1 package mailmux
2 
3 import (
4 	"encoding/json"
5 	"errors"
6 	"io"
7 	"time"
8 )
9 
10 const (
11 	Tregister = 1 + iota
12 	Rregister
13 	Rerror
14 	Tnew
15 	Rnew
16 	Tlist
17 	Rlist
18 	Tremove
19 )
20 
21 // Mcall represents a message passed between mailmux clients and servers.
22 // Operations requested by clients are T-messages (such as Tregister).
23 // Servers respond with the corresponding R-message (such as Rregister).
24 // Servers may instead respond with Rerror to inform the client, with a diagnostic message,
25 // that the request was not completed successfully.
26 // This design is loosely based on the Plan 9 network file protocol 9P.
27 type Mcall struct {
28 	Type     uint
29 	Username string    `json:",omitempty"` // Tregister, Rregister
30 	Password string    `json:",omitempty"` // Tregister
31 	Error    string    `json:",omitempty"` // Rerror
32 	Aliases  []Alias   `json:",omitempty"` // Rnew, Rlist, Tremove
33 	Expiry   time.Time `json:",omitempty"` // Tnew, Rnew
34 }
35 
36 // ParseMcall parses and validates a JSON-encoded Mcall from r.
37 func ParseMcall(r io.Reader) (*Mcall, error) {
38 	var mc Mcall
39 	if err := json.NewDecoder(r).Decode(&mc); err != nil {
40 		return nil, err
41 	}
42 	switch mc.Type {
43 	case Rerror:
44 		if mc.Error == "" {
45 			return nil, errors.New("empty error message")
46 		}
47 	case Tregister, Tnew, Tlist, Tremove:
48 		if mc.Username == "" {
49 			return nil, errors.New("empty username")
50 		} else if mc.Password == "" {
51 			return nil, errors.New("empty password")
52 		}
53 	}
54 	return &mc, nil
55 }