### Example XR and Resources Manifest

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/example/multistep/README.md

Defines an example XR, a S3 Bucket resource, and a S3 BucketACL resource, illustrating the desired state for the multistep pipeline.

```yaml
---
apiVersion: example.crossplane.io/v1
kind: XR
metadata:
  name: example-xr
status:
  conditions:
  - lastTransitionTime: "2024-01-01T00:00:00Z"
    message: 'Unready resources: bucket, bucketACL'
    reason: Creating
    status: "False"
    type: Ready
---
apiVersion: s3.aws.upbound.io/v1beta1
kind: Bucket
metadata:
  annotations:
    crossplane.io/composition-resource-name: bucket
  generateName: example-xr-
  labels:
    crossplane.io/composite: example-xr
  ownerReferences:
  - apiVersion: example.crossplane.io/v1
    blockOwnerDeletion: true
    controller: true
    kind: XR
    name: example-xr
    uid: ""
spec:
  forProvider:
    region: eu-north-1
---
apiVersion: s3.aws.upbound.io/v1beta1
kind: BucketACL
metadata:
  annotations:
    crossplane.io/composition-resource-name: bucketACL
  generateName: example-xr-
  labels:
    crossplane.io/composite: example-xr
  ownerReferences:
  - apiVersion: example.crossplane.io/v1
    blockOwnerDeletion: true
    controller: true
    kind: XR
    name: example-xr
    uid: ""
spec:
  forProvider:
    acl: private
    bucketSelector:
      matchControllerRef: true
    region: eu-north-1

```

--------------------------------

### Run Function with Default Settings

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Starts the function-patch-and-transform with all default settings.

```bash
# Basic startup with default settings
function-patch-and-transform
```

--------------------------------

### Connection Detail Extraction Configuration Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/connection-details.md

An example configuration for extracting connection details from a composed resource. It specifies how to retrieve username, password, endpoint, and port.

```yaml
resources:
- name: postgres-db
  base:
    apiVersion: rds.aws.upbound.io/v1beta1
    kind: DBInstance
  connectionDetails:
  - name: username
    type: FromConnectionSecretKey
    fromConnectionSecretKey: username
  - name: password
    type: FromConnectionSecretKey
    fromConnectionSecretKey: password
  - name: endpoint
    type: FromFieldPath
    fromFieldPath: status.atProvider.endpoint
  - name: port
    type: FromValue
    value: "5432"
```

--------------------------------

### Field Path Selection Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Demonstrates how to specify source and destination fields for a patch.

```yaml
patches:
- fromFieldPath: spec.location          # Source field on composite resource
  toFieldPath: spec.forProvider.region  # Destination field on composed resource
```

--------------------------------

### Connection Secret Patching Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/connection-details.md

An example demonstrating how to configure patches for `writeConnectionSecretToRef` using `FromCompositeFieldPath` and `CombineFromComposite` types to dynamically set the secret's name and namespace.

```yaml
writeConnectionSecretToRef:
  patches:
  - type: FromCompositeFieldPath
    fromFieldPath: metadata.name
    toFieldPath: name
  - type: CombineFromComposite
    combine:
      variables:
      - fromFieldPath: metadata.namespace
      - fromFieldPath: metadata.name
      strategy: string
      string:
        fmt: "%s-creds"
    toFieldPath: namespace
```

--------------------------------

### Multiple Readiness Checks (All Must Pass)

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Example demonstrating multiple readiness checks that must all pass for the resource to be considered ready. Includes condition, non-empty field, and string match checks.

```yaml
resources:
- name: postgres
  readinessChecks:
  - type: MatchCondition
    matchCondition:
      type: Ready
      status: "True"
  - type: NonEmpty
    fieldPath: status.atProvider.endpoint
  - type: MatchString
    fieldPath: status.state
    matchString: "available"
```

--------------------------------

### Map Transform Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/transforms.md

An example showing how to use the map transform to map a string input (e.g., location) to a specific output value (e.g., region).

```yaml
patches:
- type: FromCompositeFieldPath
  fromFieldPath: spec.location
  toFieldPath: spec.forProvider.region
  transforms:
  - type: map
    map:
      US: "us-east-1"
      EU: "eu-north-1"
      ASIA: "ap-southeast-1"
```

--------------------------------

### Combine Configuration Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Combines multiple fields from the composite resource into a single output field using string formatting.

```yaml
patches:
- type: CombineFromComposite
  combine:
    variables:
    - fromFieldPath: metadata.name
    - fromFieldPath: spec.environment
    strategy: string
    string:
      fmt: "%s-%s-credentials"
  toFieldPath: metadata.generateName
```

--------------------------------

### Math Transform Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/transforms.md

An example demonstrating how to use the math transform to multiply a numeric field value. The default operation is Multiply.

```yaml
patches:
- type: FromCompositeFieldPath
  fromFieldPath: spec.cpuMillis
  toFieldPath: spec.cpu
  transforms:
  - type: math
    math:
      type: Multiply
      multiply: 1000
```

