def insert(self, string, next_id=0, string_pos=0, at_node=None, at_chain_pos=0):
"""
Finds ``string`` in the subtrie if it exists. Inserts it if it didn't already exist.
:param next_id: Value of next pointer to be used. If ``new_insertion`` is ``True``, then a new matching node was created, so the caller should increment its own ``next_id``.
:returns: tuple (new_insertion (boolean), id (integer))
"""
self.size_valid = False
if at_node is None:
node, chain_pos, string_pos = self.follow_trie(string, string_pos)
else:
node = at_node
chain_pos = at_chain_pos
if string_pos < 0 and not node.starts_chain:
# If the node starts a chain then we will have to split it.
# Chained nodes cannot have pointers.
if node.pointer is None:
node.pointer = next_id
return True, node.pointer
else:
return False, node.pointer
if string_pos >= 0:
new_node = self._convert_remaining_string_to_chain(string, string_pos, next_id)
else:
new_node = None
if node.starts_chain:
# Y is a branching and/or matching node.
# Insert X at...
# Case 1:
# -a-*(^bc)-Y (node has in-edge of 'a', its chain is 'bc', and insert happens at start of chain)
# -> -a-*-b-*(c)-Y
# \-X
# Case 2:
# -a-*(b^c)-Y
# -> -a-*-b-*-c-*-Y
# \-X
# Case 3:
# -a-*(bc^)-Y
# -> -a-*-b-*-c-*-Y
# \-X
# Case 4:
# String already exists within chained node, special cased in each one
chain_left, chain_right = node.chain[:chain_pos], node.chain[chain_pos:]
# General rules:
# new_node is the root of the new subtree for the new string.
# the old node ('node')'s chain is cut off.
# new_node_left is the last letter in chain_left and branches at least 2.
# new_node_right is the right part of the chain and takes the old node's children.
if len(chain_left) == 0 or new_node is None and chain_pos == -1: # Cases 1 and 4
if new_node is None:
chain_right = node.chain
if len(chain_right) > 1: # a
new_node_right = Node(True, chain_right[0], len(chain_right)-1, chain=chain_right[1:])
else: # b
new_node_right = Node(False, chain_right[0], 1)
new_node_right.children = node.children
node.starts_chain = False
node.chain = []
node.children = {new_node_right.in_edge: new_node_right}
if new_node is None:
node.pointer = next_id
else:
node.children[new_node.in_edge] = new_node
elif chain_pos >= 0 and len(chain_left) < len(node.chain): # Case 2
if len(chain_left) > 1: # a
node.chain = node.chain[:chain_pos-1]
else: # b
node.starts_chain = False
node.chain = []
new_node_left = Node(False, chain_left[-1], 1)
if len(chain_right) > 1: # c
new_node_right = Node(True, chain_right[0], len(chain_right)-1, chain=chain_right[1:])
else: # d
new_node_right = Node(False, chain_right[0], 1)
new_node_right.children = node.children
node.children = {new_node_left.in_edge: new_node_left}
new_node_left.children[new_node_right.in_edge] = new_node_right
if new_node is None:
new_node_left.pointer = next_id
else:
new_node_left.children[new_node.in_edge] = new_node
elif len(chain_right) == 0: # Case 3
new_node_left = Node(False, chain_left[-1], 2)
new_node_left.children = node.children
node.children = {new_node_left.in_edge: new_node_left}
if new_node is None:
new_node_left.pointer = next_id
else:
new_node_left.children[new_node.in_edge] = new_node
if len(chain_left) > 1: # a
node.chain = chain_left[:-1]
else: # b
node.starts_chain = False
node.chain = []
else:
node.add_child(string[string_pos], new_node)
return True, next_id
