Make integer rand min and max configurable (#5)

* Add min rand_int_min and rand_int_max + rename placeholder * Add Validate and Provision w/ error handling * Adjust readme
steffenbusch · Oct 26, 2024 · 5e20efe · 5e20efe
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diff --git a/README.md b/README.md
@@ -6,16 +6,16 @@ This repository contains the **Extra Placeholders** plugin for the [Caddy](https
 
 This plugin introduces new placeholders that can be used within Caddy configurations:
 
-| Placeholder                    | Description                                       |
-|--------------------------------|---------------------------------------------------|
-| `{extra.caddy.version.simple}` | Simple version information of the Caddy server.   |
-| `{extra.caddy.version.full}`   | Full version information of the Caddy server.     |
-| `{extra.rand.float}`           | Random float value between 0.0 and 1.0.           |
-| `{extra.rand.int.0-100}`       | Random integer value between 0 and 100.           |
-| `{extra.loadavg.1}`            | System load average over the last 1 minute.       |
-| `{extra.loadavg.5}`            | System load average over the last 5 minutes.      |
-| `{extra.loadavg.15}`           | System load average over the last 15 minutes.     |
-| `{extra.hostinfo.uptime}`      | System uptime in a human-readable format.         |
+| Placeholder                    | Description                                           |
+|--------------------------------|-------------------------------------------------------|
+| `{extra.caddy.version.simple}` | Simple version information of the Caddy server.       |
+| `{extra.caddy.version.full}`   | Full version information of the Caddy server.         |
+| `{extra.rand.float}`           | Random float value between 0.0 and 1.0.               |
+| `{extra.rand.int}`             | Random integer value between the configured min and max (default is 0 to 100). |
+| `{extra.loadavg.1}`            | System load average over the last 1 minute.           |
+| `{extra.loadavg.5}`            | System load average over the last 5 minutes.          |
+| `{extra.loadavg.15}`           | System load average over the last 15 minutes.         |
+| `{extra.hostinfo.uptime}`      | System uptime in a human-readable format.             |
 
 These placeholders can be used in Caddyfiles to provide dynamic content and system information in responses.
 
@@ -36,42 +36,66 @@ To use the extra placeholders, you can add the following directive to your Caddy
 
 ```caddyfile
 :8080 {
-    extra_placeholders
+    extra_placeholders {
+        rand_int 10 50
+    }
 
-    respond "Caddy Version: {extra.caddy.version.full}, Uptime: {extra.hostinfo.uptime}"
+    respond "Caddy Version: {extra.caddy.version.full}, Uptime: {extra.hostinfo.uptime}, Random Int: {extra.rand.int}"
 }
 ```
 
-This example demonstrates how to use the additional placeholders provided by this plugin to dynamically insert Caddy version information and system uptime into an HTTP response.
+This example demonstrates how to use the additional placeholders provided by this plugin to dynamically insert Caddy version information, system uptime, and a random integer between 10 and 50 into an HTTP response.
+
+### Random Integer Configuration
+
+To configure the range for the `{extra.rand.int}` placeholder, use the `rand_int` subdirective inside the `extra_placeholders` directive. The format is:
+
+```caddyfile
+extra_placeholders {
+    rand_int <min> <max>
+}
+```
+
+- `<min>`: The minimum value for the random integer (inclusive).
+- `<max>`: The maximum value for the random integer (inclusive).
+
+If `rand_int` is not specified, the default values are:
+
+- `RandIntMin = 0`
+- `RandIntMax = 100`
+
+This means that `{extra.rand.int}` will default to generating a random integer between 0 and 100 if not explicitly configured.
 
 ### Example: Conditional Redirect Based on Random Value
 
 The following example demonstrates how you can use conditional expressions with the random integer placeholder to redirect users to different search engines based on the generated random number:
 
 ```caddyfile
 :8080 {
-    extra_placeholders
+    extra_placeholders {
+        rand_int 1 100
+    }
 
-    @redirectToGoogle expression `{extra.rand.int.0-100} <= 25`
+    @redirectToGoogle expression `{extra.rand.int} <= 25`
     redir @redirectToGoogle https://www.google.com
 
-    @redirectToBing expression `{extra.rand.int.0-100} > 25 && {extra.rand.int.0-100} <= 50`
+    @redirectToBing expression `{extra.rand.int} > 25 && {extra.rand.int} <= 50`
     redir @redirectToBing https://www.bing.com
 
-    @redirectToYahoo expression `{extra.rand.int.0-100} > 50 && {extra.rand.int.0-100} <= 75`
+    @redirectToYahoo expression `{extra.rand.int} > 50 && {extra.rand.int} <= 75`
     redir @redirectToYahoo https://www.yahoo.com
 
-    @redirectToDuckDuckGo expression `{extra.rand.int.0-100} > 75`
+    @redirectToDuckDuckGo expression `{extra.rand.int} > 75`
     redir @redirectToDuckDuckGo https://www.duckduckgo.com
 }
 ```
 
 In this example:
 
