container.go

package main

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"

	typesContainer "github.com/docker/docker/api/types/container"
	"github.com/docker/docker/api/types/events"
	"github.com/docker/docker/api/types/filters"
	"github.com/docker/docker/client"
	"ldddns.arnested.dk/internal/container"
	"ldddns.arnested.dk/internal/hostname"
	"ldddns.arnested.dk/internal/log"
)

//nolint:cyclop
func handleContainer(
	ctx context.Context,
	docker *client.Client,
	containerID string,
	egs *entryGroups,
	status string,
	config Config,
) error {
	entryGroup, commit, err := egs.get(containerID)
	defer commit()

	if err != nil {
		// The error from egs.get() already includes containerID and is descriptive
		return fmt.Errorf("cannot get Avahi entry group for container %s: %w", containerID, err)
	}

	log.Logf(log.PriDebug, "Checking if Avahi entry group for container %s is empty (before potential reset)", containerID)
	empty, err := entryGroup.IsEmpty()
	if err != nil {
		return fmt.Errorf("error checking whether Avahi entry group for container %s is empty: %w", containerID, err)
	}
	log.Logf(log.PriDebug, "Result of IsEmpty check for Avahi entry group for container %s: %t", containerID, empty)

	if !empty {
		log.Logf(log.PriDebug, "Attempting to reset Avahi entry group for container %s because it was not empty", containerID)
		err := entryGroup.Reset()
		if err != nil {
			return fmt.Errorf("error resetting Avahi entry group for container %s: %w", containerID, err)
		}
		log.Logf(log.PriDebug, "Successfully reset Avahi entry group for container %s", containerID)
	}

	if status == "die" || status == "kill" || status == "pause" {
		return nil
	}

	containerJSON, err := docker.ContainerInspect(ctx, containerID)
	if err != nil {
		return fmt.Errorf("inspecting container: %w", err)
	}

	containerInfo := container.Container{ContainerJSON: containerJSON}

	if ignoreOneoff(containerInfo, config) {
		return nil
	}

	ipNumbers := containerInfo.IPAddresses()
	if len(ipNumbers) == 0 {
		return nil
	}

	hostnames, err := hostname.Hostnames(containerInfo, config.HostnameLookup)
	if err != nil {
		return fmt.Errorf("getting hostnames: %w", err)
	}

	for _, hostname := range hostnames {
		addAddress(entryGroup, hostname, ipNumbers)
	}

	if services := containerInfo.Services(); len(hostnames) > 0 {
		addServices(entryGroup, hostnames[0], ipNumbers, services, containerInfo.Name())
	}

	return nil
}

func ignoreOneoff(containerInfo container.Container, config Config) bool {
	if !config.IgnoreDockerComposeOneoff {
		return false
	}

	oneoff, ok := containerInfo.Config.Labels["com.docker.compose.oneoff"]
	if !ok {
		return false
	}

	if oneoff != "True" {
		return false
	}

	log.Logf(log.PriNotice, "Ignoring oneoff container: %s", containerInfo.ID)

	return true
}

func handleExistingContainers(ctx context.Context, config Config, docker *client.Client, egs *entryGroups) {
	containers, err := docker.ContainerList(ctx, typesContainer.ListOptions{})
	if err != nil {
		log.Logf(log.PriErr, "getting container list: %v", err)
	}

	for _, container := range containers {
		err = handleContainer(ctx, docker, container.ID, egs, "start", config)
		if err != nil {
			log.Logf(log.PriErr, "handling container: %v", err)

			continue
		}
	}
}

func listen(ctx context.Context, config Config, docker *client.Client, egs *entryGroups, started time.Time) {
	filter := filters.NewArgs()
	filter.Add("type", "container")
	filter.Add("event", "die")
	filter.Add("event", "kill")
	filter.Add("event", "pause")
	filter.Add("event", "start")
	filter.Add("event", "unpause")

	msgs, errs := docker.Events(ctx, events.ListOptions{
		Filters: filter,
		Since:   strconv.FormatInt(started.Unix(), 10),
		Until:   "",
	})

	sig := make(chan os.Signal, 1)
	signal.Notify(sig, syscall.SIGTERM)

	for {
		select {
		case err := <-errs:
			panic(fmt.Errorf("go error reading docker events: %w", err))
		case msg := <-msgs:
			err := handleContainer(ctx, docker, msg.ID, egs, msg.Status, config)
			if err != nil {
				log.Logf(log.PriErr, "handling container: %v", err)
			}
		case <-sig:
			return
		}
	}
}