nag/nag

#!/usr/bin/env bash

# nag is a bash script for setting one-off or repeating alarms.

# MIT License
#
# Copyright (c) 2026 Lewis Wynne
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

# Enforce Bash "strict mode".
set -o nounset
set -o errexit
set -o errtrace
set -o pipefail
trap 'echo "Aborting due to errexit on line $LINENO. Exit code: $?" >&2' ERR
IFS=$'\n\t'

_ME="$(basename "${0}")"
_VERSION="2026.14"

NAG_PATH="${NAG_PATH:-${HOME}/.local/share/nag}"
_LOCKFILE="${NAG_PATH}.lock"

# The command nag runs to execute its notifications.
NAG_CMD="${NAG_CMD:-notify-send}"

# The default subcommand if no args are passed.
NAG_DEFAULT="${NAG_DEFAULT:-list}"

# The fallback subcommand if an arg is passed that is not defined.
_FALLBACK_COMMAND_IF_NO_MATCH="at"

# Usage:
#   _debug <command> <options>...
#
# Description:
#   Execute a command and print to standard error. The command is expected to
#   print a message and should typically be either `echo`, `printf`, or `cat`.
#
# Example:
#   _debug printf "Debug info. Variable: %s\\n" "$0"
__DEBUG_COUNTER=0
_debug() {
  if ((${_USE_DEBUG:-0}))
  then
    __DEBUG_COUNTER=$((__DEBUG_COUNTER+1))
    {
      # Prefix debug message with "bug (U+1F41B)"
      printf "🐛  %s " "${__DEBUG_COUNTER}"
      "${@}"
      printf "―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――\\n"
    } 1>&2
  fi
}

# Usage:
#   _exit_1 <command>
#
# Description:
#   Exit with status 1 after executing the specified command with output
#   redirected to standard error. The command is expected to print a message
#   and should typically be either `echo`, `printf`, or `cat`.
_exit_1() {
  {
    printf "%s " "$(tput setaf 1)!$(tput sgr0)"
    "${@}"
  } 1>&2
  exit 1
}

# Usage:
#   _warn <command>
#
# Description:
#   Print the specified command with output redirected to standard error.
#   The command is expected to print a message and should typically be either
#   `echo`, `printf`, or `cat`.
_warn() {
  {
    printf "%s " "$(tput setaf 1)!$(tput sgr0)"
    "${@}"
  } 1>&2
}

# Usage:
#   _function_exists <name>
#
# Exit / Error Status:
#   0 (success, true) If function with <name> is defined in the current
#                     environment.
#   1 (error,  false) If not.
_function_exists() {
  [ "$(type -t "${1}")" == 'function' ]
}

# Usage:
#   _command_exists <name>
#
# Exit / Error Status:
#   0 (success, true) If a command with <name> is defined in the current
#                     environment.
#   1 (error,  false) If not.
_command_exists() {
  hash "${1}" 2>/dev/null
}

# Usage:
#   _contains <query> <list-item>...
#
# Exit / Error Status:
#   0 (success, true)  If the item is included in the list.
#   1 (error,  false)  If not.
#
# Examples:
#   _contains "${_query}" "${_list[@]}"
_contains() {
  local _query="${1:-}"
  shift

  if [[ -z "${_query}"  ]] ||
     [[ -z "${*:-}"     ]]
  then
    return 1
  fi

  for __element in "${@}"
  do
    [[ "${__element}" == "${_query}" ]] && return 0
  done

  return 1
}

# Usage:
#   _join <delimiter> <list-item>...
#
# Description:
#   Print a string containing all <list-item> arguments separated by
#   <delimeter>.
#
# Example:
#   _join "${_delimeter}" "${_list[@]}"
_join() {
  local _delimiter="${1}"
  shift
  printf "%s" "${1}"
  shift
  printf "%s" "${@/#/${_delimiter}}" | tr -d '[:space:]'
}

# Usage:
#   _blank <argument>
#
# Exit / Error Status:
#   0 (success, true)  If <argument> is not present or null.
#   1 (error,  false)  If <argument> is present and not null.
_blank() {
  [[ -z "${1:-}" ]]
}

# Usage:
#   _present <argument>
#
# Exit / Error Status:
#   0 (success, true)  If <argument> is present and not null.
#   1 (error,  false)  If <argument> is not present or null.
_present() {
  [[ -n "${1:-}" ]]
}

# Usage:
#   _interactive_input
#
# Exit / Error Status:
#   0 (success, true)  If the current input is interactive (eg, a shell).
#   1 (error,  false)  If the current input is stdin / piped input.
_interactive_input() {
  [[ -t 0 ]]
}

