package pkg

import (
	"context"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"os"
	"path"
	"path/filepath"

	"github.com/alexellis/faasd/pkg/service"
	"github.com/alexellis/faasd/pkg/weave"
	"github.com/containerd/containerd"
	"github.com/containerd/containerd/cio"
	"github.com/containerd/containerd/containers"
	gocni "github.com/containerd/go-cni"
	"github.com/google/uuid"
	"github.com/pkg/errors"

	"github.com/containerd/containerd/namespaces"
	"github.com/containerd/containerd/oci"
	"github.com/opencontainers/runtime-spec/specs-go"
)

const defaultSnapshotter = "overlayfs"

const (
	// TODO: CNIBinDir and CNIConfDir should maybe be globally configurable?
	// CNIBinDir describes the directory where the CNI binaries are stored
	CNIBinDir = "/opt/cni/bin"
	// CNIConfDir describes the directory where the CNI plugin's configuration is stored
	CNIConfDir = "/etc/cni/net.d"
	// netNSPathFmt gives the path to the a process network namespace, given the pid
	NetNSPathFmt = "/proc/%d/ns/net"
	// defaultCNIConfFilename is the vanity filename of default CNI configuration file
	DefaultCNIConfFilename = "10-openfaas.conflist"
	// defaultNetworkName names the "docker-bridge"-like CNI plugin-chain installed when no other CNI configuration is present.
	// This value appears in iptables comments created by CNI.
	DefaultNetworkName = "openfaas-cni-bridge"
	// defaultBridgeName is the default bridge device name used in the defaultCNIConf
	DefaultBridgeName = "openfaas0"
	// defaultSubnet is the default subnet used in the defaultCNIConf -- this value is set to not collide with common container networking subnets:
	DefaultSubnet = "10.62.0.0/16"
)

type Supervisor struct {
	client *containerd.Client
}

func NewSupervisor(sock string) (*Supervisor, error) {
	client, err := containerd.New(sock)
	if err != nil {
		panic(err)
	}

	return &Supervisor{
		client: client,
	}, nil
}

func (s *Supervisor) Close() {
	defer s.client.Close()
}

func (s *Supervisor) Remove(svcs []Service) error {
	ctx := namespaces.WithNamespace(context.Background(), "default")

	for _, svc := range svcs {
		err := service.Remove(ctx, s.client, svc.Name)
		if err != nil {
			return err
		}
	}
	return nil
}

func (s *Supervisor) Start(svcs []Service) error {
	ctx := namespaces.WithNamespace(context.Background(), "default")

	wd, _ := os.Getwd()

	ip, _, _ := net.ParseCIDR(DefaultSubnet)
	ip = ip.To4()
	ip[3] = 1
	ip.String()
	hosts := fmt.Sprintf(`
127.0.0.1	localhost
%s	faas-containerd`, ip)

	writeHostsErr := ioutil.WriteFile(path.Join(wd, "hosts"),
		[]byte(hosts), 0644)

	if writeHostsErr != nil {
		return fmt.Errorf("cannot write hosts file: %s", writeHostsErr)
	}
	// os.Chown("hosts", 101, 101)

	images := map[string]containerd.Image{}

	for _, svc := range svcs {
		fmt.Printf("Preparing: %s with image: %s\n", svc.Name, svc.Image)

		img, err := service.PrepareImage(ctx, s.client, svc.Image, defaultSnapshotter)
		if err != nil {
			return err
		}
		images[svc.Name] = img
		size, _ := img.Size(ctx)
		fmt.Printf("Prepare done for: %s, %d bytes\n", svc.Image, size)
	}

	for _, svc := range svcs {
		fmt.Printf("Reconciling: %s\n", svc.Name)

		containerErr := service.Remove(ctx, s.client, svc.Name)
		if containerErr != nil {
			return containerErr
		}

		image := images[svc.Name]

		mounts := []specs.Mount{}
		if len(svc.Mounts) > 0 {
			for _, mnt := range svc.Mounts {
				mounts = append(mounts, specs.Mount{
					Source:      mnt.Src,
					Destination: mnt.Dest,
					Type:        "bind",
					Options:     []string{"rbind", "rw"},
				})
			}

