require 'htree/scan'
require 'htree/htmlinfo'
require 'htree/text'
require 'htree/tag'
require 'htree/leaf'
require 'htree/doc'
require 'htree/elem'
require 'htree/raw_string'
require 'htree/context'
require 'htree/encoder'
require 'htree/fstr'

module HTree
  # HTree.parse parses <i>input</i> and return a document tree.
  # represented by HTree::Doc.
  #
  # <i>input</i> should be a String or
  # an object which respond to read or open method.
  # For example, IO, StringIO, Pathname, URI::HTTP and URI::FTP are acceptable.
  # Note that the URIs need open-uri.
  #
  # HTree.parse guesses <i>input</i> is HTML or not and XML or not.
  #
  # If it is guessed as HTML, the default namespace in the result is set to http://www.w3.org/1999/xhtml
  # regardless of <i>input</i> has XML namespace declaration or not nor even it is pre-XML HTML.
  #
  # If it is guessed as HTML and not XML, all element and attribute names are downcaseed. 
  #
  # If opened file or read content has charset method,
  # HTree.parse decode it according to $KCODE before parsing.
  # Otherwise HTree.parse assumes the character encoding of the content is
  # compatible to $KCODE.
  # Note that the charset method is provided by URI::HTTP with open-uri.
  def HTree.parse(input)
    HTree.with_frozen_string_hash {
      parse_as(input, false)
    }
  end

  # HTree.parse_xml parses <i>input</i> as XML and
  # return a document tree represented by HTree::Doc.
  #
  # It behaves almost same as HTree.parse but it assumes <i>input</i> is XML
  # even if no XML declaration.
  # The assumption causes following differences.
  # * doesn't downcase element name.
  # * The content of <script> and <style> element is PCDATA, not CDATA.
  def HTree.parse_xml(input)
    HTree.with_frozen_string_hash {
      parse_as(input, true)
    }
  end

  # :stopdoc:

  def HTree.parse_as(input, is_xml)
    input_charset = nil
    if input.respond_to? :read # IO, StringIO
      input = input.read
      input_charset = input.charset if input.respond_to? :charset
    elsif input.respond_to? :open # Pathname, URI with open-uri
      input.open {|f|
        input = f.read
        input_charset = f.charset if f.respond_to? :charset
      }
    end
    if input_charset && input_charset != Encoder.internal_charset
      if input.respond_to? :encode
        input = input.encode(Encoder.internal_charset, input_charset)
      else
        input = Iconv.conv(Encoder.internal_charset, input_charset, input)
      end
    end

    tokens = []
    is_xml, is_html = HTree.scan(input, is_xml) {|token|
      tokens << token
    }
    context = is_html ? HTMLContext : DefaultContext
    structure_list = parse_pairs(tokens, is_xml, is_html)
    structure_list = fix_structure_list(structure_list, is_xml, is_html)
    nodes = structure_list.map {|s| build_node(s, is_xml, is_html, context) }
    Doc.new(nodes)
  end

  def HTree.parse_pairs(tokens, is_xml, is_html)
    stack = [[nil, nil, []]]
    tokens.each {|token|
      case token[0]
      when :stag
        stag_raw_string = token[1]
        stagname = stag_raw_string[Pat::Name]
        stagname = stagname.downcase if !is_xml && is_html
        stagname = HTree.frozen_string(stagname)
        stack << [stagname, stag_raw_string, []]
      when :etag
        etag_raw_string = token[1]
        etagname = etag_raw_string[Pat::Name]
        etagname = etagname.downcase if !is_xml && is_html
        etagname = HTree.frozen_string(etagname)
        matched_elem = nil
        stack.reverse_each {|elem|
          stagname, _, _ = elem
          if stagname == etagname
            matched_elem = elem
            break
          end
        }
        if matched_elem
          until matched_elem.equal? stack.last
            stagname, stag_raw_string, children = stack.pop
            stack.last[2] << [:elem, stag_raw_string, children]
          end
          stagname, stag_raw_string, children = stack.pop
          stack.last[2] << [:elem, stag_raw_string, children, etag_raw_string]
        else
          stack.last[2] << [:bogus_etag, etag_raw_string]
        end
      else
        stack.last[2] << token
      end
    }
    elem = nil
    while 1 < stack.length
      _, stag_raw_string, children = stack.pop
      stack.last[2] << [:elem, stag_raw_string, children]
    end
    stack[0][2]
  end

