### Valid Configuration Examples

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Examples of correctly formatted regex patterns for Rename and Rewrite rules.

```yaml
# Rename with valid patterns
- type: "Rename"
  header: "X-.*"          # Matches X-anything
  value: "X-New"

- type: "Rename"
  header: "X-(Old\|Legacy)"  # Matches X-Old or X-Legacy
  value: "X-New"

# Rewrite with valid patterns
- type: "RewriteValueRule"
  header: "X-.*"
  value: "\\d+"           # Matches digits
  valueReplace: "NUM"

- type: "RewriteValueRule"
  header: "X-.*"
  value: "(\\w+)-(\\d+)"  # Capture word and number
  valueReplace: "$2-$1"   # Swap them
```

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

### Start Development Environment

Source: https://github.com/tommoulard/htransformation/blob/main/README.md

Use Docker Compose to spin up the development environment.

```bash
$ docker compose up
```

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

### Example YAML configuration for rules

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/types.md

Example configurations for various rule types including Set, Delete, Join, Rename, and Rewrite.

```yaml
# Set rule
- Name: "Add-Custom-Header"
  Type: "Set"
  Header: "X-Custom"
  Value: "CustomValue"
  SetOnResponse: false

# Delete rule
- Name: "Remove-Server"
  Type: "Del"
  Header: "Server"
  SetOnResponse: true

# Join rule
- Name: "Combine-Values"
  Type: "Join"
  Header: "X-Items"
  Values:
    - "item1"
    - "^Other-Header"
  Sep: ","
  HeaderPrefix: "^"

# Rename rule
- Name: "Rename-Old"
  Type: "Rename"
  Header: "Old-Header"
  Value: "New-Header"

# Rewrite rule
- Name: "Replace-Pattern"
  Type: "RewriteValueRule"
  Header: "X-.*"
  Value: "old-(.*)"
  ValueReplace: "new-$1"
```

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

### Traefik Plugin Configuration Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Example configuration for defining header transformation rules within a Traefik plugin setup.

```yaml
// As a Traefik plugin, this is typically instantiated via New() and automatically invoked for each request
// The handler is called automatically by the HTTP server
// Usage in Traefik configuration:
// plugins:
//   htransformation:
//     moduleName: github.com/tomMoulard/htransformation
//     rules:
//       - name: "Set Custom Header"
//         header: "X-Custom"
//         value: "CustomValue"
//         type: "Set"
```

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

### Example initialization errors

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Displays common error messages returned during rule initialization.

```text
invalid rule type: MyRuleName
missing required fields: IncompleteRule
invalid regexp: BadPattern
```

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

### Initialize Set Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/set-handler.md

Example of initializing a new Set handler with a rule configuration.

```go
rule := types.Rule{
    Name:   "Set-Cache-Control",
    Type:   types.Set,
    Header: "Cache-Control",
    Value:  "max-age=3600",
}

handler, err := set.New(rule)
if err != nil {
    log.Fatal(err)
}
```

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

### Configure and Create Join Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

Example showing the definition of a Join rule and the subsequent handler initialization.

```go
rule := types.Rule{
    Name:   "Join-Cache-Control",
    Type:   types.Join,
    Header: "Cache-Control",
    Values: []string{"public", "max-age=3600"},
    Sep:    ", ",
}

handler, err := join.New(rule)
if err != nil {
    log.Fatal(err)
}
```

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

### Traefik Configuration Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/set-handler.md

Example YAML configuration for using the Set handler within a Traefik middleware plugin.

```yaml
# Traefik configuration
http:
  middlewares:
    my-header-transformation:
      plugin:
        htransformation:
          rules:
            - name: "Set-Custom-Request-Header"
              type: "Set"
              header: "X-Client-Version"
              value: "1.0.0"
            - name: "Set-Response-Cache"
              type: "Set"
              header: "Cache-Control"
              value: "public, max-age=3600"
              setOnResponse: true
  routers:
    my-router:
      rule: "Host(`example.com`)"
      middlewares:
        - my-header-transformation
      service: my-service
```

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

### Join Handler Implementation Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

Demonstrates configuring a Join rule with a HeaderPrefix to dynamically fetch values from request headers.

```go
rule := types.Rule{
    Name:   "Join-With-Header-Reference",
    Type:   types.Join,
    Header: "X-Forwarded-For",
    Values: []string{
        "Foo",
        "^CF-Connecting-IP",  // ^ is the HeaderPrefix
    },
    Sep:          ", ",
    HeaderPrefix: "^",
    SetOnResponse: false,
}
handler, _ := join.New(rule)

// Request headers:
// X-Forwarded-For: 1.1.1.1
// CF-Connecting-IP: 2.2.2.2

// After join:
// X-Forwarded-For: 1.1.1.1, Foo, 2.2.2.2
handler.Handle(responseWriter, request)
```

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

### Initialize Delete Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/delete-handler.md

Example of creating a new Delete handler using a rule configuration.

```go
rule := types.Rule{
    Name:   "Delete-Cache-Control",
    Type:   types.Delete,
    Header: "Cache-Control",
}

handler, err := deleter.New(rule)
if err != nil {
    log.Fatal(err)
}
```

