#!/bin/sh -eu

: ${MAFIA_HOME:=$HOME/.mafia}
: ${MAFIA_VERSIONS:=$MAFIA_HOME/versions}

latest_version () {
    git ls-remote https://github.com/haskell-mafia/mafia | grep refs/heads/master | cut -f 1
}

build_version() {
    MAFIA_VERSION="$1"
    MAFIA_TEMP=$(mktemp -d 2>/dev/null || mktemp -d -t 'exec_mafia')
    MAFIA_FILE=mafia-$MAFIA_VERSION
    MAFIA_PATH=$MAFIA_VERSIONS/$MAFIA_FILE
    mkdir -p $MAFIA_VERSIONS
    echo "Building $MAFIA_FILE in $MAFIA_TEMP"
    git clone https://github.com/haskell-mafia/mafia $MAFIA_TEMP
    git --git-dir="$MAFIA_TEMP/.git" --work-tree="$MAFIA_TEMP" reset --hard $MAFIA_VERSION || {
        echo "mafia version ($MAFIA_VERSION) could not be found." >&2
        exit 1
    }
    (cd "$MAFIA_TEMP" && ./bin/bootstrap) || {
        got=$?
        echo "mafia version ($MAFIA_VERSION) could not be built." >&2
        exit "$got"
    }
    chmod +x "$MAFIA_TEMP/.cabal-sandbox/bin/mafia"
    # Ensure executable is on same file-system so final mv is atomic.
    mv -f "$MAFIA_TEMP/.cabal-sandbox/bin/mafia" "$MAFIA_PATH.$$"
    mv "$MAFIA_PATH.$$" "$MAFIA_PATH" || {
        rm -f "$MAFIA_PATH.$$"
        echo "INFO: mafia version ($MAFIA_VERSION) already exists not overiding," >&2
        echo "INFO: this is expected if parallel builds of the same version of" >&2
        echo "INFO: mafia occur, we are playing by first in, wins." >&2
        exit 0
    }
}

enable_version() {
    if [ $# -eq 0 ]; then
        MAFIA_VERSION="$(latest_version)"
        echo "INFO: No explicit mafia version requested installing latest ($MAFIA_VERSION)." >&2
    else
        MAFIA_VERSION="$1"
    fi
    [ -x "$MAFIA_HOME/versions/mafia-$MAFIA_VERSION" ] || build_version "$MAFIA_VERSION"
    ln -sf "$MAFIA_HOME/versions/mafia-$MAFIA_VERSION" "$MAFIA_HOME/versions/mafia"
}

exec_mafia () {
    [ -x "$MAFIA_HOME/versions/mafia" ] || enable_version
    "$MAFIA_HOME/versions/mafia" "$@"
}

#
# The actual start of the script.....
#

case "${1:-}" in
upgrade) shift; enable_version "$@" ;;
*) exec_mafia "$@"
esac