#!/bin/bash

set -e
if [ $(id -u) -ne 0 ]; then
  echo "error: this script must be run as root">&2
  exit 1
fi

install_dir="/usr/local"
go_dir="${install_dir}/go"
url="https://github.com/golang/go/archive"

v14="go1.4.3"
v14_sum="65e8d2ea08447f02f8b6ab63778e4d98586ac4fd676401dae0eda494c7829965"
bootstrap="${install_dir}/bootstrap-${v14}"
tgz14="${v14}.tar.gz"
path_v14="${install_dir}/${tgz14}"

new="go1.14.3"
new_sum="a71f18667e8946e3a4dcec4fbe85f963fed250cef89c9f3106408b39f4332bfc"
tgznew="${new}.tar.gz"
path_new="${install_dir}/${tgznew}"

rm -rf ${go_dir}

if [[ ! -d "${bootstrap}" ]]; then
  wget -q ${url}/${tgz14} -O ${path_v14}
  if [[ "$(sha256sum ${path_v14}|cut -d" " -f1)" != "${v14_sum}" ]]; then
    echo "error: wrong checksum: ${path_v14}">&2
    exit 1
  fi
  tar xfz ${path_v14} -C ${install_dir}
  mv ${install_dir}/go-${v14} ${bootstrap}
fi

wget -q ${url}/${tgznew} -O ${path_new}
if [[ "$(sha256sum ${path_new}|cut -d" " -f1)" != "${new_sum}" ]]; then
  echo "error: wrong checksum: ${path_new}">&2
  exit 1
fi
tar xfz ${path_new} -C ${install_dir}
mv ${install_dir}/go-${new} ${go_dir}

export CGO_ENABLED=0

if [[ ! -x "${bootstrap}/bin/go" ]]; then
  cd ${bootstrap}/src
  ./make.bash &> /dev/null
fi

export GOROOT_BOOTSTRAP=${bootstrap}

[[ "$(uname -m)" == "x86_64" ]] && export GOARCH=amd64 || export GOARCH=386

cd ${go_dir}/src
./make.bash &> /dev/null

export GOROOT=${go_dir}
export PATH=${PATH}:${GOROOT}/bin:~/go/bin

cat <<EOF
add this to your .bashrc/.profile:

export CGO_ENABLED=${CGO_ENABLED}
export GOPATH=~/go
export GOROOT=${GOROOT}
export GO111MODULE=on
export PATH=\${PATH}:${GOROOT}:~/go/bin

EOF

go version