#!/bin/sh

# sunset-alarm -- Alert before or after sunset
# Displays a persistent alert when current time is within
# (sunset minus specified minutes) of midnight.

###############################################################################
# Defaults
###############################################################################
LATLONG=""
SUNSET_TIME=""
MINUTES=""
SUNSET_EPOCH=0
LAST_DATE=""
PROMPT="sunset-alarm"

###############################################################################
# Usage
###############################################################################
usage() {
    echo "Usage: sunset-alarm (-l LAT:LONG | -t HH24:MI) (-m MINUTES) [-h]" >&2
    exit 1
}

###############################################################################
# Parse arguments (handles negative values for -m by using "$@")
###############################################################################
while [ $# -gt 0 ]; do
    case "$1" in
        -l) LATLONG="$2"; shift 2 ;;
        -t) SUNSET_TIME="$2"; shift 2 ;;
        -m) MINUTES="$2"; shift 2 ;;
        -h) usage ;;
        --) shift; break ;;
        *) echo "Error: unknown argument '$1'" >&2; usage ;;
    esac
done

# Validate inputs
if [ -z "$MINUTES" ]; then
    echo "Error: -m MINUTES is required." >&2
    usage
fi

if [ -z "$LATLONG" ] && [ -z "$SUNSET_TIME" ]; then
    echo "Error: must specify either -l LAT:LONG or -t HH:MI." >&2
    usage
fi

###############################################################################
# Internet connectivity check
###############################################################################
check_internet() {
    if curl -s --max-time 5 -o /dev/null https://hyperling,com; then
        return 0
    fi
    if curl -s --max-time 5 -o /dev/null https://mullvad.net; then
        return 0
    fi
    return 1
}

###############################################################################
# Get sunset from Open Meteo API
###############################################################################
fetch_sunset_time() {
    LAT=$(echo "$LATLONG" | cut -d: -f1)
    LON=$(echo "$LATLONG" | cut -d: -f2)

    RESPONSE=$(curl -s "https://api.open-meteo.com/v1/forecast?latitude=${LAT}&longitude=${LON}&timezone=auto&daily=sunset&date=today")

    if [ -z "$RESPONSE" ]; then
        return 1
    fi

    # Extract sunset timestamp like "2025-06-15T19:32:00"
    SUNSET_RAW=$(echo "$RESPONSE" | jq -r '.daily.sunset[0]')

    if [ -z "$SUNSET_RAW" ]; then
        return 1
    fi

    # Convert to epoch
    SUNSET_EPOCH=$(date -d "$(echo "$SUNSET_RAW" | cut -dT -f1) $(echo "$SUNSET_RAW" | cut -dT -f2)" +%s 2>/dev/null)

    if [ -z "$SUNSET_EPOCH" ]; then
        return 1
    fi

    return 0
}

###############################################################################
# Show alert via fallback chain: fyi -> notify-send -> wall
###############################################################################
show_alert() {
    ALERT=$(date -d @${ALERT_WINDOW_START} +"%H:%M")
    SUNSET=$(date -d @${SUNSET_EPOCH} +"%H:%M")
    PLURAL=$(if (( $MINUTES != 1 )); then echo "s"; fi)

    TITLE="Sunset Alarm ($ALERT)"
    MESSAGE="It's ${MINUTES} minute${PLURAL} to $SUNSET."

    persistent="-t 0 --wait"
    icon="-i weather-clear -u critical"

    if command -v fyi >/dev/null 2>&1; then
        fyi $icon $persistent "$TITLE" "$MESSAGE"
    elif command -v notify-send >/dev/null 2>&1; then
        notify-send $icon $persistent "$TITLE" "$MESSAGE"
    elif command -v wall >/dev/null 2>&1; then
        echo "${TITLE}: ${MESSAGE}" | wall
    else
        echo "ERROR: No notification tool found." >&2
        echo "Install one of: fyi, notify-send (libnotify-bin), wall (bsd-write)" >&2
        return 1
    fi
}

###############################################################################
# Main loop
###############################################################################
while true; do
    TODAY=$(date +%Y-%m-%d)
    CURRENT_TIME=$(date +%s)

    # Check if we need to fetch new sunset time for a new day
    if [ "$LAST_DATE" != "$TODAY" ]; then
        LAST_DATE="$TODAY"

        if [ -n "$LATLONG" ]; then
            # Need internet to get sunset time
            if ! check_internet; then
                echo "No internet connection. Retrying in 5 minutes..." >&2
                sleep 300
                continue
            fi

            fetch_sunset_time || {
                echo "Error fetching sunset time. Retrying in 5 minutes..." >&2
                sleep 300
                continue
            }
        else
            # User provided sunset time directly, convert to epoch
            SUNSET_EPOCH=$(date -d "${TODAY} ${SUNSET_TIME}" +%s 2>/dev/null)

            if [ -z "$SUNSET_EPOCH" ]; then
                echo "Error: could not parse time '${SUNSET_TIME}'." >&2
                sleep 60
                continue
            fi
        fi
    fi

    # Calculate alert window start (sunset minus specified minutes)
    ALERT_WINDOW_START=$(( SUNSET_EPOCH - (MINUTES * 60) ))

    # Calculate midnight of the current day
    MIDNIGHT=$(date -d "${TODAY} +1 day" +%s)

    # Alert while current time is within the window (from window start until midnight)
    if [ "$CURRENT_TIME" -ge "$ALERT_WINDOW_START" ] && \
       [ "$CURRENT_TIME" -lt "$MIDNIGHT" ]; then
        show_alert
        sleep 290
    fi

    # Reset when we've passed midnight so we fetch new time tomorrow
    if [ "$CURRENT_TIME" -ge "$MIDNIGHT" ]; then
        LAST_DATE=""
    fi

    sleep 10
done