package lnwire

import (
	"fmt"
	"io"

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

// ErrorGeneric represents a generic error bound to an exact channel. The
// message format is purposefully general in order to allow expressino of a wide
// array of possible errors. Each ErrorGeneric message is directed at a particular
// open channel referenced by ChannelPoint.
type ErrorGeneric struct {
	// ChannelPoint references the active channel in which the error occured
	// within. A ChannelPoint of zeroHash:0 denotes this error applies to
	// the entire established connection.
	ChannelPoint *wire.OutPoint

	// ErrorID quickly defines the nature of the error according to error
	// type.
	ErrorID uint16

	// Problem is a human-readable string further elaborating upon the
	// nature of the exact error. The maxmium allowed length of this
	// message is 8192 bytes.
	Problem string
}

// NewErrorGeneric creates a new ErrorGeneric message.
func NewErrorGeneric() *ErrorGeneric {
	return &ErrorGeneric{}
}

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

// Decode deserializes a serialized ErrorGeneric message stored in the
// passed io.Reader observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) Decode(r io.Reader, pver uint32) error {
	// ChannelPoint(8)
	// Problem
	err := readElements(r,
		&c.ChannelPoint,
		&c.ErrorID,
		&c.Problem,
	)
	if err != nil {
		return err
	}

	return nil
}

// Encode serializes the target ErrorGeneric into the passed io.Writer
// observing the protocol version specified.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) Encode(w io.Writer, pver uint32) error {
	err := writeElements(w,
		c.ChannelPoint,
		c.ErrorID,
		c.Problem,
	)
	if err != nil {
		return err
	}

	return nil
}

// Command returns the integer uniquely identifying an ErrorGeneric message on
// the wire.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) Command() uint32 {
	return CmdErrorGeneric
}

// MaxPayloadLength returns the maximum allowed payload size for a
// ErrorGeneric complete message observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) MaxPayloadLength(uint32) uint32 {
	// 8+8192
	return 8208
}

// Validate performs any necessary sanity checks to ensure all fields present
// on the ErrorGeneric are valid.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) Validate() error {
	if len(c.Problem) > 8192 {
		return fmt.Errorf("problem string length too long")
	}

	// We're good!
	return nil
}

// String returns the string representation of the target ErrorGeneric.
//
// This is part of the lnwire.Message interface.
func (c *ErrorGeneric) String() string {
	return fmt.Sprintf("\n--- Begin ErrorGeneric ---\n") +
		fmt.Sprintf("ChannelPoint:\t%d\n", c.ChannelPoint) +
		fmt.Sprintf("ErrorID:\t%d\n", c.ErrorID) +
		fmt.Sprintf("Problem:\t%s\n", c.Problem) +
		fmt.Sprintf("--- End ErrorGeneric ---\n")
}