Merge pull request #18 from cooperwalbrun/conversion-threshold

Avoid Converting CIDRs to a New Prefix If the Result Is Over 256 CIDRs Long

CHANGELOG.md

@@ -9,72 +9,92 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 Nothing currently!
 
+## v0.3.2 - 2022-11-20
+
+### Changed
+
+* The `--prefix` argument no longer converts CIDR blocks which would result in more than 256 CIDRs
+  (previously this threshold was 1024) (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+
 ## v0.3.1 - 2022-11-20
 
 ### Changed
 
-* IPv6 subnets in an `associating` state are now recognized by `aws-cidr-finder` (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* IPv6 subnets in an `associating` state are now recognized by `aws-cidr-finder` (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.3.0 - 2022-11-16
 
 ### Added
 
-* Added project configuration for using `mypy` to statically type-check code during development and in the GitHub Actions pipeline (by [@cooperwalbrun](https://github.com/cooperwalbrun))
-* Implemented proper typing throughout the source code and added a `py.typed` file per PEP 561 (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Added project configuration for using `mypy` to statically type-check code during development and
+  in the GitHub Actions pipeline (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Implemented proper typing throughout the source code and added a `py.typed` file per PEP 561 (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.2.4 - 2022-11-08
 
 ### Added
 
-* Added support for Python 3.11 to the pipeline and project configuration (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Added support for Python 3.11 to the pipeline and project configuration (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.2.3 - 2022-10-12
 
 ### Changed
 
-* The author email address in the wheel's metadata is now set to a real email address (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* The author email address in the wheel's metadata is now set to a real email address (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.2.2 - 2022-06-13
 
 ### Changed
 
-* CIDR blocks that are in an `associating` state (instead of just the `associated` state) will now be considered in this CLI's functionality (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* CIDR blocks that are in an `associating` state (instead of just the `associated` state) will now
+  be considered in this CLI's functionality (by [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.2.1 - 2022-06-11
 
 ### Changed
 
-* Refactored the code to reduce code duplication between the IPv4 and IPv6 functionalities (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Refactored the code to reduce code duplication between the IPv4 and IPv6 functionalities (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.2.0 - 2022-06-11
 
 ### Added
 
-* Implemented support for IPv6 VPCs via the `--ipv6` CLI flag (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Implemented support for IPv6 VPCs via the `--ipv6` CLI flag (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ### Changed
 
-* The structure of the JSON output when specifying the `--json` CLI flag now includes VPC names, VPC CIDRs, and informational messages (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* The structure of the JSON output when specifying the `--json` CLI flag now includes VPC names, VPC
+  CIDRs, and informational messages (by [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ### Fixed
 
-* Gracefully handle situations where the requested `--prefix` causes a huge number of CIDRs to be returned (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Gracefully handle situations where the requested `--prefix` causes a huge number of CIDRs to be
+  returned (by [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.1.2 - 2022-05-08
 
 ### Changed
 
-* Enabled querying by a prefix which is lower than at least one prefix in the returned CIDR list (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Enabled querying by a prefix which is lower than at least one prefix in the returned CIDR list (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.1.1 - 2022-02-20
 
 ### Fixed
 
-* Fixed `find_subnet_holes` slowness and incorrectness issues (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Fixed `find_subnet_holes` slowness and incorrectness issues (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))
 
 ## v0.1.0 - 2022-02-17
 
 ### Added
 
 * Created the project (by [@cooperwalbrun](https://github.com/cooperwalbrun))
-* Implemented the initial functionality of finding subnet "holes" in IPv4 VPCs (by [@cooperwalbrun](https://github.com/cooperwalbrun))
+* Implemented the initial functionality of finding subnet "holes" in IPv4 VPCs (by
+  [@cooperwalbrun](https://github.com/cooperwalbrun))

README.md

@@ -16,11 +16,11 @@ Use `aws-cidr-finder -h` to see command options.
 
 ### An Example
 
-It is easiest to see the value of this tool through an example. Pretend that we have the following
-VPC setup in AWS:
+It is easiest to see the value of this tool through an example. Imagine that we have the following
+setup in AWS:
 
 * A VPC whose CIDR is `172.31.0.0/16`, with a `Name` tag of `Hello World`
-* Six subnets in that VPC whose CIDRs are:
+* Six subnets inside that VPC whose CIDRs are:
   * `172.31.0.0/20`
   * `172.31.16.0/20`
   * `172.31.32.0/20`
@@ -93,7 +93,7 @@ aws-cidr-finder --profile myprofile --prefix 18
 We should see this output:
 
 ```
-Note: skipping CIDR '172.31.96.0/19' because its prefix (19) is larger than the requested prefix (18)
+Note: skipping CIDR '172.31.96.0/19' because its prefix (19) is numerically greater than the requested prefix (18)
 
 Here are the available CIDR blocks in the 'Hello World' VPC (VPC CIDR block '172.31.0.0/16'):
 CIDR               IP Count

src/aws_cidr_finder/__main__.py

@@ -57,7 +57,7 @@ def _parse_arguments(arguments: list[str]) -> dict[str, Any]:
 def main() -> None:
     arguments = _parse_arguments(_get_arguments())
 
-    boto = BotoWrapper(arguments.get("PROFILE"), arguments.get("REGION"))
+    boto = BotoWrapper(profile_name=arguments.get("PROFILE"), region=arguments.get("REGION"))
 
     ipv6: bool = arguments["ipv6"]
 

src/aws_cidr_finder/boto_wrapper.py

@@ -48,7 +48,7 @@ def _parse_subnet_cidrs(subnets: list[SubnetTypeDef], *, ipv6: bool) -> list[str
 
 
 class BotoWrapper:  # pragma: no cover
-    def __init__(self, profile_name: Optional[str], region: Optional[str]):
+    def __init__(self, *, profile_name: Optional[str], region: Optional[str]):
         if profile_name is not None:
             boto = boto3.session.Session(profile_name=profile_name, region_name=region)
         else:

src/aws_cidr_finder/core.py

@@ -148,11 +148,11 @@ def break_down_to_desired_prefix(cidrs: list[str], prefix: int) -> tuple[list[st
         old_prefix = get_prefix(cidr)
         if old_prefix > prefix:
             messages.append((
-                f"Note: skipping the CIDR '{cidr}' because its prefix ({old_prefix}) is larger "
-                f"than the requested prefix ({prefix})"
+                f"Note: skipping the CIDR '{cidr}' because its prefix ({old_prefix}) is "
+                f"numerically greater than the requested prefix ({prefix})"
             ))
             continue
-        elif prefix - old_prefix > 9:
+        elif prefix - old_prefix > 8:
             messages.append((
                 f"Warning: skipping the CIDR '{cidr}' because its prefix is only {old_prefix} "
                 f"and converting it to a list of CIDRs with a prefix of {prefix} will result "