From b067ff65e7ac06d38eade15b6862798de6f3e860 Mon Sep 17 00:00:00 2001
From: Smuu <18609909+Smuu@users.noreply.github.com>
Date: Tue, 24 Oct 2023 13:57:29 +0200
Subject: [PATCH] feat: create initial proxy logic

Signed-off-by: Smuu <18609909+Smuu@users.noreply.github.com>
---
 .github/workflows/docker-build-publish.yaml | 25 +++++++
 Dockerfile                                  | 27 +++++++
 go.mod                                      |  3 +
 main.go                                     | 82 +++++++++++++++++++++
 4 files changed, 137 insertions(+)
 create mode 100644 .github/workflows/docker-build-publish.yaml
 create mode 100644 Dockerfile
 create mode 100644 go.mod
 create mode 100644 main.go

diff --git a/.github/workflows/docker-build-publish.yaml b/.github/workflows/docker-build-publish.yaml
new file mode 100644
index 0000000..ef0fef9
--- /dev/null
+++ b/.github/workflows/docker-build-publish.yaml
@@ -0,0 +1,25 @@
+name: Docker Build & Publish
+
+# Trigger on all push events, new semantic version tags, and all PRs
+on:
+  push:
+    branches:
+      - "main"
+      - "v[0-9].[0-9].x"
+      - "v[0-9].[0-9][0-9].x"
+      - "v[0-9].x"
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+"
+      - "v[0-9]+.[0-9]+.[0-9]+-alpha.[0-9]+"
+      - "v[0-9]+.[0-9]+.[0-9]+-beta.[0-9]+"
+      - "v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+"
+  pull_request:
+
+jobs:
+  docker-security-build:
+    permissions:
+      contents: write
+      packages: write
+    uses: celestiaorg/.github/.github/workflows/reusable_dockerfile_pipeline.yml@v0.2.8 # yamllint disable-line rule:line-length
+    with:
+      dockerfile: Dockerfile
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..a4d2956
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,27 @@
+# Use the official Golang image to create a build artifact.
+FROM golang:1.21.1 AS builder
+
+# Set the working directory inside the container.
+WORKDIR /app
+
+# Copy go mod and sum files
+#COPY go.mod go.sum ./
+COPY go.mod ./
+
+# Download all dependencies.
+RUN go mod download
+
+# Copy the source code into the container.
+COPY . .
+
+# Build the Go app
+RUN CGO_ENABLED=0 GOOS=linux go build -o main .
+
+# Use a lightweight image for the final image.
+FROM alpine:3
+
+# Copy the binary.
+COPY --from=builder /app/main /app/main
+
+# Run the binary.
+CMD ["/app/main"]
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..9999438
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/celestiaorg/autoscale-proxy
+
+go 1.21.1
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..75650b6
--- /dev/null
+++ b/main.go
@@ -0,0 +1,82 @@
+package main
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"strings"
+)
+
+func replaceDomainInResponse(originalSubdomain, replaceSubdomain, originalDomain string, buffer *bytes.Buffer) {
+	body := buffer.String()
+	fullReplace := replaceSubdomain + "." + "lunaroasis.net" // We know that statescale and snapscale are under this domain
+	fullOriginal := originalSubdomain + "." + originalDomain // Original domain can vary
+	replacedBody := strings.ReplaceAll(body, fullReplace, fullOriginal)
+	buffer.Reset()
+	buffer.WriteString(replacedBody)
+}
+
+func proxyRequest(fullSubdomain, path string, buffer *bytes.Buffer, r *http.Request) (int, map[string]string, error) {
+	client := &http.Client{}
+	target := "https://" + fullSubdomain + ".lunaroasis.net" + path
+	newReq, err := http.NewRequest(r.Method, target, r.Body)
+	if err != nil {
+		return 0, nil, err
+	}
+	newReq.Header = r.Header
+
+	resp, err := client.Do(newReq)
+	if err != nil {
+		return 0, nil, err
+	}
+	defer resp.Body.Close()
+
+	headers := make(map[string]string)
+	for key, values := range resp.Header {
+		for _, value := range values {
+			headers[key] = value
+		}
+	}
+
+	io.Copy(buffer, resp.Body)
+	return resp.StatusCode, headers, nil
+}
+
+func handleRequest(w http.ResponseWriter, r *http.Request) {
+	hostParts := strings.Split(r.Host, ".")
+	if len(hostParts) < 3 {
+		http.Error(w, "Invalid domain", http.StatusBadRequest)
+		return
+	}
+
+	subdomain := hostParts[0] // Extract original domain
+	originalDomain := strings.Join(hostParts[1:], ".")
+
+	buffer := new(bytes.Buffer)
+	backupBuffer := new(bytes.Buffer)
+
+	statusCode, headers, err := proxyRequest(subdomain+".statescale", r.RequestURI, buffer, r)
+	if err != nil || statusCode >= 400 {
+		backupStatusCode, backupHeaders, _ := proxyRequest(subdomain+".snapscale", r.RequestURI, backupBuffer, r)
+		replaceDomainInResponse(subdomain, subdomain+".snapscale", originalDomain, backupBuffer)
+
+		for key, value := range backupHeaders {
+			w.Header().Set(key, value)
+		}
+		w.WriteHeader(backupStatusCode)
+		io.Copy(w, backupBuffer)
+		return
+	}
+
+	replaceDomainInResponse(subdomain, subdomain+".statescale", originalDomain, buffer)
+	for key, value := range headers {
+		w.Header().Set(key, value)
+	}
+	w.WriteHeader(statusCode)
+	io.Copy(w, buffer)
+}
+
+func main() {
+	http.HandleFunc("/", handleRequest)
+	http.ListenAndServe(":8080", nil)
+}