Cannonical interface sorting

texttree.py

from itertools import groupby
import re
import typing as t

WEIGHTS: t.Dict[str, int] = {".": 10, "/": 20}


def split_interface_tuple(interface: str) -> t.Tuple[str, ...]:
    """Crappy parser-combinator hacky-hack"""
    head = interface.rstrip(r"/\0123456789. ")
    rest = interface[len(head) :].lstrip()
    idx = 0
    # we mutate tail's reference, so mypy needs help
    tail: t.Tuple[str, ...] = (head,)
    while idx < len(rest):
        part = ""
        while idx < len(rest) and re.match(r"[a-zA-Z\-]", rest[idx]):
            part += rest[idx]
            idx += 1
        if part:
            tail = (*tail, part)
        part = ""
        while idx < len(rest) and re.match(r"[0-9]", rest[idx]):
            part += rest[idx]
            idx += 1
        if part:
            tail = (*tail, part)
        part = ""
        while idx < len(rest) and re.match(r"[./]", rest[idx]):
            part += rest[idx]
            idx += 1
        if part:
            tail = (*tail, part)
    return tail


def insert_nodes(node, values) -> None:
    """Recursively updates a tree from a list of values.

    This function mutates the node dict in place."""
    if not values:
        return
    val = values[0]
    weight = WEIGHTS.get(val, 30)
    if (val, weight) not in node:
        node[(val, weight)] = {}
    insert_nodes(node[(val, weight)], values[1:])


def iter_tree(node, parents=[]):
    """Walk a tree of interface name parts.

    Weights are assigned based on domain logic to produce a
    'cannonical' ordering of names.  Child nodes are visited
    first by priority of weight, then lexicographically."""
    for _, items in groupby(node.keys(), lambda t: t[1]):
        for item in sorted(items, key=lambda v: v[0]):
            if not node[item]:
                yield "".join(parents + [item[0]])
                continue
            parents.append(item[0])
            yield from iter_tree(node[item], list(parents))
            parents.pop()


if __name__ == "__main__":
    test_data = [
        "Fa0/0/2",
        "Fa0/0/1",
        "Fa1/0/1.100",
        "Fa1/0.100",
        "Fa0/0/1.101",
        "Fa0/0/1.100",
        "Fa0/0/1.100",
        "Fa0/0/2.200",
        "Gi0/1",
        "Gi0/0/1",
        "Gi0/0/2",
        "Gi1/0/1",
        "Te1/0/1",
        "Gi1/0/2",
        "Vlan42",
        "loopback99",
        "Port-channel75",
    ]
    root: t.Dict[str, t.Any] = {}
    for ifname in test_data:
        insert_nodes(root, split_interface_tuple(ifname))

    for thing in iter_tree(root):
        print(thing)