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

### Apply Header Deletion

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/delete-handler.md

Example demonstrating how to remove headers from either the request or the response.

```go
// Request header deletion
rule := types.Rule{
    Name:   "Remove-X-Powered-By",
    Type:   types.Delete,
    Header: "X-Powered-By",
    SetOnResponse: false,
}
handler, _ := deleter.New(rule)
handler.Handle(responseWriter, request)
// "X-Powered-By" header is now removed from request

// Response header deletion
ruleResp := types.Rule{
    Name:   "Remove-Server",
    Type:   types.Delete,
    Header: "Server",
    SetOnResponse: true,
}
handlerResp, _ := deleter.New(ruleResp)
handlerResp.Handle(responseWriter, request)
// "Server" header is now removed from response
```

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

### Configure Rules in YAML

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Example configurations for various rules to avoid missing field errors.

```yaml
- type: "Set"
  header: "X-Header"  # Required - cannot be empty
  value: "value"
  name: "MySetRule"
```

```yaml
- type: "Join"
  header: "X-Header"
  values:              # Required - cannot be empty
    - "value1"
  sep: ","            # Required - cannot be empty
  name: "MyJoinRule"
```

```yaml
- type: "Rename"
  header: "X-Old"
  value: "X-New"      # Required - cannot be empty
  name: "MyRenameRule"
```

```yaml
- type: "RewriteValueRule"
  header: "X-Header"
  value: "pattern"
  valueReplace: "replacement"  # Required - cannot be empty
  name: "MyRewriteRule"
```

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

### Correct Rule Type Configuration Examples

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Valid YAML configurations for supported rule types.

```yaml
- type: "Set"
  header: "X-Custom"
  value: "value"

- type: "Del"
  header: "X-Remove"

- type: "Join"
  header: "X-Items"
  values: ["item1"]
  sep: ","

- type: "Rename"
  header: "X-Old"
  value: "X-New"

- type: "RewriteValueRule"
  header: "X-Pattern"
  value: "old"
  valueReplace: "new"
```

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

### Configure and Instantiate Rename Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rename-handler.md

Example showing how to define a rule and initialize the handler, including error handling for invalid regex patterns.

```go
rule := types.Rule{
    Name:   "Rename-Cache-Header",
    Type:   types.Rename,
    Header: "X-Cache-.*",  // Matches X-Cache-Age, X-Cache-Status, etc.
    Value:  "X-App-Cache",
}

handler, err := rename.New(rule)
if err != nil {
    log.Fatal("Invalid regex pattern:", err)
}
```

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

### Set HTTP Header Usage Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/header-utilities.md

Demonstrates setting both standard headers and the special Host header, which is handled case-insensitively.

```go
req, _ := http.NewRequest("GET", "http://example.com", nil)

// Set a regular header
header.Set(req, "X-Custom-Header", "MyValue")
// req.Header["X-Custom-Header"] = ["MyValue"]

// Set the Host header
header.Set(req, "Host", "newhost.com")
// req.Host = "newhost.com"

// Case-insensitive Host header matching
header.Set(req, "host", "anotherhost.com")
// req.Host = "anotherhost.com"
```

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

### Handle Header Transformation

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/set-handler.md

Signature and usage examples for applying header transformations to requests or responses.

```go
func (s *Set) Handle(rw http.ResponseWriter, req *http.Request)
```

```go
// Request header transformation
rule := types.Rule{
    Name:   "Set-X-Request-ID",
    Type:   types.Set,
    Header: "X-Request-ID",
    Value:  "abc-123",
    SetOnResponse: false,
}
handler, _ := set.New(rule)
handler.Handle(responseWriter, request)
// request.Header now has "X-Request-ID: abc-123"

// Response header transformation
ruleResp := types.Rule{
    Name:   "Set-Cache",
    Type:   types.Set,
    Header: "Cache-Control",
    Value:  "no-cache",
    SetOnResponse: true,
}
handlerResp, _ := set.New(ruleResp)
handlerResp.Handle(responseWriter, request)
// responseWriter headers now have "Cache-Control: no-cache"
```

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

### Configure and Create Rewrite Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rewrite-handler.md

Example demonstrating the creation of a Rewrite handler with specific regex patterns for header matching and value replacement.

```go
rule := types.Rule{
    Name:          "Rewrite-Header-Values",
    Type:          types.RewriteValueRule,
    Header:        "X-Custom-.*",
    Value:         "old-(.*)",
    ValueReplace:  "new-$1",
}

handler, err := rewrite.New(rule)
if err != nil {
    log.Fatal("Invalid regex pattern:", err)
}
```

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

### Traefik Configuration Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

Shows how to define Join middleware in a Traefik configuration file with both static and dynamic header values.

```yaml
# Traefik configuration
http:
  middlewares:
    join-headers:
      plugin:
        htransformation:
          rules:
            # Simple join without header references
            - name: "Join-Cache-Control"
              type: "Join"
              header: "Cache-Control"
              values:
                - "public"
                - "max-age=3600"
              sep: ", "
            
            # Join with header references
            - name: "Join-Forwarded-For"
              type: "Join"
              header: "X-Forwarded-For"
              headerPrefix: "^"
              values:
                - "Custom-Value"
                - "^CF-Connecting-IP"
              sep: ","
  routers:
    my-router:
      rule: "Host(`example.com`)"
      middlewares:
        - join-headers
      service: my-service
```

