require 'html5lib/constants'

module HTML5lib

class Filter
    include Enumerable
    def initialize(source)
        @source = source
    end
end

class OptionalTagFilter < Filter
    def slider
        previous1 = previous2 = nil
        @source.each do |token|
            yield previous2, previous1, token if previous1 != nil
            previous2 = previous1
            previous1 = token
        end
        yield previous2, previous1, nil
    end

    def each
        slider do |previous, token, nexttok|
            type = token[:type]
            if type == :StartTag
                yield token unless token[:data].empty? and is_optional_start(token[:name], previous, nexttok)
            elsif type == :EndTag
                yield token unless is_optional_end(token[:name], nexttok)
            else
                yield token
            end
        end
    end

    def is_optional_start(tagname, previous, nexttok)
        type = nexttok ? nexttok[:type] : nil
        if tagname == 'html'
            # An html element's start tag may be omitted if the first thing
            # inside the html element is not a space character or a comment.
            return ![:Comment, :SpaceCharacters].include?(type)
        elsif tagname == 'head'
            # A head element's start tag may be omitted if the first thing
            # inside the head element is an element.
            return type == :StartTag
        elsif tagname == 'body'
            # A body element's start tag may be omitted if the first thing
            # inside the body element is not a space character or a comment,
            # except if the first thing inside the body element is a script
            # or style element and the node immediately preceding the body
            # element is a head element whose end tag has been omitted.
            if [:Comment, :SpaceCharacters].include?(type)
                return false
            elsif type == :StartTag
                # XXX: we do not look at the preceding event, so we never omit
                # the body element's start tag if it's followed by a script or
                # a style element.
                return !%w[script style].include?(nexttok[:name])
            else
                return true
            end
        elsif tagname == 'colgroup'
            # A colgroup element's start tag may be omitted if the first thing
            # inside the colgroup element is a col element, and if the element
            # is not immediately preceeded by another colgroup element whose
            # end tag has been omitted.
            if type == :StartTag
                # XXX: we do not look at the preceding event, so instead we never
                # omit the colgroup element's end tag when it is immediately
                # followed by another colgroup element. See is_optional_end.
                return nexttok[:name] == "col"
            else
                return false
            end
        elsif tagname == 'tbody'
            # A tbody element's start tag may be omitted if the first thing
            # inside the tbody element is a tr element, and if the element is
            # not immediately preceeded by a tbody, thead, or tfoot element
            # whose end tag has been omitted.
            if type == :StartTag
                # omit the thead and tfoot elements' end tag when they are
                # immediately followed by a tbody element. See is_optional_end.
                if previous and previous[:type] == :EndTag and \
                  %w(tbody thead tfoot).include?(previous[:name])
                    return false
                end

                return nexttok[:name] == 'tr'
            else
                return false
            end
        end
        return false
    end

