#!/usr/bin/env bash

SCRIPT_DIR=$(dirname $(realpath ${BASH_SOURCE[0]}))
GIT_DIR=$(git rev-parse --git-dir)
GIT_ROOT=$(git rev-parse --show-toplevel)

MSG_FILE="$GIT_DIR/SUBSYSTEMS_SPLIT_MSG"

usage() {
    cat >&$1 <<EOF
git subsystems-split [OPTIONS]

Ardupilot's git extension.

Split HEAD commit into commits separated by subsystems (vehicles, libraries and
folders in the project's root). Basically, reset and call commit-subsystems.

If neither --copy or --edit is passed, then subsystems-split will try to make
the original commit's message into a template for commit-subsystems.

Options:
    --copy
    Make all commits have exactly the same message as the HEAD commit.

    --edit
    Edit the commit message as a template for commit-subsystems.
EOF
}

option_copy=false
option_edit=false

while [[ -n "$1" ]]; do
    opt="$1"
    case "$opt" in
    -h|--help)
        usage 1
        exit 0
        ;;
    --copy)
        option_copy=true
        ;;
    --edit)
        option_edit=true
        ;;
    *)
        usage 2
        exit 1
        ;;
    esac
    shift
done

if $option_copy && $option_edit; then
    echo "Options --copy and --edit can't be combined." >&2
    exit 1
fi

author_name=$(git log -n 1 --format=%an)
author_email=$(git log -n 1 --format=%ae)
author="$author_name <$author_email>"
git log -n 1 --format=%B > "$MSG_FILE"

if $option_edit; then
    if [[ -z $EDITOR ]]; then
        echo "Environment variable EDITOR is required for option --edit." >&2
        exit 1
    fi
    ($EDITOR "$MSG_FILE")
elif ! $option_copy; then
    if head -n 1 "$MSG_FILE" | grep "^[^: ]\+\s*:" -q; then
        sed '1 s,^[^: ]\+\s*,$subsystem,' -i "$MSG_FILE"
    else
        buff_file="$(mktemp)"
        awk '
            NR == 1 {
                l=sub(/^\s\+/, "", $line);
                print "$subsystem: " \
                      tolower(substr($l, 1, 1)) \
                      substr($l, 2);
            }
            NR != 1
            ' "$MSG_FILE" > "$buff_file"
        mv "$buff_file" "$MSG_FILE"
        rm "$buff_file"
    fi
fi

HEAD=$(git rev-parse HEAD)
git reset HEAD~1 --soft
if ! "$SCRIPT_DIR/git-commit-subsystems" -F "$MSG_FILE" --author="$author"; then
    echo "Error on calling git-commit-subsystems." >&2
    git reset $HEAD
    exit 1
fi