#!/usr/bin/env bash

# Renames a user
# Required arguments: old user name, new user name

if [[ $# -ne 2 ]]; then
    echo "Usage: $0 old-user new-user"
    exit 1
fi

old_user="$1"
new_user="$2"

# Make sure old user exists
if ! id "$old_user" >/dev/null 2>&1; then
    echo "The user $old_user does not exist."
    exit 1
fi

# Make sure old user is not logged in
if pgrep -u "$old_user" >/dev/null; then
    echo "The user $old_user is currently logged in or has running processes. Cannot continue."
    echo "Would you like to forcibly log out $old_user? (Y/N)"
    read -r answer
    answer="${answer:0:1}"
    answer="${answer^}"
    if [[ "$answer" != "Y" ]]; then
        exit 1
    fi
    loginctl terminate-user "$old_user"
    sleep 2
    if pgrep -u "$old_user" >/dev/null; then
        echo "The user $old_user still has running processes after termination. Cannot continue."
        exit 1
    fi
fi

# Make sure new user does not exist
if id "$new_user" >/dev/null 2>&1; then
    echo "The user name $new_user is already taken."
    exit 1
fi

# Make sure the new name is acceptable
if ! [[ "$new_user" =~ ^[a-z_][a-z0-9_-]{0,31}$ ]]; then
    echo "$new_user is not an acceptable user name."
    exit 1
fi

# Passed all safety checks, proceed with the rename
groups=$(id -nG "$old_user")
groups="${groups// /,}"
usermod -G "$groups" -m -d "/home/$new_user" -l "$new_user" "$old_user"

# Update nodm.conf if it exists
if [[ -e /etc/nodm.conf ]]; then
    sed -i -e "s#^NODM_USER=.*#NODM_USER='$new_user'#" -e "s#^NODM_XSESSION=.*#NODM_XSESSION='/home/$new_user/.xinitrc'#" /etc/nodm.conf
fi

# Copy over crontab if it exists
if crontab -u "$old_user" -l >/tmp/${old_user}_crontab.bak 2>/dev/null; then
    if crontab -u "$new_user" "/tmp/${old_user}_crontab.bak"; then
        rm "/tmp/${old_user}_crontab.bak"
    else
        echo "Warning: failed to restore crontab for $new_user."
        rm "/tmp/${old_user}_crontab.bak"
    fi
fi

# Optionally update files in new home directory
echo "Would you like to search for references to $old_user and update them to $new_user in files located in /home/$new_user?"
echo "This can take a while. (Y/N)"
read -r answer
answer="${answer:0:1}"
answer="${answer^}"
if [[ "$answer" == "Y" ]]; then
    find "/home/$new_user" -type f -exec sed -i "s|$old_user|$new_user|g" "{}" \;
fi

exit 0