#!/usr/bin/env bash
# sunset-alarm — persistent alert at a calculated offset before sunset
# Usage: sunset-alarm (-l LAT:LONG | -t HH24:MI) (-m MINUTES) [-h]
set -uo pipefail

SUNSET_EPOCH=""     # epoch of today's sunset
ALERT_EPOCH=""      # epoch when the window opens (sunset - offset)
OFFSET_MIN=0        # signed minute offset from sunset
LAT=""              # latitude   (-l/--location)
LON=""              # longitude
HARDCODED_TIME=""  # HH:MM string (-t/--hardcoded)

usage() {
    cat <<'EOF'
Usage: sunset-alarm (-l LAT:LONG | -t HH24:MI) (-m MINUTES) [-h]

Options:
  -l LAT:LONG        Latitude and longitude, e.g. 32.123:-111.111
                     (queried from Open-Meteo for today's sunset time)
  -t HH24:MI         Hardcoded sunset time to use instead.
                     When combined with -l the offset is applied against
                     this time and the network call is skipped.
  -m MINUTES         Minutes before (-), at (= 0), or after (+) sunset
                     to trigger the alert.  May be negative.
  -h                 Show this help message and exit.

Examples:
  sunset-alarm -l 32.123:-111.111 -m 90   # 90 min before actual sunset
  sunset-alarm -t 18:00 -m -5             # 5 min after the hardcoded time
EOF
}

die() { echo "Error: $*" >&2; exit 1; }

# ── resolve a fallback command at startup ──────────────────────────
NOTIFY_CMD=""
for _cmd in fyi notify-send wall; do
    if command -v "$_cmd" >/dev/null 2>&1; then
        NOTIFY_CMD="$_cmd"; break
    fi
done

fire_alert() {
    local body="$1"
    case "$NOTIFY_CMD" in
        fyi)         fyi "Sunset Alarm: ${body}" ;;
        notify-send) notify-send -u normal "Sunset Alarm" "${body}" 2>/dev/null || true ;;
        wall)        echo "Sunset Alarm: ${body}" | wall 2>/dev/null || printf 'Sunset Alarm: %s\n' "$body" ;;
    esac
}

# ── open-meteo helper ─────────────────────────────────────────────
fetch_sunset_epoch() {
    local lat="$1" lon="$2"
    # curl –silent + HTTP code tail so we can detect failures.
    local resp; resp=$(curl -sfw "\n%{http_code}" \
        "https://api.open-meteo.com/v1/forecast?latitude=${lat}&longitude=${lon}&current=sunset&timezone=auto" \
        --connect-timeout 10 --max-time 30) || return 1

    local code="${resp##*$'\n'}"
    resp="${resp%$'\n'*}"                          # strip the trailing HTTP code

    [[ "${code:-599}" == "200" ]] || return 2

    local iso; iso=$(printf '%s\n' "$resp" | jq -r '.current.sunset // empty')
    [[ -n "$iso" ]] || return 3                    # null / missing field

    SUNSET_EPOCH=$(date -d "$iso" +%s)             # local-time epoch
}

# Build today's sunset epoch from a hardcoded HH:MM when -t is used.
set_sunset_from_time() {
    local hhmm="$1"
    local Y M D h m
    read -r Y M D h m <<< "$(date +%Y-%m-%d) $(echo "$hhmm" | tr ':' ' ')"
    SUNSET_EPOCH=$(date -d "${Y}-${M}-${D} ${h}:${m}:00" 2>/dev/null +%s \
                 || die "Invalid time format '${hhmm}')")