// Copyright (c) 2015-2021 Tigera, Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package upgrade

import (
	"context"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path"
	"strings"
	"time"

	"github.com/containernetworking/plugins/plugins/ipam/host-local/backend/disk"
	log "github.com/sirupsen/logrus"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	corev1 "k8s.io/api/core/v1"

	apiv3 "github.com/projectcalico/api/pkg/apis/projectcalico/v3"

	"github.com/projectcalico/calico/cni-plugin/internal/pkg/utils"
	libapiv3 "github.com/projectcalico/calico/libcalico-go/lib/apis/v3"
	bapi "github.com/projectcalico/calico/libcalico-go/lib/backend/api"
	"github.com/projectcalico/calico/libcalico-go/lib/backend/k8s"
	client "github.com/projectcalico/calico/libcalico-go/lib/clientv3"
	"github.com/projectcalico/calico/libcalico-go/lib/errors"
	"github.com/projectcalico/calico/libcalico-go/lib/ipam"
	"github.com/projectcalico/calico/libcalico-go/lib/net"
	cnet "github.com/projectcalico/calico/libcalico-go/lib/net"
	"github.com/projectcalico/calico/libcalico-go/lib/options"
)

const (
	ipAllocPath = "/var/lib/cni/networks/k8s-pod-network"
)

var (
	binariesToDisable = []string{
		"/host/opt/cni/bin/calico",
		"/host/opt/cni/bin/host-local",
	}
)

type accessor interface {
	Backend() bapi.Client
}

func Migrate(ctxt context.Context, c client.Interface, nodename string) error {
	// k8sClient directly calls the k8s apiserver.
	k8sClient := c.(accessor).Backend().(*k8s.KubeClient).ClientSet

	// Check to see if the system is still using host-local
	// by checking the existence of the path.
	log.Info("checking host-local IPAM data dir dir existence...")
	if _, err := os.Stat(ipAllocPath); err != nil && os.IsNotExist(err) {
		log.Info("host-local IPAM data dir dir not found; no migration necessary, successfully exiting...")
		return nil
	}

	// Get node resource to check for IPIP tunnel address.
	log.Info("retrieving node for IPIP tunnel address")
	node, err := c.Nodes().Get(ctxt, nodename, options.GetOptions{})
	if err != nil {
		return fmt.Errorf("failed to get calico node resource: %s", err)
	}

	// Migrate IPIP tunnel address if the field is empty.
	if node.Spec.BGP == nil || node.Spec.BGP.IPv4IPIPTunnelAddr == "" {
		log.Info("IPIP tunnel address not found, assigning...")

		// Fetch k8s node.
		k8sNode, err := k8sClient.CoreV1().Nodes().Get(context.Background(), nodename, metav1.GetOptions{})
		if err != nil {
			return fmt.Errorf("failed to get k8s node resource: %s", err)
		}

		// Parse PodCIDR.
		ip, cidr, err := net.ParseCIDR(k8sNode.Spec.PodCIDR)
		if err != nil {
			return fmt.Errorf("PodCIDR %s did not parse successfully: %s", k8sNode.Spec.PodCIDR, err)
		} else if cidr.Version() == 4 {
			// We need to get the IP for the podCIDR and increment it to the
			// first IP in the CIDR to match the behavior used by Calico when using host-local IPAM.
			tunIp := ip.To4()
			if tunIp == nil {
				return fmt.Errorf("Cannot pick an IPv4 tunnel address from the given CIDR: %s", k8sNode.Spec.PodCIDR)
			}
			tunIp[3]++

			// Assign the address via Calico IPAM.
			ipipTunnelAddr := cnet.ParseIP(tunIp.String())
			handle := fmt.Sprintf("ipip-tunnel-addr-%s", nodename)
			if err = c.IPAM().AssignIP(ctxt, ipam.AssignIPArgs{
				IP:       *ipipTunnelAddr,
				Hostname: nodename,
				HandleID: &handle,
				Attrs: map[string]string{
					ipam.AttributeNode: nodename,
					ipam.AttributeType: ipam.AttributeTypeIPIP,
				},
			}); err != nil {
				if _, ok := err.(errors.ErrorResourceAlreadyExists); !ok {
					return fmt.Errorf("failed to get add IPIP tunnel addr %s: %s", tunIp.String(), err)
				}
				log.Info("IPIP tunnel address already assigned in IPAM, continuing...")
			}

			// Implemented retry on conflict, because we get stuck if the upgrade-ipam
			// container fails here and retries assigning an IP which is already assigned
			for i := uint(0); i < 5; i++ {
				node, err := c.Nodes().Get(ctxt, nodename, options.GetOptions{})
				if err != nil {
					return fmt.Errorf("failed to get calico node resource: %s", err)
				}
				if node.Spec.BGP == nil {
					node.Spec.BGP = &libapiv3.NodeBGPSpec{}
				}
				node.Spec.BGP.IPv4IPIPTunnelAddr = tunIp.String()
				if _, err = c.Nodes().Update(ctxt, node, options.SetOptions{}); err != nil {
					if _, ok := err.(errors.ErrorResourceUpdateConflict); ok {
						log.Info("Encountered update conflict, retrying...")
						time.Sleep(1 * time.Second)
						continue
					}
					return fmt.Errorf("failed to update node: %s", err)
				}
				break
			}

			log.WithField("ip", node.Spec.BGP.IPv4IPIPTunnelAddr).Info("Assigned IPIP tunnel address to node")
		} else if cidr.Version() == 6 {
			log.Info("IPv6 podCIDR - no need to migrate IPIP address")
		}
	}