  def HTree.fix_structure_list(structure_list, is_xml, is_html)
    result = []
    rest = structure_list.dup
    until rest.empty?
      structure = rest.shift
      if structure[0] == :elem
        elem, rest2 = fix_element(structure, [], [], is_xml, is_html)
        result << elem
        rest = rest2 + rest
      else
        result << structure
      end
    end
    result
  end

  def HTree.fix_element(elem, excluded_tags, included_tags, is_xml, is_html)
    stag_raw_string = elem[1]
    children = elem[2]
    if etag_raw_string = elem[3]
      return [:elem, stag_raw_string, fix_structure_list(children, is_xml, is_html), etag_raw_string], []
    else
      tagname = stag_raw_string[Pat::Name]
      tagname = tagname.downcase if !is_xml && is_html
      if ElementContent[tagname] == :EMPTY
        return [:elem, stag_raw_string, []], children
      else
        if ElementContent[tagname] == :CDATA
          possible_tags = []
        else
          possible_tags = ElementContent[tagname]
        end
        if possible_tags
          excluded_tags2 = ElementExclusions[tagname]
          included_tags2 = ElementInclusions[tagname]
          excluded_tags |= excluded_tags2 if excluded_tags2
          included_tags |= included_tags2 if included_tags2
          containable_tags = (possible_tags | included_tags) - excluded_tags
          uncontainable_tags = ElementContent.keys - containable_tags
        else
          # If the tagname is unknown, it is assumed that any element
          # except excluded can be contained.
          uncontainable_tags = excluded_tags
        end
        fixed_children = []
        rest = children
        until rest.empty?
          if rest[0][0] == :elem
            elem = rest.shift
            elem_tagname = elem[1][Pat::Name]
            elem_tagname = elem_tagname.downcase if !is_xml && is_html
            if uncontainable_tags.include? elem_tagname
              rest.unshift elem
              break
            else
              fixed_elem, rest2 = fix_element(elem, excluded_tags, included_tags, is_xml, is_html)
              fixed_children << fixed_elem
              rest = rest2 + rest
            end
          else
            fixed_children << rest.shift
          end
        end
        return [:elem, stag_raw_string, fixed_children], rest
      end
    end
  end

  def HTree.build_node(structure, is_xml, is_html, inherited_context=DefaultContext)
    case structure[0]
    when :text_pcdata
      Text.parse_pcdata(structure[1])
    when :elem
      _, stag_rawstring, children, etag_rawstring = structure
      etag = etag_rawstring && ETag.parse(etag_rawstring, is_xml, is_html)
      stag = STag.parse(stag_rawstring, true, is_xml, is_html, inherited_context)
      if !children.empty? || etag ||
         stag.element_name.namespace_uri != 'http://www.w3.org/1999/xhtml' ||
         HTree::ElementContent[stag.element_name.local_name] != :EMPTY
        Elem.new!(stag,
                  children.map {|c| build_node(c, is_xml, is_html, stag.context) },
                  etag)
      else
        Elem.new!(stag)
      end
    when :emptytag
      Elem.new!(STag.parse(structure[1], false, is_xml, is_html, inherited_context))
    when :bogus_etag
      BogusETag.parse(structure[1], is_xml, is_html)
    when :xmldecl
      XMLDecl.parse(structure[1])
    when :doctype
      DocType.parse(structure[1], is_xml, is_html)
    when :procins
      ProcIns.parse(structure[1])
    when :comment
      Comment.parse(structure[1])
    when :text_cdata_content
      Text.parse_cdata_content(structure[1])
    when :text_cdata_section
      Text.parse_cdata_section(structure[1])
    else
      raise Exception, "[bug] unknown structure: #{structure.inspect}"
    end
  end

