Downgrade (download and switch) a brew package

brew-download-switch

#!/usr/bin/env bash
# Downloads from bintray and extracts into cellar

# Intended as support brew switch <formula> <version>
#   in case that the given version is no longer available in cellar

# e.g.
# $0 terraform 0.11.11 should download the following
#   https://bintray.com/homebrew/bottles/download_file?file_path=terraform-0.11.11.sierra.bottle.tar.gz
# Which allows brew switch terraform 0.11.11 to succeed

set -euo pipefail

[ -n "${CELLAR_PATH:-}" ] || CELLAR_PATH="$(brew --cellar)"
test -n "${CELLAR_PATH}"
[ -n "${OSX_VERSION:-}" ] || OSX_VERSION=sierra
[ -n "${BOTTLE_REPO_DOMAIN:-}" ] || BOTTLE_REPO_DOMAIN=bintray.com

BOTTLE_FORMULA="${1?}"
BOTTLE_FORMULA="$( brew info "${BOTTLE_FORMULA}" | awk -F: 'NR == 1 {print $1}' )"
test -n "${BOTTLE_FORMULA}"

BOTTLE_VERSION="${2?}"
test -n "${BOTTLE_VERSION}"

BOTTLE_FILES_URL="https://${BOTTLE_REPO_DOMAIN}/version/files/homebrew/bottles/${BOTTLE_FORMULA}/${BOTTLE_VERSION}"
BOTTLE_DOWNLOAD_PATH="$(
  nvim -c '%normal 0dt/f"D' -c '%print' -es <(
    curl '-#L' "${BOTTLE_FILES_URL}" |
      grep -w 'data-id="downloadRef' |
      grep -w "${OSX_VERSION}"
  )
)"
test -n "${BOTTLE_DOWNLOAD_PATH}"

BOTTLE_DOWNLOAD_URL="https://${BOTTLE_REPO_DOMAIN}${BOTTLE_DOWNLOAD_PATH}"
test -n "${BOTTLE_DOWNLOAD_URL}"

cd "${CELLAR_PATH}"
curl '-#L' "${BOTTLE_DOWNLOAD_URL}" | tar -zx

brew switch "${BOTTLE_FORMULA}" "${BOTTLE_VERSION}"