// Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
//
// 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 config

import (
	"fmt"
	"net"
	"path/filepath"
	"regexp"
	"strconv"

	"github.com/osrg/gobgp/pkg/packet/bgp"
)

// Returns config file type by retrieving extension from the given path.
// If no corresponding type found, returns the given def as the default value.
func detectConfigFileType(path, def string) string {
	switch ext := filepath.Ext(path); ext {
	case ".toml":
		return "toml"
	case ".yaml", ".yml":
		return "yaml"
	case ".json":
		return "json"
	default:
		return def
	}
}

// yaml is decoded as []interface{}
// but toml is decoded as []map[string]interface{}.
// currently, viper can't hide this difference.
// handle the difference here.
func extractArray(intf interface{}) ([]interface{}, error) {
	if intf != nil {
		list, ok := intf.([]interface{})
		if ok {
			return list, nil
		}
		l, ok := intf.([]map[string]interface{})
		if !ok {
			return nil, fmt.Errorf("invalid configuration: neither []interface{} nor []map[string]interface{}")
		}
		list = make([]interface{}, 0, len(l))
		for _, m := range l {
			list = append(list, m)
		}
		return list, nil
	}
	return nil, nil
}

func getIPv6LinkLocalAddress(ifname string) (string, error) {
	ifi, err := net.InterfaceByName(ifname)
	if err != nil {
		return "", err
	}
	addrs, err := ifi.Addrs()
	if err != nil {
		return "", err
	}
	for _, addr := range addrs {
		ip := addr.(*net.IPNet).IP
		if ip.To4() == nil && ip.IsLinkLocalUnicast() {
			return fmt.Sprintf("%s%%%s", ip.String(), ifname), nil
		}
	}
	return "", fmt.Errorf("no ipv6 link local address for %s", ifname)
}

func (b *BgpConfigSet) getPeerGroup(n string) (*PeerGroup, error) {
	if n == "" {
		return nil, nil
	}
	for _, pg := range b.PeerGroups {
		if n == pg.Config.PeerGroupName {
			return &pg, nil
		}
	}
	return nil, fmt.Errorf("no such peer-group: %s", n)
}

func (d *DynamicNeighbor) validate(b *BgpConfigSet) error {
	if d.Config.PeerGroup == "" {
		return fmt.Errorf("dynamic neighbor requires the peer group config")
	}

	if _, err := b.getPeerGroup(d.Config.PeerGroup); err != nil {
		return err
	}
	if _, _, err := net.ParseCIDR(d.Config.Prefix); err != nil {
		return fmt.Errorf("invalid dynamic neighbor prefix %s", d.Config.Prefix)
	}
	return nil
}

func (n *Neighbor) IsConfederationMember(g *Global) bool {
	for _, member := range g.Confederation.Config.MemberAsList {
		if member == n.Config.PeerAs {
			return true
		}
	}
	return false
}

func (n *Neighbor) IsConfederation(g *Global) bool {
	if n.Config.PeerAs == g.Config.As {
		return true
	}
	return n.IsConfederationMember(g)
}

func (n *Neighbor) IsEBGPPeer(g *Global) bool {
	return n.Config.PeerAs != g.Config.As
}

func (n *Neighbor) CreateRfMap() map[bgp.RouteFamily]bgp.BGPAddPathMode {
	rfMap := make(map[bgp.RouteFamily]bgp.BGPAddPathMode)
	for _, af := range n.AfiSafis {
		mode := bgp.BGP_ADD_PATH_NONE
		if af.AddPaths.State.Receive {
			mode |= bgp.BGP_ADD_PATH_RECEIVE
		}
		if af.AddPaths.State.SendMax > 0 {
			mode |= bgp.BGP_ADD_PATH_SEND
		}
		rfMap[af.State.Family] = mode
	}
	return rfMap
}

func (n *Neighbor) GetAfiSafi(family bgp.RouteFamily) *AfiSafi {
	for _, a := range n.AfiSafis {
		if string(a.Config.AfiSafiName) == family.String() {
			return &a
		}
	}
	return nil
}

func (n *Neighbor) ExtractNeighborAddress() (string, error) {
	addr := n.State.NeighborAddress
	if addr == "" {
		addr = n.Config.NeighborAddress
		if addr == "" {
			return "", fmt.Errorf("NeighborAddress is not configured")
		}
	}
	return addr, nil
}

func (n *Neighbor) IsAddPathReceiveEnabled(family bgp.RouteFamily) bool {
	for _, af := range n.AfiSafis {
		if af.State.Family == family {
			return af.AddPaths.State.Receive
		}
	}
	return false
}

type AfiSafis []AfiSafi

func (c AfiSafis) ToRfList() ([]bgp.RouteFamily, error) {
	rfs := make([]bgp.RouteFamily, 0, len(c))
	for _, af := range c {
		rfs = append(rfs, af.State.Family)
	}
	return rfs, nil
}

func inSlice(n Neighbor, b []Neighbor) int {
	for i, nb := range b {
		if nb.State.NeighborAddress == n.State.NeighborAddress {
			return i
		}
	}
	return -1
}

func existPeerGroup(n string, b []PeerGroup) int {
	for i, nb := range b {
		if nb.Config.PeerGroupName == n {
			return i
		}
	}
	return -1
}

func isAfiSafiChanged(x, y []AfiSafi) bool {
	if len(x) != len(y) {
		return true
	}
	m := make(map[string]bool)
	for _, e := range x {
		m[string(e.Config.AfiSafiName)] = true
	}
	for _, e := range y {
		if !m[string(e.Config.AfiSafiName)] {
			return true
		}
	}
	return false
}

func (n *Neighbor) NeedsResendOpenMessage(new *Neighbor) bool {
	return !n.Config.Equal(&new.Config) ||
		!n.Transport.Config.Equal(&new.Transport.Config) ||
		!n.AddPaths.Config.Equal(&new.AddPaths.Config) ||
		!n.GracefulRestart.Config.Equal(&new.GracefulRestart.Config) ||
		isAfiSafiChanged(n.AfiSafis, new.AfiSafis)
}

// TODO: these regexp are duplicated in api
var _regexpPrefixMaskLengthRange = regexp.MustCompile(`(\d+)\.\.(\d+)`)

func ParseMaskLength(prefix, mask string) (int, int, error) {
	_, ipNet, err := net.ParseCIDR(prefix)
	if err != nil {
		return 0, 0, fmt.Errorf("invalid prefix: %s", prefix)
	}
	if mask == "" {
		l, _ := ipNet.Mask.Size()
		return l, l, nil
	}
	elems := _regexpPrefixMaskLengthRange.FindStringSubmatch(mask)
	if len(elems) != 3 {
		return 0, 0, fmt.Errorf("invalid mask length range: %s", mask)
	}
	// we've already checked the range is sane by regexp
	min, _ := strconv.ParseUint(elems[1], 10, 8)
	max, _ := strconv.ParseUint(elems[2], 10, 8)
	if min > max {
		return 0, 0, fmt.Errorf("invalid mask length range: %s", mask)
	}
	if ipv4 := ipNet.IP.To4(); ipv4 != nil {
		f := func(i uint64) bool {
			return i <= 32
		}
		if !f(min) || !f(max) {
			return 0, 0, fmt.Errorf("ipv4 mask length range outside scope :%s", mask)
		}
	} else {
		f := func(i uint64) bool {
			return i <= 128
		}
		if !f(min) || !f(max) {
			return 0, 0, fmt.Errorf("ipv6 mask length range outside scope :%s", mask)
		}
	}
	return int(min), int(max), nil
}