html.lua

-- $Id: html.lua,v 1.2 2007-05-12 04:37:20 tclua Exp $



module(..., package.seeall)



entity = {

  nbsp = " ",

  lt = "<",

  gt = ">",

  quot = "\"",

  amp = "&",

}



-- keep unknown entity as is

setmetatable(entity, {

  __index = function (t, key)

    return "&" .. key .. ";"

  end

})



block = {

  "address",

  "blockquote",

  "center",

  "dir", "div", "dl",

  "fieldset", "form",

  "h1", "h2", "h3", "h4", "h5", "h6", "hr", 

  "isindex",

  "menu",

  "noframes",

  "ol",

  "p",

  "pre",

  "table",

  "ul",

}



inline = {

  "a", "abbr", "acronym", "applet",

  "b", "basefont", "bdo", "big", "br", "button",

  "cite", "code",

  "dfn",

  "em",

  "font",

  "i", "iframe", "img", "input",

  "kbd",

  "label",

  "map",

  "object",

  "q",

  "s", "samp", "select", "small", "span", "strike", "strong", "sub", "sup",

  "textarea", "tt",

  "u",

  "var",

}



tags = {

  a = { empty = false },

  abbr = {empty = false} ,

  acronym = {empty = false} ,

  address = {empty = false} ,

  applet = {empty = false} ,

  area = {empty = true} ,

  b = {empty = false} ,

  base = {empty = true} ,

  basefont = {empty = true} ,

  bdo = {empty = false} ,

  big = {empty = false} ,

  blockquote = {empty = false} ,

  body = { empty = false, },

  br = {empty = true} ,

  button = {empty = false} ,

  caption = {empty = false} ,

  center = {empty = false} ,

  cite = {empty = false} ,

  code = {empty = false} ,

  col = {empty = true} ,

  colgroup = {

    empty = false,

    optional_end = true,

    child = {"col",},

  },

  dd = {empty = false} ,

  del = {empty = false} ,

  dfn = {empty = false} ,

  dir = {empty = false} ,

  div = {empty = false} ,

  dl = {empty = false} ,

  dt = {

    empty = false,

    optional_end = true,

    child = {

      inline,

      "del",

      "ins",

      "noscript",

      "script",

    },

  },

  em = {empty = false} ,

  fieldset = {empty = false} ,

  font = {empty = false} ,

  form = {empty = false} ,

  frame = {empty = true} ,

  frameset = {empty = false} ,

  h1 = {empty = false} ,

  h2 = {empty = false} ,

  h3 = {empty = false} ,

  h4 = {empty = false} ,

  h5 = {empty = false} ,

  h6 = {empty = false} ,

  head = {empty = false} ,

  hr = {empty = true} ,

  html = {empty = false} ,

  i = {empty = false} ,

  iframe = {empty = false} ,

  img = {empty = true} ,

  input = {empty = true} ,

  ins = {empty = false} ,

  isindex = {empty = true} ,

  kbd = {empty = false} ,

  label = {empty = false} ,

  legend = {empty = false} ,

  li = {

    empty = false,

    optional_end = true,

    child = {

      inline,

      block,

      "del",

      "ins",

      "noscript",

      "script",

    },

  },

  link = {empty = true} ,

  map = {empty = false} ,

  menu = {empty = false} ,

  meta = {empty = true} ,

  noframes = {empty = false} ,

  noscript = {empty = false} ,

  object = {empty = false} ,

  ol = {empty = false} ,

  optgroup = {empty = false} ,

  option = {

    empty = false,

    optional_end = true,

    child = {},

  },

  p = {

    empty = false,

    optional_end = true,

    child = {

      inline,

      "del",

      "ins",

      "noscript",

      "script",

    },

  } ,

  param = {empty = true} ,

  pre = {empty = false} ,

  q = {empty = false} ,

  s =  {empty = false} ,

  samp = {empty = false} ,

  script = {empty = false} ,

  select = {empty = false} ,

  small = {empty = false} ,

  span = {empty = false} ,

  strike = {empty = false} ,

  strong = {empty = false} ,

  style = {empty = false} ,

  sub = {empty = false} ,

  sup = {empty = false} ,

  table = {empty = false} ,

  tbody = {empty = false} ,

  td = {

    empty = false,

    optional_end = true,

    child = {

      inline,

      block,

      "del",

      "ins",

      "noscript",

      "script",

    },

  },

  textarea = {empty = false} ,

  tfoot = {

    empty = false,

    optional_end = true,

    child = {"tr",},

  },

  th = {

    empty = false,

    optional_end = true,

    child = {

      inline,

      block,

      "del",

      "ins",

      "noscript",

      "script",

    },

  },

  thead = {

    empty = false,

    optional_end = true,

    child = {"tr",},

  },

  title = {empty = false} ,

  tr = {

    empty = false,

    optional_end = true,

    child = {

      "td", "th",

    },

  },

  tt = {empty = false} ,

  u = {empty = false} ,

  ul = {empty = false} ,

  var = {empty = false} ,

}



setmetatable(tags, {

  __index = function (t, key)

    return {empty = false}

  end

})



