Download packages from brew repos directly, without actually installing brew

brew.sh

#!/bin/bash

# check for curl and jq
if [[ ! -f $(which curl) ]]; then
    echo "curl is missing"
    exit 1
fi

if [[ ! -f $(which jq) ]]; then
    echo "jq is missing"
    exit 2
fi

# detect the OS version
OS=""
case $(sw_vers -productVersion) in
    26*) OS="tahoe"    ;;
    15*) OS="sequoia"  ;;
    14*) OS="sonoma"   ;;
    13*) OS="ventura"  ;;
    12*) OS="monterey" ;;
    11*) OS="big_sur"  ;;
esac

# architecture
ARCH=$(machine)

# arm64e -> arm64, I guess?
if [[ "$ARCH" == "arm64e" ]]; then
    ARCH="arm64"
fi

PLATFORM=$ARCH"_"$OS
echo "Your platform:" $PLATFORM

# download brew's formula.json, if we don't have it
if [[ ! -f "formula.json" ]]; then
    echo "Downloading https://formulae.brew.sh/api/formula.json ..."
    curl -s "https://formulae.brew.sh/api/formula.json" --output formula.json
else
    echo "Using cached formula.json (delete to refresh)"
fi

# get a flat list of package names
PACKAGES=$(cat formula.json | jq -r ".[] | select(.bottle.stable.files.$PLATFORM.url) | .name")

# figure out operation mode
if [[ "$1" == "list" ]]; then
    echo "$PACKAGES"
elif [[ "$1" == "install" ]]; then
    PACKAGE="$2"
    if [[ "$PACKAGES" == *"$PACKAGE"* ]]; then
        URL=$(cat formula.json | jq -r ".[] | select(.name == \"$PACKAGE\") | .bottle.stable.files.$PLATFORM.url")
        echo "Downloading $URL ..."
        OUT_FILE=$PACKAGE"_"$PLATFORM.tar.gz
        curl -L -s -H "Authorization: Bearer QQ==" "$URL" --output $OUT_FILE
        echo "Extracting..."
        tar xzvf $OUT_FILE
    else
        echo "Package $PACKAGE not found"
    fi
elif [[ "$1" == "remove" ]]; then
    echo "TODO" # TODO: list out the contents of the tar file (download it first) and then delete those files
else
    echo "Usage: ./brew.sh list"
    echo "Usage: ./brew.sh install [package]"
fi