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

### Standard HTTP Request Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

A standard HTTP request that does not require connection hijacking.

```http
GET / HTTP/1.1
Host: example.com
```

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

### Rename Header Rule

Source: https://github.com/tommoulard/htransformation/blob/main/README.md

Configuration examples for renaming headers using regex patterns.

```yaml
- Rule:
      Name: 'Header rename'
      Header: 'Cache-Control'
      Value: 'NewHeader'
      Type: 'Rename'
```

```yaml
# Old header:
Cache-Control: gzip, deflate

# New header:
NewHeader: gzip, deflate
```

```yaml
- Rule:
      Name: 'Header Renaming'
      Header: 'X-Traefik-*'
      Value: 'X-Traefik-merged'
      Type: 'Rename'
```

```yaml
# Old header:
X-Traefik-uuid: 0
X-Traefik-date: mer. 21 oct. 2020 11:57:39 CEST
# New header:
X-Traefik-merged: 0 # A value from old headers
```

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

### Invalid Configuration Examples

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

YAML configurations that trigger ErrInvalidRegexp due to malformed regex patterns.

```yaml
- type: "Rename"
  header: "[invalid"      # Error: unclosed character class
  value: "X-New"
  name: "BadRename"

# Causes: invalid regexp: BadRename
```

```yaml
- type: "RewriteValueRule"
  header: "X-Header"
  value: "(unclosed"      # Error: unclosed group
  valueReplace: "new"
  name: "BadRewrite"

# Causes: invalid regexp: BadRewrite
```

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

### Multi-Value Header Processing Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rewrite-handler.md

Demonstrates how individual values in a multi-value header are processed independently when a pattern matches.

```text
Original header: X-Custom: value1
                 X-Custom: value2

If pattern matches both values:
After rewrite:   X-Custom: new_value1
                 X-Custom: new_value2
```

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

### Traefik Middleware Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Example configuration for enabling the htransformation plugin within a Traefik environment.

```yaml
# docker-compose or Traefik config
providers:
  file:
    filename: /path/to/traefik.yml

plugins:
  htransformation:
    moduleName: github.com/tomMoulard/htransformation
    version: v1

http:
  middlewares:
    my-headers:
      plugin:
        htransformation:
          rules:
            - type: "Set"
              header: "X-Custom"
              value: "value"

  routers:
    my-router:
      rule: "Host(`example.com`)"
      middlewares:
        - my-headers
      service: my-service
```

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

### Invalid Rule Type Configuration Examples

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Examples of YAML configurations that will trigger the ErrInvalidRuleType error due to incorrect casing or unsupported values.

```yaml
- type: "delete"        # Wrong case (should be "Del")
- type: "DELETE"        # Wrong case
- type: "Remove"        # Unsupported type name
- type: "SetHeader"     # Unsupported variation
- type: "Rewrite"       # Wrong (should be "RewriteValueRule")
- type: ""              # Empty type
```

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

### Configure Traefik Middleware

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Example YAML configuration for defining header transformation rules within Traefik.

```yaml
http:
  middlewares:
    my-transformations:
      plugin:
        htransformation:
          rules:
            # Add authentication header
            - name: "Add-Auth"
              type: "Set"
              header: "Authorization"
              value: "Bearer my-token"
              setOnResponse: false
            
            # Remove sensitive response headers
            - name: "Remove-Server"
              type: "Del"
              header: "Server"
              setOnResponse: true
            
            - name: "Remove-X-Powered-By"
              type: "Del"
              header: "X-Powered-By"
              setOnResponse: true
            
            # Rename headers
            - name: "Rename-Old"
              type: "Rename"
              header: "X-Old-Name"
              value: "X-New-Name"
            
            # Add cache headers
            - name: "Cache-Static"
              type: "Join"
              header: "Cache-Control"
              values:
                - "public"
                - "max-age=31536000"
              sep: ", "
              setOnResponse: true
            
            # Rewrite header values
            - name: "Sanitize-UA"
              type: "RewriteValueRule"
              header: "User-Agent"
              value: "Mozilla/(.*)"
              valueReplace: "Mozilla/REDACTED"

  routers:
    my-service:
      rule: "Host(`example.com`)"
      middlewares:
        - my-transformations
      service: my-backend
```

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

### WebSocket Upgrade Request Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

HTTP request headers that trigger a connection upgrade, potentially leading to this error if hijacking is unsupported.

```http
GET / HTTP/1.1
Host: example.com
Upgrade: websocket
Connection: Upgrade
```

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

### Example Error Message

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

The resulting error message format when a rule name is provided.

```text
missing required fields: MyRuleName
```

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

### Trigger ErrNotHTTPHijacker in Hijack method

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Example implementation showing how the error is returned when the underlying response writer lacks Hijacker support.

```go
func (wrw *wrappedResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
    hijacker, ok := wrw.rw.(http.Hijacker)
    if !ok {
        return nil, nil, types.ErrNotHTTPHijacker
    }
    // ...
}
```