    def is_optional_end(tagname, nexttok)
        type = nexttok ? nexttok[:type] : nil
        if %w[html head body].include?(tagname)
            # An html element's end tag may be omitted if the html element
            # is not immediately followed by a space character or a comment.
            return ![:Comment, :SpaceCharacters].include?(type)
        elsif %w[li optgroup option tr].include?(tagname)
            # A li element's end tag may be omitted if the li element is
            # immediately followed by another li element or if there is
            # no more content in the parent element.
            # An optgroup element's end tag may be omitted if the optgroup
            # element is immediately followed by another optgroup element,
            # or if there is no more content in the parent element.
            # An option element's end tag may be omitted if the option
            # element is immediately followed by another option element,
            # or if there is no more content in the parent element.
            # A tr element's end tag may be omitted if the tr element is
            # immediately followed by another tr element, or if there is
            # no more content in the parent element.
            if type == :StartTag
                return nexttok[:name] == tagname
            else
                return type == :EndTag || type == nil
            end
        elsif %w(dt dd).include?(tagname)
            # A dt element's end tag may be omitted if the dt element is
            # immediately followed by another dt element or a dd element.
            # A dd element's end tag may be omitted if the dd element is
            # immediately followed by another dd element or a dt element,
            # or if there is no more content in the parent element.
            if type == :StartTag
                return %w(dt dd).include?(nexttok[:name])
            elsif tagname == 'dd'
                return type == :EndTag || type == nil
            else
                return false
            end
        elsif tagname == 'p'
            # A p element's end tag may be omitted if the p element is
            # immediately followed by an address, blockquote, dl, fieldset,
            # form, h1, h2, h3, h4, h5, h6, hr, menu, ol, p, pre, table,
            # or ul  element, or if there is no more content in the parent
            # element.
            if type == :StartTag
                return %w(address blockquote dl fieldset form h1 h2 h3 h4 h5
                    h6 hr menu ol p pre table ul).include?(nexttok[:name])
            else
                return type == :EndTag || type == nil
            end
        elsif tagname == 'colgroup'
            # A colgroup element's end tag may be omitted if the colgroup
            # element is not immediately followed by a space character or
            # a comment.
            if [:Comment, :SpaceCharacters].include?(type)
                return false
            elsif type == :StartTag
                # XXX: we also look for an immediately following colgroup
                # element. See is_optional_start.
                return nexttok[:name] != 'colgroup'
            else
                return true
            end
        elsif %w(thead tbody).include? tagname
            # A thead element's end tag may be omitted if the thead element
            # is immediately followed by a tbody or tfoot element.
            # A tbody element's end tag may be omitted if the tbody element
            # is immediately followed by a tbody or tfoot element, or if
            # there is no more content in the parent element.
            # A tfoot element's end tag may be omitted if the tfoot element
            # is immediately followed by a tbody element, or if there is no
            # more content in the parent element.
            # XXX: we never omit the end tag when the following element is
            # a tbody. See is_optional_start.
            if type == :StartTag
                return %w(tbody tfoot).include?(nexttok[:name])
            elsif tagname == 'tbody'
                return (type == :EndTag or type == nil)
            else
                return false
            end
        elsif tagname == 'tfoot'
            # A tfoot element's end tag may be omitted if the tfoot element
            # is immediately followed by a tbody element, or if there is no
            # more content in the parent element.
            # XXX: we never omit the end tag when the following element is
            # a tbody. See is_optional_start.
            if type == :StartTag
                return nexttok[:name] == 'tbody'
            else
                return type == :EndTag || type == nil
            end
        elsif %w(td th).include? tagname
            # A td element's end tag may be omitted if the td element is
            # immediately followed by a td or th element, or if there is
            # no more content in the parent element.
            # A th element's end tag may be omitted if the th element is
            # immediately followed by a td or th element, or if there is
            # no more content in the parent element.
            if type == :StartTag
                return %w(td th).include?(nexttok[:name])
            else
                return type == :EndTag || type == nil
            end
        end
        return false
    end
end

class HTMLSerializer
    CDATA_ELEMENTS = %w[style script xmp iframe noembed noframes noscript]

    def self.serialize(stream, options = {})
        new(options).serialize(stream)
    end

    def initialize(options={})
        @quote_attr_values = false
        @quote_char = '"'
        @use_best_quote_char = true
        @minimize_boolean_attributes = true

        @use_trailing_solidus = false
        @space_before_trailing_solidus = true

        @omit_optional_tags = true
        @sanitize = false

        @strip_whitespace = false

        @inject_meta_charset = true

        options.each do |name, value|
            next unless %w(quote_attr_values quote_char use_best_quote_char
              minimize_boolean_attributes use_trailing_solidus
              space_before_trailing_solidus omit_optional_tags sanitize
              strip_whitespace inject_meta_charset).include? name.to_s
            @use_best_quote_char = false if name.to_s == 'quote_char'
            instance_variable_set("@#{name}", value)
        end

        @errors = []
    end

    def serialize(treewalker, encoding=nil)
        in_cdata = false
        @errors = []
        if encoding and @inject_meta_charset
            treewalker = filter_inject_meta_charset(treewalker, encoding)
        end
        if @strip_whitespace
            treewalker = filter_whitespace(treewalker)
        end
        if @sanitize
            require 'html5lib/sanitizer'
            treewalker = HTMLSanitizeFilter.new(treewalker)
        end
        if @omit_optional_tags
            treewalker = OptionalTagFilter.new(treewalker)
        end

        result = []
        treewalker.each do |token|
            type = token[:type]
            if type == :Doctype
                doctype = "<!DOCTYPE %s>" % token[:name]
                if encoding
                    result << doctype.encode(encoding)
                else
                    result << doctype
                end

