#!/bin/sh

################################################################################
# A script that shows a battery warning on i3wm                                #
#                                                                              #
# It supports multiple batteries                                               #
# (like my thinkpad T450s has)                                                 #
#                                                                              #
# When tcl/tk (wish) is installed, it shows a nice popup                       #
# Which you can configure to show on all workspaces                            #
# by adding the following to your i3 config:                                   #
# "for_window [title="Battery Warning"] sticky enable"                         #
#                                                                              #
# By default, the script will show two messages:                               #
# One at 10% and one at 5% battery                                             #
#                                                                              #
# The script takes the following options:                                      #
# -L : The percentage at which the first popup shows (default: 10)             #
#                                                                              #
# -l : The percentage at which the second popup shows                          #
#      Default: half of the percentage given by -L                             #
#                                                                              #
# -m : The message to show to the User                                         #
#                                                                              #
# -t : The time interval the script waits before checking the battery again.   #
#      Give this a value in seconds: 5s, 10s, or in minutes: 5m                #
#      Default: 5m                                                             #
#                                                                              #
# -n : Don't use Tcl/Tk dialog. Use i3-nagbar.                                 #
#                                                                              #
# By R-J Ekker, 2016                                                           #
################################################################################

error () {
    echo $1 >&2
    echo "Exiting" >&2
    exit $2
}

while getopts 'L:l:m:t:F:n' opt; do
    case $opt in
        L)
            [[ $OPTARG =~ ^[0-9]+$ ]] || error "${opt}: ${OPTARG} is not a number" 2
            UPPER_LIMIT="${OPTARG}"
            ;;
        l)
            [[ $OPTARG =~ ^[0-9]+$ ]] || error "${opt}: ${OPTARG} is not a number" 2
            LOWER_LIMIT="${OPTARG}"
            ;;
        m)
            MESSAGE="${OPTARG}"
            ;;
        n)
            DONT_USE_WISH="-n"
            ;;
        t)
            [[ $OPTARG =~ ^[0-9]+[ms]?$ ]] || error "${opt}: ${OPTARG} is not a valid period" 2
            SLEEP_TIME="${OPTARG}"
            ;;
        F)
            LOGFILE="${OPTARG}"
            ;;
        :)
            error "Option -$OPTARG requires an argument." 2
            ;;
        \?)
            exit 2
            ;;
    esac
done

# This function returns an awk script
# Which prints the battery percentage
# It's an ugly way to include a nicely indented awk script here

get_awk_source() {
    cat <<EOF
BEGIN {
    FS="=";
}
\$1 ~ /ENERGY_FULL_DESIGN$/ {
    f += \$2;
}
\$1 ~ /ENERGY_NOW\$/ {
    n += \$2;
}
END {
    print int(100*n/f);
}
EOF
}

is_battery_discharging() {
    cat $BATTERIES | grep Charging && return 1
    return 0
} >/dev/null

get_battery_perc() {
    cat $BATTERIES | awk -f <(get_awk_source)
}

show_popup() {
    # WISH_SCRIPT="wm state . withdrawn; tk_messageBox -icon warning -title \"Battery Warning\" -message \"${MESSAGE}\"; exit"
    # echo "$WISH_SCRIPT" | wish
    notify-send --urgency=critical --icon=warning "Battery Warning" "${MESSAGE}"
}

show_nagbar(){
    /usr/bin/i3-nagbar -m "${MESSAGE}"
}

show_message(){
    echo "showing warning" >&2
    # if [[ -z $DONT_USE_WISH ]] && which wish; then
    show_popup
    # else
    #     show_nagbar
    # fi
}

main (){
    # Setting defaults
    UPPER_LIMIT="${UPPER_LIMIT:-10}"
    UPPER_HALF=$(( $UPPER_LIMIT / 2 ))
    LOWER_LIMIT=${LOWER_LIMIT:-$UPPER_HALF}
    MESSAGE="${MESSAGE:-Warning: Battery is getting low}"
    SLEEP_TIME="${SLEEP_TIME:-5m}"

    BATTERIES=/sys/class/power_supply/BAT*/uevent

    echo "Upper ${UPPER_LIMIT}; Lower ${LOWER_LIMIT}; sleep ${SLEEP_TIME}"
    echo "Current: $(get_battery_perc)%"

    LIMIT="${UPPER_LIMIT}"
    # This will be set to "y" after first click
    # So we know when to stop nagging
    POPUP_CLICKED=""

    while true; do
        echo -n "Checking.. "

        PERC=$(get_battery_perc)
        echo "got ${PERC}%"

        if is_battery_discharging; then
            if [[ $PERC -lt $LIMIT ]]; then
                show_message

                if [[ -z $POPUP_CLICKED ]]; then
                    # first click; set limit lower
                    POPUP_CLICKED="y"
                    LIMIT=${LOWER_LIMIT}
                else
                    # We clicked twice; No more popups
                    LIMIT=0
                fi
            fi
        else
            echo "Battery Charging"
            # restart messages, reset limits
            POPUP_CLICKED=""
            if [[ $PERC -gt $UPPER_LIMIT ]]; then
                LIMIT=${UPPER_LIMIT}
            else
                LIMIT=${LOWER_LIMIT}
            fi
        fi
        echo "sleeping ${SLEEP_TIME}; current limit ${LIMIT}%; ${POPUP_CLICKED:+Popup was clicked}"
        sleep "${SLEEP_TIME}"
    done
} >&2

LOCK_FILE="${HOME}/.battery_state.lock"
(
    if [[ -n $LOGFILE ]]; then
        exec >>$LOGFILE 2>&1
    fi

    flock -xn 200 || error "Cannot acquire lock ${LOCK_FILE}" 3

    main
) 200>"${LOCK_FILE}"