		}

		mounts = append(mounts, specs.Mount{
			Destination: "/etc/resolv.conf",
			Type:        "bind",
			Source:      path.Join(wd, "resolv.conf"),
			Options:     []string{"rbind", "ro"},
		})

		mounts = append(mounts, specs.Mount{
			Destination: "/etc/hosts",
			Type:        "bind",
			Source:      path.Join(wd, "hosts"),
			Options:     []string{"rbind", "ro"},
		})

		newContainer, containerCreateErr := s.client.NewContainer(
			ctx,
			svc.Name,
			containerd.WithImage(image),
			containerd.WithNewSnapshot(svc.Name+"-snapshot", image),
			containerd.WithNewSpec(oci.WithImageConfig(image),
				oci.WithCapabilities(svc.Caps),
				oci.WithMounts(mounts),
				withOCIArgs(svc.Args),
				oci.WithEnv(svc.Env)),
		)

		if containerCreateErr != nil {
			log.Printf("Error creating container %s\n", containerCreateErr)
			return containerCreateErr
		}

		log.Printf("Created container %s\n", newContainer.ID())

		task, err := newContainer.NewTask(ctx, cio.NewCreator(cio.WithStdio))
		if err != nil {
			log.Printf("Error creating task: %s\n", err)
			return err
		}

		id := uuid.New().String()
		netns := fmt.Sprintf(NetNSPathFmt, task.Pid())

		cni, err := gocni.New(gocni.WithPluginConfDir(CNIConfDir),
			gocni.WithPluginDir([]string{CNIBinDir}))

		if err != nil {
			return errors.Wrapf(err, "error creating CNI instance")
		}

		// Load the cni configuration
		if err := cni.Load(gocni.WithLoNetwork, gocni.WithConfListFile(filepath.Join(CNIConfDir, DefaultCNIConfFilename))); err != nil {
			return errors.Wrapf(err, "failed to load cni configuration: %v", err)
		}

		labels := map[string]string{}

		_, err = cni.Setup(ctx, id, netns, gocni.WithLabels(labels))
		if err != nil {
			return errors.Wrapf(err, "failed to setup network for namespace %q: %v", id, err)
		}

		// Get the IP of the default interface.
		// defaultInterface := gocni.DefaultPrefix + "0"
		// ip := &result.Interfaces[defaultInterface].IPConfigs[0].IP
		ip := getIP(newContainer.ID(), task.Pid())
		log.Printf("%s has IP: %s\n", newContainer.ID(), ip)

		hosts, _ := ioutil.ReadFile("hosts")

		hosts = []byte(string(hosts) + fmt.Sprintf(`
%s	%s
`, ip, svc.Name))
		writeErr := ioutil.WriteFile("hosts", hosts, 0644)

		if writeErr != nil {
			log.Printf("Error writing file %s %s\n", "hosts", writeErr)
		}
		// os.Chown("hosts", 101, 101)

		_, err = task.Wait(ctx)
		if err != nil {
			log.Printf("Wait err: %s\n", err)
			return err
		}

		log.Printf("Task: %s\tContainer: %s\n", task.ID(), newContainer.ID())
		// log.Println("Exited: ", exitStatusC)

		if err = task.Start(ctx); err != nil {
			log.Printf("Task err: %s\n", err)
			return err
		}
	}

	return nil
}

func getIP(containerID string, taskPID uint32) string {
	// https://github.com/weaveworks/weave/blob/master/net/netdev.go

	peerIDs, err := weave.ConnectedToBridgeVethPeerIds(DefaultBridgeName)
	if err != nil {
		log.Fatal(err)
	}

	addrs, addrsErr := weave.GetNetDevsByVethPeerIds(int(taskPID), peerIDs)
	if addrsErr != nil {
		log.Fatal(addrsErr)
	}
	if len(addrs) > 0 {
		return addrs[0].CIDRs[0].IP.String()
	}

	return ""
}

type Service struct {
	Image  string
	Env    []string
	Name   string
	Mounts []Mount
	Caps   []string
	Args   []string
}

type Mount struct {
	Src  string
	Dest string
}

func withOCIArgs(args []string) oci.SpecOpts {
	if len(args) > 0 {
		return oci.WithProcessArgs(args...)
	}

	return func(_ context.Context, _ oci.Client, _ *containers.Container, s *oci.Spec) error {

		return nil
	}

}