-- If `{extra.rand.int.0-100}` is between 0 and 25, the request is redirected to **Google** ([https://www.google.com](https://www.google.com)).
-- If `{extra.rand.int.0-100}` is between 26 and 50, the request is redirected to **Bing** ([https://www.bing.com](https://www.bing.com)).
-- If `{extra.rand.int.0-100}` is between 51 and 75, the request is redirected to **Yahoo** ([https://www.yahoo.com](https://www.yahoo.com)).
-- If `{extra.rand.int.0-100}` is greater than 75, the request is redirected to **DuckDuckGo** ([https://www.duckduckgo.com](https://www.duckduckgo.com)).
+- If `{extra.rand.int}` is between 1 and 25, the request is redirected to **Google** ([https://www.google.com](https://www.google.com)).
+- If `{extra.rand.int}` is between 26 and 50, the request is redirected to **Bing** ([https://www.bing.com](https://www.bing.com)).
+- If `{extra.rand.int}` is between 51 and 75, the request is redirected to **Yahoo** ([https://www.yahoo.com](https://www.yahoo.com)).
+- If `{extra.rand.int}` is greater than 75, the request is redirected to **DuckDuckGo** ([https://www.duckduckgo.com](https://www.duckduckgo.com)).
 
 This example demonstrates how to use the random integer placeholder in combination with conditional expressions to create dynamic redirection rules.
 

diff --git a/extra_placeholders.go b/extra_placeholders.go
@@ -15,8 +15,10 @@
 package extraplaceholders
 
 import (
+	"fmt"
 	"math/rand"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
@@ -28,7 +30,10 @@ import (
 )
 
 // ExtraPlaceholders represents the structure for the plugin.
-type ExtraPlaceholders struct{}
+type ExtraPlaceholders struct {
+	RandIntMin int `json:"rand_int_min,omitempty"`
+	RandIntMax int `json:"rand_int_max,omitempty"`
+}
 
 func init() {
 	// Register the module with Caddy and specify where in the directive order it should be applied.
@@ -42,7 +47,7 @@ func init() {
 // `{extra.caddy.version.simple}` | Simple version information of the Caddy server.
 // `{extra.caddy.version.full}` | Full version information of the Caddy server.
 // `{extra.rand.float}` | Random float value between 0.0 and 1.0.
-// `{extra.rand.int.0-100}` | Random integer value between 0 and 100.
+// `{extra.rand.int}` | Random integer value between the configured min and max (default is 0 to 100).
 // `{extra.loadavg.1}` | System load average over the last 1 minute.
 // `{extra.loadavg.5}` | System load average over the last 5 minutes.
 // `{extra.loadavg.15}` | System load average over the last 15 minutes.
@@ -56,8 +61,26 @@ func (ExtraPlaceholders) CaddyModule() caddy.ModuleInfo {
 	}
 }
 
+// Provision sets up the module. It is called once the module is instantiated.
+func (e *ExtraPlaceholders) Provision(ctx caddy.Context) error {
+	// Set default values if not configured
+	if e.RandIntMin == 0 && e.RandIntMax == 0 {
+		e.RandIntMin = 0
+		e.RandIntMax = 100
+	}
+	return nil
+}
+
+// Validate ensures the configuration is correct.
+func (e *ExtraPlaceholders) Validate() error {
+	if e.RandIntMax <= e.RandIntMin {
+		return fmt.Errorf("invalid configuration: RandIntMax (%d) must be greater than RandIntMin (%d)", e.RandIntMax, e.RandIntMin)
+	}
+	return nil
+}
+
 // ServeHTTP adds new placeholders and passes the request to the next handler in the chain.
-func (ExtraPlaceholders) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
+func (e ExtraPlaceholders) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
 	// Retrieve the replacer from the request context.
 	repl, ok := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	if !ok {
@@ -71,7 +94,11 @@ func (ExtraPlaceholders) ServeHTTP(w http.ResponseWriter, r *http.Request, next
 
 	// Set placeholders for random float and integer values.
 	repl.Set("extra.rand.float", rand.Float64())
-	repl.Set("extra.rand.int.0-100", rand.Intn(101))
+	if e.RandIntMax > e.RandIntMin {
+		repl.Set("extra.rand.int", rand.Intn(e.RandIntMax-e.RandIntMin+1)+e.RandIntMin)
+	} else {
+		repl.Set("extra.rand.int", rand.Intn(101)) // Default range 0-100 if not properly configured
+	}
 
 	// Set placeholders for system load averages (1, 5, and 15 minutes).
 	loadAvg, err := load.Avg()
@@ -103,16 +130,32 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 
 // UnmarshalCaddyfile processes the configuration from the Caddyfile.
 func (e *ExtraPlaceholders) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
-	// Consume the directive name and ensure no extra arguments are provided.
+	// Consume the directive name.
 	d.Next()
-	if d.NextArg() {
-		return d.ArgErr()
+
+	for d.NextBlock(0) {
+		switch d.Val() {
+		case "rand_int":
+			args := d.RemainingArgs()
+			if len(args) != 2 {
+				return d.ArgErr()
+			}
+			min, err1 := strconv.Atoi(args[0])
+			max, err2 := strconv.Atoi(args[1])
+			if err1 != nil || err2 != nil {
+				return d.ArgErr()
+			}
+			e.RandIntMin = min
+			e.RandIntMax = max
+		}
 	}
 	return nil
 }
 
 // Interface guards to ensure ExtraPlaceholders implements the necessary interfaces.
 var (
 	_ caddy.Module                = (*ExtraPlaceholders)(nil)
+	_ caddy.Provisioner           = (*ExtraPlaceholders)(nil)
+	_ caddy.Validator             = (*ExtraPlaceholders)(nil)
 	_ caddyhttp.MiddlewareHandler = (*ExtraPlaceholders)(nil)
 )