/*
Copyright 2023 The Ceph-CSI Authors.

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 networkfence

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"strconv"
	"strings"
	"time"

	"github.com/ceph/ceph-csi/internal/util"
	"github.com/ceph/ceph-csi/internal/util/log"

	"github.com/csi-addons/spec/lib/go/fence"
)

const (
	blocklistTime     = "157784760"
	invalidCommandStr = "invalid command"
	// we can always use mds rank 0, since all the clients have a session with rank-0.
	mdsRank = "0"
)

// NetworkFence contains the CIDR blocks to be blocked.
type NetworkFence struct {
	Cidr     []string
	Monitors string
	cr       *util.Credentials
}

// activeClient represents the structure of an active client.
type activeClient struct {
	Inst string `json:"inst"`
}

// NewNetworkFence returns a networkFence struct object from the Network fence/unfence request.
func NewNetworkFence(
	ctx context.Context,
	cr *util.Credentials,
	cidrs []*fence.CIDR,
	fenceOptions map[string]string,
) (*NetworkFence, error) {
	var err error
	nwFence := &NetworkFence{}

	nwFence.Cidr, err = GetCIDR(cidrs)
	if err != nil {
		return nil, fmt.Errorf("failed to get list of CIDRs: %w", err)
	}

	clusterID, err := util.GetClusterID(fenceOptions)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch clusterID: %w", err)
	}

	nwFence.Monitors, _, err = util.GetMonsAndClusterID(ctx, clusterID, false)
	if err != nil {
		return nil, fmt.Errorf("failed to get monitors for clusterID %q: %w", clusterID, err)
	}

	nwFence.cr = cr

	return nwFence, nil
}

// addCephBlocklist adds an IP to ceph osd blocklist.
func (nf *NetworkFence) addCephBlocklist(ctx context.Context, ip string, useRange bool) error {
	arg := []string{
		"--id", nf.cr.ID,
		"--keyfile=" + nf.cr.KeyFile,
		"-m", nf.Monitors,
	}
	// TODO: add blocklist till infinity.
	// Currently, ceph does not provide the functionality to blocklist IPs
	// for infinite time. As a workaround, add a blocklist for 5 YEARS to
	// represent infinity from ceph-csi side.
	// At any point in this time, the IPs can be unblocked by an UnfenceClusterReq.
	// This needs to be updated once ceph provides functionality for the same.
	cmd := []string{"osd", "blocklist"}
	if useRange {
		cmd = append(cmd, "range")
	}
	cmd = append(cmd, "add", ip, blocklistTime)
	cmd = append(cmd, arg...)
	_, stdErr, err := util.ExecCommand(ctx, "ceph", cmd...)
	if err != nil {
		return fmt.Errorf("failed to blocklist IP %q: %w stderr: %q", ip, err, stdErr)
	}
	log.DebugLog(ctx, "blocklisted IP %q successfully", ip)

	return nil
}

// AddNetworkFence blocks access for all the IPs in the IP range mentioned via the CIDR block
// using a network fence.
func (nf *NetworkFence) AddNetworkFence(ctx context.Context) error {
	hasBlocklistRangeSupport := true
	// for each CIDR block, convert it into a range of IPs so as to perform blocklisting operation.
	for _, cidr := range nf.Cidr {
		// try range blocklist cmd, if invalid fallback to
		// iterating through IP range.
		if hasBlocklistRangeSupport {
			err := nf.addCephBlocklist(ctx, cidr, true)
			if err == nil {
				continue
			}
			if !strings.Contains(err.Error(), invalidCommandStr) {
				return fmt.Errorf("failed to add blocklist range %q: %w", cidr, err)
			}
			hasBlocklistRangeSupport = false
		}
		// fetch the list of IPs from a CIDR block
		hosts, err := getIPRange(cidr)
		if err != nil {
			return fmt.Errorf("failed to convert CIDR block %s to corresponding IP range: %w", cidr, err)
		}

