go_install

#!/bin/sh
#
# Copyright 2026 Samvel Khalatyan. All rights reserved.
#
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file.

set -x
set -e

# keep-sorted start
readonly CACHE_PATH=${HOME}/.cache/go_install
readonly GO_ROOT_PREFIX=/usr/local
readonly GO_VERSION=${GO_VERSION:-1.26.0}
readonly LOG_PATH=go_install.log # relative to TMPDIR
# keep-sorted end

CHECKSUM_FILE=$(realpath go_checksum_sha256) # relative to script
readonly CHECKSUM_FILE

err() {
  echo "$@" >&2
}

check_platform() {
  case $(uname -s) in
    *Linux*) ;;
    *)
      return 1
      ;;
  esac
  case $(uname -v) in
    *FreeBSD*) ;;
    *)
      return 1
      ;;
  esac
}

check_privileges() {
  if [ $(id -u) = "0" ]; then
    return
  fi
  case $(id -nG) in
    *sudoer*)
      return
      ;;
  esac
  return 1
}

is_go_installed() {
  local go_version=
  if ! go_version=$(go env GOVERSION 2>/dev/null); then
    return 1
  fi
  if [ "$go_version" != "go${GO_VERSION}" ]; then
    return 1
  fi
  return
}

make_url() {
  local os=${1:?'make_url: missing os'}
  echo "https://go.dev/dl/go${GO_VERSION}.${os}-amd64.tar.gz"
}

download() {
  local os=${1:?'install: missing os'}
  local url
  url=$(make_url ${os})
  local archive
  archive=$(basename ${url})
  local archive_in_cache
  archive_in_cache="${CACHE_PATH}/${archive}"
  if test -e "${archive_in_cache}"; then
    echo ".. download ${url} (cached)"
    return
  fi
  echo ".. download ${url}"
  {
    wget --quiet --show-progress ${url}
    sha256sum -c ${CHECKSUM_FILE} --ignore-missing
    mv -nv ${archive} ${archive_in_cache}
  } >>${LOG_PATH}
}

extract() {
  local os=${1:?'extract: missing os'}
  local url
  url=$(make_url ${os})
  local archive
  archive=$(basename ${url})
  local archive_in_cache
  archive_in_cache="${CACHE_PATH}/${archive}"
  echo ".. extract ${archive}"
  {
    tar -xzf "${archive_in_cache}"
  } >>${LOG_PATH}
}

patch_from() {
  local os=${1:?'patch_from: missing os'}
  local url
  url=$(make_url ${os})
  local archive
  archive=$(basename ${url})
  local archive_in_cache
  archive_in_cache="${CACHE_PATH}/${archive}"
  local link_freebsd_path=go/pkg/tool/freebsd_amd64/link
  local link_linux_path=go/pkg/tool/linux_amd64/link
  echo ".. patch ${link_linux_path}"
  {
    tar -xzf ${archive_in_cache} ${link_freebsd_path}
  } >>${LOG_PATH}
  mv ${link_freebsd_path} ${link_linux_path}
  rm -rf ${link_freebsd_path%/*}
}

make_goroot() {
  local version=${GO_VERSION%.*}              # MAJOR.MINOR
  local suffix=$(echo ${version} | tr -d '.') # {MAJOR}{MINOR}
  echo ${GO_ROOT_PREFIX}/go${suffix}
}

install() {
  local goroot
  goroot=$(make_goroot)
  echo ".. install ${goroot} [need sudo]"
  if test -d ${goroot}; then
    sudo rm -rf ${goroot}
  fi
  sudo mv -i ${PWD}/go ${goroot}
}

run() {
  local tmpdir
  tmpdir=$(mktemp -d)
  trap "rm -rf ${tmpdir}" EXIT
  cd ${tmpdir}
  if ! test -d "${CACHE_PATH}"; then
    mkdir ${CACHE_PATH}
  fi
  download freebsd
  download linux
  extract linux
  patch_from freebsd
  install
}

main() {
  if ! check_platform; then
    err "unsupported platform - want Linux compatibility under FreeBSD"
    return 1
  fi
  if ! check_privileges; then
    err "the effective user does not have sudo privileges"
    return 1
  fi
  if is_go_installed; then
    echo "Go is installed to $(go env GOROOT)"
    return 0
  fi
  run
}

main