--------------------------------

### Example Patch with Match Transform

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/transforms.md

Demonstrates a patch using a 'match' transform to map composite field paths to provider configurations based on literal values or regular expressions.

```yaml
patches:
- type: FromCompositeFieldPath
  fromFieldPath: spec.instanceSize
  toFieldPath: spec.forProvider.instanceType
  transforms:
  - type: match
    match:
      patterns:
      - type: literal
        literal: small
        result: '"t2.micro"'
      - type: literal
        literal: medium
        result: '"t2.small"'
      - type: regexp
        regexp: '^large.*'
        result: '"m5.xlarge"'
      fallbackValue: '"t2.micro"'
```

--------------------------------

### Transform Pipeline Examples

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Shows sequential application of transforms to patch values. Includes map and string transforms.

```yaml
transforms:
- type: map
  map:
    US: us-east-1
    EU: eu-north-1
- type: string
  string:
    type: Format
    fmt: "region-%s"
```

--------------------------------

### Example Warning: Cannot Check Readiness

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This warning indicates a failure in the readiness check for a composed resource, but composition will continue. The resource will be marked as not ready. Fix the readiness check configuration or accept the initial not-ready state.

```go
Warning: "cannot check readiness of composed resource 'my-service': readiness check at index 0 failed"
```

--------------------------------

### Basic Ready Condition Check (Default)

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Example of a ComposedTemplate where no readinessChecks are explicitly defined, thus using the default check for the 'Ready' condition.

```yaml
resources:
- name: database
  base:
    apiVersion: rds.aws.upbound.io/v1beta1
    kind: DBInstance
  # No readinessChecks specified - defaults to checking Ready condition
```

--------------------------------

### Example Composition with Patch and Transform Function

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

This example demonstrates a Crossplane Composition that utilizes the patch-and-transform function. It defines a pipeline with a step to patch and transform resources, including common metadata, dynamic storage allocation based on composite fields, and connection details.

```yaml
apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: aws-postgresql
spec:
  compositeTypeRef:
    apiVersion: example.crossplane.io/v1
    kind: PostgreSQLInstance
  mode: Pipeline
  pipeline:
  - step: patch-and-transform
    functionRef:
      name: function-patch-and-transform
    input:
      apiVersion: pt.fn.crossplane.io/v1beta1
      kind: Resources
      patchSets:
      - name: common-metadata
        patches:
        - type: FromCompositeFieldPath
          fromFieldPath: metadata.labels
          toFieldPath: metadata.labels
          policy:
            toFieldPath: MergeObjects
      resources:
      - name: rds-instance
        base:
          apiVersion: rds.aws.upbound.io/v1beta1
          kind: DBInstance
          spec:
            forProvider:
              engine: postgres
              engineVersion: "13"
              allocated Storage: 20
              dbInstanceClass: db.t3.micro
        patches:
        - type: PatchSet
          patchSetName: common-metadata
        - type: FromCompositeFieldPath
          fromFieldPath: spec.size
          toFieldPath: spec.forProvider.allocatedStorage
          transforms:
          - type: map
            map:
              small: 20
              medium: 100
              large: 500
        - type: FromCompositeFieldPath
          fromFieldPath: spec.region
          toFieldPath: spec.forProvider.region
        connectionDetails:
        - name: username
          type: FromConnectionSecretKey
          fromConnectionSecretKey: username
        - name: password
          type: FromConnectionSecretKey
          fromConnectionSecretKey: password
        - name: endpoint
          type: FromFieldPath
          fromFieldPath: status.atProvider.endpoint
        - name: port
          type: FromValue
          value: "5432"
        readinessChecks:
        - type: MatchCondition
          matchCondition:
            type: Ready
            status: "True"
        - type: NonEmpty
          fieldPath: status.atProvider.endpoint
      writeConnectionSecretToRef:
        namespace: default
        patches:
        - type: CombineFromComposite
          combine:
            variables:
            - fromFieldPath: metadata.name
            strategy: string
            string:
              fmt: "%s-postgres-credentials"
          toFieldPath: name

```

--------------------------------

### Run Function with Combined Options

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Starts the function-patch-and-transform with a combination of debug logging, custom address, TLS certificates, and increased message size.

```bash
# Combined options
function-patch-and-transform \
  --debug \
  --address :9443 \
  --tls-server-certs-dir /etc/ssl/function \
  --max-recv-message-size 8
```

--------------------------------

### Example Error: Cannot Apply Environment Patch

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error occurs when a patch operation between the Composite Resource (XR) and the environment fails. Verify that the patch configuration correctly references valid field paths on both the XR and the environment.

```go
Error: "cannot apply the 'FromCompositeFieldPath' environment patch at index 0: [details]"
```

--------------------------------

### Use Function in Kubernetes Composition

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/README.md

Example of how to integrate the patch-and-transform function into a Kubernetes Composition pipeline.

```yaml
pipeline:
- step: patch-and-transform
  functionRef:
    name: function-patch-and-transform
  input:
    apiVersion: pt.fn.crossplane.io/v1beta1
    kind: Resources
    resources:
    # ...

