# The function takes as input an attribute name, as a list of name's components,
# and the value of the attribute.
# The accumulator is used for recursion.
#
# It returns the tree representation of the JSON object representing the lsit of attributes
# eg:
#  Given the following attributes:
#  {"occi.example.attr1", "value1"}
#  {"occi.example.attr2.with.additional.namespace", "value2"}
#  {"occi.example.attr1.type", "value3"}
#
#  1/ attributes names are splitted:
#    {[ "occi", "example", "attr1" ], "value1"}
#    {[ "occi", "example", "attr2", "with", "additional", "namespace" ], "value2"}
#    {[ "occi", "example", "attr1", "type" ], "value3"}
#
#  2/ this pair list is given to insert_attr and should output:
# {[
#    { "occi", [
#          { "example", [
#                { "attr1", "value },
#                { "attr2", [
#                      { "with", [
#                          { "additional", [
#                              {"namespace", "value2"}
#                             ]}
#                        ]}
#                   ]},
#                { "attr1", [
#                    { "type": "value3" }
#                 ]}
#              ]}
#        ]}
#  ]}
#
# This structure of tuple and lists is then transformed into JSON syntax with a pretty
# straightforward algorithm: 
#  { "key", "value" }  -> "key": "value"
#  [ {"key1", "value1"}, {"key2", "value2"}] -> { "key1": "value1", "key2": "value2" }
# etc.
#

# Name: list of attribute name components
# Value: any object
# Acc: a list of { Key, Value } pairs
function insert_attr(Name, Value, Acc):
  if length(Name) == 1:
    # Last name component, we insert the value
    return prepend({Name, Value}, Acc);

  { ActualNS, Children } = first(Acc);
  if first(Name) == ActualNS:
    # This name component is already present in Acc,
    # insert attribute in the existing tree
    Tree = insert_attr(tail(Name), Value, Children);
    return prepend({Name, Tree}, tail(Acc));
  else:
    # This name component does not exist in Acc,
    # creates a new branch
    Tree = insert_attr(tail(Name), Value, []);
    return prepend({Name, Tree}, Acc);