split frontend build from multiarch build workflow

Author: Stefan Ernst

Dockerfile

@@ -1,9 +1,27 @@
 # Multi-stage build for Windshift server
-# Stage 1: Build the application
+
+# Stage 1: Build frontend on HOST platform (no QEMU emulation needed)
+# Using --platform=$BUILDPLATFORM ensures this runs natively on x86-64
+# which avoids QEMU issues with native Node.js binaries (esbuild, rollup, etc.)
+FROM --platform=$BUILDPLATFORM node:22-alpine AS frontend-builder
+
+WORKDIR /build
+
+# Copy package files first for better layer caching
+COPY frontend/package*.json ./
+
+# Install dependencies (npm ci is faster and more reliable for CI)
+RUN npm ci
+
+# Copy frontend source and build
+COPY frontend/ ./
+RUN npm run build
+
+# Stage 2: Build Go binary (target platform, uses QEMU for arm64)
 FROM golang:1.24.6-alpine AS builder
 
-# Install build dependencies
-RUN apk add --no-cache gcc musl-dev nodejs npm git tzdata
+# Install build dependencies (nodejs/npm no longer needed)
+RUN apk add --no-cache gcc musl-dev git tzdata
 
 # Set working directory
 WORKDIR /build
@@ -14,24 +32,16 @@ COPY go.mod go.sum ./
 # Copy source code
 COPY . .
 
-# Build frontend - clean install with explicit platform targeting
-WORKDIR /build/frontend
-ARG TARGETPLATFORM
-ARG TARGETARCH
-RUN rm -rf node_modules package-lock.json && \
-    npm config set target_arch ${TARGETARCH:-x64} && \
-    npm config set target_platform linux && \
-    npm install --force --ignore-scripts && \
-    npm rebuild && \
-    npm run build
-
-# Build backend with static linking (native architecture)
-WORKDIR /build
+# Copy pre-built frontend from frontend-builder stage
+# Static files (JS/CSS/HTML) are architecture-independent
+COPY --from=frontend-builder /build/dist ./frontend/dist
+
+# Build backend with static linking
 RUN CGO_ENABLED=1 \
     go build -ldflags '-s -w -linkmode external -extldflags "-static"' \
     -o windshift main.go
 
-# Stage 2: Scratch runtime (minimal image)
+# Stage 3: Scratch runtime (minimal image)
 FROM scratch
 
 # Copy CA certificates for HTTPS requests