```

--------------------------------

### Composition Configuration for Patch-and-Transform Function

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/function.md

Example of how to configure a Composition to use the patch-and-transform function in its pipeline.

```yaml
apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: example
spec:
  mode: Pipeline
  pipeline:
  - step: patch-and-transform
    functionRef:
      name: function-patch-and-transform
    input:
      apiVersion: pt.fn.crossplane.io/v1beta1
      kind: Resources
      resources:
      - name: my-bucket
        base:
          apiVersion: s3.aws.upbound.io/v1beta1
          kind: Bucket
          spec:
            forProvider:
              region: us-east-1
        patches:
        - type: FromCompositeFieldPath
          fromFieldPath: spec.location
          toFieldPath: spec.forProvider.region
          transforms:
          - type: map
            map:
              EU: eu-north-1
              US: us-east-1

```

--------------------------------

### Validation Error Example 2

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/validation.md

Example of a validation error for an unsupported value.

```yaml
field: "resources.connectionDetails[1].type"
reason: "Unsupported"
message: "FromUnknown is not a supported connection detail type"
```

--------------------------------

### Example Function Reference in Workflow

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This snippet shows how a previous function in a workflow might be referenced. Ensure that the referenced function produces the expected resource, in this case, a resource named 'my-resource'.

```yaml
- step: previous-function
  functionRef:
    name: other-function
  # ... this must produce a resource named "my-resource"
```

--------------------------------

### Example Warning: Cannot Extract Connection Details

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This warning signifies that connection detail extraction failed, but the processing will continue. Common causes include missing secret keys or invalid field paths. The resource will proceed without the specific connection detail.

```go
Warning: "cannot extract composite resource connection details from composed resource 'my-db': field path 'status.invalid' not found"
```

--------------------------------

### Validation Error Example 1

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/validation.md

Example of a validation error indicating a required field is missing.

```yaml
field: "resources[0].patches[0].fromFieldPath"
reason: "Required"
message: "fromFieldPath must be set for patch type FromCompositeFieldPath"
```

--------------------------------

### Example Error: Cannot Compose Connection Secret

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error indicates a failure in creating a v2 XR connection secret. It can stem from issues generating a valid secret reference or setting secret data. Ensure the `writeConnectionSecretToRef` configuration is correct and that patches reference valid XR fields.

```go
Error: "cannot compose connection secret: cannot generate connection secret reference: [details]"
```

--------------------------------

### Connection Secret Configuration Example

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Configures a connection secret for v2 XRs, including field path patches and combine transformations.

```yaml
writeConnectionSecretToRef:
  name: app-connection-secret
  namespace: default
  patches:
  - type: FromCompositeFieldPath
    fromFieldPath: metadata.namespace
    toFieldPath: namespace
  - type: CombineFromComposite
    combine:
      variables:
      - fromFieldPath: metadata.name
      - fromFieldPath: spec.environment
      strategy: string
      string:
        fmt: "%s-%s-creds"
    toFieldPath: name
```

--------------------------------

### Fatal Error: Cannot Get Observed Composed Resources

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error arises from an internal Crossplane function SDK problem during the retrieval of observed composed resources. Examine Crossplane logs for details.

```go
Error: "cannot get Observed Composed Resources"
```

--------------------------------

### Fatal Error: Cannot Get Desired Composed Resources

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error points to an internal Crossplane function SDK issue when fetching desired composed resources. Consult Crossplane logs for further insights.

```go
Error: "cannot get Desired Composed Resources"
```

--------------------------------

### Fatal Error: Cannot Get Desired Composite Resource

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error indicates an internal Crossplane function SDK issue when retrieving the desired XR. Review Crossplane logs for additional information.

```go
Error: "cannot get Desired Composite Resource"
```

--------------------------------

### Render Pipeline Resources

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/example/multistep/README.md

Use the `make render` target to visualize the XR, composition, and functions configuration for the multistep pipeline.

```bash
crossplane beta render xr.yaml composition.yaml functions.yaml -r
```

--------------------------------

### Extend Function with Custom Interfaces

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/README.md

Illustrates how to extend the function's capabilities by implementing custom interfaces for connection details extraction and readiness checking.

```go
type ConnectionDetailsExtractor interface {
    ExtractConnection(cd xpresource.Composed, ...) (managed.ConnectionDetails, error)
}

type ReadinessChecker interface {
    IsReady(ctx context.Context, o ConditionedObject, ...) (bool, error)
}

```

--------------------------------

### Default Readiness Check Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Specifies the default readiness check, which verifies if the resource has a 'Ready' condition with a 'True' status.

```go
ReadinessChecks: []ReadinessCheck{
    {
        Type: ReadinessCheckTypeMatchCondition,
        MatchCondition: &MatchConditionReadinessCheck{
            Type:   "Ready",
            Status: "True",
        },
    },
}
```

