#!/bin/sh

# RFC 8908 requires application/captive+json and no-cache headers[cite: 2]
printf "Content-Type: application/captive+json\r\n"[cite: 2]
printf "Cache-Control: private, no-cache, no-store, must-revalidate\r\n\r\n"[cite: 2]

CLIENT_IP="$REMOTE_ADDR"[cite: 2]
PORTAL_URL="https://portal.example.com:8443/cgi-bin/entry.sh"
VENUE_URL="https://example.com"[cite: 2]

IS_CAPTIVE="true"[cite: 2]
SECONDS_REMAINING=0[cite: 2]

if [ -n "$CLIENT_IP" ]; then[cite: 2]
    CLIENT_DATA=$(ndsctl json "$CLIENT_IP" 2>/dev/null)[cite: 2]
    
    # openNDS outputs capitalized "state":"Authenticated"
    if echo "$CLIENT_DATA" | grep -qi '"state":"authenticated"'; then
        IS_CAPTIVE="false"[cite: 2]
        
        SESSION_END=$(echo "$CLIENT_DATA" | grep -i '"session_end"' | tr -dc '0-9')
        NOW=$(date +%s)[cite: 2]
        
        if [ -n "$SESSION_END" ] && [ "$SESSION_END" -gt "$NOW" ]; then[cite: 2]
            SECONDS_REMAINING=$((SESSION_END - NOW))[cite: 2]
        else
            SECONDS_REMAINING=86400[cite: 2]
        fi
    fi
fi[cite: 2]

cat <<EOF
{
  "captive": ${IS_CAPTIVE},
  "user-portal-url": "${PORTAL_URL}",
  "venue-info-url": "${VENUE_URL}",
  "seconds-remaining": ${SECONDS_REMAINING},
  "can-extend-session": false
}
EOF