jbe/bsw@0: --[[--
jbe/bsw@0: json_string =  -- JavaScript code representing the given datum (with quotes, if needed)
jbe/bsw@0: encode.json(
jbe/bsw@0:   obj          -- true, false, nil or a number or string
jbe/bsw@0: )
jbe/bsw@0: 
jbe/bsw@0: This function encodes any native datatype or atom in JavaScript object notation (JSON).
jbe@1: TODO: can't distinguish unambiguously between empty object and empty list!
jbe/bsw@0: 
jbe/bsw@0: --]]--
jbe/bsw@0: 
jbe@1: -- TODO: check if numeric representations are JSON compatible
jbe@1: 
jbe/bsw@0: function encode.json(obj)
jbe/bsw@0:   if obj == nil then
jbe/bsw@0:     return "null";
jbe/bsw@0:   elseif atom.has_type(obj, atom.boolean) then
jbe/bsw@0:     return tostring(obj)
jbe/bsw@0:   elseif atom.has_type(obj, atom.number) then
jbe/bsw@0:     return tostring(obj)
jbe@1:   elseif type(obj) == "table" then
jbe@1:     local parts = {}
jbe@1:     local first = true
jbe@1:     if #obj > 0 then
jbe@1:       parts[#parts+1] = "["
jbe@1:       for idx, value in ipairs(obj) do
jbe@1:         if first then
jbe@1:           first = false
jbe@1:         else
jbe@1:           parts[#parts+1] = ","
jbe@1:         end
jbe@1:         parts[#parts+1] = tostring(value)
jbe@1:       end
jbe@1:       parts[#parts+1] = "]"
jbe@1:     else
jbe@1:       parts[#parts+1] = "{"
jbe@1:       for key, value in pairs(obj) do
jbe@1:         if first then
jbe@1:           first = false
jbe@1:         else
jbe@1:           parts[#parts+1] = ","
jbe@1:         end
jbe@1:         parts[#parts+1] = encode.json(key)
jbe@1:         parts[#parts+1] = ":"
jbe@1:         parts[#parts+1] = encode.json(value)
jbe@1:       end
jbe@1:       parts[#parts+1] = "}"
jbe@1:     end
jbe@1:     return table.concat(parts)
jbe/bsw@0:   else
jbe/bsw@0:     return
jbe@1:       '"' ..
jbe/bsw@0:       string.gsub(atom.dump(obj), ".",
jbe/bsw@0:         function (char)
jbe@1:           if char == '\r' then return '\\r'  end
jbe@1:           if char == '\n' then return '\\n'  end
jbe@1:           if char == '\\' then return '\\\\' end
jbe@1:           if char == '"'  then return '\\"'  end
jbe@1:           if char == '/'  then return '\\/'  end  -- allowed according to RFC4627, needed for </script>
jbe/bsw@0:           local byte = string.byte(char)
jbe/bsw@0:           if byte < 32 then return string.format("\\u%04x", byte) end
jbe/bsw@0:         end
jbe/bsw@0:       ) ..
jbe@1:       '"'
jbe/bsw@0:   end
jbe/bsw@0: end