--------------------------------

### Project File Structure

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/MANIFEST.md

Overview of the generated documentation's file structure, including the purpose and line count for each file.

```text
output/
├── README.md                           (369 lines) - Project overview and architecture
├── INDEX.md                            (401 lines) - Navigation guide and quick reference
├── MANIFEST.md                         (this file) - Documentation manifest
├── configuration.md                    (577 lines) - CLI and function input configuration
├── types.md                            (745 lines) - Complete type definitions
├── errors.md                           (632 lines) - Error reference and solutions
└── api-reference/
    ├── function.md                     (100 lines) - Main composition function
    ├── patches.md                      (248 lines) - Patch application functions
    ├── transforms.md                   (455 lines) - Transform operations
    ├── connection-details.md           (288 lines) - Connection secret handling
    ├── readiness-checks.md             (342 lines) - Readiness determination
    └── validation.md                   (427 lines) - Input validation
```

--------------------------------

### Import and Use Function in Go

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/README.md

Demonstrates how to import and use the patch-and-transform function's types and structure within a Go application.

```go
import "github.com/crossplane-contrib/function-patch-and-transform/input/v1beta1"

func someFunction() {
    input := &v1beta1.Resources{}
    // ... populate input
    fn := &Function{log: logger}
    response, err := fn.RunFunction(ctx, request)
}

```

--------------------------------

### Fatal Error: Cannot Get Observed Composite Resource

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error signifies an internal Crossplane function SDK issue when retrieving the observed XR. Check Crossplane logs for more context.

```go
Error: "cannot get Observed Composite Resource"
```

--------------------------------

### Render Composed Resources Locally with Crossplane CLI

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

This shell command demonstrates how to use the Crossplane CLI to locally render composed resources defined by a composition, XR, and function configuration. This is useful for testing P&T logic without applying changes to a cluster.

```shell
crossplane beta render xr.yaml composition.yaml functions.yaml

```

--------------------------------

### Project Documentation Structure

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/INDEX.md

This snippet shows the directory structure for the project's documentation, indicating the purpose of each file.

```text
/output/
├── README.md                          # Start here
├── INDEX.md                           # This file
├── configuration.md                   # CLI and YAML config
├── types.md                          # Type definitions
├── errors.md                         # Error reference
└── api-reference/
    ├── function.md                   # Main function
    ├── patches.md                    # Patch functions
    ├── transforms.md                 # Transform functions
    ├── connection-details.md          # Connection functions
    ├── readiness-checks.md            # Readiness functions
    └── validation.md                 # Validation functions
```

--------------------------------

### Define Connection Detail Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Configures how to extract connection details from a composed resource. Specify the 'Name' for the secret key, 'Type' of source, and relevant source details like 'FromConnectionSecretKey', 'FromFieldPath', or a 'Value'.

```go
type ConnectionDetail struct {
    Name                    string
    Type                    ConnectionDetailType
    FromConnectionSecretKey *string
    FromFieldPath           *string
    Value                   *string
}
```

--------------------------------

### Fatal Error: Cannot Get Function Input

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error occurs when the function input cannot be parsed from the request. Ensure the 'input' field in the Composition pipeline step contains valid YAML with proper indentation.

```go
Error: "cannot get Function input: [parsing error details]"
```

--------------------------------

### StringCombine Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Defines the format string for combining multiple string values. Use Go's format string syntax with placeholders for the values to be combined.

```go
type StringCombine struct {
    Format string
}
```

--------------------------------

### Dynamically Construct Secret Name using Patches

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

Utilize patches with `CombineFromComposite` to dynamically construct the connection secret name by combining XR fields. This example formats the name using a string pattern.

```yaml
writeConnectionSecretToRef:
  patches:
  - type: CombineFromComposite
    toFieldPath: name
    combine:
      variables:
      - fromFieldPath: metadata.name
      - fromFieldPath: spec.parameters.environment
      strategy: string
      string:
        fmt: "%s-%s-credentials"
```

--------------------------------

### Validation Error: Missing Required Field in Patch

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This validation error indicates that a required field for a specific patch type is missing. For example, `fromFieldPath` is necessary for `FromCompositeFieldPath` patches. Ensure the correct fields are specified based on the patch type.

```yaml
Error field: resources[i].patches[j].fromFieldPath
Message: "fromFieldPath must be set for patch type FromCompositeFieldPath"
```

--------------------------------

### Run Function Tests

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

Execute `go test ./...` to run all unit and integration tests defined in the function's test files, such as `fn_test.go`.

```shell
$ go test ./...
```

--------------------------------

### Configure Writing Connection Secrets

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Configures where and how to write connection secrets for v2 XR resources. Specify the 'Name' and 'Namespace' for the secret, or use 'Patches' for dynamic construction.

```go
type WriteConnectionSecretToRef struct {
    Name    string
    Namespace string
    Patches []ConnectionSecretPatch
}
```

--------------------------------

### Build Crossplane Package

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

Build a Crossplane package (`.xpkg`) using `crossplane xpkg build`. This command embeds the runtime image and creates a deployable package for the function.

```shell
$ crossplane xpkg build -f package --embed-runtime-image=runtime
```

