package cni

import (
	"fmt"
	"net"

	"github.com/vishvananda/netlink"
	"github.com/vishvananda/netns"

	"github.com/guildhouse-co/kedge/internal/topology"
)

// programPodRoutes programs routes inside the pod's network namespace for
// both overlay and underlay destinations.
func programPodRoutes(podNetnsPath string, ifName string, overlay, underlay []SubnetRoute) error {
	ns, err := netns.GetFromPath(podNetnsPath)
	if err != nil {
		return fmt.Errorf("failed to get pod netns: %w", err)
	}
	defer ns.Close()

	return inNamespace(ns, func() error {
		link, err := netlink.LinkByName(ifName)
		if err != nil {
			return fmt.Errorf("interface %s not found: %w", ifName, err)
		}

		allRoutes := append(overlay, underlay...)
		for _, sr := range allRoutes {
			_, dst, err := net.ParseCIDR(sr.Dst)
			if err != nil {
				return fmt.Errorf("invalid CIDR %s: %w", sr.Dst, err)
			}

			route := &netlink.Route{
				LinkIndex: link.Attrs().Index,
				Dst:       dst,
			}
			if err := netlink.RouteAdd(route); err != nil {
				return fmt.Errorf("failed to add route %s: %w", sr.Dst, err)
			}
		}
		return nil
	})
}

// verifyRoutes checks that expected routes exist in the pod's network namespace.
func verifyRoutes(podNetnsPath string, overlay, underlay []SubnetRoute) error {
	ns, err := netns.GetFromPath(podNetnsPath)
	if err != nil {
		return fmt.Errorf("failed to get pod netns: %w", err)
	}
	defer ns.Close()

	return inNamespace(ns, func() error {
		routes, err := netlink.RouteList(nil, netlink.FAMILY_V4)
		if err != nil {
			return fmt.Errorf("failed to list routes: %w", err)
		}

		routeMap := make(map[string]bool)
		for _, r := range routes {
			if r.Dst != nil {
				routeMap[r.Dst.String()] = true
			}
		}

		allExpected := append(overlay, underlay...)
		for _, sr := range allExpected {
			if !routeMap[sr.Dst] {
				return fmt.Errorf("missing route: %s", sr.Dst)
			}
		}
		return nil
	})
}

// loadMeshTopology reads the mesh topology file written by the DaemonSet.
func loadMeshTopology(meshConfigPath string) (*topology.MeshTopology, error) {
	if meshConfigPath == "" {
		meshConfigPath = "/etc/kedge/mesh.json"
	}
	return topology.LoadFromFile(meshConfigPath)
}