Make Dockerfile cross-platform (ARM support) #1

# syntax=docker/dockerfile:1
# ── Frontend build stage ───────────────────────────────────────────────────────
FROM node:22-alpine AS frontend-builder
# Pin pnpm to the version in package.json's `packageManager` field (not @latest)
# so CI builds are reproducible and match the committed lockfile.
RUN corepack enable && corepack prepare pnpm@10.32.1 --activate
WORKDIR /app
COPY frontend/package.json frontend/pnpm-lock.yaml ./
RUN pnpm install --frozen-lockfile
COPY frontend/ .
RUN pnpm build
# ── Go build stage ─────────────────────────────────────────────────────────────
FROM golang:1.26-alpine AS builder
RUN apk add --no-cache ca-certificates wget
WORKDIR /build
COPY go.mod go.sum ./
RUN go mod download
COPY . .
COPY --from=frontend-builder /app/build ./frontend/build
# Build natively for whatever architecture this stage is running on
# (TARGETARCH is auto-populated by Docker buildx; falls back correctly
# on ARM hosts where the original hardcoded amd64 would produce a
# binary that can't execute at all).
ARG TARGETARCH
RUN CGO_ENABLED=0 GOOS=linux GOARCH=${TARGETARCH} go build \
    -ldflags="-s -w" \
    -o calnode ./cmd/calnode
# Download Litestream for the deployment target, matching TARGETARCH
ARG LITESTREAM_VERSION=0.3.13
RUN wget -qO- \
    "https://github.com/benbjohnson/litestream/releases/download/v${LITESTREAM_VERSION}/litestream-v${LITESTREAM_VERSION}-linux-${TARGETARCH}.tar.gz" \
    | tar -xz -C /usr/local/bin litestream
# ── Runtime stage ─────────────────────────────────────────────────────────────
# alpine (not scratch) — needed for the shell entrypoint and Litestream.
# No --platform pin here: inherits the build host's native architecture,
# matching whatever TARGETARCH the binary above was actually compiled for.
FROM alpine:3.21
RUN apk add --no-cache ca-certificates tzdata
COPY --from=builder /usr/local/bin/litestream /usr/local/bin/litestream
COPY --from=builder /build/calnode /calnode
COPY litestream.yml /etc/litestream.yml
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh
# Note: no `VOLUME` directive — persistent storage is provided by the platform's
# managed volume mounted at /data (Railway rejects the Docker VOLUME instruction;
# Fly mounts via fly.toml). The dir is created at runtime by entrypoint.sh.
EXPOSE 3000
ENV PORT=3000 \
    DATABASE_URL=sqlite:///data/calnode.db
ENTRYPOINT ["/entrypoint.sh"]