#!/usr/bin/env bash

set -e

GO_VERSION=${GO_VERSION:-1.14.1}

PREFIX_DIR=/usr/local
#BIN_DIR=${PREFIX_DIR}/bin

GO_PREFIX_DIR=${PREFIX_DIR}/golang
GO_DEST_DIR=${GO_PREFIX_DIR}/${GO_VERSION}
GO_CURRENT=${PREFIX_DIR}/go

OS=
if [[ $OSTYPE =~ linux ]]; then
    OS=linux
elif [[  $OSTYPE =~ darwin ]]; then
    OS=darwin
else
    echo unknown os: $OSTYPE
    exit 1
fi

ARCH=
if [[ $(uname -m) == x86_64 ]]; then
    ARCH=amd64
else
    echo arch not yet supported: $(uname -m)
    exit 1
fi

[[ -d ${GO_DEST_DIR} ]] || sudo mkdir -p ${GO_DEST_DIR}

TMP_DIR=
if [[ ! -d ${GO_DEST_DIR}/bin ]]; then
    TMP_DIR=$(mktemp --directory)
    DEST_FILE=$TMP_DIR/go.tar.gz
    URL=https://dl.google.com/go/go${GO_VERSION}.${OS}-${ARCH}.tar.gz
    echo downloading go $GO_VERSION to temp directory ${TMP_DIR}
    curl --silent --output ${DEST_FILE} ${URL}

    sudo tar xf ${DEST_FILE} --directory ${GO_DEST_DIR} --strip-components 1
    sudo chown --recursive root:root ${GO_DEST_DIR}
else
    echo go $GO_VERSION already installed
fi

cd ${PREFIX_DIR}
[[ -s go ]] && sudo unlink go
sudo ln --symbolic ${GO_DEST_DIR} go
echo current version set to ${GO_VERSION}

[[ -f /etc/profile.d/go-path.sh ]] \
    || echo 'export PATH=$PATH:/usr/local/go/bin' \
    | sudo tee /etc/profile.d/go-path.sh

if [[ $TMP_DIR != "" ]]; then
    rm -rf ${TMP_DIR}
    echo removed up temp directory ${TMP_DIR}
fi