--------------------------------

### StringTransform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Provides configuration for various string manipulation operations, including formatting, conversion, trimming, regex matching, joining, and replacing.

```go
type StringTransform struct {
    Type    StringTransformType
    Format  *string
    Convert *StringConversionType
    Trim    *string
    Regexp  *StringTransformRegexp
    Join    *StringTransformJoin
    Replace *StringTransformReplace
}
```

--------------------------------

### IsReady

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Determines if a composed resource is ready based on configured readiness checks. It can operate with default behavior (checking the 'Ready' condition) or with custom readiness check configurations.

```APIDOC
## IsReady

### Description
Determines if a composed resource is ready based on configured readiness checks. It can operate with default behavior (checking the 'Ready' condition) or with custom readiness check configurations.

### Signature
```go
func IsReady(_ context.Context, o ConditionedObject, rc ...v1beta1.ReadinessCheck) (bool, error)
```

### Parameters
#### Context
- **ctx** (`context.Context`) - Required - Context (currently unused but may be used for cancellation)

#### Resource Object
- **o** (`ConditionedObject`) - Required - The resource to check readiness for

#### Readiness Checks
- **rc** (`[]v1beta1.ReadinessCheck`) - Optional - Readiness check configurations

### Returns
- **bool**: True if the resource is ready, false otherwise
- **error**: Error if check validation or execution fails

### Behavior
1. If no readiness checks provided:
   - Returns true if the "Ready" condition has status "True"
   - This is the default behavior
2. If readiness checks provided:
   - All checks must pass for the resource to be considered ready
   - Returns false if any check fails
   - Stops on first error
```

--------------------------------

### Composed Resource Template: Readiness Checks

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Defines checks to determine if a composed resource is ready.

```yaml
readinessChecks:
- type: MatchCondition
  matchCondition:
    type: Ready
    status: "True"
- type: NonEmpty
  fieldPath: status.atProvider.endpoint
```

--------------------------------

### String Transform: Format

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/transforms.md

Applies a Go format string to the input, appending a suffix. Ensure the format string is correctly defined.

```yaml
transforms:
- type: string
  string:
    type: Format
    fmt: "%s-prod"
```

--------------------------------

### IsReady Function Signature

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

The IsReady function checks resource readiness based on provided readiness checks. It returns true if the resource is ready, false otherwise, or an error if validation or execution fails. If no checks are provided, it defaults to checking the 'Ready' condition.

```go
func IsReady(_ context.Context, o ConditionedObject, rc ...v1beta1.ReadinessCheck) (bool, error)
```

--------------------------------

### Readiness Check Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

Valid readiness check types include None, NonEmpty, MatchString, MatchInteger, MatchTrue, MatchFalse, and MatchCondition.

```yaml
resources:
- name: my-resource
  readinessChecks:
  - type: MatchString
    fieldPath: status.ready
    matchString: "true"
```

--------------------------------

### Build Function Runtime Image

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

Build the Docker image for the function's runtime environment using `docker build . --tag=runtime`. This image contains the compiled function.

```shell
$ docker build . --tag=runtime
```

--------------------------------

### Function Input: Environment Configuration (Alpha)

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Configures composition environment patches within the function's input. This feature is currently in Alpha.

```yaml
environment:
  patches:
  - type: FromCompositeFieldPath
    fromFieldPath: spec.environment
    toFieldPath: environment.name
```

--------------------------------

### Combine Transform Strategy

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

A 'strategy' must be provided for the 'combine' configuration. Currently, 'string' is the only supported strategy.

```yaml
resources:
- name: my-resource
  patches:
  - combine:
      strategy: string
```

--------------------------------

### Resources Input Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Defines the top-level input structure for the patch-and-transform function. It includes patch sets, environment configuration, composed resource templates, and connection secret references.

```Go
type Resources struct {
    TypeMeta   metav1.TypeMeta
    ObjectMeta metav1.ObjectMeta
    
    PatchSets                 []PatchSet
    Environment               *Environment
    Resources                 []ComposedTemplate
    WriteConnectionSecretToRef *WriteConnectionSecretToRef
}
```

--------------------------------

### Patch and Transform Execution Flow

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/README.md

Details the step-by-step execution of the Patch and Transform function, from parsing input to returning the desired state.

```text
RunFunction(request) →
├─ Parse & validate input
├─ Get observed/desired XR and composed resources
├─ Resolve PatchSets
├─ For each resource template:
│  ├─ Render/get base template
│  ├─ Apply all patches (XR → Resource, Resource → XR, Combines)
│  ├─ Extract connection details from observed resource
│  ├─ Check readiness
│  └─ Add to desired composed resources
├─ Apply environment patches (if configured)
├─ Create connection Secret for v2 XRs (if needed)
└─ Return desired state
```

--------------------------------

### ReadinessCheckType Constants

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Defines the available types for readiness checks. These constants specify the kind of check to be performed on a resource's fields or conditions.

```go
type ReadinessCheckType string

const (
    ReadinessCheckTypeNone           ReadinessCheckType = "None"
    ReadinessCheckTypeNonEmpty       ReadinessCheckType = "NonEmpty"
    ReadinessCheckTypeMatchString    ReadinessCheckType = "MatchString"
    ReadinessCheckTypeMatchInteger   ReadinessCheckType = "MatchInteger"
    ReadinessCheckTypeMatchTrue      ReadinessCheckType = "MatchTrue"
    ReadinessCheckTypeMatchFalse     ReadinessCheckType = "MatchFalse"
    ReadinessCheckTypeMatchCondition ReadinessCheckType = "MatchCondition"
)
```