  def STag.parse(raw_string, is_stag, is_xml, is_html, inherited_context=DefaultContext)
    attrs = []
    if (is_stag ? /\A#{Pat::ValidStartTag_C}\z/o : /\A#{Pat::ValidEmptyTag_C}\z/o) =~ raw_string
      qname = $1
      $2.scan(Pat::ValidAttr_C) {
        attrs << ($5 ? [nil, $5] : [$1, $2 || $3 || $4])
      }
    elsif (is_stag ? /\A#{Pat::InvalidStartTag_C}\z/o : /\A#{Pat::InvalidEmptyTag_C}\z/o) =~ raw_string
      qname = $1
      last_attr = $3
      $2.scan(Pat::InvalidAttr1_C) {
        attrs << ($5 ? [nil, $5] : [$1, $2 || $3 || $4])
      }
      if last_attr
        /#{Pat::InvalidAttr1End_C}/o =~ last_attr
        attrs << [$1, $2 || $3]
      end
    else
      raise HTree::Error, "cannot recognize as start tag or empty tag: #{raw_string.inspect}"
    end

    qname = qname.downcase if !is_xml && is_html

    attrs.map! {|aname, aval|
      if aname
        aname = (!is_xml && is_html) ? aname.downcase : aname
        [aname, Text.parse_pcdata(aval)]
      else
        if val2name = OmittedAttrName[qname]
          aval_downcase = aval.downcase
          aname = val2name.fetch(aval_downcase, aval_downcase)
        else
          aname = aval
        end
        [aname, Text.new(aval)]
      end
    }

    result = STag.new(qname, attrs, inherited_context)
    result.raw_string = raw_string
    result
  end

  def ETag.parse(raw_string, is_xml, is_html)
    unless /\A#{Pat::EndTag_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as end tag: #{raw_string.inspect}"
    end

    qname = $1
    qname = qname.downcase if !is_xml && is_html

    result = self.new(qname)
    result.raw_string = raw_string
    result
  end

  def BogusETag.parse(raw_string, is_xml, is_html)
    unless /\A#{Pat::EndTag_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as end tag: #{raw_string.inspect}"
    end

    qname = $1
    qname = qname.downcase if !is_xml && is_html

    result = self.new(qname)
    result.raw_string = raw_string
    result
  end

  def Text.parse_pcdata(raw_string)
    fixed = raw_string.gsub(/&(?:(?:#[0-9]+|#x[0-9a-fA-F]+|([A-Za-z][A-Za-z0-9]*));?)?/o) {|s|
      name = $1
      case s
      when /;\z/
        s
      when /\A&#/
        "#{s};"
      when '&'
        '&amp;'
      else 
        if NamedCharactersPattern =~ name
          "&#{name};"
        else
          "&amp;#{name}"
        end
      end
    }
    fixed = raw_string if fixed == raw_string
    result = Text.new_internal(fixed)
    result.raw_string = raw_string
    result
  end

  def Text.parse_cdata_content(raw_string)
    result = Text.new(raw_string)
    result.raw_string = raw_string
    result
  end

  def Text.parse_cdata_section(raw_string)
    unless /\A#{Pat::CDATA_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as CDATA section: #{raw_string.inspect}"
    end

    content = $1

    result = Text.new(content)
    result.raw_string = raw_string
    result
  end

  def XMLDecl.parse(raw_string)
    unless /\A#{Pat::XmlDecl_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as XML declaration: #{raw_string.inspect}"
    end

    version = $1 || $2
    encoding = $3 || $4
    case $5 || $6
    when 'yes'
      standalone = true
    when 'no'
      standalone = false
    else
      standalone = nil
    end

    result = XMLDecl.new(version, encoding, standalone)
    result.raw_string = raw_string
    result
  end

  def DocType.parse(raw_string, is_xml, is_html)
    unless /\A#{Pat::DocType_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as XML declaration: #{raw_string.inspect}"
    end

    root_element_name = $1
    public_identifier = $2 || $3
    system_identifier = $4 || $5

    root_element_name = root_element_name.downcase if !is_xml && is_html

    result = DocType.new(root_element_name, public_identifier, system_identifier)
    result.raw_string = raw_string
    result
  end

  def ProcIns.parse(raw_string)
    unless /\A#{Pat::XmlProcIns_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as processing instruction: #{raw_string.inspect}"
    end

    target = $1
    content = $2

    result = ProcIns.new(target, content)
    result.raw_string = raw_string
    result
  end

  def Comment.parse(raw_string)
    unless /\A#{Pat::Comment_C}\z/o =~ raw_string
      raise HTree::Error, "cannot recognize as comment: #{raw_string.inspect}"
    end

    content = $1

    result = Comment.new(content)
    result.raw_string = raw_string
    result
  end

  # :startdoc:
end