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// Copyright 2011 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Network interface identification

package net

import (
        "bytes"
        "errors"
        "fmt"
)

var (
        errInvalidInterface         = errors.New("net: invalid interface")
        errInvalidInterfaceIndex    = errors.New("net: invalid interface index")
        errInvalidInterfaceName     = errors.New("net: invalid interface name")
        errNoSuchInterface          = errors.New("net: no such interface")
        errNoSuchMulticastInterface = errors.New("net: no such multicast interface")
)

// A HardwareAddr represents a physical hardware address.
type HardwareAddr []byte

func (a HardwareAddr) String() string {
        var buf bytes.Buffer
        for i, b := range a {
                if i > 0 {
                        buf.WriteByte(':')
                }
                fmt.Fprintf(&buf, "%02x", b)
        }
        return buf.String()
}

// ParseMAC parses s as an IEEE 802 MAC-48, EUI-48, or EUI-64 using one of the
// following formats:
//   01:23:45:67:89:ab
//   01:23:45:67:89:ab:cd:ef
//   01-23-45-67-89-ab
//   01-23-45-67-89-ab-cd-ef
//   0123.4567.89ab
//   0123.4567.89ab.cdef
func ParseMAC(s string) (hw HardwareAddr, err error) {
        if len(s) < 14 {
                goto error
        }

        if s[2] == ':' || s[2] == '-' {
                if (len(s)+1)%3 != 0 {
                        goto error
                }
                n := (len(s) + 1) / 3
                if n != 6 && n != 8 {
                        goto error
                }
                hw = make(HardwareAddr, n)
                for x, i := 0, 0; i < n; i++ {
                        var ok bool
                        if hw[i], ok = xtoi2(s[x:], s[2]); !ok {
                                goto error
                        }
                        x += 3
                }
        } else if s[4] == '.' {
                if (len(s)+1)%5 != 0 {
                        goto error
                }
                n := 2 * (len(s) + 1) / 5
                if n != 6 && n != 8 {
                        goto error
                }
                hw = make(HardwareAddr, n)
                for x, i := 0, 0; i < n; i += 2 {
                        var ok bool
                        if hw[i], ok = xtoi2(s[x:x+2], 0); !ok {
                                goto error
                        }
                        if hw[i+1], ok = xtoi2(s[x+2:], s[4]); !ok {
                                goto error
                        }
                        x += 5
                }
        } else {
                goto error
        }
        return hw, nil

error:
        return nil, errors.New("invalid MAC address: " + s)
}

// Interface represents a mapping between network interface name
// and index.  It also represents network interface facility
// information.
type Interface struct {
        Index        int          // positive integer that starts at one, zero is never used
        MTU          int          // maximum transmission unit
        Name         string       // e.g., "en0", "lo0", "eth0.100"
        HardwareAddr HardwareAddr // IEEE MAC-48, EUI-48 and EUI-64 form
        Flags        Flags        // e.g., FlagUp, FlagLoopback, FlagMulticast
}

type Flags uint

const (
        FlagUp           Flags = 1 << iota // interface is up
        FlagBroadcast                      // interface supports broadcast access capability
        FlagLoopback                       // interface is a loopback interface
        FlagPointToPoint                   // interface belongs to a point-to-point link
        FlagMulticast                      // interface supports multicast access capability
)

var flagNames = []string{
        "up",
        "broadcast",
        "loopback",
        "pointtopoint",
        "multicast",
}

func (f Flags) String() string {
        s := ""
        for i, name := range flagNames {
                if f&(1<<uint(i)) != 0 {
                        if s != "" {
                                s += "|"
                        }
                        s += name
                }
        }
        if s == "" {
                s = "0"
        }
        return s
}

// Addrs returns interface addresses for a specific interface.
func (ifi *Interface) Addrs() ([]Addr, error) {
        if ifi == nil {
                return nil, errInvalidInterface
        }
        return interfaceAddrTable(ifi.Index)
}

// MulticastAddrs returns multicast, joined group addresses for
// a specific interface.
func (ifi *Interface) MulticastAddrs() ([]Addr, error) {
        if ifi == nil {
                return nil, errInvalidInterface
        }
        return interfaceMulticastAddrTable(ifi.Index)
}

// Interfaces returns a list of the systems's network interfaces.
func Interfaces() ([]Interface, error) {
        return interfaceTable(0)
}

// InterfaceAddrs returns a list of the system's network interface
// addresses.
func InterfaceAddrs() ([]Addr, error) {
        return interfaceAddrTable(0)
}

// InterfaceByIndex returns the interface specified by index.
func InterfaceByIndex(index int) (*Interface, error) {
        if index <= 0 {
                return nil, errInvalidInterfaceIndex
        }
        ift, err := interfaceTable(index)
        if err != nil {
                return nil, err
        }
        for _, ifi := range ift {
                return &ifi, nil
        }
        return nil, errNoSuchInterface
}

// InterfaceByName returns the interface specified by name.
func InterfaceByName(name string) (*Interface, error) {
        if name == "" {
                return nil, errInvalidInterfaceName
        }
        ift, err := interfaceTable(0)
        if err != nil {
                return nil, err
        }
        for _, ifi := range ift {
                if name == ifi.Name {
                        return &ifi, nil
                }
        }
        return nil, errNoSuchInterface
}