--------------------------------

### Full ReadinessCheck Struct Definition

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Defines the structure for configuring readiness checks, including various matching types and field paths.

```go
type ReadinessCheck struct {
    Type            ReadinessCheckType
    FieldPath       *string
    MatchString     *string
    MatchInteger    *int64
    MatchCondition  *MatchConditionReadinessCheck
}
```

--------------------------------

### ComposedTemplate Structure

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Specifies the configuration for a single composed resource. It includes a name, base resource template, patches to apply, connection details to extract, and readiness checks.

```Go
type ComposedTemplate struct {
    Name                string
    Base                *runtime.RawExtension
    Patches             []ComposedPatch
    ConnectionDetails   []ConnectionDetail
    ReadinessChecks     []ReadinessCheck
}
```

--------------------------------

### Check Specific Condition Readiness Check

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Configures a readiness check to verify if the 'Available' condition has a status of 'True'.

```yaml
resources:
- name: deployment
  readinessChecks:
  - type: MatchCondition
    matchCondition:
      type: Available
      status: "True"
```

--------------------------------

### Fatal Error: Missing Composed Resource (No Base)

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

This error happens when a resource template lacks a base and was not produced by a preceding function. Either add a 'base' template to the resource or ensure a previous function creates a resource with the same name.

```go
Error: "composed resource 'my-resource' has no base template, and was not produced by a previous Function in the pipeline"
```

--------------------------------

### MatchTransform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Enables pattern matching to select a result. It includes a list of patterns to match against and a fallback value or behavior if no pattern matches.

```go
type MatchTransform struct {
    Patterns      []MatchTransformPattern
    FallbackValue extv1.JSON
    FallbackTo    MatchFallbackTo
}
```

--------------------------------

### MathTransform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Specifies a mathematical operation to be performed. Supported operations include Multiply, ClampMin, and ClampMax, each requiring specific parameters.

```go
type MathTransform struct {
    Type     MathTransformType
    Multiply *int64
    ClampMin *int64
    ClampMax *int64
}
```

--------------------------------

### Handler: Cannot Render Patch

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

For 'Cannot render patch' errors, check that field paths exist and that transforms are correctly configured and produce the expected types.

```go
// Check field paths exist and transforms are valid
patches:
- type: FromCompositeFieldPath
  fromFieldPath: spec.valid.field.path  # Use correct field path
  toFieldPath: spec.dest.field
  transforms:  # Ensure transforms produce the right type
  - type: map
    map:
      expectedKey: expectedValue
```

--------------------------------

### Run Function on Custom Address

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Configures the function-patch-and-transform to listen on a custom address and port.

```bash
# Custom address and port
function-patch-and-transform --address :8443
```

--------------------------------

### Function Input: Resources Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Specifies the list of composed resource templates required for the function's input configuration.

```yaml
resources:
- name: my-bucket
  base:
    apiVersion: s3.aws.upbound.io/v1beta1
    kind: Bucket
    spec:
      forProvider:
        region: us-east-1
```

--------------------------------

### Environment Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Defines the configuration for composition environment patches, an Alpha feature. It contains a list of environment-specific patches.

```Go
type Environment struct {
    Patches []EnvironmentPatch
}
```

--------------------------------

### Generate Go Code for Function

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

Run `go generate ./...` to execute code generation tasks, typically for updating API types or other generated code within the function project.

```shell
$ go generate ./...
```

--------------------------------

### Readiness Check Field Path

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

A 'fieldPath' must be specified for readiness checks, except for 'None' and 'MatchCondition' types.

```yaml
resources:
- name: my-resource
  readinessChecks:
  - type: NonEmpty
    fieldPath: status.observedGeneration
```

--------------------------------

### Run Function with TLS Certificates

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Specifies the directory for server TLS certificates and the CA for client verification when running the function.

```bash
# Specify TLS certificates
function-patch-and-transform \
  --tls-server-certs-dir /etc/ssl/certs \
  --address :9443
```

--------------------------------

### Composed Resource Template: Connection Details

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Specifies how to extract and propagate connection details from a composed resource to the XR.

```yaml
connectionDetails:
- name: username
  type: FromConnectionSecretKey
  fromConnectionSecretKey: username
- name: endpoint
  type: FromFieldPath
  fromFieldPath: status.atProvider.endpoint
- name: port
  type: FromValue
  value: "5432"
```

--------------------------------

### Define Convert Transform Formats

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/types.md

Specifies the input formats for type conversion operations. Options include 'none' (default), 'quantity' for Kubernetes Quantity, and 'json' for JSON strings.

```go
type ConvertTransformFormat string

const (
    ConvertTransformFormatNone     ConvertTransformFormat = "none"
    ConvertTransformFormatQuantity ConvertTransformFormat = "quantity"
    ConvertTransformFormatJSON     ConvertTransformFormat = "json"
)
```

