#moonmail

let message = @moonmail.Message::parse(raw[:])
message.subject()          // encoded words already decoded
message.from()             // the mailboxes, display names decoded
message.text()             // the body a reader would show, by its charset
message.attachments()      // name, type, octets, inline and Content-ID

let reply = @moonmail.Message::new(
  from=@moonmail.Mailbox::new("alice@example.com", name="Alice"),
  to=[Mailbox(@moonmail.Mailbox::new("bob@example.com"))],
  subject="Re: lunch",
  text="Noon works.",
  attachments=[@moonmail.Attachment::new("map.png", png)],
)
let wire = reply.encode()  // CRLF, folded, encoded words; reads back the same

moon run src/examples/tour

#What it does

• Messages — Message::parse and encode: the header unfolded and folded again at 78 columns, a Headers table that keeps order and ignores case and refuses a value that would start a second field, Body as a leaf, parts or an attached message, and the transfer encodings taken off and put back. Writing what was read and reading it again gives the same tree; what 7bit cannot carry goes out in quoted-printable or base64.
• Addresses and dates — RFC 5322's address grammar in full, groups and the obsolete forms included, checked against Python's email; RFC 5322 dates with the old two-digit years and named zones.
• Building — Message::new picks alternative, related and mixed from what it carries. Quoted-printable, encoded words and charsets come from moonmime.
• SASL (@moonmail/sasl) — PLAIN, LOGIN, CRAM-MD5, XOAUTH2, OAUTHBEARER (RFC 7628) and SCRAM-SHA-256 (RFC 7677) with SASLprep (RFC 4013). A mechanism is a trait: one you write goes to authenticate like these.
• POP3 (@moonmail/pop3) — client with no I/O, RFC 1939 and RFC 2449: USER/PASS, APOP, SASL AUTH, STLS, CAPA, PIPELINING, STAT, LIST, UIDL, RETR and TOP dot-unstuffed with their octets kept.
• SMTP / LMTP (@moonmail/smtp) — client and server as state machines with no I/O, RFC 5321 and RFC 2033: PIPELINING groups, SIZE, 8BITMIME, BINARYMIME and CHUNKING, SMTPUTF8, DSN parameters, STARTTLS, SASL AUTH, and RFC 3463 enhanced status codes off any reply.
• Over a socket (@moonmail/net, native and wasm) — the SMTP, LMTP, IMAP and POP3 state machines on moonnet: implicit TLS, STARTTLS that a server must offer, or the clear; sending one message in one call.
• IMAP (@moonmail/imap) — IMAP4rev2 client with no I/O (RFC 9051) that also speaks to IMAP4rev1 servers: the response grammar with literals and response codes, pipelined UID commands, IDLE, CONDSTORE, LITERAL+, SASL-IR, and modified UTF-7 names toward rev1 servers.
• DKIM (@moonmail/dkim) — RFC 6376 canonicalization (simple and relaxed), body hash, and RSA-SHA256 sign and verify.

#POP3

let pop = @pop3.Client::new()
pop.user("alice")
pop.pass("secret")
pop.retr(1)
// ... write pop.next_write(), feed the server's octets
for event in pop.feed(octets) {
  if event is Reply(Retr(_), Content(message)) {
    println(message.length())
  }
}

#SMTP / LMTP

let smtp = @smtp.Client::new()
smtp.ehlo("client.example")
// ... write smtp.next_write(), feed the server's octets until the EHLO reply
smtp.send("alice@example.com", ["bob@example.com"], raw[:])
smtp.quit()
for event in smtp.feed(octets) {
  match event {
    Reply(Rcpt(to), reply) if !reply.is_ok() => println("refused: " + to)
    _ => ()
  }
}

let server = @smtp.Server::new("mx.example", auth=["PLAIN"])
server.feed(octets)
while server.next() is Some(request) {
  match request {
    Rcpt(to, _) if !known(to) => server.reply(550, "5.1.1 No such user")
    Data(message) => { store(message); server.accept() }
    Rset | Quit => ()
    _ => server.accept()
  }
}
// write server.next_write() back to the client

