#!/bin/bash

python_path=""
module_to_import=""
skip_import=False
pip_package=""

function usage
{
    retval="$1"
    case "$retval" in
        0)
            ;;
        *)
            exec 1>&2
            ;;
    esac
    echo "Usage: $0"
    echo "    --python-path /where/python/lives/python"
    echo "    --module-to-import module_name"
    echo "    --skip-import"
    echo "    --pip-package pip-package-name"
    echo
    echo "This program installs a package from pypi, but only if module_name"
    echo "is not yet importable (or --skip-import is specified)."
    echo
    echo "This cuts down on unnecessary sudoing."
    exit "$retval"
}

while [ "$#" -ge 1 ]
do
    case "$1" in
        --python-path)
            python_path="$2"
            shift
            ;;
        --skip-import)
            skip_import=True
            ;;
        --module-to-import)
            module_to_import="$2"
            shift
            ;;
        --pip-package)
            pip_package="$2"
            shift
            ;;
        -h|--help)
            usage 0
            ;;
        *)
            echo "$0: Unrecognized option: $1" 1>&2
            usage 1
            ;;
    esac
    shift
done

case "$python_path" in
    "")
        echo --python-path is a required option 1>&2
        usage 1
        ;;
esac

function count_trues
{
    sum=0
    for cmd in "$@"
    do
        if eval "$cmd" > /dev/null 2>&1
        then
            sum=$((sum+1))
        fi
    done
    echo "$sum"
}

all_good=True

if [[ $(count_trues "[[ $module_to_import != '' ]]" "[[ $skip_import = True ]]") != 1 ]]
then
    echo "$0: You must specify exactly one of --module-to-import and --skip-import" 1>&2
    all_good=False
fi

case "$pip_package" in
    "")
        echo --pip-package is a required option 1>&2
        all_good=False
        ;;
esac

case "$all_good" in
    True)
        ;;
    False)
        echo "$0: One or more items in preflight check failed" 1>&2
        usage 1
        ;;
    *)
        echo "$0: internal error: \$all_good is neither True nor False: $all_good" 1>&2
        ;;
esac

function import_test
{
    "$python_path" -c "import $module_to_import" > /dev/null 2>&1
}

function pip_test
{
    "$python_path" -m pip list | grep -q "^$pip_package\$" > /dev/null 2>&1
}

if import_test || pip_test
then
    :
else
    "$python_path" -m pip install --break-system-packages "$pip_package" \
        || sudo "$python_path" -m pip install --break-system-packages "$pip_package" \
        || "$python_path" -m pip install "$pip_package" \
        || sudo "$python_path" -m pip install "$pip_package"
fi