Add functionality to parse multiple prefixes (#35)

This change introduces a new function `multiprefixloop` as a convenience
function for splitting multiple cidr prefixes govorned by the number of
bits and required offset inside each prefix.

This function might be used in instances such as dividing additional VPC
cidrs into subnets without requiring multiple instances of the funtion
to be declared in a given composition.

Additionally this contributes towards issue #2 by introducing happy path
unit tests for each function.

Makefile

@@ -1,8 +1,12 @@
 render:
 			@for file in examples/xr-*.yaml; do \
+			 	echo ""; \
 				echo "Rendering $$file..."; \
 				crossplane beta render \
 					"$$file" \
 					apis/composition.yaml \
 					examples/functions.yaml; \
 			done
+
+debug:
+			go run . --insecure --debug

README.md

@@ -5,98 +5,119 @@ A [Crossplane](https://www.crossplane.io/)
 for calculating Classless Inter-Domain Routing
 ([CIDR](https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing))
 numbers.
+
 A CIDR is an IP address allocation method that is used to improve
 data routing efficiency on the internet.
 
 ## Overview
 
-This composition function offers 4 HashiCorp compatible
-IP Network Functions plus one custom wrapper. Follow the
-function links for detailed explanations of the function
-semantics.
+This composition function offers 4 HashiCorp compatible IP Network Functions
+plus two custom wrappers. Follow the function links for detailed explanations of
+the function semantics.
+
 - [cidrhost](https://developer.hashicorp.com/terraform/language/functions/cidrhost)
 - [cidrnetmask](https://developer.hashicorp.com/terraform/language/functions/cidrnetmask)
 - [cidrsubnet](https://developer.hashicorp.com/terraform/language/functions/cidrsubnet)
 - [cidrsubnets](https://developer.hashicorp.com/terraform/language/functions/cidrsubnets)
 - cidrsubnetloop wraps [cidrsubnet](https://developer.hashicorp.com/terraform/language/functions/cidrsubnet)
+- multiprefixloop wraps [cidrsubnets](https://developer.hashicorp.com/terraform/language/functions/cidrsubnets)
 
 To use this function, apply the following
 [functions.yaml](examples/functions.yaml)
 to your Crossplane management cluster.
-```
+
+```bash
 cat <<EOF|kubectl apply -f -
 apiVersion: pkg.crossplane.io/v1beta1
 kind: Function
 metadata:
   name: upbound-function-cidr
 spec:
-  package: xpkg.upbound.io/upbound/function-cidr:v0.1.0
+  package: xpkg.upbound.io/upbound/function-cidr:v0.4.0
 EOF
 ```
+
 Call the function from a Crossplane composition as described below.
 
 ## Terminology
+
 The `cidrfunc` IP Network Functions have various input parameters.
 Below are brief descriptions for context.
 
 - `prefix` must be given in CIDR notation, as defined in [RFC 4632 section 3.1.](https://datatracker.ietf.org/doc/html/rfc4632#section-3.1)
-- `hostnum` is a whole number that can be represented as a binary integer with no more than the number of digits remaining in the address after the given prefix.
-- `newbits` is the number of additional bits with which to extend the prefix. For example, if given a prefix ending in /16 and a newbits value of 4, the resulting subnet address will have length /20.
-- `netnum` is a whole number that can be represented as a binary integer with no more than newbits binary digits, which will be used to populate the additional bits added to the prefix.
+- `hostnum` is a whole number that can be represented as a binary integer with
+  no more than the number of digits remaining in the address after the given
+  prefix.
+- `newbits` is the number of additional bits with which to extend the prefix.
+  For example, if given a prefix ending in /16 and a newbits value of 4, the
+  resulting subnet address will have length /20.
+- `netnum` is a whole number that can be represented as a binary integer with no
+  more than newbits binary digits, which will be used to populate the additional
+  bits added to the prefix.
 
 ## Usage
+
 Specify the `cidrfunc` calculation type in the composition function input.
+
 Valid values are as follows:
-```
+
+```yaml
 - cidrhost
 - cidrnetmask
 - cidrsubnet
 - cidrsubnets
 - cidrsubnetloop
+- multiprefixloop
 ```
-Specify a custom `outputfield` in the function input parameters
-when the output should appear at a different path
-than the respective `status.atFunction.cidr` sub field default path.
+
+Specify a custom `outputfield` in the function input parameters when the output
+should appear at a different path than the respective `status.atFunction.cidr`
+sub field default path.
 
 All `cidrfunc` IP Network Functions require a CIDR `prefix` as input.
-Provide the `prefix` directly in the
-function input or specify a `prefixfield` in the XR where
-the function shall pick up the `prefix` value.
 
-Function input field names ending in `field` indicate that
-the function shall read the field path value from the specified
-field path in the XR.
+Provide the `prefix` directly in the function input or specify a `prefixfield`
+in the XR where the function shall pick up the `prefix` value.
+
+Function input field names ending in `field` indicate that the function shall
+read the field path value from the specified field path in the XR.
 
 ### cidrhost
+
 The `cidrhost cidrfunc` requires a `hostnum` or `hostnumfield` as
 function input. `hostnum` is an integer.
 