		// add ceph blocklist for each IP in the range mentioned by the CIDR
		for _, host := range hosts {
			err = nf.addCephBlocklist(ctx, host, false)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func listActiveClients(ctx context.Context) ([]activeClient, error) {
	// FIXME: replace the ceph command with go-ceph API in future
	cmd := []string{"tell", fmt.Sprintf("mds.%s", mdsRank), "client", "ls"}
	stdout, stdErr, err := util.ExecCommandWithTimeout(ctx, 2*time.Minute, "ceph", cmd...)
	if err != nil {
		return nil, fmt.Errorf("failed to list active clients: %w, stderr: %q", err, stdErr)
	}

	var activeClients []activeClient
	if err := json.Unmarshal([]byte(stdout), &activeClients); err != nil {
		return nil, fmt.Errorf("failed to unmarshal JSON: %w", err)
	}

	return activeClients, nil
}

func evictCephFSClient(ctx context.Context, clientID int) error {
	// FIXME: replace the ceph command with go-ceph API in future
	cmd := []string{"tell", fmt.Sprintf("mds.%s", mdsRank), "client", "evict", fmt.Sprintf("id=%d", clientID)}
	_, stdErr, err := util.ExecCommandWithTimeout(ctx, 2*time.Minute, "ceph", cmd...)
	if err != nil {
		return fmt.Errorf("failed to evict client %d: %w, stderr: %q", clientID, err, stdErr)
	}
	log.DebugLog(ctx, "client %s has been evicted from CephFS\n", clientID)

	return nil
}

func isIPInCIDR(ctx context.Context, ip, cidr string) bool {
	// Parse the CIDR block
	_, ipCidr, err := net.ParseCIDR(cidr)
	if err != nil {
		log.ErrorLog(ctx, "error parsing CIDR block %s: %w\n", cidr, err)

		return false
	}

	// Parse the IP address
	ipAddress := net.ParseIP(ip)
	if ipAddress == nil {
		log.ErrorLog(ctx, "error parsing IP address %s\n", ip)

		return false
	}

	// Check if the IP address is within the CIDR block
	return ipCidr.Contains(ipAddress)
}

func (ac *activeClient) fetchIP() (string, error) {
	// example: "inst": "client.4305 172.21.9.34:0/422650892",
	// then returning value will be 172.21.9.34
	clientInfo := ac.Inst
	parts := strings.Fields(clientInfo)
	if len(parts) >= 2 {
		ip := strings.Split(parts[1], ":")[0]

		return ip, nil
	}

	return "", fmt.Errorf("failed to extract IP address, incorrect format: %s", clientInfo)
}

func (ac *activeClient) fetchID() (int, error) {
	// example: "inst": "client.4305 172.21.9.34:0/422650892",
	// then returning value will be 4305
	clientInfo := ac.Inst
	parts := strings.Fields(clientInfo)
	if len(parts) >= 1 {
		clientIDStr := strings.TrimPrefix(parts[0], "client.")
		clientID, err := strconv.Atoi(clientIDStr)
		if err != nil {
			return 0, fmt.Errorf("failed to convert client ID to int: %w", err)
		}

		return clientID, nil
	}

	return 0, fmt.Errorf("failed to extract client ID, incorrect format: %s", clientInfo)
}

// AddClientEviction blocks access for all the IPs in the CIDR block
// using client eviction.
// blocks the active clients listed in cidr, and the IPs
// for whom there is no active client present too.
func (nf *NetworkFence) AddClientEviction(ctx context.Context) error {
	evictedIPs := make(map[string]bool)
	// fetch active clients
	activeClients, err := listActiveClients(ctx)
	if err != nil {
		return err
	}
	// iterate through CIDR blocks and check if any active client matches
	for _, cidr := range nf.Cidr {
		for _, client := range activeClients {
			clientIP, err := client.fetchIP()
			if err != nil {
				return fmt.Errorf("error fetching client IP: %w", err)
			}
			// check if the clientIP is in the CIDR block
			if isIPInCIDR(ctx, clientIP, cidr) {
				clientID, err := client.fetchID()
				if err != nil {
					return fmt.Errorf("error fetching client ID: %w", err)
				}
				// evict the client
				err = evictCephFSClient(ctx, clientID)
				if err != nil {
					return fmt.Errorf("error evicting client %d: %w", clientID, err)
				}
				log.DebugLog(ctx, "client %d has been evicted\n", clientID)
				// add the CIDR to the list of blocklisted IPs
				evictedIPs[clientIP] = true
			}
		}
	}

