Merge pull request #6 from ThorstenHans/feature/spin-component

Rework spin-redirect to Non-WAGI & support for custom status codes

Author: vdice

Makefile

@@ -2,7 +2,7 @@ ENABLE_WASM_OPT ?= true
 
 .PHONY: build
 build:
-	tinygo build -wasm-abi=generic -target=wasi -gc=leaking -o redirect.wasm redirect.go
+	tinygo build -target=wasi -gc=leaking -o redirect.wasm ./
 ifeq ($(ENABLE_WASM_OPT),true)
 	wasm-opt -Os -o redirect.wasm redirect.wasm
 endif

README.md

@@ -4,15 +4,72 @@ This is a simple HTTP redirect component written in Go.
 
 This is not a Spin application in itself but a component that can be used in applications to redirect a route.
 
-Example usage:
+## Configuration
 
+The `spin-redirect` component can be configured to address your needs in different scenarios. `spin-redirect` tries to load configuration data from multiple places in the specified order:
+
+1. Spin component configuration
+2. Environment variables
+
+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`            |
+
+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.
+
+### Valid redirection status codes
+
+The `spin-redirect` component supports the following HTTP status codes to perform a redirect:
+
+- `301` Moved Permanently
+- `302` Found (Moved Temporarily)
+- `303` See Other: Only supported for `PUT` and `POST` requests
+- `307` Temporary Redirect
+- `308` Permanent Redirect
+
+## Example usage
+
+The following snippet shows how to add and configure `spin-redirect` in your `spin.toml` using environment variables
+
+```toml
+spin_manifest_version = "1"
+description = ""
+name = "test"
+trigger = { type = "http", base = "/" }
+version = "0.1.0"
+
+# Redirect / to /index.html using HTTP status code 301
+[[component]]
+id = "redirect-sample"
+source = "path/to/redirect.wasm"
+environment = { DESTINATION = "/index.html", STATUSCODE = "301" }
+
+[component.trigger]
+route = "/"
 ```
-# Redirect / to /index.html
+
+Alternatively, you can use component configuration to configure `spin-redirect` as shown below:
+
+```toml
+spin_manifest_version = "1"
+description = ""
+name = "test"
+trigger = { type = "http", base = "/" }
+version = "0.1.0"
+
+# Redirect / to /index.html using HTTP status code 301
 [[component]]
-id = "redirect-to-index"
+id = "redirect-sample"
 source = "path/to/redirect.wasm"
-environment = { DESTINATION = "/index.html" }
+
+[component.config]
+destination="/index.html"
+statuscode="301"
+
 [component.trigger]
 route = "/"
-executor = { type = "wagi" }
+
 ```

config.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"os"
+	"strings"
+
+	config "github.com/fermyon/spin/sdk/go/config"
+)
+
+type ConfigReader interface {
+	Get(key string) string
+}
+
+/*
+DefaultConfigReader implements ConfigReader interface
+and provides a Get method for reading configuration values.
+
+It first tries to find the value in Spin configuration.
+If the key is not found in Spin configuration, it will try
+to find the value in the environment variables.
+*/
+type DefaultConfigReader struct{}
+
+// NewDefaultConfigReader returns a new DefaultConfigReader
+func NewDefaultConfigReader() DefaultConfigReader {
+	return DefaultConfigReader{}
+}
+
+/*
+Get returns the configuration value for the given key
+If the key is not found in Spin configuration, it will try
+to find the value in the environment variables.
+
+For looking up a value in spin configuration, keys are used as is (case sensitive).
+For looking up a value in environment variables, keys are converted to uppercase.
+
+If key is neither found in Spin configuration nor in environment variables,
+an empty string is returned.
+
+Usage:
+
+	cfg := NewDefaultConfigReader()
+	value := cfg.Get("destination")
+*/
+func (c DefaultConfigReader) Get(key string) string {
+	v, err := config.Get(key)
+	if err != nil {
+		return os.Getenv(strings.ToUpper(key))
+	}
+	return v
+}

