# Based on jlu5's custom filters
# https://github.com/jlu5/ansible-dn42
# Adapted for AS4242421411 - C4TG1RL5
#
function lower_pref(int x) {
    if (bgp_local_pref > x) then {
        bgp_local_pref = bgp_local_pref - x;
    } else {
        bgp_local_pref = 0;
    }
}

function get_region_tag(int region_tag) {
    if (region_tag = 44) then {
        return 1;  # North America - West
    } else if (region_tag ~ [42..43]) then {
        return 2;  # North America - Central/East
    } else if (region_tag = 41) then {
        return 3;  # Europe
    } else if (region_tag ~ [51..53]) then {
        return 4;  # Asia E/SE + Oceania
    }
    return 0;
}

function prefer_same_region_origin(int base_weight) 
    int region_tag;
    int incoming_tag;
{
    region_tag = get_region_tag(DN42_REGION);
    incoming_tag = 0;

    if ((64511, 41) ~ bgp_community) then {
        incoming_tag = get_region_tag(41);
    }
    else if ((64511, 42) ~ bgp_community) then {
        incoming_tag = get_region_tag(42);
    }
    else if ((64511, 43) ~ bgp_community) then {
        incoming_tag = get_region_tag(43);
    }
    else if ((64511, 44) ~ bgp_community) then {
        incoming_tag = get_region_tag(44);
    }
    else if ((64511, 50) ~ bgp_community) then {
        incoming_tag = get_region_tag(50);
    }
    else if ((64511, 51) ~ bgp_community) then {
        incoming_tag = get_region_tag(51);
    }
    else if ((64511, 52) ~ bgp_community) then {
        incoming_tag = get_region_tag(52);
    }
    else if ((64511, 53) ~ bgp_community) then {
        incoming_tag = get_region_tag(53);
    }

    if (incoming_tag = 0 || incoming_tag = region_tag) then {
        # print "Route ", net, " has incoming tag ", incoming_tag, " matching ours ", region_tag;
        bgp_local_pref = bgp_local_pref + 50;
    }
}

function bgp_import_filter() {
    # Reject routes with long path lengths
    if (bgp_path.len > 12) then {         
        reject;
    }

    bgp_local_pref = bgp_local_pref + 1400;
    lower_pref(bgp_path.len * 100);
    prefer_same_region_origin(200);

    if (source = RTS_BGP && (65535, 666) ~ bgp_community) then {
        dest = RTD_BLACKHOLE;
    }
};

function ibgp_import_filter() {
    if (source != RTS_BGP) then {
        reject;
    }
    if (!is_valid_network() && !is_valid_network_v6()) then {
        reject;
    }

    bgp_local_pref = bgp_local_pref + 1400;
    lower_pref(bgp_path.len * 100);
    if (bgp_path.len = 0) then {
        bgp_local_pref = bgp_local_pref + 2000;
    }

    accept;
}

# TODO: implement exports with the bgp_med attribute

function ibgp_export_filter() {
    if (source != RTS_BGP && !is_ibgp_network()) then {
        reject;
    }
    # Don't export device routes for dn42 anycast networks. These will be filled in via a static route config
    # triggered by service start/stop
    if (is_ibgp_network() && source = RTS_DEVICE) then {
        reject;
    }
    accept;
}