feat(redirect): add include_path (and trim_prefix) for wildcard redirect support

Signed-off-by: Vaughn Dice <[email protected]>

Author: vdice

README.md

@@ -13,10 +13,12 @@ The `spin-redirect` component can be configured to address your needs in differe
 
 The following table outlines available configuration values:
 
-| Key           | Description                                           | Default Value    |
-|---------------|-------------------------------------------------------|------------------|
-| `destination` | Where should the component redirect to                | `/`              |
-| `statuscode`  | What HTTP status code should be used when redirecting | `302`            |
+| Key            | Description                                                                                                             | Default Value |
+|----------------|-------------------------------------------------------------------------------------------------------------------------|---------------|
+| `destination`  | Where should the component redirect to                                                                                  | `/`           |
+| `statuscode`   | What HTTP status code should be used when redirecting                                                                   | `302`         |
+| `include_path` | Whether to include the original request path on the destination redirect; see [wildcard redirects](#wildcard-redirects) | `false`       |
+| `trim_prefix`  | A specific prefix portion of the original request path to trim (when `include_path` is `true`)                          |               |
 
 The `spin-redirect` component tries to look up the config value in the Spin component configuration using the keys shown in the table above (lower case). If desired key is not present, it transforms the key to upper case (e.g., `DESTINATION`) and checks environment variables.
 
@@ -73,3 +75,47 @@ statuscode="301"
 route = "/"
 
 ```
+
+### Wildcard redirects
+
+Wildcard redirects can be enabled by setting `include_path` to `true`.  In the example below,
+all requests to the application will be redirected to `/foo`, with the original request path included,
+e.g. `/bar` will redirect to `/foo/bar`, `/baz` will redirect to `/foo/baz` and so on.
+
+```toml
+spin_manifest_version = 2
+
+[application]
+name = "wildcard-redirect"
+version = "0.1.0"
+
+[[trigger.http]]
+id = "trigger-redirect-to-foo"
+component = "redirect-to-foo"
+route = "/..."
+
+[component.redirect-to-foo]
+source = "modules/redirect.wasm"
+environment = { DESTINATION = "/foo", INCLUDE_PATH = "true" }
+```
+
+A prefix portion of the original request path can be trimmed via the `trim_prefix` configuration.
+
+In this example, the `/v1/` prefix is trimmed, such that requests to `/v1/bar` will redirect to `/v2/bar` and so on.
+
+```toml
+spin_manifest_version = 2
+
+[application]
+name = "wildcard-redirect"
+version = "0.1.0"
+
+[[trigger.http]]
+id = "trigger-redirect-v1-to-v2"
+component = "redirect-v1-to-v2"
+route = "/v1/..."
+
+[component.redirect-v1-to-v2]
+source = "modules/redirect.wasm"
+environment = { DESTINATION = "/v2", INCLUDE_PATH = "true", TRIM_PREFIX = "/v1/" }
+```

redirect.go

@@ -2,7 +2,10 @@ package main
 
 import (
 	"net/http"
+	"net/url"
+	"path"
 	"strconv"
+	"strings"
 
 	spinhttp "github.com/fermyon/spin/sdk/go/http"
 )
@@ -16,6 +19,10 @@ const (
 	destinationKey string = "destination"
 	// Key for loading desired HTTP status code
 	statusCodeKey string = "statuscode"
+	// Key to enable adding original path in redirect
+	includePathKey string = "include_path"
+	// Key for trimming a preceding portion of the included path
+	trimPrefixKey string = "trim_prefix"
 )
 
 func init() {
@@ -43,7 +50,7 @@ func (s SpinRedirect) handleFunc(w http.ResponseWriter, r *http.Request) {
 	dest, _ := s.getDestination()
 	code, _ := s.getStatusCode(r.Method)
 
-	w.Header().Set("Location", dest)
+	w.Header().Set("Location", s.WithPath(dest, r))
 	w.WriteHeader(code)
 }
 
@@ -92,3 +99,21 @@ func isValidRedirectStatusCode(code int, method string) bool {
 	}
 	return false
 }
+
+// WithPath returns the provided dest with the path portion of the request,
+// assuming the includePathKey has a value of true
+func (s SpinRedirect) WithPath(dest string, r *http.Request) string {
+	includePath := s.cfg.Get(includePathKey)
+	if includePath != "true" {
+		return dest
+	}
+
+	u, err := url.Parse(dest)
+	if err != nil {
+		return dest
+	}
+
+	u.Path = path.Join(u.Path, strings.TrimPrefix(r.URL.Path, s.cfg.Get(trimPrefixKey)))
+
+	return u.String()
+}