package lnwire

import (
	"bytes"
	"fmt"
	"image/color"
	"io"
	"net"
	"unicode/utf8"

	"github.com/roasbeef/btcd/btcec"
)

var (
	startPort uint16 = 1024
	endPort   uint16 = 49151
)

// NodeAlias a hex encoded UTF-8 string that may be displayed as an alternative
// to the node's ID. Notice that aliases are not unique and may be freely
// chosen by the node operators.
type NodeAlias [32]byte

// NewNodeAlias creates a new instance of a NodeAlias. Verification is
// performed on the passed string to ensure it meets the alias requirements.
func NewNodeAlias(s string) (NodeAlias, error) {
	var n NodeAlias

	if len(s) > 32 {
		return n, fmt.Errorf("alias too large: max is %v, got %v", 32, len(s))
	}

	if !utf8.ValidString(s) {
		return n, fmt.Errorf("invalid utf8 string")
	}

	copy(n[:], []byte(s))
	return n, nil
}

// String returns a utf8 string representation of the alias bytes.
func (n NodeAlias) String() string {
	return string(n[:])
}

// NodeAnnouncement message is used to announce the presence of a Lightning
// node and also to signal that the node is accepting incoming connections.
// Each NodeAnnouncement authenticating the advertised information within the
// announcement via a signature using the advertised node pubkey.
type NodeAnnouncement struct {
	// Signature is used to prove the ownership of node id.
	Signature *btcec.Signature

	// Features is the list of protocol features this node supports.
	Features *RawFeatureVector

	// Timestamp allows ordering in the case of multiple announcements.
	Timestamp uint32

	// NodeID is a public key which is used as node identification.
	NodeID *btcec.PublicKey

	// RGBColor is used to customize their node's appearance in maps and
	// graphs
	RGBColor color.RGBA

	// Alias is used to customize their node's appearance in maps and
	// graphs
	Alias NodeAlias

	// Address includes two specification fields: 'ipv6' and 'port' on
	// which the node is accepting incoming connections.
	Addresses []net.Addr
}

// A compile time check to ensure NodeAnnouncement implements the
// lnwire.Message interface.
var _ Message = (*NodeAnnouncement)(nil)

// Decode deserializes a serialized NodeAnnouncement stored in the passed
// io.Reader observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (a *NodeAnnouncement) Decode(r io.Reader, pver uint32) error {
	return readElements(r,
		&a.Signature,
		&a.Features,
		&a.Timestamp,
		&a.NodeID,
		&a.RGBColor,
		a.Alias[:],
		&a.Addresses,
	)
}

// Encode serializes the target NodeAnnouncement into the passed io.Writer
// observing the protocol version specified.
//
func (a *NodeAnnouncement) Encode(w io.Writer, pver uint32) error {
	return writeElements(w,
		a.Signature,
		a.Features,
		a.Timestamp,
		a.NodeID,
		a.RGBColor,
		a.Alias[:],
		a.Addresses,
	)
}

// MsgType returns the integer uniquely identifying this message type on the
// wire.
//
// This is part of the lnwire.Message interface.
func (a *NodeAnnouncement) MsgType() MessageType {
	return MsgNodeAnnouncement
}

// MaxPayloadLength returns the maximum allowed payload size for this message
// observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (a *NodeAnnouncement) MaxPayloadLength(pver uint32) uint32 {
	return 65533
}

// DataToSign returns the part of the message that should be signed.
func (a *NodeAnnouncement) DataToSign() ([]byte, error) {

	// We should not include the signatures itself.
	var w bytes.Buffer
	err := writeElements(&w,
		a.Features,
		a.Timestamp,
		a.NodeID,
		a.RGBColor,
		a.Alias[:],
		a.Addresses,
	)
	if err != nil {
		return nil, err
	}

	// TODO(roasbeef): also capture the excess bytes in msg padded out?

	return w.Bytes(), nil
}