            elsif [:Characters, :SpaceCharacters].include? type
                if type == :SpaceCharacters or in_cdata
                    if in_cdata and token[:data].include?("</")
                        serializeError(_("Unexpected </ in CDATA"))
                    end
                    if encoding
                        result << token[:data].encode(encoding, errors || "strict")
                    else
                        result << token[:data]
                    end
                elsif encoding
                    result << token[:data].replace("&", "&amp;") \
                        .encode(encoding, unicode_encode_errors)
                else
                    result << token[:data] \
                        .gsub("&", "&amp;") \
                        .gsub("<", "&lt;")  \
                        .gsub(">", "&gt;")
                end

            elsif [:StartTag, :EmptyTag].include? type
                name = token[:name]
                if CDATA_ELEMENTS.include?(name)
                    in_cdata = true
                elsif in_cdata
                    serializeError(_("Unexpected child element of a CDATA element"))
                end
                attrs = token[:data].to_a
                attrs.sort()
                attributes = []
                for k,v in attrs
                    if encoding
                        k = k.encode(encoding)
                    end
                    attributes << ' '

                    attributes << k
                    if not @minimize_boolean_attributes or \
                      (!(BOOLEAN_ATTRIBUTES[name]||[]).include?(k) \
                      and !BOOLEAN_ATTRIBUTES[:global].include?(k))
                        attributes << "="
                        if @quote_attr_values or v.empty?
                            quote_attr = true
                        else
                            quote_attr = (SPACE_CHARACTERS + %w(< > " ')).any? {|c| v.include?(c)}
                        end
                        v = v.gsub("&", "&amp;")
                        if encoding
                            v = v.encode(encoding, unicode_encode_errors)
                        end
                        if quote_attr
                            quote_char = @quote_char
                            if @use_best_quote_char
                                if v.index("'") and !v.index('"')
                                    quote_char = '"'
                                elsif v.index('"') and !v.index("'")
                                    quote_char = "'"
                                end
                            end
                            if quote_char == "'"
                                v = v.gsub("'", "&#39;")
                            else
                                v = v.gsub('"', "&quot;")
                            end
                            attributes << quote_char << v << quote_char
                        else
                            attributes << v
                        end
                    end
                end
                if VOID_ELEMENTS.include?(name) and @use_trailing_solidus
                    if @space_before_trailing_solidus
                        attributes << " /"
                    else
                        attributes << "/"
                    end
                end
                if encoding
                    result << "<%s%s>" % [name.encode(encoding), attributes.join('')]
                else
                    result << "<%s%s>" % [name, attributes.join('')]
                end

            elsif type == :EndTag
                name = token[:name]
                if CDATA_ELEMENTS.include?(name)
                    in_cdata = false
                elsif in_cdata
                    serializeError(_("Unexpected child element of a CDATA element"))
                end
                end_tag = "</%s>" % name
                if encoding
                    end_tag = end_tag.encode(encoding)
                end
                result << end_tag

            elsif type == :Comment
                data = token[:data]
                if data.index("--")
                    serializeError(_("Comment contains --"))
                end
                comment = "<!--%s-->" % token[:data]
                if encoding
                    comment = comment.encode(encoding, unicode_encode_errors)
                end
                result << comment

            else
                serializeError(token[:data])
            end
        end
        result.join('')
    end

    def render(treewalker, encoding=nil)
        if encoding
            return "".join(list(serialize(treewalker, encoding)))
        else
            return "".join(list(serialize(treewalker)))
        end
    end

    def serializeError(data="XXX ERROR MESSAGE NEEDED")
        # XXX The idea is to make data mandatory.
        @errors.push(data)
        if @strict
            raise SerializeError
        end
    end

    def filter_inject_meta_charset(treewalker, encoding)
        done = false
        for token in treewalker
            if not done and token[:type] == :StartTag \
              and token[:name].lower() == "head"
                yield({:type => :EmptyTag, :name => "meta", \
                    :data => {"charset" => encoding}})
            end
            yield token
        end
    end

    def filter_whitespace(treewalker)
        raise NotImplementedError
    end
end

# Error in serialized tree
class SerializeError < Exception
end
end