# Usage:
#   _piped_input
#
# Exit / Error Status:
#   0 (success, true)  If the current input is stdin / piped input.
#   1 (error,  false)  If the current input is interactive (eg, a shell).
_piped_input() {
  ! _interactive_input
}

# Usage:
#   describe <name> <description>
#   describe --get <name>
#
# Options:
#   --get  Print the description for <name> if one has been set.
describe() {
  _debug printf "describe() \${*}: %s\\n" "$@"
  [[ -z "${1:-}" ]] && _exit_1 printf "describe(): <name> required.\\n"

  if [[ "${1}" == "--get" ]]
  then
    [[ -z "${2:-}" ]] &&
      _exit_1 printf "describe(): <description> required.\\n"

    local _name="${2:-}"
    local _describe_var="___describe_${_name}"

    if [[ -n "${!_describe_var:-}" ]]
    then
      printf "%s\\n" "${!_describe_var}"
    else
      printf "No additional information for \`%s\`\\n" "${_name}"
    fi
  else
    if [[ -n "${2:-}" ]]
    then
      read -r -d '' "___describe_${1}" <<HEREDOC
${2}
HEREDOC
    else
      read -r -d '' "___describe_${1}" || true
    fi
  fi
}

# Iterate over options, breaking -ab into -a -b and --foo=bar into --foo bar
# also turns -- into --endopts to avoid issues with things like '-o-', the '-'
# should not indicate the end of options, but be an invalid option (or the
# argument to the option, such as wget -qO-)
# Source:
#   https://github.com/e36freak/templates/blob/master/options
unset options
# while the number of arguments is greater than 0
while ((${#}))
do
  case "${1}" in
    # if option is of type -ab
    -[!-]?*)
      # loop over each character starting with the second
      for ((i=1; i<${#1}; i++))
      do
        # extract 1 character from position 'i'
        c="${1:i:1}"
        # add current char to options
        options+=("-${c}")
      done
      ;;
    # if option is of type --foo=bar, split on first '='
    --?*=*)
      options+=("${1%%=*}" "${1#*=}")
      ;;
    # end of options, stop breaking them up
    --)
      options+=(--endopts)
      shift
      options+=("${@}")
      break
      ;;
    # otherwise, nothing special
    *)
      options+=("${1}")
      ;;
  esac

  shift
done
# set new positional parameters to altered options. Set default to blank.
set -- "${options[@]:-}"
unset options

_SUBCOMMAND=""
_SUBCOMMAND_ARGUMENTS=()
_USE_DEBUG=0
_YES=0

while ((${#}))
do
  __opt="${1}"
  shift
  case "${__opt}" in
    -h|--help)
      _SUBCOMMAND="help"
      ;;
    --version)
      _SUBCOMMAND="version"
      ;;
    --debug)
      _USE_DEBUG=1
      ;;
    --yes)
      _YES=1
      ;;
    *)
      # The first non-option argument is assumed to be the subcommand name.
      # All subsequent arguments are added to $_SUBCOMMAND_ARGUMENTS.
      if [[ -n "${_SUBCOMMAND}" ]]
      then
        _SUBCOMMAND_ARGUMENTS+=("${__opt}")
      else
        _SUBCOMMAND="${__opt}"
      fi
      ;;
  esac
done

###############################################################################
# Main
###############################################################################

_DEFINED_SUBCOMMANDS=()
_main() {
  if [[ -z "${_SUBCOMMAND}" ]]
  then
    _SUBCOMMAND="${NAG_DEFAULT}"
  fi

  for __name in $(declare -F)
  do
    local _function_name
    _function_name=$(printf "%s" "${__name}" | awk '{ print $3 }')

    if ! { [[ -z "${_function_name:-}"                      ]] ||
           [[ "${_function_name}" =~ ^_(.*)                 ]] ||
           [[ "${_function_name}" == "bats_readlinkf"       ]] ||
           [[ "${_function_name}" == "describe"             ]] ||
           [[ "${_function_name}" == "shell_session_update" ]]
    }
    then
      _DEFINED_SUBCOMMANDS+=("${_function_name}")
    fi
  done

  # If our _SUBCOMMAND is defined, execute it. Otherwise, attempt to
  # execute _create_alarm. _create_alarm must check its own args, and
  # _exit_1 if inappropriate.
  if _contains "${_SUBCOMMAND}" "${_DEFINED_SUBCOMMANDS[@]:-}"
  then
    ${_SUBCOMMAND} "${_SUBCOMMAND_ARGUMENTS[@]:-}"
  else
    "${_FALLBACK_COMMAND_IF_NO_MATCH}" "${_SUBCOMMAND}" "${_SUBCOMMAND_ARGUMENTS[@]:-}"
  fi
}


