-- Roberto Ierusalimschy's simple/simplistic XML parser, modified to
-- fit the LxpTree interface. 

-- As an XML parser, it's quite incomplete but it works enough to
-- handle most XML-RPC servers.

-- Now supports entity unquoting as well.

-- Tag names may contain ".".

if LxpTree then return end

local Public, Private = {}, {}
LxpTree = Public

Private.unquote_entity_map = {quot='"', apos="'", amp="&", lt="<", gt=">"}

function Private.unquote_entity(name)
  local charcode
  if strsub(name, 1, 1) == "#" then
    if strsub(name, 2, 2) == "x" then
      charcode = tonumber(strsub(name, 3), 16)
    else
      charcode = tonumber(strsub(name, 2), 10)
    end
    return strchar(charcode)
  end
  local replacement = %Private.unquote_entity_map[name]
  if not replacement then error("unknown XML entity") end
  return replacement
end

function Private.unquote(s)
  local new_s = gsub(s, "&([xa-zA-Z0-9#]+);", %Private.unquote_entity)
  return new_s
end

function Private.parseargs (s)
  local arg = {}
  local unquote = %Private.unquote
  gsub(s, "(%w+)=([\"'])(.-)%2", function (w, _, a)
                                   %arg[w] = %unquote(a)
  end)
  return arg
end

function Private.parseMethod(self, s)
  return %Public.parse(s)
end

function Public.makeParser ()
  return {parse=%Private.parseMethod}
end

function Public.parse (s)
  local stack = {n=0}
  local top = {n=0}
  tinsert(stack, top)
  local ni,c,label,args, empty
  local i, j = 1, 1
  while 1 do
    ni,j,c,label,args, empty = strfind(s, "<(%/?)([%w.]+)(.-)(%/?)>", j)
    if not ni then break end
    local text = strsub(s, i, ni-1)
    if not strfind(text, "^%s*$") then
      tinsert(top, %Private.unquote(text))
    end
    if empty == "/" then  -- empty element tag
      tinsert(top, {label; n=1, attr=%Private.parseargs(args), empty=1})
    elseif c == "" then   -- start tag
      top = {label; n=1, attr=%Private.parseargs(args)}
      tinsert(stack, top)   -- new level
    else  -- end tag
      local toclose = tremove(stack)  -- remove top
      top = stack[stack.n]
      if stack.n < 1 then
        error("nothing to close with "..label)
      end
      if toclose[1] ~= label then
        error("trying to close "..toclose[1].." with "..label)
      end
      tinsert(top, toclose)
    end 
    i = j+1
  end
  local text = strsub(s, i)
  if not strfind(text, "^%s*$") then
    tinsert(stack[stack.n], %Private.unquote(text))
  end
  if stack.n > 1 then
    error("unclosed "..stack[stack.n][1])
  end
  -- Gross hack
  local lead = stack[1][1]
  if type(lead) == "string" and strfind(lead, "^<%?xml") then
    return stack[1][2]
  else
    return stack[1][1]
  end
end