FROM alpine:3.13

ENV PATH /usr/local/go/bin:$PATH

RUN set -eux; \
	apk add --no-cache ca-certificates jq curl; \
	([ ! -e /etc/nsswitch.conf ] && echo 'hosts: files dns' > /etc/nsswitch.conf); \
	apk add --no-cache --virtual .fetch-deps gnupg; \
	arch="$(apk --print-arch)"; \
	export GOVERSION="$(curl -fsSL 'https://go.dev/dl/?mode=json&include=1.18' | jq -r '.[0].version')"; \
	case "$arch" in \
		'x86_64') \
			export GOAMD64='v1' GOARCH='amd64' GOOS='linux'; \
			;; \
		'armhf') \
			export GOARCH='arm' GOARM='6' GOOS='linux'; \
			;; \
		'armv7') \
			export GOARCH='arm' GOARM='7' GOOS='linux'; \
			;; \
		'aarch64') \
			export GOARCH='arm64' GOOS='linux'; \
			;; \
		'x86') \
			export GOARCH='386' GOOS='linux'; \
			;; \
		'ppc64le') \
			export GOARCH='ppc64le' GOOS='linux'; \
			;; \
		's390x') \
			export GOARCH='s390x' GOOS='linux'; \
			;; \
		*) echo >&2 "error: unsupported architecture '$arch' (likely packaging update needed)"; exit 1 ;; \
	esac; \
# https://github.com/golang/go/issues/38536#issuecomment-616897960
	url="https://dl.google.com/go/$GOVERSION.src.tar.gz"; \
	sha256='4525aa6b0e3cecb57845f4060a7075aafc9ab752bb7b6b4cf8a212d43078e1e4'; \
# the precompiled binaries published by Go upstream are not compatible with Alpine, so we always build from source here 😅
	\
	wget -O go.tgz.asc "$url.asc"; \
	wget -O go.tgz "$url"; \
	echo "$sha256 *go.tgz" | sha256sum -c -; \
	\
# https://github.com/golang/go/issues/14739#issuecomment-324767697
	GNUPGHOME="$(mktemp -d)"; export GNUPGHOME; \
# https://www.google.com/linuxrepositories/
	gpg --batch --keyserver keyserver.ubuntu.com --recv-keys 'EB4C 1BFD 4F04 2F6D DDCC  EC91 7721 F63B D38B 4796'; \
# let's also fetch the specific subkey of that key explicitly that we expect "go.tgz.asc" to be signed by, just to make sure we definitely have it
	gpg --batch --keyserver keyserver.ubuntu.com --recv-keys '2F52 8D36 D67B 69ED F998  D857 78BD 6547 3CB3 BD13'; \
	gpg --batch --verify go.tgz.asc go.tgz; \
	gpgconf --kill all; \
	rm -rf "$GNUPGHOME" go.tgz.asc; \
	\
	tar -C /usr/local -xzf go.tgz; \
	rm go.tgz; \
	\
	apk add --no-cache --virtual .build-deps \
		bash \
		gcc \
		go \
		musl-dev \
	; \
	\
	export GOCACHE='/tmp/gocache'; \
	\
	( \
		cd /usr/local/go/src; \
# set GOROOT_BOOTSTRAP + GOHOST* such that we can build Go successfully
		export GOROOT_BOOTSTRAP="$(go env GOROOT)" GOHOSTOS="$GOOS" GOHOSTARCH="$GOARCH"; \
		./make.bash; \
	); \
	\
	apk del --no-network .build-deps; \
	\
# remove a few intermediate / bootstrapping files the official binary release tarballs do not contain
	rm -rf \
		/usr/local/go/pkg/*/cmd \
		/usr/local/go/pkg/bootstrap \
		/usr/local/go/pkg/obj \
		/usr/local/go/pkg/tool/*/api \
		/usr/local/go/pkg/tool/*/go_bootstrap \
		/usr/local/go/src/cmd/dist/dist \
		"$GOCACHE" \
	; \
	\
	apk del --no-network .fetch-deps; \
	\
	go version

ENV GOPATH /go
ENV PATH $GOPATH/bin:$PATH
RUN mkdir -p "$GOPATH/src" "$GOPATH/bin" && chmod -R 777 "$GOPATH"
WORKDIR $GOPATH

RUN set -eux; \
    apk add --no-cache bash make git gcc libc-dev dumb-init && \
    go install github.com/go-delve/delve/cmd/dlv@latest && \
	go install github.com/cosmtrek/air@latest && \
	go install github.com/jstemmer/go-junit-report@latest && \
	go install github.com/axw/gocov/gocov@latest && \
    chmod -R 777 "$GOPATH"
WORKDIR /
ENTRYPOINT ["/usr/bin/dumb-init", "--"]