###############################################################################
# Storage
###############################################################################

# Global array holding raw TSV alarm lines (one element per alarm).
_ALARMS=()

# Usage:
#   _ensure_nag_dir
#
# Description:
#   Create the parent directory for NAG_PATH if it doesn't already exist.
_ensure_nag_dir() {
  local _dir
  _dir="$(dirname "${NAG_PATH}")"
  [[ -d "${_dir}" ]] || mkdir -p "${_dir}"
}

# Usage:
#   _acquire_lock
#
# Description:
#   Acquire an exclusive lock on ${_LOCKFILE} using flock. Exits with an
#   error if the lock cannot be obtained (another instance is running).
_acquire_lock() {
  _ensure_nag_dir
  exec {_LOCK_FD}>"${_LOCKFILE}"
  if ! flock -n "${_LOCK_FD}"
  then
    _exit_1 printf "Could not acquire lock: %s\\n" "${_LOCKFILE}"
  fi
}

# Usage:
#   _release_lock
#
# Description:
#   Release the exclusive lock previously acquired by _acquire_lock.
_release_lock() {
  if [[ -n "${_LOCK_FD:-}" ]]
  then
    exec {_LOCK_FD}>&-
  fi
}

# Usage:
#   _read_alarms
#
# Description:
#   Read alarms from NAG_PATH into the global _ALARMS array. Each element
#   is one raw TSV line. If the file is missing or empty, _ALARMS is set to
#   an empty array.
_read_alarms() {
  _ALARMS=()
  if [[ -f "${NAG_PATH}" ]] && [[ -s "${NAG_PATH}" ]]
  then
    local _line
    while IFS= read -r _line || [[ -n "${_line}" ]]
    do
      _ALARMS+=("${_line}")
    done < "${NAG_PATH}"
  fi
}

# Usage:
#   _write_alarms
#
# Description:
#   Write the _ALARMS array atomically to NAG_PATH. Writes to a temporary
#   file first, then moves it over the original. If _ALARMS is empty, an
#   empty file is written.
_write_alarms() {
  _ensure_nag_dir
  local _tmp
  _tmp="$(mktemp "${NAG_PATH}.XXXXXX")"
  if (( ${#_ALARMS[@]} > 0 ))
  then
    printf "%s\n" "${_ALARMS[@]}" > "${_tmp}"
  else
    : > "${_tmp}"
  fi
  mv -f "${_tmp}" "${NAG_PATH}"
}

# Usage:
#   _next_id
#
# Description:
#   Find the next available alarm ID (the first gap in the existing ID
#   sequence starting from 1). Prints the ID to stdout.
_next_id() {
  _read_alarms
  if (( ${#_ALARMS[@]} == 0 ))
  then
    printf "%s\n" "1"
    return
  fi

  local _ids=()
  local _line
  for _line in "${_ALARMS[@]}"
  do
    _ids+=("$(printf "%s" "${_line}" | cut -f1)")
  done

  # Sort numerically
  local _sorted
  _sorted="$(printf "%s\n" "${_ids[@]}" | sort -n)"

  local _expected=1
  local _id
  while IFS= read -r _id
  do
    if (( _id != _expected ))
    then
      printf "%s\n" "${_expected}"
      return
    fi
    _expected=$((_expected + 1))
  done <<< "${_sorted}"

  printf "%s\n" "${_expected}"
}

# Usage:
#   _get_alarm_field <line> <field-number>
#
# Description:
#   Extract a field from a TSV alarm line.
#   Fields: 1=id, 2=timestamp, 3=rule, 4=message.
#   For field 4 (message), returns everything after the 3rd tab.
_get_alarm_field() {
  local _line="${1}"
  local _field="${2}"
  if (( _field == 4 ))
  then
    printf "%s" "${_line}" | cut -f4-
  else
    printf "%s" "${_line}" | cut -f"${_field}"
  fi
}

# Usage:
#   _parse_time <time-string>
#
# Description:
#   Parse a human-readable time string via `date -d` and print a unix
#   timestamp. If the resulting time is in the past, roll forward to
#   the same time-of-day tomorrow.
_parse_time() {
  local _time_str="${1:-}"
  [[ -n "${_time_str}" ]] || _exit_1 printf "No time specified.\\n"

  local _timestamp
  _timestamp="$(date -d "${_time_str}" +%s 2>/dev/null)" ||
    _exit_1 printf "Invalid time: %s\\n" "${_time_str}"

  local _now
  _now="$(date +%s)"