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

### Define header transformation rules in YAML

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Configuration examples for various header transformation operations including Set, Del, Join, Rename, and RewriteValueRule.

```yaml
# Set: Create or replace a header
- type: "Set"
  header: "X-Custom"
  value: "MyValue"

# Delete: Remove a header
- type: "Del"
  header: "Server"

# Join: Concatenate values to existing header
- type: "Join"
  header: "Cache-Control"
  values: ["public", "max-age=3600"]
  sep: ", "

# Rename: Rename a header using regex
- type: "Rename"
  header: "X-Old-.*"
  value: "X-New"

# Rewrite: Replace values using regex with capture groups
- type: "RewriteValueRule"
  header: "X-.*"
  value: "old-(.*)"
  valueReplace: "new-$1"
```

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

### Configure htransformation in Traefik

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Example YAML configuration for using htransformation within a Traefik router.

```yaml
# In Traefik, htransformation works with all middleware:
http:
  middlewares:
    htransformation:
      plugin:
        htransformation:
          rules:
            - type: "Set"
              header: "X-Custom"
              value: "value"
  routers:
    websocket-router:
      rule: "Host(`ws.example.com`)"
      middlewares:
        - htransformation  # Safe for WebSocket upgrades
      service: websocket-service
```

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

### Validate Handler Usage

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/delete-handler.md

Example of calling the validation method, which always returns nil for the Delete handler.

```go
handler, _ := deleter.New(rule)
if err := handler.Validate(); err != nil {
    log.Printf("Validation error: %v", err)
}
// For Delete, this will always return nil
```

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

### Multiple Matches Within Single Value Example

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rewrite-handler.md

Shows how the handler replaces all occurrences of a pattern within a single header value.

```text
Header: X-Items: old_1; old_2; old_3
Pattern: old_(\d+)
Replace: new_$1

Result: X-Items: new_1; new_2; new_3
```

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

### Rename Handler Traefik Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rename-handler.md

Example configuration for the Rename handler within a Traefik middleware definition, demonstrating both exact and regex-based header renaming.

```yaml
# Traefik configuration
http:
  middlewares:
    rename-headers:
      plugin:
        htransformation:
          rules:
            - name: "Rename-Old-To-New"
              type: "Rename"
              header: "X-Old-Header"
              value: "X-New-Header"
            - name: "Merge-Traefik-Headers"
              type: "Rename"
              header: "X-Traefik-.*"
              value: "X-Traefik-Info"
  routers:
    my-router:
      rule: "Host(`example.com`)"
      middlewares:
        - rename-headers
      service: my-service
```

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

### Populate Configuration and Initialize

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Shows how to create a new configuration, append rules, and pass it to the New constructor.

```go
config := CreateConfig()
config.Rules = append(config.Rules, types.Rule{
    Name:   "Set-Custom-Header",
    Type:   types.Set,
    Header: "X-Custom-Header",
    Value:  "CustomValue",
})

handler, err := New(context.Background(), nextHandler, config, "my-transformation")
```

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

### Configure and Instantiate Middleware

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Demonstrates setting up a configuration with multiple rules and initializing the middleware handler.

```go
config := &Config{
    Rules: []types.Rule{
        {
            Name:   "Set-Custom-Header",
            Type:   types.Set,
            Header: "X-My-Header",
            Value:  "MyValue",
        },
        {
            Name:          "Delete-Cache-Control",
            Type:          types.Delete,
            Header:        "Cache-Control",
            SetOnResponse: true,
        },
    },
}

handler, err := New(context.Background(), nextHandler, config, "my-transformation")
if err != nil {
    log.Fatal("Failed to create middleware:", err)
}

// Use handler as http.Handler in your router
http.Handle("/", handler)
```

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

### Validation Error Messages

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Examples of error messages generated when rule validation fails.

```text
Error: invalid rule type: unsupported-type: (rule name: "My-Rule")
Error: missing required fields: (rule name: "Incomplete-Rule")
Error: invalid regexp: invalid regex pattern: (rule name: "Bad-Pattern")
```

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

### Create Configuration Instance

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Defines the signature for the CreateConfig function used to initialize an empty configuration.

```go
func CreateConfig() *Config
```

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

### Project Documentation File Structure

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/MANIFEST.md

Displays the directory tree for the project's documentation files located in /workspace/home/output/.

```text
/workspace/home/output/
├── INDEX.md                          (Master navigation)
├── README.md                         (Overview)
├── QUICK_REFERENCE.md                (Cheat sheet)
├── types.md                          (Type reference)
├── configuration.md                  (Config guide)
├── errors.md                         (Error reference)
├── MANIFEST.md                       (This file)
└── api-reference/                    (API documentation)
    ├── headers-transformation.md
    ├── set-handler.md
    ├── delete-handler.md
    ├── join-handler.md
    ├── rename-handler.md
    ├── rewrite-handler.md
    └── header-utilities.md
```

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

### Demonstrate HTTP Header Normalization

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/header-utilities.md

Shows how Go's http.Header normalizes header names, causing subsequent sets to overwrite previous values regardless of casing.

```go
req, _ := http.NewRequest("GET", "http://example.com", nil)

header.Set(req, "content-type", "text/html")
header.Set(req, "Content-Type", "application/json")  // Overwrites previous

// Both refer to the same header due to Go's normalization
fmt.Println(req.Header.Get("Content-Type"))     // application/json
fmt.Println(req.Header.Get("CONTENT-TYPE"))     // application/json
```

