1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99

use std::io::Write;

#[cfg(feature = "serdex")]
use serde::{Deserialize, Serialize};

use crate::{
    codec::Encode,
    types::{address::Address, core::NString},
    List1OrNil,
};

/// The fields of the envelope structure are in the following
/// order: date, subject, from, sender, reply-to, to, cc, bcc,
/// in-reply-to, and message-id.
/// The date, subject, in-reply-to, and message-id fields are strings.
/// The from, sender, reply-to, to, cc, and bcc fields are parenthesized lists of address structures.
///
/// See [Address](struct.Address.html).
///
/// [RFC-2822] group syntax is indicated by a special form of
/// address structure in which the host name field is NIL.  If the
/// mailbox name field is also NIL, this is an end of group marker
/// (semi-colon in RFC 822 syntax).  If the mailbox name field is
/// non-NIL, this is a start of group marker, and the mailbox name
/// field holds the group name phrase.
///
/// If the Date, Subject, In-Reply-To, and Message-ID header lines
/// are absent in the [RFC-2822] header, the corresponding member
/// of the envelope is NIL; if these header lines are present but
/// empty the corresponding member of the envelope is the empty
/// string.
///
///    Note: some servers may return a NIL envelope member in the
///    "present but empty" case.  Clients SHOULD treat NIL and
///    empty string as identical.
///
///    Note: [RFC-2822] requires that all messages have a valid
///    Date header.  Therefore, the date member in the envelope can
///    not be NIL or the empty string.
///
///    Note: [RFC-2822] requires that the In-Reply-To and
///    Message-ID headers, if present, have non-empty content.
///    Therefore, the in-reply-to and message-id members in the
///    envelope can not be the empty string.
///
/// If the From, To, cc, and bcc header lines are absent in the
/// [RFC-2822] header, or are present but empty, the corresponding
/// member of the envelope is NIL.
///
/// If the Sender or Reply-To lines are absent in the [RFC-2822]
/// header, or are present but empty, the server sets the
/// corresponding member of the envelope to be the same value as
/// the from member (the client is not expected to know to do
/// this).
///
///    Note: [RFC-2822] requires that all messages have a valid
///    From header.  Therefore, the from, sender, and reply-to
///    members in the envelope can not be NIL.
/// TODO: many invariants here...
#[cfg_attr(feature = "serdex", derive(Serialize, Deserialize))]
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Envelope {
    pub date: NString, // TODO: must not be empty string
    pub subject: NString,
    pub from: Vec<Address>,     // encode as nil if empty?
    pub sender: Vec<Address>,   // TODO: set to from if absent or empty
    pub reply_to: Vec<Address>, // TODO: set to from if absent or empty
    pub to: Vec<Address>,       // encode as nil if empty?
    pub cc: Vec<Address>,       // encode as nil if empty?
    pub bcc: Vec<Address>,      // encode as nil if empty?
    pub in_reply_to: NString,   // TODO: must not be empty string
    pub message_id: NString,    // TODO: must not be empty string
}

impl Encode for Envelope {
    fn encode(&self, writer: &mut impl Write) -> std::io::Result<()> {
        writer.write_all(b"(")?;
        self.date.encode(writer)?;
        writer.write_all(b" ")?;
        self.subject.encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.from, b"").encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.sender, b"").encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.reply_to, b"").encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.to, b"").encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.cc, b"").encode(writer)?;
        writer.write_all(b" ")?;
        List1OrNil(&self.bcc, b"").encode(writer)?;
        writer.write_all(b" ")?;
        self.in_reply_to.encode(writer)?;
        writer.write_all(b" ")?;
        self.message_id.encode(writer)?;
        writer.write_all(b")")
    }
}