  if [[ "${_timestamp}" -le "${_now}" ]]
  then
    local _time_of_day
    _time_of_day="$(date -d "@${_timestamp}" +%H:%M:%S)"
    _timestamp="$(date -d "tomorrow ${_time_of_day}" +%s)" ||
      _exit_1 printf "Could not compute next day for: %s\\n" "${_time_str}"
  fi

  printf "%s" "${_timestamp}"
}

# Usage:
#   _prompt_cron
#
# Description:
#   Check whether a cron entry for `nag check` exists. If not, prompt the
#   user to install one (or install automatically when --yes is set).
_prompt_cron() {
  if ! _command_exists crontab
  then
    _warn printf "crontab not found. Without a cron daemon, alarms will not trigger.\\n"
    return 0
  fi

  if crontab -l 2>/dev/null | grep -qF "${_ME} check"
  then
    return 0
  fi

  if ((_YES))
  then
    _install_cron
    return 0
  fi

  if _interactive_input
  then
    printf "A cron job for '%s check' is needed to trigger timers. Add one? [Y/n] " "${_ME}"
    local _reply
    read -r _reply
    case "${_reply}" in
      [nN]*)
        return 0
        ;;
      *)
        _install_cron
        ;;
    esac
  fi
}

# Usage:
#   _install_cron
#
# Description:
#   Append a `* * * * * nag check` entry to the current user's crontab.
_install_cron() {
  local _nag_path
  _nag_path="$(command -v nag 2>/dev/null || printf "%s" "$(cd "$(dirname "${0}")" && pwd)/nag")"
  (crontab -l 2>/dev/null; printf "* * * * * %s check\\n" "${_nag_path}") | crontab -
  printf "cron entry added.\\n"
}

###############################################################################
# Subcommands
###############################################################################

# help ########################################################################

describe "help" <<HEREDOC
Usage:
  ${_ME} help [<subcommand>]

Description:
  Display help information for ${_ME} or a specified subcommand.
HEREDOC
help() {
  if [[ -n "${1:-}" ]]
  then
    describe --get "${1}"
  else
    cat <<HEREDOC
nag

Version: ${_VERSION}

Usage:
  ${_ME} <time> <message...>                 one-shot alarm
  ${_ME} every <rules> <time> <message...>   repeating alarm
  ${_ME} stop <id>                           delete alarm
  ${_ME} skip <id>                           skip next occurrence
  ${_ME} check                               fire expired alarms (cron)
  ${_ME} help [<subcommand>]                 show help
  ${_ME}                                     list all alarms

Options:
  --yes  Skip all prompts.

Help:
  ${_ME} help [<subcommand>]
HEREDOC
  fi
}

# version #####################################################################

describe "version" <<HEREDOC
Usage:
  ${_ME} ( version | --version )

Description:
  Display the current program version.
HEREDOC
version() {
  printf "%s\\n" "${_VERSION}"
}

# list ########################################################################

describe "list" <<HEREDOC
Usage:
  ${_ME} list

Description:
  List all alarms. This is the default when no subcommand is given.
HEREDOC
list() {
  if [[ ! -f "${NAG_PATH}" ]] || [[ ! -s "${NAG_PATH}" ]]
  then
    printf "Nothing to nag about.\\n"
    return 0
  fi
}

# at ##########################################################################

describe "at" <<HEREDOC
Usage:
  ${_ME} [at] <time> <message...>

Description:
  Create a one-shot alarm. The "at" is optional. If the first argument
  doesn't match any other subcommand of ${_ME}, it'll fallback to "at".

Examples:
  ${_ME} 3pm take a break
  ${_ME} at 3pm take a break
  ${_ME} "tomorrow 9am" dentist appointment
HEREDOC
at() {
  local _time_str="${1:-}"
  shift || true
  local _message="${*:-}"

  [[ -n "${_time_str}" ]] || _exit_1 printf "Usage: ${_ME} [at] <time> <message>\\n"
  [[ -n "${_message}" ]]  || _exit_1 printf "No message specified.\\n"

  local _timestamp
  _timestamp="$(_parse_time "${_time_str}")"

  _acquire_lock
  local _id
  _id="$(_next_id)"

  # _next_id calls _read_alarms in a subshell, so _ALARMS isn't populated here.
  _read_alarms
  _ALARMS+=("$(printf "%s\t%s\t\t%s" "${_id}" "${_timestamp}" "${_message}")")
  _write_alarms
  _release_lock

  _prompt_cron

  local _human_time
  _human_time="$(date -d "@${_timestamp}" "+%a %b %-d %-I:%M%p" | sed 's/AM/am/;s/PM/pm/')"
  printf "[%s] %s — %s\\n" "${_id}" "${_human_time}" "${_message}"
}

# _main must be called after everything has been defined.
_main