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

### Trigger ErrInvalidRegexp in Rename Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Example of how the Rename handler triggers the error when the header regex fails to compile.

```go
func New(rule types.Rule) (types.Handler, error) {
    re, err := regexp.Compile(rule.Header)
    if err != nil {
        return nil, fmt.Errorf("%w: %s", types.ErrInvalidRegexp, rule.Name)
    }
    // ...
}
```

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

### New

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Creates and initializes a new HeadersTransformation middleware handler with the provided configuration.

```APIDOC
## func New(context.Context, http.Handler, *Config, string) (http.Handler, error)

### Description
Creates and initializes a new `HeadersTransformation` middleware handler. It validates all rules and creates appropriate handlers for each rule type.

### Parameters
- **_** (context.Context) - Required - Context for the plugin lifecycle (unused)
- **next** (http.Handler) - Required - The next HTTP handler in the middleware chain
- **config** (*Config) - Required - Configuration containing rules to apply
- **name** (string) - Required - The name of the middleware instance

### Returns
- **http.Handler** - The initialized middleware handler
- **error** - Error if rule configuration is invalid or a handler cannot be created
```

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

### Initialize Middleware Constructor

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Used by Traefik during plugin loading to instantiate the middleware.

```go
func New(ctx context.Context, next http.Handler, config *Config, name string) (http.Handler, error)
```

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

### Constructor Signature

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/set-handler.md

Defines the signature for creating a new Set handler instance.

```go
func New(rule types.Rule) (types.Handler, error)
```

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

### Initialize HeadersTransformation Middleware

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Defines the signature for the New constructor function used to create a middleware handler.

```go
func New(_ context.Context, next http.Handler, config *Config, name string) (http.Handler, error)
```

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

### Trigger ErrInvalidRegexp in Rewrite Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Example of how the Rewrite handler triggers the error when either the header or value regex fails to compile.

```go
func New(rule types.Rule) (types.Handler, error) {
    reg, err := regexp.Compile(rule.Header)
    if err != nil {
        return nil, fmt.Errorf("%w: %s: %q", types.ErrInvalidRegexp, rule.Name, rule.Header)
    }
    
    reg, err = regexp.Compile(rule.Value)
    if err != nil {
        return nil, fmt.Errorf("%w: %s: %q", types.ErrInvalidRegexp, rule.Name, rule.Value)
    }
    // ...
}
```

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

### CreateConfig

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Creates a new empty Config instance for populating with rules.

```APIDOC
## func CreateConfig() *Config

### Description
Creates a new empty `Config` instance for populating with rules.

### Returns
- ***Config** - A new config with an empty rules slice
```

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

### Implement Handler Usage

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/types.md

Handlers are instantiated via specific constructor functions and require validation before execution.

```go
rule := types.Rule{...}

// Set handler
setHandler, _ := set.New(rule)
if err := setHandler.Validate(); err != nil {
    return err
}
setHandler.Handle(responseWriter, request)

// Delete handler
delHandler, _ := deleter.New(rule)
if err := delHandler.Validate(); err != nil {
    return err
}
delHandler.Handle(responseWriter, request)
```

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

### Sequential Rule Evaluation

Source: https://github.com/tommoulard/htransformation/blob/main/README.md

Demonstrates how multiple rules are processed in the order they are defined.

```yaml
- Rule:
  Name: 'Header addition'
  Header: 'X-Custom-2'
  Value: 'True'
  Type: 'Set'
- Rule:
  Name: 'Header deletion'
  Header: 'X-Custom-2'
  Type: 'Del'
- Rule:
  Name: 'Header join'
  Header: 'X-Custom-2'
  Value: 'False'
  Type: 'Set'
```

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

### Perform Case-Insensitive Host Header Matching

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/header-utilities.md

Uses strings.EqualFold to ensure Host header comparisons are case-insensitive.

```go
strings.EqualFold(header, "Host")  // true for "Host", "host", "HOST", etc.
```

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

### Verify Header Transformations with curl

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Use these curl commands to validate that Set, Delete, and Join rules are correctly applied to HTTP headers.

```bash
# Test a Set rule
curl -H "Host: example.com" http://traefik-address/
# Check: Response has X-Custom header

# Test a Delete rule
curl -H "Host: example.com" http://traefik-address/
# Check: Server header not in response

# Test a Join rule
curl -H "Host: example.com" http://traefik-address/
# Check: Cache-Control has appended values
```

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

### Implement HTTP Handler

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Processes incoming requests and applies header transformations to both requests and responses.

```go
func (u *HeadersTransformation) ServeHTTP(rw http.ResponseWriter, req *http.Request)
```

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

### Header Forwarding with Prefix

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Joins header values with a specified separator and prefix.

```yaml
- type: "Join"
  header: "X-Forwarded-For"
  headerPrefix: "^"
  values:
    - "^CF-Connecting-IP"
  sep: ","
```

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

### Define Rule Execution Order

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Rules are processed sequentially in the order they appear in the configuration file.

```yaml
rules:
  - name: "First-Rule"    # Executed first
  - name: "Second-Rule"   # Executed after first
  - name: "Third-Rule"    # Executed after second
```

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

### Implement Hijacker in Custom ResponseWriter

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Pattern for ensuring a custom response writer supports the http.Hijacker interface.

```go
type MyResponseWriter struct {
    http.ResponseWriter
    // ... custom fields
}

// Implement http.Hijacker
func (w *MyResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
    hijacker, ok := w.ResponseWriter.(http.Hijacker)
    if !ok {
        return nil, nil, fmt.Errorf("hijacker not supported")
    }
    return hijacker.Hijack()
}
```