	// Open k8s-pod-directory to check for emptiness.
	log.Info("checking if host-local IPAM data dir dir is empty...")
	ipamDir, err := os.Open(ipAllocPath)
	if err != nil {
		return fmt.Errorf("failed to open host-local IPAM data dir dir: %s", err)
	}

	// Check if the directory is empty.
	if _, err = ipamDir.Readdirnames(1); err != nil {
		if os.IsNotExist(err) || err == io.EOF {
			log.Info("host-local IPAM data dir empty; no migration necessary...")
			log.Info("removing host-local IPAM data directory...")
			if err = os.Remove(ipAllocPath); err != nil {
				log.WithError(err).Error("failed to remove host-local IPAM data dir directory")
				return err
			}
			log.Info("successfully removed host-local IPAM data directory!")
			return nil
		}
		if closeErr := ipamDir.Close(); closeErr != nil {
			return fmt.Errorf("failed to close host-local IPAM data dir directory on read failure: %s", err)
		}
		return fmt.Errorf("failed to read host-local IPAM data dir names: %s", err)
	}
	log.Info("host-local IPAM data dir is not empty, migrating...")

	// Close the host-local IPAM data directory file pointer.
	if closeErr := ipamDir.Close(); closeErr != nil {
		return fmt.Errorf("failed to close host-local IPAM data dir directory: %s", err)
	}

	// Disable cni by setting DatastoreReady to false.
	log.Info("setting datastore readiness to false")
	var clusterInfo *apiv3.ClusterInformation
	for i := uint(0); i < 5; i++ {
		clusterInfo, err = c.ClusterInformation().Get(ctxt, "default", options.GetOptions{})
		if err != nil {
			return fmt.Errorf("failed to fetch cluster information: %s", err)
		}
		if clusterInfo.Spec.DatastoreReady == nil || *clusterInfo.Spec.DatastoreReady {
			f := false
			clusterInfo.Spec.DatastoreReady = &f
			if clusterInfo, err = c.ClusterInformation().Update(ctxt, clusterInfo, options.SetOptions{}); err != nil {
				if _, ok := err.(errors.ErrorResourceUpdateConflict); ok {
					log.Info("Encountered update conflict, retrying...")
					time.Sleep(1 * time.Second)
					continue
				}
				return fmt.Errorf("failed to disable cluster: %s", err)
			}
			break
		}
	}
	log.Info("successfully set datastore readiness to false")

	// Also disable cni by deleting the binaries.
	log.Info("removing cni binaries...")
	for _, binary := range binariesToDisable {
		if err = os.Remove(binary); err != nil && !os.IsNotExist(err) {
			return fmt.Errorf("failed to remove binary %s: %s", binary, err)
		}
		log.WithField("binary", binary).Info("successfully removed cni binary!")
	}
	time.Sleep(5 * time.Second)

	// Acquire a lock on the host-local cni backend. This serves as extra precaution
	// against racing with any remaining host-local processes which might be allocating
	// IP addresses.
	log.Info("acquiring lock on host-local IPAM")
	hostLocal, err := disk.New("", ipAllocPath)
	if err != nil {
		return fmt.Errorf("failed to initialize host-local IPAM: %s", err)
	}
	if err = hostLocal.Lock(); err != nil {
		return fmt.Errorf("failed to acquire lock on host-local IPAM: %s", err)
	}
	log.Info("successfully acquired lock on host-local IPAM")
	defer func() {
		// Release the lock on host local backend
		log.Info("releasing lock on host-local backend...")
		if err = hostLocal.Unlock(); err != nil {
			log.WithError(err).Error("failed to release lock on host local backend")
		} else {
			log.Info("successfully released lock on host-local backend!")
		}
	}()

	// Establishing a mapping of IP addresses to Pods on this node. We need this
	// to populate Calico IPAM's allocation attributes below.
	log.Info("mapping pod ips to pods...")
	podList, err := k8sClient.CoreV1().Pods("").List(context.Background(), metav1.ListOptions{
		FieldSelector: fmt.Sprintf("spec.nodeName=%s", nodename),
	})
	if err != nil {
		return fmt.Errorf("failed to list pods: %s", err)
	}
	podIPMap := make(map[string]*corev1.Pod)
	for i := 0; i < len(podList.Items); i++ {
		pod := &podList.Items[i]
		log.WithFields(log.Fields{"pod": pod.Name, "IP": pod.Status.PodIP, "namespace": pod.Namespace}).Info("mapping in pod")
		podIPMap[pod.Status.PodIP] = pod
	}
	log.Info("successfully mapped pod ips to pods!")

