#!/usr/bin/env bash

OPML_FILE=""
DAYS=90

usage() {
    echo "Usage: $0 -f <opml_file> [-d <days>]"
    echo "Example: $0 -f subscriptions.opml -d 180"
    exit 1
}

while getopts "f:d:h" opt; do
    case ${opt} in
        f ) OPML_FILE=$OPTARG ;;
        d ) DAYS=$OPTARG ;;
        h ) usage ;;
        * ) usage ;;
    esac
done

if [[ -z "$OPML_FILE" || ! -f "$OPML_FILE" ]]; then
    echo "Error: Please provide a valid OPML file."
    usage
fi

NOW=$(date +%s)
LIMIT_SEC=$((DAYS * 86400))

echo "Analysing feeds in $OPML_FILE (flagging older than $DAYS days)..."
echo "------------------------------------------------------------------"

feed_urls=$(tr '><' '\n\n' < "$OPML_FILE" | grep -Eiho 'xmlUrl="[^"]+"' | cut -d'"' -f2)

for url in $feed_urls; do
    # Fetch feed, handle compression, and extract the first date-like element.
    # grep -m 1 stops parsing after the first match, terminating the curl download early.
    date_str=$(curl -sL --compressed --max-time 10 "$url" 2>/dev/null | \
        grep -Eio -m 1 '<(pubDate|updated|lastBuildDate|published)>[^<]+|"date_published":"[^"]+|"date_modified":"[^"]+' | \
        head -n 1 | \
        sed -E 's/<[^>]+>|"date_(published|modified)":"//g' | tr -d '\r\n')
    
    if [[ -z "$date_str" ]]; then
        echo "[UNKNOWN] $url - No parsable date found (or feed is unreachable)."
        continue
    fi

    feed_ts=""

    # Try GNU date
    if date -d "$date_str" +%s >/dev/null 2>&1; then
        feed_ts=$(date -d "$date_str" +%s)
    # Try gdate (macOS if GNU coreutils is installed)
    elif command -v gdate >/dev/null 2>&1 && gdate -d "$date_str" +%s >/dev/null 2>&1; then
        feed_ts=$(gdate -d "$date_str" +%s)
    fi

    if [[ -z "$feed_ts" ]]; then
        echo "[PARSE ERROR] $url - Found date but couldn't parse format: '$date_str'"
        continue
    fi

    diff=$((NOW - feed_ts))
    
    if (( diff > LIMIT_SEC )); then
        days_old=$((diff / 86400))
        echo "[STALE] $url - $days_old days old (Last updated: $date_str)"
    fi

done

echo "------------------------------------------------------------------"
echo "Finished."