#!/usr/bin/env bash
# Policy routing: send traffic to specified domains via Starlink interface.
# Run on Linux host (e.g. Linux Mint) that has both main connection and WiFi to Starlink.
# Usage: sudo ./policy-route-starlink.sh [setup|remove]
# Configure STARLINK_IF, STARLINK_GW, DOMAINS below or via env.

set -e

# Starlink WiFi interface (e.g. wlan0)
STARLINK_IF="${STARLINK_IF:-wlan0}"
# Starlink gateway IP (get from: ip route show dev "$STARLINK_IF" | head -1)
STARLINK_GW="${STARLINK_GW:-}"
# Domains to route via Starlink (space-separated)
DOMAINS="${DOMAINS:-polymarket.com www.polymarket.com}"
# Routing table id for Starlink
TABLE_ID=200

action="${1:-setup}"

resolve_domains() {
    local list=""
    for d in $DOMAINS; do
        local ips
        ips=$(getent ahosts "$d" 2>/dev/null | awk '$1 !~ /^:/ {print $1}' | sort -u) || true
        for ip in $ips; do
            [[ -n "$ip" ]] && list="$list $ip"
        done
    done
    echo "$list"
}

get_starlink_gw() {
    if [[ -n "$STARLINK_GW" ]]; then
        echo "$STARLINK_GW"
        return
    fi
    ip route show dev "$STARLINK_IF" 2>/dev/null | awk '/default via/ {print $3; exit}'
}

do_setup() {
    if ! ip link show "$STARLINK_IF" &>/dev/null; then
        echo "Interface $STARLINK_IF not found. Set STARLINK_IF (e.g. wlan0)."
        exit 1
    fi
    local gw
    gw=$(get_starlink_gw)
    if [[ -z "$gw" ]]; then
        echo "Could not determine Starlink gateway. Set STARLINK_GW or ensure $STARLINK_IF has a route."
        exit 1
    fi
    # Ensure table 200 has default via Starlink (idempotent)
    ip route replace default via "$gw" dev "$STARLINK_IF" table "$TABLE_ID" 2>/dev/null || true
    local ips
    ips=$(resolve_domains)
    if [[ -z "$ips" ]]; then
        echo "No IPs resolved for domains: $DOMAINS. Check DNS/connectivity."
        exit 1
    fi
    for ip in $ips; do
        ip rule add to "$ip" table "$TABLE_ID" 2>/dev/null || true
    done
    echo "Routing via Starlink ($STARLINK_IF): $ips"
}

do_remove() {
    local ips
    ips=$(resolve_domains)
    for ip in $ips; do
        ip rule del to "$ip" table "$TABLE_ID" 2>/dev/null || true
    done
    ip route flush table "$TABLE_ID" 2>/dev/null || true
    echo "Removed policy rules for table $TABLE_ID."
}

case "$action" in
    setup)   do_setup ;;
    remove) do_remove ;;
    *)
        echo "Usage: $0 [setup|remove]"
        echo "Env: STARLINK_IF ($STARLINK_IF), STARLINK_GW, DOMAINS"
        exit 1
        ;;
esac