-- string buffer implementation

function newbuf ()

  local buf = {

    _buf = {},

    clear =   function (self) self._buf = {}; return self end,

    content = function (self) return table.concat(self._buf) end,

    append =  function (self, s)

      self._buf[#(self._buf) + 1] = s

      return self

    end,

    set =     function (self, s) self._buf = {s}; return self end,

  }

  return buf

end



-- unescape character entities

function unescape (s)

  function entity2string (e)

    return entity[e]

  end

  return s.gsub(s, "&(#?%w+);", entity2string)

end



-- iterator factory

function makeiter (f)

  local co = coroutine.create(f)

  return function ()

    local code, res = coroutine.resume(co)

    return res

  end

end



-- constructors for token

function Tag (s) 

  return string.find(s, "^</") and

    {type = "End",   value = s} or

    {type = "Start", value = s}

end



function Text (s)

  local unescaped = unescape(s) 

  return {type = "Text", value = unescaped} 

end



-- lexer: text mode

function text (f, buf)

  local c = f:read(1)

  if c == "<" then

    if buf:content() ~= "" then coroutine.yield(Text(buf:content())) end

    buf:set(c)

    return tag(f, buf)

  elseif c then

    buf:append(c)

    return text(f, buf)

  else

    if buf:content() ~= "" then coroutine.yield(Text(buf:content())) end

  end

end



-- lexer: tag mode

function tag (f, buf)

  local c = f:read(1)

  if c == ">" then

    coroutine.yield(Tag(buf:append(c):content()))

    buf:clear()

    return text(f, buf)

  elseif c then

    buf:append(c)

    return tag(f, buf)

  else

    if buf:content() ~= "" then coroutine.yield(Tag(buf:content())) end

  end

end



function parse_starttag(tag)

  local tagname = string.match(tag, "<%s*(%w+)")

  local elem = {_attr = {}}

  elem._tag = tagname

  for key, _, val in string.gmatch(tag, "(%w+)%s*=%s*([\"'])(.-)%2", i) do

    local unescaped = unescape(val)

    elem._attr[key] = unescaped

  end

  return elem

end



function parse_endtag(tag)

  local tagname = string.match(tag, "<%s*/%s*(%w+)")

  return tagname

end



-- find last element that satisfies given predicate

function rfind(t, pred)

  local length = #t

  for i=length,1,-1 do

    if pred(t[i]) then

      return i, t[i]

    end

  end

end



function flatten(t, acc)

  acc = acc or {}

  for i,v in ipairs(t) do

    if type(v) == "table" then

      flatten(v, acc)

    else

      acc[#acc + 1] = v

    end

  end

  return acc

end



function optional_end_p(elem)

  if tags[elem._tag].optional_end then

    return true

  else

    return false

  end

end



function valid_child_p(child, parent)

  local schema = tags[parent._tag].child

  if not schema then return true end



  for i,v in ipairs(flatten(schema)) do

    if v == child._tag then

      return true

    end

  end



  return false

end



-- tree builder

function parse(f)

  local root = {_tag = "#document", _attr = {}}

  local stack = {root}

  for i in makeiter(function () return text(f, newbuf()) end) do

    if i.type == "Start" then

      local new = parse_starttag(i.value)

      local top = stack[#stack]



      while

        top._tag ~= "#document" and 

        optional_end_p(top) and

        not valid_child_p(new, top)

      do

        stack[#stack] = nil 

        top = stack[#stack]

      end



      top[#top+1] = new -- appendchild

      if not tags[new._tag].empty then 

        stack[#stack+1] = new -- push

      end

    elseif i.type == "End" then

      local tag = parse_endtag(i.value)

      local openingpos = rfind(stack, function(v) 

          if v._tag == tag then

            return true

          else

            return false

          end

        end)

      if openingpos then

        local length = #stack

        for j=length,openingpos,-1 do

          table.remove(stack, j)

        end

      end

    else -- Text

      local top = stack[#stack]

      top[#top+1] = i.value

    end

  end

  return root

end



function parsestr(s)

  local handle = {

    _content = s,

    _pos = 1,

    read = function (self, length)

      if self._pos > string.len(self._content) then return end

      local ret = string.sub(self._content, self._pos, self._pos + length - 1)

      self._pos = self._pos + length

      return ret

    end

  }

  return parse(handle)

end