#JMAP

let request = @jmap.Request::new()
let tag = request.mailbox_get(account_id)          // Mailbox/get
let body = request.to_string()                     // POST this to session.api_url

let answer = @jmap.Response::parse(reply)
for box in @jmap.mailboxes(answer, tag) {
  println("\{box.name}: \{box.unread} unread of \{box.total}")
}

#The writing desk, and the post office beside it

• JMAP — JSON over HTTPS, so the page fetches the server itself. Nothing to install, but only a server that speaks JMAP can be reached.
• Local office — the page hands the letter to 127.0.0.1, and a small server there opens the SMTP, IMAP or POP3 connection. Works with any provider; needs that server to be running.

flowchart LR
  page["writing desk<br/>(a page, no socket)"]
  desk["moonmail<br/>composes the MIME"]
  jmap["JMAP server<br/>HTTPS · no helper"]
  office["local post office<br/>127.0.0.1:12000"]
  smtp["SMTP · IMAP · POP3"]
  page --> desk
  desk -->|"jmap.request"| jmap
  desk -->|"compose"| office
  office -->|"@moonmail/net"| smtp

#Over a socket

let smtp = @net.Smtp::connect("smtp.example.com", StartTls(tls))
smtp.auth(@sasl.Plain::new("alice", password))
let refused = smtp.send("alice@example.com", ["bob@example.com"], raw[:])
smtp.quit()

let imap = @net.Imap::connect("imap.example.com", Tls(tls))
imap.login("alice", password)
let inbox = imap.wait(imap.client().select("INBOX"))

let pop = @net.Pop3::connect("pop.example.com", Tls(tls))
pop.login("alice", password)
let first = pop.retr(1)

#SASL

// SCRAM never sends the password, and refuses a server that cannot prove it
// holds the salted key. The nonce is fresh random printable ASCII each time.
smtp.auth(@sasl.ScramSha256::new("alice", "secret", nonce~))
imap.authenticate(@sasl.OAuthBearer::new(token, username="alice@example.com"))

#IMAP

let imap = @imap.Client::new()
let _ = imap.login("alice", "secret")
let _ = imap.select("INBOX")
let fetch = imap.fetch("1:*", "(FLAGS BODY.PEEK[HEADER])", uid=true)
// ... write imap.next_write(), feed the server's octets
for event in imap.feed(octets) {
  match event {
    Data(Fetch(n, items)) => println(n.to_string() + " " + items.length().to_string())
    Done(tag, No, _, text) if tag == fetch => println("fetch failed: " + text)
    _ => ()
  }
}

#DKIM

let options = @dkim.SignOptions::new(
  domain="example.com",
  selector="sel",
  headers=["From", "To", "Subject", "Date"],
)
let signature = @dkim.sign(raw[:], private_key, options)
// "DKIM-Signature: " + signature is the header to add; verify() checks it back.

#Beyond the basics

// IMAP: ask about a mailbox without selecting it, wait for changes, and
// store flags only where nothing changed them since (CONDSTORE).
let _ = imap.status("INBOX", ["MESSAGES", "UIDNEXT", "UIDVALIDITY"])
let _ = imap.idle()                    // changes arrive as Data until done()
imap.done()
let _ = imap.store("1:5", "+FLAGS (\\Seen)", uid=true, unchangedsince=modseq)

// SMTP: chunk the body instead of using DATA, and ask for delivery status.
smtp.mail("alice@example.com", size=1234, body=Binary)
smtp.rcpt("bob@example.com", notify=[Success, Failure])
smtp.bdat(chunk[:], last=true)   // LAST ends the transaction

#What it is not

#The gate

moon clean && moon fmt && moon check --target all --deny-warn \
  && moon build --target all && moon test --target all

#Licence