"""A VM's snapshot tree, flattened, and snapshot lookup by name."""

from __future__ import annotations

from collections.abc import Iterator
from typing import Any

from napalm_device_types.models import SnapshotDict


def _walk(nodes: list[dict[str, Any]], parent: str) -> Iterator[tuple[dict[str, Any], str]]:
    for node in nodes:
        yield node, parent
        yield from _walk(node.get("childSnapshotList", []), node.get("name", ""))


def _nodes(vm: dict[str, Any]) -> Iterator[tuple[dict[str, Any], str]]:
    return _walk((vm.get("snapshot") or {}).get("rootSnapshotList", []), "")


def snapshot_list(vm: dict[str, Any]) -> list[SnapshotDict]:
    """Every snapshot, depth first, each naming its parent (``""`` for a root)."""
    return [
        {
            "name": node.get("name", ""),
            "vm": vm.get("name", ""),
            "created": float(node.get("createTime", 0.0)),
            "description": node.get("description", ""),
            # A snapshot taken with memory records the VM as powered on.
            "has_memory": node.get("state") == "poweredOn",
            "parent": parent,
        }
        for node, parent in _nodes(vm)
    ]


def find_snapshot(vm: dict[str, Any], name: str) -> str:
    """MoRef of the one snapshot called ``name``.

    Raises ``ValueError`` when there is none -- or more than one: vSphere does
    not require snapshot names to be unique, and choosing one of two
    candidates could delete or roll back to the wrong state.
    """
    matches = [node["snapshot"] for node, _ in _nodes(vm) if node.get("name") == name]
    if not matches:
        raise ValueError(f"VM {vm.get('name')!r} has no snapshot named {name!r}")
    if len(matches) > 1:
        raise ValueError(
            f"VM {vm.get('name')!r} has {len(matches)} snapshots named {name!r}; "
            "rename one in vSphere first"
        )
    return matches[0]