Timer (simplified)

#!/bin/bash

# The time to count down is entered as a number of minutes, via a
# dialog. The remaining time is shown in the notification area as an
# icon with two digits. A number of minutes greater than 99 is
# indicated as the number of hours and the number of tens of minutes
# and is shown in an icon with separate formatting. When the number of
# remaining minutes is triangular, the remaining time is spoken; so
# the intervals between the times announced as audio decrease, e.g.
# ... 36, 28, 21, 15, 10, 6, 3, 1. The script has been tested on
# Xubuntu. It requires espeak and yad. It uses images for icons that
# appear in the notification area, so they need to be ready, properly
# named -- 00.png, 01.png, 10.png, etc. -- and the paths to the actual
# directories containing them should be specified in the script. The
# ones tested have the size 16x16 pixels and backgrounds of two
# different colors.

function quit()
{
    espeak "$1" &
    exit "$2"
}

function value_is_triangular()
{
    # If the square root of a number preliminarily multiplied by eight
    # and incremented is an integer, the number is triangular. If the
    # number is an integer, bc outputs it with a dot and trailing
    # zeros nonetheless. The dot and the zeros are pattern-matched by
    # grep.

    if echo "sqrt($1 * 8 + 1)" | bc -l | grep -Eo '\.0+$' > /dev/null; then
        return 0
    else
        return 1
    fi
}

function format_announcement_values_units()
{
    value="$1"
    if [ "$1" -eq 0 ]; then
        value=""
        unit=""
    elif [ "$1" -eq 1 ]; then
        unit="$2"
    else
        unit="${2}s"
    fi
}

function announce()
{
    hours_number=$(($1 / 60))
    format_announcement_values_units "$hours_number" "hour"
    hours="$value $unit"
    minutes_number=$(($1 % 60))
    format_announcement_values_units "$minutes_number" "minute"
    minutes="$value $unit"
    espeak -v "whisper" "$hours $minutes left"
}

function display_minutes()
{
    file_name_no_extension=$(printf "%02d" "$1")
    yad --notification --image "${MINUTES_IMAGES_DIRECTORY}/${file_name_no_extension}.png" --timeout 60 && quit "Aborted!" 1
}

function display_hours_minutes()
{
    hours_number=$(($1 / 60))
    tens_of_minutes_number=$(($1 % 60 / 10))
    file_name_no_extension="${hours_number}${tens_of_minutes_number}"
    yad --notification --image "${HOURS_MINUTES_IMAGES_DIRECTORY}/${file_name_no_extension}.png" --timeout 60 && quit "Aborted!" 1
}

# Change the following paths to the ones containing actual images for
# the notification area.
MINUTES_IMAGES_DIRECTORY=~/images/icons/timer/purple
HOURS_MINUTES_IMAGES_DIRECTORY=~/images/icons/timer/blue

VALID_INPUT_PATTERN='^[1-9][0-9]*$'

input=$(yad --entry --title "Timer" --text "Enter the number of minutes: " --entry-text "30" --borders "8") || quit "Aborted!" 1

[[ $input =~ $VALID_INPUT_PATTERN ]] || quit "Invalid input! Exiting!" 1
[ "$input" -lt 960 ] || quit "Maximum value of 959 is exceeded! Exiting!" 1

remaining_time=$input

while [ "$remaining_time" -gt 0 ]; do

    if value_is_triangular "$remaining_time"; then
        announce "$remaining_time" &
    fi

    if [ "$remaining_time" -lt 100 ]; then
        display_minutes "$remaining_time"
    else
        display_hours_minutes "$remaining_time"
    fi

    remaining_time=$((remaining_time - 1))
done

yad --notification --image "emblem-urgent" &
quit "Time's up!" 0