#!/usr/bin/env bash

set -e

SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

# When this script is used as is, SCRIPT_DIR is ok. If it's used as
# part of kernelDevTools, we have to inject the path to the flake.
if [ -z "$FLAKE_DIR" ]; then
   FLAKE_DIR="$SCRIPT_DIR"
fi

gcc_flag=false

# Parse command-line options
TEMP=$(getopt -o '' --longoptions gcc -- "$@")
eval set -- "$TEMP"

# Extract options into variables
while true; do
    case "$1" in
	--gcc)
	    gcc_flag=true
	    shift
	    ;;
	--)
	    shift
	    break
	    ;;
	*)
	    echo "Error: Invalid option"
	    echo "Usage: $0 [--gcc]"
	    exit 1
	    ;;
    esac
done

OLDEST_VERSION=$(git tag --contains=HEAD | grep -oE 'v[0-9]+\.[0-9]+' | sort | head -n1)

if [ -z "$OLDEST_VERSION" ]; then
    tput bold
    echo -n "Failed to recognize kernel version."
    tput sgr0
    echo " This could have different reasons:"
    echo
    echo "1. This is not a Git checkout of the Linux kernel sources. To checkout Linux, try:"
    echo "   \$ linux-checkout linux-src"
    echo
    echo "2. The repository has no remote that contains the version tags. Try:"
    echo "   \$ git remote add stable git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    echo "   \$ git fetch stable"
    exit 1
fi

ATTRIBUTE="linux_$(echo "$OLDEST_VERSION" | tr -d 'v' | tr '.' '_')"

if $gcc_flag; then
    ATTRIBUTE=${ATTRIBUTE}_gcc
fi

echo -n "Entering environment "
tput bold
echo -n "$ATTRIBUTE"
tput sgr0			# reset
echo ". This might take a moment. Exit via ^D."

exec nix develop "$FLAKE_DIR"\#"$ATTRIBUTE" --command "$SHELL"