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

### Multi-Value Header Transformation

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rename-handler.md

Demonstration of how the Rename handler preserves multiple values when renaming a header.

```text
Original: X-Tag: value1
Original: X-Tag: value2

After rename to X-Tags:
X-Tags: value1
X-Tags: value2
```

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

### Configure Request Tracing

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Set static request IDs or join multiple headers to create trace identifiers.

```yaml
- type: "Set"
  header: "X-Request-ID"
  value: "req-123"

- type: "Join"
  header: "X-Trace-ID"
  values:
    - "^X-Traefik-Request-ID"
  sep: "-"
  headerPrefix: "^"
```

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

### Handle Header Rewriting

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rewrite-handler.md

Applies header value transformations to requests or responses based on the configured regex patterns.

```go
func (r *Rewrite) Handle(rw http.ResponseWriter, req *http.Request)
```

```go
// Simple value rewrite
rule := types.Rule{
    Name:          "Rewrite-Content-Type",
    Type:          types.RewriteValueRule,
    Header:        "Content-Type",
    Value:         "text/(.*)",
    ValueReplace:  "application/$1",
    SetOnResponse: false,
}
handler, _ := rewrite.New(rule)

// Before:
// Content-Type: text/plain
// After:
// Content-Type: application/plain
handler.Handle(responseWriter, request)
```

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

### Configure Response Header Rule

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Sets a response header by setting setOnResponse to true.

```yaml
- name: "Add-Security-Headers"
  type: "Set"
  header: "X-Content-Type-Options"
  value: "nosniff"
  setOnResponse: true  # Applies to response
```

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

### Handler.Handle

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

The Handle method is the primary entry point for processing HTTP requests and responses within the library.

```APIDOC
## Handle(rw http.ResponseWriter, req *http.Request)

### Description
Processes an HTTP request and response using the configured transformation rules.

### Parameters
- **rw** (http.ResponseWriter) - Required - The response writer to send the response.
- **req** (*http.Request) - Required - The incoming HTTP request to be transformed.
```

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

### Cache Control Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Sets cache-control headers for static assets.

```yaml
- type: "Set"
  header: "Cache-Control"
  value: "public, max-age=31536000"
  setOnResponse: true
  name: "Cache-Static"
```

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

### Define Plugin Configuration Structure

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

The Config struct defines the slice of transformation rules applied by the plugin.

```go
type Config struct {
    Rules []types.Rule
}
```

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

### ServeHTTP Method Signature

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/headers-transformation.md

Method signature for processing HTTP requests and responses within the middleware chain.

```go
func (u *HeadersTransformation) ServeHTTP(responseWriter http.ResponseWriter, request *http.Request)
```

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

### Validate Rewrite Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rewrite-handler.md

Checks if the handler configuration contains all required fields, specifically ensuring ValueReplace is not empty.

```go
func (r *Rewrite) Validate() error
```

```go
handler, _ := rewrite.New(rule)
if err := handler.Validate(); err != nil {
    log.Printf("Invalid configuration: %v", err)
}
```

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

### Handle Header Deletion

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/delete-handler.md

Signature for the handle method.

```go
func (d *Deleter) Handle(rw http.ResponseWriter, req *http.Request)
```

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

### Validate Handler Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/delete-handler.md

Signature for the validation method.

```go
func (d *Deleter) Validate() error
```

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

### Handle Header Concatenation

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

Applies the join logic to request or response headers based on the handler configuration.

```go
func (j *Join) Handle(rw http.ResponseWriter, req *http.Request)
```

```go
// Basic join
rule := types.Rule{
    Name:   "Join-Cache-Values",
    Type:   types.Join,
    Header: "Cache-Control",
    Values: []string{"public", "max-age=3600"},
    Sep:    ", ",
    SetOnResponse: false,
}
handler, _ := join.New(rule)
// Request headers: Cache-Control: no-cache
// After join: Cache-Control: no-cache, public, max-age=3600
handler.Handle(responseWriter, request)
```

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

### Define Rule configuration structure

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/types.md

Configuration structure for a single header transformation rule, including fields for header matching and transformation logic.

```go
type Rule struct {
    Header       string         `yaml:"Header"`
    HeaderPrefix string         `yaml:"HeaderPrefix"`
    Name         string         `yaml:"Name"`
    Regexp       *regexp.Regexp `yaml:"-"`
    Sep          string         `yaml:"Sep"`
    Type         RuleType       `yaml:"Type"`
    Value        string         `yaml:"Value"`
    ValueReplace string         `yaml:"ValueReplace"`
    Values       []string       `yaml:"Values"`
    SetOnResponse bool          `yaml:"SetOnResponse"`
}
```