	// blocklist the IPs in CIDR without any active clients
	for _, cidr := range nf.Cidr {
		// check if the CIDR is evicted
		// fetch the list of IPs from a CIDR block
		hosts, err := getIPRange(cidr)
		if err != nil {
			return fmt.Errorf("failed to convert CIDR block %s to corresponding IP range: %w", cidr, err)
		}

		// add ceph blocklist for each IP in the range mentioned by the CIDR
		for _, host := range hosts {
			if evictedIPs[host] {
				continue
			}
			err = nf.addCephBlocklist(ctx, host, false)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

// getIPRange returns a list of IPs from the IP range
// corresponding to a CIDR block.
func getIPRange(cidr string) ([]string, error) {
	var hosts []string
	netIP, ipnet, err := net.ParseCIDR(cidr)
	if err != nil {
		return nil, err
	}
	for ip := netIP.Mask(ipnet.Mask); ipnet.Contains(ip); incIP(ip) {
		hosts = append(hosts, ip.String())
	}

	return hosts, nil
}

// incIP is an helper function for getIPRange() for incrementing
// IP values to return all IPs in a range.
func incIP(ip net.IP) {
	for j := len(ip) - 1; j >= 0; j-- {
		ip[j]++
		if ip[j] > 0 {
			break
		}
	}
}

// Cidrs is a list of CIDR structs.
type Cidrs []*fence.CIDR

// GetCIDR converts a CIDR struct list to a list.
func GetCIDR(cidrs Cidrs) ([]string, error) {
	var cidrList []string
	for _, cidr := range cidrs {
		cidrList = append(cidrList, cidr.Cidr)
	}
	if len(cidrList) < 1 {
		return nil, errors.New("the CIDR cannot be empty")
	}

	return cidrList, nil
}

// removeCephBlocklist removes an IP from ceph osd blocklist.
func (nf *NetworkFence) removeCephBlocklist(ctx context.Context, ip string, useRange bool) error {
	arg := []string{
		"--id", nf.cr.ID,
		"--keyfile=" + nf.cr.KeyFile,
		"-m", nf.Monitors,
	}
	cmd := []string{"osd", "blocklist"}
	if useRange {
		cmd = append(cmd, "range")
	}
	cmd = append(cmd, "rm", ip)
	cmd = append(cmd, arg...)

	_, stdErr, err := util.ExecCommand(ctx, "ceph", cmd...)
	if err != nil {
		return fmt.Errorf("failed to unblock IP %q: %v %w", ip, stdErr, err)
	}
	log.DebugLog(ctx, "unblocked IP %q successfully", ip)

	return nil
}

// RemoveNetworkFence unblocks access for all the IPs in the IP range mentioned via the CIDR block
// using a network fence.
func (nf *NetworkFence) RemoveNetworkFence(ctx context.Context) error {
	hasBlocklistRangeSupport := true
	// for each CIDR block, convert it into a range of IPs so as to undo blocklisting operation.
	for _, cidr := range nf.Cidr {
		// try range blocklist cmd, if invalid fallback to
		// iterating through IP range.
		if hasBlocklistRangeSupport {
			err := nf.removeCephBlocklist(ctx, cidr, true)
			if err == nil {
				continue
			}
			if !strings.Contains(err.Error(), invalidCommandStr) {
				return fmt.Errorf("failed to remove blocklist range %q: %w", cidr, err)
			}
			hasBlocklistRangeSupport = false
		}
		// fetch the list of IPs from a CIDR block
		hosts, err := getIPRange(cidr)
		if err != nil {
			return fmt.Errorf("failed to convert CIDR block %s to corresponding IP range", cidr)
		}
		// remove ceph blocklist for each IP in the range mentioned by the CIDR
		for _, host := range hosts {
			err := nf.removeCephBlocklist(ctx, host, false)
			if err != nil {
				return err
			}
		}
	}

	return nil
}