#!/usr/bin/lua
help=[[

USAGE:  wrl2json fname.wrl

PURPOSE

Lua (>=5.2)  script to convert  George Hart's VRML polyhedra  files to
JSON.   

DISCLAIMER

This code is not a general  VRML to JSON converter.  It rather assumes
the particular  structure of  the VRML  fileset of  George Hart  to be
found at  http://www.georgehart.com/virtual-polyhedra/vp.html. This is
a  quick-and-dirty solution  with  no guarantee.   It extracts  title,
point and  facet data from  a polyhedron file  and writes them  into a
simple JSON file named fname.js. 

COPYRIGHT 

(c)  Juergen  Fuhrmann, 2013,  juergen-fuhrmann@web.de

LICENSE 

This file is in the public domain
]]



if #arg<1 then print(help) os.exit() end

wrlname=arg[1]
jsname=wrlname:gsub('wrl$', 'js')

wrl=io.open(wrlname,"r")
json=io.open(jsname,"w")


function split (line)
   local tbn={}   
   string.gsub(line,"([%w.%+%-%[%]%{%}_]+)",function(s) table.insert(tbn,s) end)
   return tbn
end

points={}
faces={}
title=""
for line in wrl:lines() do 
  tokens=split(line)

  if tokens[1]=="DEF" and tokens[2]=="Title" and tokens[3]=="Info" and tokens[4]=="{" then
     grab_title0=true
  elseif tokens[1]=="string" and grab_title0 then
     title=tokens[2] for i=3,#tokens do  title=title.." "..tokens[i] end
     grab_title0=false
  elseif tokens[1]=="point" and tokens[2]=="[" then 
     grab_points=true 
--       print("grab points")	      				  
  elseif  tokens[1]=="IndexedFaceSet" and tokens[2]=="{" then 
    grab_faces0=true 	      				  
  elseif  tokens[1]=="coordIndex" and tokens[2]=="[" and grab_faces0 then 
    grab_faces=true 
--    print("grab faces")	      				  
  elseif tokens[1]=="]" then 
     grab_points=false
     grab_faces=false
     grab_faces0=false
--     print("end grab")
  elseif grab_points then
    local point={} for i=1,#tokens do table.insert(point,tonumber(tokens[i])) end	
    table.insert(points,point)
  elseif grab_faces then
    assert(tokens[#tokens]=="-1")
    local face={} 
    for i=1,#tokens-1 do 
        local ip=tonumber(tokens[i])+1
        assert(ip>0) 
	assert(ip<=#points)
	table.insert(face,ip) 
    end	
    table.insert(faces,face)
  end
end

json:write("{\n")
   json:write(string.format('  "title" : "%s",\n',title))
   json:write(string.format('  "data_source" : "http://www.georgehart.com/virtual-polyhedra/vrml/%s",\n',wrlname))
   json:write(string.format('  "data_author" : "George W. Hart, george@georgehart.com",\n'))
   json:write(string.format('  "conversion_author" : "Juergen Fuhrmann, juergen-fuhrmann@web.de",\n'))
   json:write(string.format('  "license" : "Freely distributable for noncommercial purposes",\n'))
   json:write(string.format('  "points_offset" : 1, \n'))
   json:write('  "points" : [\n') 
   for i=1,#points do
      json:write("    [")  
      for j=1,#points[i]  do   
         json:write(points[i][j]) 
	 if j<#points[i] then  json:write(", ") end
       end 
       if i<#points then 
          json:write("],\n")
       else
          json:write("]\n")
       end
   end		 
   json:write('  ],\n') 
   json:write('  "faces" : [\n') 
   for i=1,#faces do
      json:write("    [")  
      for j=1,#faces[i]  do   
         json:write(faces[i][j])  
	 if j<#faces[i] then  json:write(", ") end
      end  			   
      if i<#faces then 
          json:write("],\n")
      else
          json:write("]\n")
      end
   end		 
   json:write('  ]\n') 
json:write("}\n")

json:close()