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

### Project Directory Structure

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/INDEX.md

Overview of the htransformation package and module organization.

```text
github.com/tomMoulard/htransformation/
├── htransformation.go
│   ├── HeadersTransformation      [headers-transformation.md]
│   ├── Config                      [types.md]
│   └── wrappedResponseWriter       (internal)
│
├── pkg/
│   ├── types/
│   │   └── types.go
│   │       ├── RuleType           [types.md]
│   │       ├── Rule               [types.md]
│   │       ├── Handler            [types.md]
│   │       └── Errors             [errors.md]
│   │
│   ├── handler/
│   │   ├── set/set.go             [set-handler.md]
│   │   ├── deleter/delete.go      [delete-handler.md]
│   │   ├── join/join.go           [join-handler.md]
│   │   ├── rename/rename.go       [rename-handler.md]
│   │   └── rewrite/rewrite.go     [rewrite-handler.md]
│   │
│   └── utils/
│       └── header/
│           ├── set.go             [header-utilities.md]
│           ├── add.go             [header-utilities.md]
│           └── delete.go          [header-utilities.md]
```

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

### Configure Set Rule

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/INDEX.md

Defines a rule to create or replace a specific header with a static value.

```yaml
- type: "Set"
  header: "X-Custom"
  value: "MyValue"
```

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

### Set Header Rule

Source: https://github.com/tommoulard/htransformation/blob/main/README.md

Configuration to create or replace a header value.

```yaml
- Rule:
      Name: 'Set Cache-Control'
      Header: 'Cache-Control'
      Value: 'Foo'
      Type: 'Set'
```

```yaml
# New header:
Cache-Control: Foo
```

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

### Join Rule Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Defines a rule to join multiple header values with a separator.

```yaml
type: "Join"
header: string              # Required: Header name
values: []string            # Required: Values to join
sep: string                 # Required: Separator
headerPrefix: string        # Optional: Prefix for header refs
name: string                # Optional: Rule name
setOnResponse: bool         # Optional: Default false
```

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

### Configure Cache Headers

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Define Cache-Control headers for static assets and API responses to manage browser and proxy caching.

```yaml
rules:
  - name: "Cache-Static-Assets"
    type: "Set"
    header: "Cache-Control"
    value: "public, max-age=31536000"
    setOnResponse: true
  
  - name: "Cache-API-Responses"
    type: "Set"
    header: "Cache-Control"
    value: "private, max-age=3600"
    setOnResponse: true
```

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

### Validate Handler Configurations

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Validation logic for different handlers that return ErrMissingRequiredFields when required fields are empty.

```go
func (s *Set) Validate() error {
    if s.rule.Header == "" {
        return types.ErrMissingRequiredFields
    }
    return nil
}
```

```go
func (j *Join) Validate() error {
    if len(j.rule.Values) == 0 || j.rule.Sep == "" {
        return types.ErrMissingRequiredFields
    }
    return nil
}
```

```go
func (r *Rename) Validate() error {
    if r.rule.Value == "" {
        return types.ErrMissingRequiredFields
    }
    return nil
}
```

```go
func (r *Rewrite) Validate() error {
    if r.rule.ValueReplace == "" {
        return types.ErrMissingRequiredFields
    }
    return nil
}
```

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

### Handle Header Renaming

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/rename-handler.md

Applies header renaming based on a regex pattern to either the request or response.

```go
func (r *Rename) Handle(rw http.ResponseWriter, req *http.Request)
```

```go
// Request header renaming
rule := types.Rule{
    Name:   "Rename-All-X-Traefik",
    Type:   types.Rename,
    Header: "X-Traefik-.*",  // Matches X-Traefik-uuid, X-Traefik-date, etc.
    Value:  "X-Traefik-merged",
    SetOnResponse: false,
}
handler, _ := rename.New(rule)
handler.Handle(responseWriter, request)

// Before:
// X-Traefik-uuid: abc123
// X-Traefik-date: 2024-01-01
// X-Other-Header: unchanged

// After:
// X-Traefik-merged: abc123
// X-Traefik-merged: 2024-01-01
// X-Other-Header: unchanged
```

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

### Configure Request Header Rule

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Sets a request header by setting setOnResponse to false.

```yaml
- name: "Add-Auth-Header"
  type: "Set"
  header: "Authorization"
  value: "Bearer token123"
  setOnResponse: false  # Applies to request
```

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

### Set Cache Control Headers

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Configure cache-control policies for static assets using the Set type.

```yaml
- type: "Set"
  header: "Cache-Control"
  value: "public, max-age=31536000"
  setOnResponse: true
  name: "Cache-Static-Assets"
```

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

### Set Rule Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Defines a rule to set a specific header value.

```yaml
type: "Set"
header: string              # Required: Header name
value: string               # Required: Header value
name: string                # Optional: Rule name
setOnResponse: bool         # Optional: Default false
```

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

### Define ErrMissingRequiredFields

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

The base error definition for missing configuration fields.

```go
var ErrMissingRequiredFields = errors.New("missing required fields")
```

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

### Join Header Rule

Source: https://github.com/tommoulard/htransformation/blob/main/README.md

Configuration to concatenate values into an existing header, optionally using header prefixes.

```yaml
- Rule:
      Name: 'Header join'
      Header: 'Cache-Control'
      Sep: ','
      Values:
        - 'Foo'
        - 'Bar'
      Type: 'Join'
```

```yaml
# Old header:
Cache-Control: gzip, deflate

# Joined header:
Cache-Control: gzip, deflate,Foo,Bar
```

```yaml
- Rule:
  Name: 'Header set'
  Header: 'X-Forwarded-For'
  HeaderPrefix: "^"
  Sep: ','
  Values:
      - 'Foo'
      - '^CF-Connecting-IP'
  Type: 'Join'
```

```yaml
# Old header:
X-Forwarded-For: 1.1.1.1
CF-Connecting-IP: 2.2.2.2
# New headers:
X-Forwarded-For: 1.1.1.1,Foo,2.2.2.2
CF-Connecting-IP: 2.2.2.2
```

