Add TLS support and limit inbox fetch to last 50 messages

Support both plain and TLS IMAP connections via an ImapSession enum,
enabling use with Gmail and other TLS-only servers. Limit fetch range
to the most recent 50 messages to avoid hanging on large mailboxes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -524,6 +524,7 @@ version = "0.1.0"
 dependencies = [
  "crossterm",
  "imap",
+ "native-tls",
  "ratatui",
  "serde",
  "toml",

Cargo.toml

@@ -7,5 +7,6 @@ edition = "2024"
 ratatui = "0.30"
 crossterm = "0.29"
 imap = "2.4"
+native-tls = "0.2"
 serde = { version = "1.0", features = ["derive"] }
 toml = "1.0"

src/lib.rs

@@ -3,6 +3,7 @@ use std::net::TcpStream;
 use std::time::{Duration, Instant};
 use crossterm::event;
 use crossterm::event::{Event, KeyCode};
+use native_tls::TlsStream;
 use ratatui::backend::CrosstermBackend;
 use ratatui::layout::{Constraint, Direction, Layout};
 use ratatui::prelude::{Color, Modifier, Style};
@@ -20,28 +21,57 @@ struct Email {
     date: String,
 }
 
-type ImapSession = imap::Session<TcpStream>;
+enum ImapSession {
+    Plain(imap::Session<TcpStream>),
+    Tls(imap::Session<TlsStream<TcpStream>>),
+}
+
+impl ImapSession {
+    fn noop(&mut self) -> imap::error::Result<()> {
+        match self {
+            Self::Plain(s) => s.noop(),
+            Self::Tls(s) => s.noop(),
+        }
+    }
+
+    fn logout(&mut self) -> imap::error::Result<()> {
+        match self {
+            Self::Plain(s) => s.logout(),
+            Self::Tls(s) => s.logout(),
+        }
+    }
+}
 
 fn connect(config: &Config) -> Result<ImapSession, String> {
     let imap_cfg = &config.imap;
-    let stream =
-        TcpStream::connect((&*imap_cfg.host, imap_cfg.port)).map_err(|e| e.to_string())?;
-    let client = imap::Client::new(stream);
-    let session = client
-        .login(&imap_cfg.username, &imap_cfg.password)
-        .map_err(|(e, _)| e.to_string())?;
-    Ok(session)
+    if imap_cfg.use_tls {
+        let tls = native_tls::TlsConnector::builder()
+            .build()
+            .map_err(|e| e.to_string())?;
+        let client = imap::connect(
+            (&*imap_cfg.host, imap_cfg.port),
+            &imap_cfg.host,
+            &tls,
+        )
+        .map_err(|e| e.to_string())?;
+        let session = client
+            .login(&imap_cfg.username, &imap_cfg.password)
+            .map_err(|(e, _)| e.to_string())?;
+        Ok(ImapSession::Tls(session))
+    } else {
+        let stream =
+            TcpStream::connect((&*imap_cfg.host, imap_cfg.port)).map_err(|e| e.to_string())?;
+        let client = imap::Client::new(stream);
+        let session = client
+            .login(&imap_cfg.username, &imap_cfg.password)
+            .map_err(|(e, _)| e.to_string())?;
+        Ok(ImapSession::Plain(session))
+    }
 }
 
-fn fetch_inbox(session: &mut ImapSession) -> Result<Vec<Email>, String> {
-    session.select("INBOX").map_err(|e| e.to_string())?;
-
-    let messages = session
-        .fetch("1:*", "BODY.PEEK[HEADER.FIELDS (SUBJECT FROM DATE)]")
-        .map_err(|e| e.to_string())?;
-
+fn parse_emails(fetches: &[imap::types::Fetch]) -> Vec<Email> {
     let mut emails = Vec::new();
-    for message in messages.iter() {
+    for message in fetches {
         if let Some(body) = message.header() {
             let header = String::from_utf8_lossy(body);
             let mut subject = String::new();
@@ -61,8 +91,41 @@ fn fetch_inbox(session: &mut ImapSession) -> Result<Vec<Email>, String> {
             emails.push(Email { subject, from, date });
         }
     }
+    emails
+}
 
-    Ok(emails)
+const MAX_FETCH: u32 = 50;
+
+fn fetch_range(exists: u32) -> String {
+    let start = exists.saturating_sub(MAX_FETCH - 1).max(1);
+    format!("{}:{}", start, exists)
+}
+
+fn fetch_inbox(session: &mut ImapSession) -> Result<Vec<Email>, String> {
+    match session {
+        ImapSession::Plain(s) => {
+            let mailbox = s.select("INBOX").map_err(|e| e.to_string())?;
+            if mailbox.exists == 0 {
+                return Ok(Vec::new());
+            }
+            let range = fetch_range(mailbox.exists);
+            let messages = s
+                .fetch(range, "BODY.PEEK[HEADER.FIELDS (SUBJECT FROM DATE)]")
+                .map_err(|e| e.to_string())?;
+            Ok(parse_emails(&messages))
+        }
+        ImapSession::Tls(s) => {
+            let mailbox = s.select("INBOX").map_err(|e| e.to_string())?;
+            if mailbox.exists == 0 {
+                return Ok(Vec::new());
+            }
+            let range = fetch_range(mailbox.exists);
+            let messages = s
+                .fetch(range, "BODY.PEEK[HEADER.FIELDS (SUBJECT FROM DATE)]")
+                .map_err(|e| e.to_string())?;
+            Ok(parse_emails(&messages))
+        }
+    }
 }
 
 /// Refresh inbox using NOOP + fetch. Reconnects on error.