go.mod

@@ -1,3 +1,7 @@
 module github.com/fermyon/finicky-whiskers/redirect
 
-go 1.17
+go 1.17
+
+require github.com/fermyon/spin/sdk/go v1.4.2
+
+require github.com/julienschmidt/httprouter v1.3.0 // indirect

go.sum

@@ -0,0 +1,4 @@
+github.com/fermyon/spin/sdk/go v1.4.2 h1:4U2J2WooKptCa4zeBetKctz/DEJxv3RvGauW0bZ+e6U=
+github.com/fermyon/spin/sdk/go v1.4.2/go.mod h1:yb8lGesopgj/GwPzLPATxcOeqWZT/HjrzEFfwbztAXE=
+github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=
+github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=

redirect.go

@@ -1,11 +1,94 @@
 package main
 
 import (
-	"fmt"
-	"os"
+	"net/http"
+	"strconv"
+
+	spinhttp "github.com/fermyon/spin/sdk/go/http"
+)
+
+const (
+	// Default value for HTTP status code
+	DefaultStatusCode int = http.StatusFound
+	// Default value for redirection target
+	DefaultRedirectionTarget string = "/"
+	// Key for loading desired destination
+	destinationKey string = "destination"
+	// Key for loading desired HTTP status code
+	statusCodeKey string = "statuscode"
 )
 
+func init() {
+	r := NewSpinRedirect()
+	spinhttp.Handle(r.handleFunc)
+}
+
 func main() {
-	dest := os.Getenv("DESTINATION")
-	fmt.Printf("status: 302\nlocation: %s\n\n", dest)
+}
+
+// SpinRedirect is a struct that provides a handleFunc
+// for redirecting to a destination URL using configurable HTTP status code.
+type SpinRedirect struct {
+	cfg ConfigReader
+}
+
+// NewSpinRedirect returns a new SpinRedirect
+func NewSpinRedirect() SpinRedirect {
+	return SpinRedirect{
+		cfg: NewDefaultConfigReader(),
+	}
+}
+
+func (s SpinRedirect) handleFunc(w http.ResponseWriter, r *http.Request) {
+	dest, _ := s.getDestination()
+	code, _ := s.getStatusCode(r.Method)
+
+	w.Header().Set("Location", dest)
+	w.WriteHeader(code)
+}
+
+// getDestination returns the destination URL and a boolean indicating if the user provided a destination URL.
+// If no destination is found, DefaultRedirectionTarget (/) is returned.
+func (s SpinRedirect) getDestination() (string, bool) {
+	d := s.cfg.Get(destinationKey)
+	if len(d) == 0 {
+		return DefaultRedirectionTarget, false
+	}
+	return d, true
+}
+
+// getStatusCode returns the HTTP status code
+// If no status code is found, or if the provided value is invalid,
+// DefaultStatusCode is returned along with a boolean indicating if the user provided a valid status code.
+func (s SpinRedirect) getStatusCode(method string) (int, bool) {
+	str := s.cfg.Get(statusCodeKey)
+	code, err := strconv.Atoi(str)
+	if err != nil {
+		return DefaultStatusCode, false
+	}
+	if !isValidRedirectStatusCode(code, method) {
+		return DefaultStatusCode, false
+	}
+	return code, true
+}
+
+// isValidRedirectStatusCode returns true if the provided status code is valid for redirection
+func isValidRedirectStatusCode(code int, method string) bool {
+	if code == http.StatusSeeOther &&
+		(method == http.MethodPut || method == http.MethodPost) {
+		return true
+	}
+	validCodes := []int{
+		http.StatusMovedPermanently,
+		http.StatusFound,
+		http.StatusTemporaryRedirect,
+		http.StatusPermanentRedirect,
+	}
+
+	for _, c := range validCodes {
+		if c == code {
+			return true
+		}
+	}
+	return false
 }