	// Read in all the files in the host-local directory.
	log.Info("reading files from host-local IPAM data dir...")
	files, err := ioutil.ReadDir(ipAllocPath)
	if err != nil {
		return fmt.Errorf("failed to read path %s: %s", ipAllocPath, err)
	}

	// For each file, convert it into an IP allocation and then delete the file.
	for _, f := range files {
		logCtxt := log.WithField("file", f.Name())
		logCtxt.Info("processing file...")
		fname := path.Join(ipAllocPath, f.Name())

		// Delete and skip the last reserved IP.
		if strings.Contains(f.Name(), "last") {
			logCtxt.Info("skipping and removing last reserved ip file...")
			if err = os.Remove(fname); err != nil && !os.IsNotExist(err) {
				return fmt.Errorf("failed to remove file %s: %s", fname, err)
			}
			logCtxt.Info("removed last reserved ip file")
			continue
		}

		// Skip the lock
		if f.Name() == "lock" {
			logCtxt.Info("skipping the lock...")
			continue
		}

		// The name of the file is its IP address.
		ip, _, err := cnet.ParseCIDR(fmt.Sprintf("%s/32", f.Name()))
		if err != nil {
			return fmt.Errorf("failed to parse IP %s: %s", f.Name(), err)
		}

		// The contents are the container ID.
		b, err := ioutil.ReadFile(fname)
		if err != nil {
			return fmt.Errorf("failed to read file %s: %s", fname, err)
		}
		// The containerID is the first line in the file.
		containerID := strings.TrimSpace(strings.Split(string(b), "\n")[0])

		// Get the pod resource associated with the IP.
		pod, ok := podIPMap[f.Name()]
		if !ok {
			logCtxt.WithField("ip", f.Name()).Info("pod not found for IP, deleting and continuing")
			if err = os.Remove(fname); err != nil && !os.IsNotExist(err) {
				return fmt.Errorf("failed to remove file %s: %s", fname, err)
			}
			continue
		}

		// Store allocation to Calico datastore.
		handleID := utils.GetHandleID("k8s-pod-network", containerID, "")
		logCtxt.Info("assinging pod IP to Calico IPAM...")
		if err = c.IPAM().AssignIP(ctxt, ipam.AssignIPArgs{
			IP:       *ip,
			HandleID: &handleID,
			Hostname: nodename,
			Attrs: map[string]string{
				ipam.AttributeNode:      nodename,
				ipam.AttributePod:       pod.Name,
				ipam.AttributeNamespace: pod.Namespace,
			},
		}); err != nil {
			if _, ok := err.(errors.ErrorResourceAlreadyExists); !(ok || strings.Contains(err.Error(), "already assigned")) {
				return fmt.Errorf("failed to assign IP to calico backend: %s", err)
			}
			// Pod IP already assigned - likely failed to remove the file on the last attempt.
			// continue, but log a warning.
			logCtxt.Warn("pod IP already assigned, skipping")
		}
		logCtxt.Info("pod IP assigned in Calico IPAM")

		// Delete the file from the host-local directory.
		logCtxt.Info("removing host-local allocation file")
		if err = os.Remove(fname); err != nil && !os.IsNotExist(err) {
			return fmt.Errorf("failed to remove file %s: %s", fname, err)
		}
		logCtxt.Info("successfully removed file")
	}

	// Release the lock.
	if err = hostLocal.Unlock(); err != nil {
		log.WithError(err).Error("failed to release lock on host local backend")
	} else {
		log.Info("successfully released lock on host-local backend!")
	}

	// Always re-enable datastoreReady. This leaves a very small chance that an address may be assigned by calico-ipam
	// that is already in use by host-local. Any pods stuck in this situation will be fixed once they are restarted.
	// TODO: Re-enable datastoreReady if all of the nodes have been picked up for the rolling update.
	// This logic has not been used because of the potential length of time it would bring normal operation
	// of the cluster down for by locking the datastore until the update has been applied to all nodes.
	// calicoDS, err := k8sClient.AppsV1().DaemonSets("kube-system").Get(context.Background(), "calico-node", metav1.GetOptions{})
	// if calicoDS.Status.UpdatedNumberScheduled == calicoDS.Status.DesiredNumberScheduled {
	log.Info("setting Calico datastore readiness to true...")
	t := true
	clusterInfo.Spec.DatastoreReady = &t
	if _, err = c.ClusterInformation().Update(ctxt, clusterInfo, options.SetOptions{}); err != nil {
		return fmt.Errorf("failed to re-enable cluster: %s", err)
	}
	log.Info("successfully set Calico datastore readiness to true!")

	// Delete the host-local IPAM data directory.
	log.Info("removing host-local IPAM data directory")
	if err = os.RemoveAll(ipAllocPath); err != nil && !os.IsNotExist(err) {
		log.WithError(err).Error("failed to remove host-local IPAM data dir directory")
	}
	log.Info("successfully removed host-local IPAM data directory!")

	return nil
}
