// Copyright 2018 CNI 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 main

import (
	"encoding/json"
	"fmt"
	"net"

	"github.com/containernetworking/cni/pkg/skel"
	"github.com/containernetworking/cni/pkg/types"
	"github.com/containernetworking/cni/pkg/types/current"
	"github.com/containernetworking/cni/pkg/version"

	types020 "github.com/containernetworking/cni/pkg/types/020"
)

// The top-level network config - IPAM plugins are passed the full configuration
// of the calling plugin, not just the IPAM section.
type Net struct {
	Name       string      `json:"name"`
	CNIVersion string      `json:"cniVersion"`
	IPAM       *IPAMConfig `json:"ipam"`
}

type IPAMConfig struct {
	Name      string
	Type      string         `json:"type"`
	Routes    []*types.Route `json:"routes"`
	Addresses []Address      `json:"addresses,omitempty"`
	DNS       types.DNS      `json:"dns"`
}

type IPAMEnvArgs struct {
	types.CommonArgs
	IP      types.UnmarshallableString `json:"ip,omitempty"`
	GATEWAY net.IP                     `json:"gateway,omitempty"`
}

type Address struct {
	AddressStr string `json:"address"`
	Gateway    net.IP `json:"gateway,omitempty"`
	Address    net.IPNet
	Version    string
}

func main() {
	skel.PluginMain(cmdAdd, cmdDel, version.All)
}

// canonicalizeIP makes sure a provided ip is in standard form
func canonicalizeIP(ip *net.IP) error {
	if ip.To4() != nil {
		*ip = ip.To4()
		return nil
	} else if ip.To16() != nil {
		*ip = ip.To16()
		return nil
	}
	return fmt.Errorf("IP %s not v4 nor v6", *ip)
}

// NewIPAMConfig creates a NetworkConfig from the given network name.
func LoadIPAMConfig(bytes []byte, envArgs string) (*IPAMConfig, string, error) {
	n := Net{}
	if err := json.Unmarshal(bytes, &n); err != nil {
		return nil, "", err
	}

	if n.IPAM == nil {
		return nil, "", fmt.Errorf("IPAM config missing 'ipam' key")
	}

	// Validate all ranges
	numV4 := 0
	numV6 := 0

	for i := range n.IPAM.Addresses {
		ip, addr, err := net.ParseCIDR(n.IPAM.Addresses[i].AddressStr)
		if err != nil {
			return nil, "", fmt.Errorf("invalid CIDR %s: %s", n.IPAM.Addresses[i].AddressStr, err)
		}
		n.IPAM.Addresses[i].Address = *addr
		n.IPAM.Addresses[i].Address.IP = ip

		if err := canonicalizeIP(&n.IPAM.Addresses[i].Address.IP); err != nil {
			return nil, "", fmt.Errorf("invalid address %d: %s", i, err)
		}

		if n.IPAM.Addresses[i].Address.IP.To4() != nil {
			n.IPAM.Addresses[i].Version = "4"
			numV4++
		} else {
			n.IPAM.Addresses[i].Version = "6"
			numV6++
		}
	}

	if envArgs != "" {
		e := IPAMEnvArgs{}
		err := types.LoadArgs(envArgs, &e)
		if err != nil {
			return nil, "", err
		}

		if e.IP != "" {
			ip, subnet, err := net.ParseCIDR(string(e.IP))
			if err != nil {
				return nil, "", fmt.Errorf("invalid CIDR %s: %s", e.IP, err)
			}

			addr := Address{Address: net.IPNet{IP: ip, Mask: subnet.Mask}}
			if e.GATEWAY != nil {
				addr.Gateway = e.GATEWAY
			}
			if addr.Address.IP.To4() != nil {
				addr.Version = "4"
				numV4++
			} else {
				addr.Version = "6"
				numV6++
			}
			n.IPAM.Addresses = append(n.IPAM.Addresses, addr)
		}
	}

	// CNI spec 0.2.0 and below supported only one v4 and v6 address
	if numV4 > 1 || numV6 > 1 {
		for _, v := range types020.SupportedVersions {
			if n.CNIVersion == v {
				return nil, "", fmt.Errorf("CNI version %v does not support more than 1 address per family", n.CNIVersion)
			}
		}
	}

	// Copy net name into IPAM so not to drag Net struct around
	n.IPAM.Name = n.Name

	return n.IPAM, n.CNIVersion, nil
}

func cmdAdd(args *skel.CmdArgs) error {
	ipamConf, confVersion, err := LoadIPAMConfig(args.StdinData, args.Args)
	if err != nil {
		return err
	}

	result := &current.Result{}
	result.DNS = ipamConf.DNS
	result.Routes = ipamConf.Routes
	for _, v := range ipamConf.Addresses {
		result.IPs = append(result.IPs, &current.IPConfig{
			Version: v.Version,
			Address: v.Address,
			Gateway: v.Gateway})
	}

	result.Routes = ipamConf.Routes
	return types.PrintResult(result, confVersion)
}

func cmdDel(args *skel.CmdArgs) error {
	// Nothing required because of no resource allocation in static plugin.
	return nil
}