package lnwire

import (
	"bytes"
	"fmt"
	"io"
	"net"

	"github.com/go-errors/errors"
	"github.com/roasbeef/btcd/btcec"
	"github.com/roasbeef/btcd/wire"
)

var (
	startPort    uint16 = 1024
	endPort      uint16 = 49151
	aliasSpecLen        = 21
)

// RGB is used to represent the color.
type RGB struct {
	red   uint8
	green uint8
	blue  uint8
}

// Alias 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 Alias [32]byte

// NewAlias create the alias from string and also checks spec requirements.
func NewAlias(s string) (Alias, error) {
	var a Alias

	data := []byte(s)
	if len(data) > aliasSpecLen {
		return a, errors.Errorf("alias too long the size "+
			"must be less than %v", aliasSpecLen)
	}

	copy(a[:], data)
	return a, nil
}

func (a *Alias) String() string {
	return string(a[:])
}

// Validate check that alias data lenght is lower than spec size.
func (a *Alias) Validate() error {
	nonzero := len(a)
	for a[nonzero-1] == 0 && nonzero > 0 {
		nonzero--
	}

	if nonzero > aliasSpecLen {
		return errors.New("alias should be less then 21 bytes")
	}
	return nil
}

// NodeAnnouncement message is used to announce the presence of a lightning node
// and signal that the node is accepting incoming connections.
type NodeAnnouncement struct {
	// Signature is used to prove the ownership of node id.
	Signature *btcec.Signature

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

	// Address includes two specification fields: 'ipv6' and 'port' on which
	// the node is accepting incoming connections.
	Address *net.TCPAddr

	// 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 RGB

	// pad is used to reserve to additional bytes for future usage.
	pad uint16

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

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

// Validate performs any necessary sanity checks to ensure all fields present
// on the NodeAnnouncement are valid.
//
// This is part of the lnwire.Message interface.
func (a *NodeAnnouncement) Validate() error {
	if err := a.Alias.Validate(); err != nil {
		return err
	}

	data, err := a.DataToSign()
	if err != nil {
		return err
	}

	dataHash := wire.DoubleSha256(data)
	if !a.Signature.Verify(dataHash, a.NodeID) {
		return errors.New("can't check the node annoucement signature")
	}

	return 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 (c *NodeAnnouncement) Decode(r io.Reader, pver uint32) error {
	err := readElements(r,
		&c.Signature,
		&c.Timestamp,
		&c.Address,
		&c.NodeID,
		&c.RGBColor,
		&c.pad,
		&c.Alias,
	)
	if err != nil {
		return err
	}

	return nil
}

// Encode serializes the target NodeAnnouncement into the passed
// io.Writer observing the protocol version specified.
//
// This is part of the lnwire.Message interface.
func (c *NodeAnnouncement) Encode(w io.Writer, pver uint32) error {
	err := writeElements(w,
		c.Signature,
		c.Timestamp,
		c.Address,
		c.NodeID,
		c.RGBColor,
		c.pad,
		c.Alias,
	)
	if err != nil {
		return err
	}

	return nil
}

// Command returns the integer uniquely identifying this message type on the
// wire.
//
// This is part of the lnwire.Message interface.
func (c *NodeAnnouncement) Command() uint32 {
	return CmdNodeAnnoucmentMessage
}

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

	// Signature - 64 bytes
	length += 64

	// Timestamp - 4 bytes
	length += 4

	// Ipv6 - 16 bytes
	length += 16

	// Port - 4 bytes
	length += 4

	// NodeID - 33 bytes
	length += 33

	// RGBColor - 3 bytes
	length += 3

	// pad - 2 bytes
	length += 2

	// Alias - 32 bytes
	length += 32

	// 158
	return length
}

// String returns the string representation of the target NodeAnnouncement.
//
// This is part of the lnwire.Message interface.
func (c *NodeAnnouncement) String() string {
	return fmt.Sprintf("\n--- Begin NodeAnnouncement ---\n") +
		fmt.Sprintf("Signature:\t\t%v\n", c.Signature) +
		fmt.Sprintf("Timestamp:\t\t%v\n", c.Timestamp) +
		fmt.Sprintf("Address:\t\t%v\n", c.Address.String()) +
		fmt.Sprintf("NodeID:\t\t%v\n", c.NodeID) +
		fmt.Sprintf("RGBColor:\t\t%v\n", c.RGBColor) +
		fmt.Sprintf("Alias:\t\t%v\n", c.Alias) +
		fmt.Sprintf("--- End NodeAnnouncement ---\n")
}

// dataToSign...
func (c *NodeAnnouncement) DataToSign() ([]byte, error) {

	// We should not include the signatures itself.
	var w bytes.Buffer
	err := writeElements(&w,
		c.Timestamp,
		c.Address,
		c.NodeID,
		c.RGBColor,
		c.pad,
		c.Alias,
	)
	if err != nil {
		return nil, err
	}

	return w.Bytes(), nil
}