#!/usr/bin/env bash
#smcommit = "!f() { git commit -m \"$(printf \"Updated $1 Submodule\n\n\"; git diff \"$1\")\" --edit -- $1; }; f"

submod="${1%/}"

# Check if the specified submodule exists. If it doesn't, this will have a non-zero return code.
# This will cause the script to exit. The "./" in front allows relative paths to the submodule
# directories to be used from any directory
last_sha1=$(git rev-parse ":./$submod" 2> /dev/null)
if [[ $? != 0 ]]; then
    echo "ERROR: The specified submodule does not exist"
    exit 1
fi

# If the submodule has not physically changed (i.e. pointing to a different SHA1) then we don't
# care.
diff_result=$(git diff --submodule=short --ignore-submodules=dirty -- "$submod")
if [[ -z "$diff_result" ]]; then
    echo "ERROR: That submodule is already up to date"
    exit 1
fi

cd "$1"

getChangelogs() {
    git --no-pager log --oneline --no-decorate --no-merges $1..$2 | sed "s/^/    /g"
}

commits_forward=$(getChangelogs $last_sha1 HEAD)
commits_backward=$(getChangelogs HEAD $last_sha1)

cd - > /dev/null

buildLogSection() {
    # $1: The header message for the group of logs
    # $2: The string of logs to add
    if [[ ! -z "$2" ]]; then
        echo -e "$1\n\n$2"
    fi
}

introduced_section=$(buildLogSection "Introduced Commits:" "$commits_forward")
rewound_section=$(buildLogSection "Rewound Commits:" "$commits_backward")

if [ "$commits_forward" ]; then addspace=$'\n\n'; fi

read -r -d '' commit_message << EOF
Updated $submod Submodule

${introduced_section}${addspace}${rewound_section}
EOF

git commit -m "$commit_message" --edit -- "$submod"