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

### Migrate API Version Headers

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Rename headers or rewrite values to facilitate API version transitions.

```yaml
- type: "Rename"
  header: "X-API-v1"
  value: "X-API-v2"

- type: "RewriteValueRule"
  header: "Content-Type"
  value: "application/v1\\+json"
  valueReplace: "application/v2+json"
```

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

### Migrate API Headers

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Rename or rewrite header values to support API version transitions.

```yaml
rules:
  - name: "Rename-Old-API-Headers"
    type: "Rename"
    header: "X-API-v1-.*"
    value: "X-API-v2"
  
  - name: "Update-Content-Type"
    type: "RewriteValueRule"
    header: "Content-Type"
    value: "application/v1\\+json"
    valueReplace: "application/v2+json"
```

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

### Configure htransformation in TOML

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/configuration.md

Defines static configuration for the htransformation plugin using TOML syntax for header rule definitions.

```toml
[http.middlewares.htransformation.plugin.htransformation]

[[http.middlewares.htransformation.plugin.htransformation.rules]]
name = "Set-Custom-Header"
type = "Set"
header = "X-Custom"
value = "CustomValue"
setOnResponse = false

[[http.middlewares.htransformation.plugin.htransformation.rules]]
name = "Delete-Cache"
type = "Del"
header = "Cache-Control"
setOnResponse = true

[[http.middlewares.htransformation.plugin.htransformation.rules]]
name = "Join-Headers"
type = "Join"
header = "X-Items"
sep = ","
values = ["item1", "item2"]
```

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

### Define RuleType constants

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Enumerates the supported transformation types for header manipulation.

```go
type RuleType string

const (
    Set              RuleType = "Set"
    Join             RuleType = "Join"
    Delete           RuleType = "Del"
    Rename           RuleType = "Rename"
    RewriteValueRule RuleType = "RewriteValueRule"
)
```

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

### Wrap Error with Context

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Wraps the validation error with the rule name during plugin initialization.

```go
return nil, fmt.Errorf("%w: %s", err, rule.Name)
```

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

### Define Rule structure

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/README.md

Represents the configuration schema for a transformation rule.

```go
type Rule struct {
    Header       string         // Header name or regex pattern
    HeaderPrefix string         // Prefix for header references
    Name         string         // Rule name for debugging
    Sep          string         // Separator for Join
    Type         RuleType       // Rule type
    Value        string         // New value or pattern
    ValueReplace string         // Replacement for Rewrite
    Values       []string       // Values for Join
    SetOnResponse bool          // Apply to response instead of request
}
```

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

### Add Security Headers

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Configuration to inject security-related headers into responses.

```yaml
- type: "Set"
  header: "X-Content-Type-Options"
  value: "nosniff"
  setOnResponse: true

- type: "Set"
  header: "X-Frame-Options"
  value: "DENY"
  setOnResponse: true
```

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

### Handle missing header in Go

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

The handler returns early if the target header is not present in the request.

```go
val, ok := req.Header[j.rule.Header]
if !ok {
    return  // Returns early, no header is created
}
```

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

### Validate Join Handler Configuration

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/join-handler.md

Checks that the handler configuration contains required fields, specifically ensuring Values and Sep are populated.

```go
func (j *Join) Validate() error
```

```go
handler, _ := join.New(rule)
if err := handler.Validate(); err != nil {
    log.Printf("Validation failed: %v", err)
}
```

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

### Wrap Error with Context

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/errors.md

Implementation of error wrapping to include the rule name in the error message.

```go
return nil, fmt.Errorf("%w: %s", types.ErrInvalidRuleType, rule.Name)
```

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

### Go Package Imports

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Required imports for utilizing htransformation handlers and types in a Go project.

```go
import (
    "net/http"
    "github.com/tomMoulard/htransformation"
    "github.com/tomMoulard/htransformation/pkg/handler/deleter"
    "github.com/tomMoulard/htransformation/pkg/handler/join"
    "github.com/tomMoulard/htransformation/pkg/handler/rename"
    "github.com/tomMoulard/htransformation/pkg/handler/rewrite"
    "github.com/tomMoulard/htransformation/pkg/handler/set"
    "github.com/tomMoulard/htransformation/pkg/types"
    "github.com/tomMoulard/htransformation/pkg/utils/header"
)
```

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

### Set HTTP Header Function Signature

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/api-reference/header-utilities.md

Defines the function signature for setting or replacing HTTP header values.

```go
func Set(req *http.Request, header string, value string)
```

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

### Capture Group Swap Rule

Source: https://github.com/tommoulard/htransformation/blob/main/_autodocs/QUICK_REFERENCE.md

Reorders header values using regex capture groups.

```yaml
- type: "RewriteValueRule"
  header: "X-Date"
  value: "(\d{4})-(\d{2})-(\d{2})"  # YYYY-MM-DD
  valueReplace: "$3/$2/$1"              # DD/MM/YYYY
```