--------------------------------

### Check Field Existence Readiness Check

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Configures a readiness check to verify if a specific field (status.loadBalancer.ingress) is non-empty.

```yaml
resources:
- name: service
  readinessChecks:
  - type: NonEmpty
    fieldPath: status.loadBalancer.ingress
```

--------------------------------

### Validate ReadinessCheck Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/validation.md

Validates a ReadinessCheck configuration. Ensures the type is valid and required fields are present based on the type.

```go
func ValidateReadinessCheck(r v1beta1.ReadinessCheck) *field.Error
```

--------------------------------

### Check Field Value Readiness Check

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Configures a readiness check to verify if the 'status.state' field matches the string 'running'.

```yaml
resources:
- name: instance
  readinessChecks:
  - type: MatchString
    fieldPath: status.state
    matchString: "running"
```

--------------------------------

### Match Transform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Applies transformations based on matching patterns (literal or regex) and provides a fallback.

```yaml
transforms:
- type: match
  match:
    patterns:
    - type: literal
      literal: us-east
      result: "1"
    - type: regexp
      regexp: '^eu-.*'
      result: "2"
    fallbackValue: "0"
    fallbackTo: Value
```

--------------------------------

### Handler: Cannot Parse Base Template

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

If you encounter 'Cannot parse base template', verify that your base configuration is valid YAML or JSON and has correct indentation.

```go
// Verify your base is valid YAML/JSON
resources:
- name: my-resource
  base:
    apiVersion: example.com/v1beta1
    kind: MyResource
    # Ensure valid YAML indentation
```

--------------------------------

### RunReadinessCheck Function Signature

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

The RunReadinessCheck function executes a single readiness check against a resource. It validates the check configuration and returns true if the check passes, false otherwise, or an error if validation or execution fails. Missing field paths are treated as check failures.

```go
func RunReadinessCheck(c v1beta1.ReadinessCheck, o ConditionedObject) (bool, error)
```

--------------------------------

### RunReadinessCheck

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Executes a single readiness check against a resource. This function validates the check configuration and then performs the check based on its type.

```APIDOC
## RunReadinessCheck

### Description
Executes a single readiness check against a resource. This function validates the check configuration and then performs the check based on its type.

### Signature
```go
func RunReadinessCheck(c v1beta1.ReadinessCheck, o ConditionedObject) (bool, error)
```

### Parameters
#### Readiness Check Configuration
- **c** (`v1beta1.ReadinessCheck`) - Required - The readiness check configuration

#### Resource Object
- **o** (`ConditionedObject`) - Required - The resource to check

### Returns
- **bool**: True if the check passes, false otherwise
- **error**: Error if validation or check execution fails

### Behavior
1. Validates the readiness check configuration
2. Executes the check based on its type
3. Returns silently (no error) for missing field paths (treats as check failure)
```

--------------------------------

### Connection Detail Type-Specific Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

Provide the required field based on the connection detail type: 'fromConnectionSecretKey' for FromConnectionSecretKey, 'fromFieldPath' for FromFieldPath, and 'value' for FromValue.

```yaml
resources:
- name: my-resource
  connectionDetails:
  - type: FromFieldPath
    fromFieldPath: spec.claim.status.endpoint
```

```yaml
resources:
- name: my-resource
  connectionDetails:
  - type: FromValue
    value: "my-static-value"
```

--------------------------------

### Connection Detail Type

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

Specify the 'type' for connection details. Supported types are FromConnectionSecretKey, FromFieldPath, and FromValue.

```yaml
resources:
- name: my-resource
  connectionDetails:
  - type: FromConnectionSecretKey
    fromConnectionSecretKey: my-secret-key
```

--------------------------------

### Check Boolean Field True Readiness Check

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Configures a readiness check to verify if the 'status.completed' field is true.

```yaml
resources:
- name: job
  readinessChecks:
  - type: MatchTrue
    fieldPath: status.completed
```

--------------------------------

### Transform Pipeline Flow

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/README.md

Illustrates the sequential application of transforms in the pipeline. Each transform processes the output of the previous one.

```text
Input → [Transform 1] → [Transform 2] → ... → [Transform N] → Output
```

--------------------------------

### Define Transform I/O Types

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/transforms.md

Defines the possible input and output types for transformations.

```go
type TransformIOType string

const (
    TransformIOTypeString  TransformIOType = "string"
    TransformIOTypeBool    TransformIOType = "bool"
    TransformIOTypeInt     TransformIOType = "int"
    TransformIOTypeInt64   TransformIOType = "int64"
    TransformIOTypeFloat64 TransformIOType = "float64"
    TransformIOTypeObject  TransformIOType = "object"
    TransformIOTypeArray   TransformIOType = "array"
)
```

--------------------------------

### Handler: Composed Resource Has No Base

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

If a composed resource has no base, you need to add one. This involves defining the 'base' field with the resource's API version and kind.

```go
// Either add a base
resources:
- name: my-resource
  base:
    apiVersion: s3.aws.upbound.io/v1beta1
    kind: Bucket
```

