#!/usr/bin/env bash

set -e

GO_VERSION=${GO_VERSION:-1.15.2}

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

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

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