 ### cidrnetmask
-The `cidrnetmask cidrfunc` does not require additional parameters
-beyond the `prefix`. The `prefix` can be read from an XR field
-when the `prefixField` path is specified in the function input
-instead of a `prefix` value.
+
+The `cidrnetmask cidrfunc` does not require additional parameters beyond the
+`prefix`. The `prefix` can be read from an XR field when the `prefixField` path
+is specified in the function input instead of a `prefix` value.
 
 ### cidrsubnet
-The `cidrhost cidrsubnet` reauires a `netnum` or `netnumfield`,
-and a `newbits` or `newbitsfield` as function input.
+
+The `cidrhost cidrsubnet` requires a `netnum` or `netnumfield`, and a `newbits`
+or `newbitsfield` as function input.
 
 `netNum` is an integer.
 `newBits` is one integer in an array of integers.
 
 ### cidrsubnets
-The `cidrhost cidrsubnets` reauires a `newBits`
- or `newBitsField` as function input.
+
+The `cidrhost cidrsubnets` requires a `newBits` or `newBitsField` as function
+input.
 
 `newBits` is an array of integers.
 
 ### cidrsubnetloop
+
 The `cidrhost cidrsubnetloop` reauires the following input fields.
+
 - `newBits` (integer array) or `newBitsField`
 - `netNumCount` (integer) or `netNumCountField`
 - `netNumItems` (string array) or `netNumItemsField`
 - `offset` or `offsetfield`
-** netNumCount and netNumItems are mutually exclusive **
+
+**`netNumCount` and `netNumItems` are mutually exclusive**
 
 The `cidrsubnetloop` wrapper calculates `cidrsubnet` CIDRs using
 the `prefix` and `newBits` parameters as input. It performs the
@@ -105,7 +126,27 @@ iteration from `iteration`+`offset`. The iterations are either from
 0 to `netNumCount` -1 or from 0 to number of items in `netNumItemsCount`
 or their respective values from their XR field references.
 
+### multiprefixloop
+
+This is an additional convenience function that takes a list of objects, each
+describing a cidr prefix to split and returns the result as a
+`map[string][]string` key'd on the prefix for that block.
+
+It is most useful for scenarios where your composition requires multiple cidr
+prefixes, such as splitting VPC additional CIDRs for subnet creation.
+
+The `multiprefixloop` function requires a list of inputs with each input
+containing:
+
+- `prefix` The CIDR prefix to create subnets for
+- `newBits` An integer array defining how to split the prefix
+- `offset` An optional bit size to start the subnet range after
+
+If `offset` is specified, this is prepended to the `newBits` field immediately
+before calculations and then removed after the calculation is completed.
+
 ## Testing The Function
+
 Clone the repo. Run `make debug` and in a second terminal run `make render`
-and examine the output. Corresponding compositions and XR yaml can be
-found in the `examples` folder.
+and examine the output. Corresponding compositions and XR yaml can be found in
+the `examples` folder.

apis/composition.yaml

@@ -14,10 +14,10 @@ spec:
       input:
         apiVersion: cidr.fn.crossplane.io/v1beta1
         kind: Parameters
-        cidrFunc: spec.parameters.cidrFunc
+        cidrFuncField: spec.parameters.cidrFunc
         prefixField: spec.parameters.cidrBlock
         newBitsField: spec.parameters.newBits
         netNumItemsField: spec.parameters.azs
         hostNumField: spec.parameters.hostNum
         offsetField: spec.parameters.offset
-        outputField: spec.parameters.output
+        multiPrefixField: spec.parameters.subnets

apis/definition.yaml

@@ -33,6 +33,18 @@ spec:
                         - cidrhost
                         - cidrnetmask
                         - cidrsubnetloop
+                        - multiprefixloop
+                    subnets:
+                      type: array
+                      items:
+                        type: object
+                        properties:
+                          prefix:
+                            type: string
+                          newBits:
+                            type: array
+                            items:
+                              type: integer
                     cidrBlock:
                       type: string
                     newBits:

examples/xr-cidrhost.yaml

@@ -7,4 +7,3 @@ spec:
     cidrFunc: cidrhost
     cidrBlock: 10.0.0.0/20
     hostNum: 111
-    output: status.atFunction.cidr.hostAddress

examples/xr-cidrnetmask.yaml

@@ -6,4 +6,3 @@ spec:
   parameters:
     cidrFunc: cidrnetmask
     cidrBlock: 172.16.0.0/12
-    output: status.atFunction.cidr.netmask

examples/xr-cidrsubnet.yaml

@@ -9,4 +9,3 @@ spec:
     newBits:
       - 8
     netNum: 3
-    output: status.atFunction.cidr.subnet-a

examples/xr-multicidrsubnetsloop.yaml

@@ -0,0 +1,20 @@
+apiVersion: platform.upbound.io/v1alpha1
+kind: XCIDR
+metadata:
+  name: cidr-multiprefixloop
+spec:
+  parameters:
+    cidrFunc: multiprefixloop
+    subnets:
+      - prefix: 10.0.0.0/20
+        newBits:
+        - 8
+        - 4
+        - 2
+      - prefix: 127.0.0.0/20
+        newBits: [
+          4, 4, 4,
+          4, 4, 4,
+          5, 5, 5,
+          5, 5, 5,
+        ]