }
    #     # <FORM METHOD="post" ENCTYPE="enctype">string</FORM>
    def form(method = "post", action = script_name, enctype = "application/x-www-form-urlencoded")
      attributes = if method.kind_of?(String)
                     { "METHOD" => method, "ACTION" => action,
                       "ENCTYPE" => enctype }
                   else
                     unless method.has_key?("METHOD")
                       method["METHOD"] = "post"
                     end
                     unless method.has_key?("ENCTYPE")
                       method["ENCTYPE"] = enctype
                     end
                     method
                   end
      if block_given?
        body = yield
      else
        body = ""
      end
      if @output_hidden
        body += @output_hidden.collect{|k,v|
          "<INPUT TYPE=\"HIDDEN\" NAME=\"#{k}\" VALUE=\"#{v}\">"
        }.join
      end
      super(attributes){body}
    end

    # Generate a Hidden Input element as a string.
    #