1 package mailmux
2 
3 import (
4 	"encoding/json"
5 	"errors"
6 	"io"
7 	"time"
8 
9 	"mailmux.net/aliases"
10 )
11 
12 const (
13 	Tregister = 1 + iota
14 	Rregister
15 	Rerror
16 	Tnew
17 	Rnew
18 	Tlist
19 	Rlist
20 	Tremove
21 )
22 
23 // Mcall represents a message passed between mailmux clients and servers.
24 // Operations requested by clients are T-messages (such as Tregister).
25 // Servers respond with the corresponding R-message (such as Rregister).
26 // Servers may instead respond with Rerror to inform the client, with a diagnostic message,
27 // that the request was not completed successfully.
28 // This design is loosely based on the Plan 9 network file protocol 9P.
29 type Mcall struct {
30 	Type     uint
31 	Username string          // Tregister, Rregister
32 	Password string          // Tregister
33 	Error    string          // Rerror
34 	Aliases  aliases.Aliases // Rnew, Rlist, Tremove
35 	Expiry   time.Time       // Tnew, Rnew
36 }
37 
38 // ParseMcall parses and validates a JSON-encoded Mcall from r.
39 func ParseMcall(r io.Reader) (*Mcall, error) {
40 	var mc Mcall
41 	if err := json.NewDecoder(r).Decode(&mc); err != nil {
42 		return nil, err
43 	}
44 	switch mc.Type {
45 	case Rerror:
46 		if mc.Error == "" {
47 			return nil, errors.New("empty error message")
48 		}
49 	case Tregister, Tnew, Tlist, Tremove:
50 		if mc.Username == "" {
51 			return nil, errors.New("empty username")
52 		} else if mc.Password == "" {
53 			return nil, errors.New("empty password")
54 		}
55 	}
56 	return &mc, nil
57 }