lnwire: convert ErrorGeneric to Error

With this change we move one step closer to matching the wire protocol
currently defined within the spec.

lnwire/error.go

@@ -0,0 +1,123 @@
+package lnwire
+
+import (
+	"fmt"
+	"io"
+	"math"
+
+	"google.golang.org/grpc/codes"
+)
+
+// ErrorCode represents the short error code for each of the defined errors
+// within the Lightning Network protocol spec.
+type ErrorCode uint16
+
+// ToGrpcCode is used to generate gRPC specific code which will be propagated
+// to the ln rpc client. This code is used to have more detailed view of what
+// goes wrong and also in order to have the ability pragmatically determine
+// the error and take specific actions on the client side.
+func (e ErrorCode) ToGrpcCode() codes.Code {
+	return (codes.Code)(e) + 100
+}
+
+const (
+	// ErrMaxPendingChannels is returned by remote peer when the number of
+	// active pending channels exceeds their maximum policy limit.
+	ErrMaxPendingChannels ErrorCode = 1
+
+	// ErrSynchronizingChain is returned by a remote peer that receives a
+	// channel update or a funding request while their still syncing to the
+	// latest state of the blockchain.
+	ErrSynchronizingChain ErrorCode = 2
+)
+
+// ErrorData is a set of bytes associated with a particular sent error. A
+// receiving node SHOULD only print out data verbatim if the string is composed
+// solely of printable ASCII characters. For reference, the printable character
+// set includes byte values 32 through 127 inclusive.
+type ErrorData []byte
+
+// Error represents a generic error bound to an exact channel. The message
+// format is purposefully general in order to allow expression of a wide array
+// of possible errors. Each Error message is directed at a particular open
+// channel referenced by ChannelPoint.
+type Error struct {
+	// ChanID references the active channel in which the error occurred
+	// within. If the ChanID is all zeroes, then this error applies to the
+	// entire established connection.
+	ChanID ChannelID
+
+	// Code is the short error code that succinctly identifies the error
+	// code. This is similar field is similar to HTTP error codes.
+	//
+	// TODO(roasbeef): make PR to repo to add error codes, in addition to
+	// what's there atm
+	Code ErrorCode
+
+	// Data is the attached error data that describes the exact failure
+	// which caused the error message to be sent.
+	Data ErrorData
+}
+
+// NewError creates a new Error message.
+func NewError() *Error {
+	return &Error{}
+}
+
+// A compile time check to ensure Error implements the lnwire.Message
+// interface.
+var _ Message = (*Error)(nil)
+
+// Decode deserializes a serialized Error message stored in the passed
+// io.Reader observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *Error) Decode(r io.Reader, pver uint32) error {
+	return readElements(r,
+		&c.ChanID,
+		&c.Code,
+		&c.Data,
+	)
+}
+
+// Encode serializes the target Error into the passed io.Writer observing the
+// protocol version specified.
+//
+// This is part of the lnwire.Message interface.
+func (c *Error) Encode(w io.Writer, pver uint32) error {
+	return writeElements(w,
+		c.ChanID,
+		c.Code,
+		c.Data,
+	)
+}
+
+// Command returns the integer uniquely identifying an Error message on the
+// wire.
+//
+// This is part of the lnwire.Message interface.
+func (c *Error) Command() uint32 {
+	return CmdError
+}
+
+// MaxPayloadLength returns the maximum allowed payload size for a Error
+// complete message observing the specified protocol version.
+//
+// This is part of the lnwire.Message interface.
+func (c *Error) MaxPayloadLength(uint32) uint32 {
+	// 32 + 2 + 655326
+	return 65536
+}
+
+// Validate performs any necessary sanity checks to ensure all fields present
+// on the Error are valid.
+//
+// This is part of the lnwire.Message interface.
+func (c *Error) Validate() error {
+	if len(c.Data) > math.MaxUint16 {
+		return fmt.Errorf("problem string length too long")
+	}
+
+	// We're good!
+	return nil
+}