// SPDX-License-Identifier: Apache-2.0

package vpp

import (
	"fmt"
	"net"

	"go.fd.io/govpp/adapter"
	"go.fd.io/govpp/binapi/ip"
	"go.fd.io/govpp/binapi/ip_types"
)

// routeToStatPath is the VPP stats-segment path exposing the per-FIB-entry
// "route-to" combined counter (packets + bytes), indexed by the load-
// balance index of each FIB entry. See lbm_to_counters in
// src/vnet/dpo/load_balance.c.
const routeToStatPath = "/net/route/to"

// fibStatsIndex returns the FIB entry's stats_index (load_balance index)
// for the host prefix of addr. Uses exact=0 (longest-match) so a covering
// route is returned if there is no host-prefix entry — note this means
// two maglev entities sharing a covering route will report identical
// /net/route/to counters.
func fibStatsIndex(ch *loggedChannel, addr net.IP) (uint32, error) {
	var prefix ip_types.Prefix
	if v4 := addr.To4(); v4 != nil {
		prefix.Address.Af = ip_types.ADDRESS_IP4
		copy(prefix.Address.Un.XXX_UnionData[:4], v4)
		prefix.Len = 32
	} else {
		prefix.Address.Af = ip_types.ADDRESS_IP6
		copy(prefix.Address.Un.XXX_UnionData[:], addr.To16())
		prefix.Len = 128
	}
	req := &ip.IPRouteLookup{
		TableID: 0,
		Exact:   0,
		Prefix:  prefix,
	}
	reply := &ip.IPRouteLookupReply{}
	if err := ch.SendRequest(req).ReceiveReply(reply); err != nil {
		return 0, fmt.Errorf("ip_route_lookup: %w", err)
	}
	if reply.Retval != 0 {
		return 0, fmt.Errorf("ip_route_lookup: retval=%d", reply.Retval)
	}
	return reply.Route.StatsIndex, nil
}

// findCombinedCounter returns the CombinedCounterStat matching name, or
// nil if not found or the wrong type.
func findCombinedCounter(entries []adapter.StatEntry, name string) adapter.CombinedCounterStat {
	for _, e := range entries {
		if string(e.Name) != name {
			continue
		}
		if s, ok := e.Data.(adapter.CombinedCounterStat); ok {
			return s
		}
	}
	return nil
}

// reduceCombinedCounter sums the (packets, bytes) CombinedCounter across
// workers at column i, tolerating short per-worker vectors.
func reduceCombinedCounter(s adapter.CombinedCounterStat, i int) (pkts, byts uint64) {
	for _, thread := range s {
		if i >= 0 && i < len(thread) {
			pkts += thread[i][0]
			byts += thread[i][1]
		}
	}
	return pkts, byts
}

// vipKeyToIP extracts the VIP address from a vipKey's CIDR string. The
// second return is the prefix length. Used by the scrape path to feed
// a VIP prefix into fibStatsIndex.
func vipKeyToIP(k vipKey) (net.IP, int, error) {
	ip, ipnet, err := net.ParseCIDR(k.prefix)
	if err != nil {
		return nil, 0, err
	}
	ones, _ := ipnet.Mask.Size()
	return ip, ones, nil
}