response.go

package commands

import (
	"encoding/json"
	"encoding/xml"
	"fmt"
	"strings"
)

type ErrorType uint

const (
	Normal ErrorType = iota // general errors
	Client                  // error was caused by the client, (e.g. invalid CLI usage)
	// TODO: add more types of errors for better error-specific handling
)

// Error is a struct for marshalling errors
type Error struct {
	Message string
	Code    ErrorType
}

type EncodingType string

const (
	Json = "json"
	Xml  = "xml"
	// TODO: support more encoding types
)

type Marshaller func(v interface{}) ([]byte, error)

var marshallers = map[EncodingType]Marshaller{
	Json: json.Marshal,
	Xml:  xml.Marshal,
}

type Response struct {
	req       *Request
	Error     error
	ErrorType ErrorType
	Value     interface{}
}

func (r *Response) SetError(err error, errType ErrorType) {
	r.Error = err
	r.ErrorType = errType
}

func (r *Response) FormatError() Error {
	return Error{r.Error.Error(), r.ErrorType}
}

func (r *Response) Marshal() ([]byte, error) {
	if r.Error == nil && r.Value == nil {
		return nil, fmt.Errorf("No error or value set, there is nothing to marshal")
	}

	enc := r.req.Option("enc")
	if enc == nil {
		return nil, fmt.Errorf("No encoding type was specified")
	}
	encType := EncodingType(strings.ToLower(enc.(string)))

	marshaller, ok := marshallers[encType]
	if !ok {
		return nil, fmt.Errorf("No marshaller found for encoding type '%s'", enc)
	}

	if r.Error != nil {
		err := r.FormatError()
		return marshaller(err)
	} else {
		return marshaller(r.Value)
	}
}