feat: add support for ALBTargetGroupRequest/Response

Author: its-felix

README.md

@@ -8,6 +8,7 @@ Simple HTTP adapter for AWS Lambda
 - AWS Lambda Function URL (both normal and streaming)
 - API Gateway (v1)
 - API Gateway (v2)
+- Application Load Balancer
 
 ## Builtin support for these HTTP frameworks:
 - `net/http`
@@ -252,6 +253,7 @@ Once this build-tag is present, the following build-tags are available:
 - `lambdahttpadapter.apigwv1` (enables API Gateway V1 handler)
 - `lambdahttpadapter.apigwv2` (enables API Gateway V2 handler)
 - `lambdahttpadapter.functionurl` (enables Lambda Function URL handler)
+- `lambdahttpadapter.alb` (enables Application Load Balancer handler)
 
 Also note that Lambda Function URL in Streaming-Mode requires the following build-tag to be set:
 - `lambda.norpc`

handler/alb.go

@@ -0,0 +1,165 @@
+//go:build !lambdahttpadapter.partial || (lambdahttpadapter.partial && lambdahttpadapter.alb)
+
+package handler
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"github.com/aws/aws-lambda-go/events"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"unicode/utf8"
+)
+
+func convertALBRequest(ctx context.Context, event events.ALBTargetGroupRequest) (*http.Request, error) {
+	q := make(url.Values)
+
+	if len(event.MultiValueQueryStringParameters) > 0 {
+		for k, values := range event.MultiValueQueryStringParameters {
+			for _, v := range values {
+				q.Add(k, v)
+			}
+		}
+	} else if len(event.QueryStringParameters) > 0 {
+		for k, v := range event.QueryStringParameters {
+			q.Add(k, v)
+		}
+	}
+
+	headers := make(http.Header)
+	if event.Headers != nil {
+		for k, v := range event.Headers {
+			headers.Add(k, v)
+		}
+	}
+
+	if event.MultiValueHeaders != nil {
+		for k, values := range event.MultiValueHeaders {
+			for _, v := range values {
+				headers.Add(k, v)
+			}
+		}
+	}
+
+	host := headers.Get("X-Forwarded-Host")
+	if host == "" {
+		host = headers.Get("Host")
+		if host == "" {
+			host = "127.0.0.1"
+		}
+	}
+
+	sourceIp := headers.Get("X-Forwarded-For")
+	if sourceIp == "" {
+		sourceIp = "127.0.0.1"
+	}
+
+	proto := headers.Get("X-Forwarded-Proto")
+	if proto == "" {
+		proto = "http"
+	}
+
+	rUrl := buildFullRequestURLWithProto(proto, host, event.Path, "", q.Encode())
+	req, err := http.NewRequestWithContext(ctx, event.HTTPMethod, rUrl, getBody(event.Body, event.IsBase64Encoded))
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header = headers
+	req.RemoteAddr = buildRemoteAddr(sourceIp)
+	req.RequestURI = req.URL.RequestURI()
+
+	return req, nil
+}
+
+type albResponseWriter struct {
+	multiValueHeaders bool
+	headersWritten    bool
+	contentTypeSet    bool
+	contentLengthSet  bool
+	headers           http.Header
+	body              bytes.Buffer
+	res               events.ALBTargetGroupResponse
+}
+
+func (w *albResponseWriter) Header() http.Header {
+	return w.headers
+}
+
+func (w *albResponseWriter) Write(p []byte) (int, error) {
+	w.WriteHeader(http.StatusOK)
+	return w.body.Write(p)
+}
+
+func (w *albResponseWriter) WriteHeader(statusCode int) {
+	if !w.headersWritten {
+		w.headersWritten = true
+		w.res.StatusCode = statusCode
+
+		for k, values := range w.headers {
+			if w.multiValueHeaders {
+				w.res.MultiValueHeaders[k] = values
+			} else {
+				w.res.Headers[k] = strings.Join(values, ",")
+			}
+		}
+	}
+}
+
+func handleALB(multiValueHeaders bool) func(ctx context.Context, event events.ALBTargetGroupRequest, adapter AdapterFunc) (events.ALBTargetGroupResponse, error) {
+	return func(ctx context.Context, event events.ALBTargetGroupRequest, adapter AdapterFunc) (events.ALBTargetGroupResponse, error) {
+		req, err := convertALBRequest(ctx, event)
+		if err != nil {
+			var def events.ALBTargetGroupResponse
+			return def, err
+		}
+
+		w := albResponseWriter{
+			multiValueHeaders: multiValueHeaders,
+			headers:           make(http.Header),
+			res:               events.ALBTargetGroupResponse{},
+		}
+
+		if multiValueHeaders {
+			w.res.MultiValueHeaders = make(map[string][]string)
+		} else {
+			w.res.Headers = make(map[string]string)
+		}
+
+		if err = adapter(ctx, req, &w); err != nil {
+			var def events.ALBTargetGroupResponse
+			return def, err
+		}
+
+		b, err := io.ReadAll(&w.body)
+		if err != nil {
+			var def events.ALBTargetGroupResponse
+			return def, err
+		}
+
+		if !w.contentTypeSet {
+			w.res.Headers["Content-Type"] = http.DetectContentType(b)
+		}
+
+		if !w.contentLengthSet {
+			w.res.Headers["Content-Length"] = strconv.Itoa(len(b))
+		}
+
+		if utf8.Valid(b) {
+			w.res.Body = string(b)
+		} else {
+			w.res.IsBase64Encoded = true
+			w.res.Body = base64.StdEncoding.EncodeToString(b)
+		}
+
+		return w.res, nil
+	}
+}
+
+func NewALBHandler(adapter AdapterFunc, multiValueHeaders bool) func(context.Context, events.ALBTargetGroupRequest) (events.ALBTargetGroupResponse, error) {
+	return NewHandler(handleALB(multiValueHeaders), adapter)
+}

handler/common.go

@@ -24,7 +24,11 @@ func buildQuery(rawQuery string, queryParams map[string]string) string {
 	return ""
 }
 
-func buildFullRequestURL(host string, path string, altPath string, query string) string {
+func buildFullRequestURL(host, path, altPath, query string) string {
+	return buildFullRequestURLWithProto("https", host, path, altPath, query)
+}
+
+func buildFullRequestURLWithProto(proto, host, path, altPath, query string) string {
 	rUrl := path
 
 	if rUrl == "" {
@@ -35,7 +39,7 @@ func buildFullRequestURL(host string, path string, altPath string, query string)
 		rUrl = "/" + rUrl
 	}
 
-	rUrl = "https://" + host + rUrl
+	rUrl = proto + "://" + host + rUrl
 
 	if query != "" {
 		rUrl += "?" + query