--------------------------------

### supportsConnectionDetails Function Signature

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/connection-details.md

Determines if an XR supports native v1 connection details or v2 style. It checks for the presence of the `spec.crossplane` field to differentiate.

```go
func supportsConnectionDetails(xr *resource.Composite) bool
```

--------------------------------

### Function Input: WriteConnectionSecretToRef Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Configures the location for writing connection secrets, applicable to v2 XRs only.

```yaml
writeConnectionSecretToRef:
  name: my-app-connection
  namespace: default
  patches:
  - type: FromCompositeFieldPath
    fromFieldPath: metadata.namespace
    toFieldPath: namespace
```

--------------------------------

### String Transform: Trim Prefix

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Removes a specified prefix from a string.

```yaml
transforms:
- type: string
  string:
    type: TrimPrefix
    trim: "prefix-"
```

--------------------------------

### Run Function on Unix Socket

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Configures the function-patch-and-transform to listen on a Unix socket instead of TCP.

```bash
# Listen on Unix socket
function-patch-and-transform --network unix --address /tmp/function.sock
```

--------------------------------

### Check Integer Field Readiness Check

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/readiness-checks.md

Configures a readiness check to verify if the 'status.readyReplicas' field equals the integer 3.

```yaml
resources:
- name: replica-set
  readinessChecks:
  - type: MatchInteger
    fieldPath: status.readyReplicas
    matchInteger: 3
```

--------------------------------

### Output of Local Resource Rendering

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/README.md

This YAML output shows the resources that would be composed by Crossplane based on the provided `xr.yaml`, `composition.yaml`, and `functions.yaml`. It illustrates the resulting XR and the composed S3 Bucket resource with its specified region.

```yaml
---
apiVersion: example.crossplane.io/v1
kind: XR
metadata:
  name: example-xr
---
apiVersion: s3.aws.upbound.io/v1beta1
kind: Bucket
metadata:
  annotations:
    crossplane.io/composition-resource-name: bucket
  generateName: example-xr-
  labels:
    crossplane.io/composite: example-xr
  ownerReferences:
    # Omitted for brevity
spec:
  forProvider:
    region: us-east-2

```

--------------------------------

### String Transform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

When using the 'string' transform type, provide 'fmt' or 'convert' for string manipulation.

```yaml
resources:
- name: my-resource
  patches:
  - transforms:
    - type: string
      fmt: "%s-suffix"
```

--------------------------------

### Apply Environment Patch

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/patches.md

Applies patches between the composition environment and the composite resource. Used for integrating environment-specific configurations.

```go
err := ApplyEnvironmentPatch(p, env, oxr, dxr)
```

--------------------------------

### Validate Resources in RunFunction

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/validation.md

Demonstrates calling ValidateResources early in the RunFunction to check for invalid input. Fatal validation errors will halt function execution.

```go
input := &v1beta1.Resources{}
if err := request.GetInput(req, input); err != nil {
    response.Fatal(rsp, errors.Wrap(err, "cannot get Function input"))
    return rsp, nil
}

if err := ValidateResources(input); err != nil {
    response.Fatal(rsp, errors.Wrap(err, "invalid Function input"))
    return rsp, nil
}
```

--------------------------------

### Function Input: PatchSets Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Defines named sets of reusable patches within the function's input configuration.

```yaml
patchSets:
- name: common-labels
  patches:
  - type: FromCompositeFieldPath
    fromFieldPath: metadata.labels
    toFieldPath: metadata.labels
    policy:
      toFieldPath: MergeObjects
```

--------------------------------

### PatchInterface Methods

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/api-reference/patches.md

Defines the interface that all patch types must implement, specifying methods to retrieve patch type, field paths, combine configurations, transforms, and policies.

```go
type PatchInterface interface {
    GetType() v1beta1.PatchType
    GetFromFieldPath() string
    GetToFieldPath() string
    GetCombine() *v1beta1.Combine
    GetTransforms() []v1beta1.Transform
    GetPolicy() *v1beta1.PatchPolicy
}
```

--------------------------------

### Math Transform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

When using the 'math' transform type, ensure you provide the 'type' and the corresponding field (e.g., 'multiply', 'clampMin', 'clampMax').

```yaml
resources:
- name: my-resource
  patches:
  - transforms:
    - type: math
      multiply: 10
```

--------------------------------

### Map Transform Configuration

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/configuration.md

Maps input values to predefined output values.

```yaml
transforms:
- type: map
  map:
    small: "t2.micro"
    medium: "t2.small"
    large: "m5.xlarge"
```

--------------------------------

### Readiness Check Match Value

Source: https://github.com/crossplane-contrib/function-patch-and-transform/blob/main/_autodocs/errors.md

For the 'MatchString' readiness check type, the 'matchString' value cannot be nil.

```yaml
resources:
- name: my-resource
  readinessChecks:
  - type: MatchString
    fieldPath: status.phase
    matchString: "Succeeded"
```