#!/bin/sh

usage() {
    echo "git-precheck [--quiet] [--ignore-dirty] [--ignore-untracked]"
    echo ""
    echo "If the current working directory is inside a git repository, examine"
    echo "the repo for any abnormal state and return an exit code indicating"
    echo "the status.  If unclean, print a line of text describing each"
    echo "condition found."
    echo ""
    echo "  --quiet"
    echo "      Don't actually print anything."
    echo ""
    echo "  --ignore-dirty"
    echo "      Don't consider the presence of uncommitted changes to tracked"
    echo "      files as an abnormal state."
    echo ""
    echo "  --ignore-untracked"
    echo "      Don't consider the presence of untracked files as an abnormal"
    echo "      state."
    echo ""
    echo "  Exit codes:"
    echo "      0   If inside a repository and all checks return normal"
    echo "      1   If untracked files detected"
    echo "      2   If dirty/modified files detected"
    echo "      3   If any ongoing git operation is in progress"
    echo "      4   If not inside a git repository"
    echo ""
    echo "      Exit any other value on error or if 'precheck' operation is"
    echo "      not completed, such as when viewing this help text."
    exit 128
}

quiet=""
opt_dirty="true"
opt_untracked="true"

while true; do
    case "$1" in
        --quiet) quiet="true" ;;
        --ignore-dirty) opt_dirty="" ;;
        --ignore-untracked) opt_untracked="" ;;
        --help) usage ;;
        -h) usage ;;
        *) break
    esac
    shift
done

if [ $# -ne 0 ]; then
    printf 'git-precheck: Unrecognized option given: %s\n' "$1"
    exit 128
fi

CS="\\033[0;31m"
CE="\\033[0m"

cond=""
dirty=""
untracked=""

# If outside repo, always exit immediately.
if ! [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
    [ -z "$quiet" ] && printf '%bnot inside a git work tree%b\n' "$CS" "$CE"
    exit 4
fi

# Otherwise, only exit immediately if --quiet was given.
# Keep running to report all potential conditions that apply.

check() {
    if [ -e "$(git rev-parse --git-path "$1" 2>/dev/null)" ]; then
        [ -n "$quiet" ] && exit 3
        printf '%b%s in progress%b\n' "$CS" "$2" "$CE"
        cond="true"
    fi
}

check rebase-merge rebase
check rebase-apply rebase/am
check MERGE_HEAD merge
check REVERT_HEAD revert
check CHERRY_PICK_HEAD cherry-pick
check BISECT_EXPECTED_REV bisect

if [ -n "$opt_dirty" ] || [ -n "$opt_untracked" ]; then
    git_status="$(git status --porcelain 2>/dev/null)"

    if [ -n "$opt_dirty" ] && printf '%s' "$git_status" | grep -qvE '^\?\? '; then
        [ -n "$quiet" ] && exit 2
        printf '%bmodified files detected%b\n' "$CS" "$CE"
        dirty="true"
    fi

    if [ -n "$opt_untracked" ] && printf '%s' "$git_status" | grep -qE '^\?\? '; then
        [ -n "$quiet" ] && exit 1
        printf '%buntracked files detected%b\n' "$CS" "$CE"
        untracked="true"
    fi
fi

# Still here?  Return the highest applicable code based on what has been seen.
[ -n "$cond" ] && exit 3
[ -n "$dirty" ] && exit 2
[ -n "$untracked" ] && exit 1
exit 0