posta: generic IMAP/SMTP mail CLI with JSON outputHEADmain

1 files changed, 168 insertions, 0 deletions

diff --git a/src/message.rs b/src/message.rs
new file mode 100644
index 0000000..57d50d0
--- /dev/null
+++ b/src/message.rs
@@ -0,0 +1,168 @@
+//! Message summaries and body extraction.
+
+use mailparse::{MailHeaderMap, ParsedMail};
+use serde::Serialize;
+
+#[derive(Debug, Serialize)]
+pub struct MsgSummary {
+    pub uid: u32,
+    pub flags: Vec<String>,
+    pub size: Option<u32>,
+    pub date: Option<String>,
+    pub from: Option<String>,
+    pub to: Option<String>,
+    pub subject: Option<String>,
+}
+
+/// The header fields shown in listings, decoded (RFC 2047) by mailparse.
+#[derive(Debug, Default, PartialEq)]
+pub struct HeaderSummary {
+    pub date: Option<String>,
+    pub from: Option<String>,
+    pub to: Option<String>,
+    pub subject: Option<String>,
+}
+
+pub fn parse_header_summary(raw: &[u8]) -> HeaderSummary {
+    match mailparse::parse_headers(raw) {
+        Ok((headers, _)) => HeaderSummary {
+            date: headers.get_first_value("Date"),
+            from: headers.get_first_value("From"),
+            to: headers.get_first_value("To"),
+            subject: headers.get_first_value("Subject"),
+        },
+        Err(_) => HeaderSummary::default(),
+    }
+}
+
+pub fn flag_to_string(f: &imap::types::Flag) -> String {
+    use imap::types::Flag::*;
+    match f {
+        Seen => "\\Seen".into(),
+        Answered => "\\Answered".into(),
+        Flagged => "\\Flagged".into(),
+        Deleted => "\\Deleted".into(),
+        Draft => "\\Draft".into(),
+        Recent => "\\Recent".into(),
+        Custom(c) => c.to_string(),
+        other => format!("{other:?}"),
+    }
+}
+
+pub fn summarize(f: &imap::types::Fetch) -> Option<MsgSummary> {
+    let uid = f.uid?;
+    let h = f.header().map(parse_header_summary).unwrap_or_default();
+    Some(MsgSummary {
+        uid,
+        flags: f.flags().iter().map(flag_to_string).collect(),
+        size: f.size,
+        date: h.date,
+        from: h.from,
+        to: h.to,
+        subject: h.subject,
+    })
+}
+
+fn find_part(mail: &ParsedMail, mimetype: &str) -> Option<String> {
+    if mail.ctype.mimetype.eq_ignore_ascii_case(mimetype) {
+        return mail.get_body().ok();
+    }
+    mail.subparts.iter().find_map(|sp| find_part(sp, mimetype))
+}
+
+/// Picks the best displayable body: text/plain by default, text/html on request,
+/// falling back to the other one when the preferred part is missing.
+pub fn extract_body(mail: &ParsedMail, prefer_html: bool) -> Option<String> {
+    let order: [&str; 2] = if prefer_html {
+        ["text/html", "text/plain"]
+    } else {
+        ["text/plain", "text/html"]
+    };
+    order.iter().find_map(|mt| find_part(mail, mt))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const PLAIN: &[u8] = b"From: Alice <alice@example.com>\r\n\
+To: bob@example.com\r\n\
+Date: Fri, 17 Jul 2026 10:00:00 -0300\r\n\
+Subject: Hello\r\n\
+Content-Type: text/plain; charset=utf-8\r\n\
+\r\n\
+Just checking in.\r\n";
+
+    // Subject uses RFC 2047 encoded words; body parts use quoted-printable/base64.
+    const MULTIPART: &[u8] = b"From: =?utf-8?Q?Mar=C3=ADa?= <maria@example.com>\r\n\
+To: bob@example.com\r\n\
+Subject: =?utf-8?B?SG9sYSDwn5qA?=\r\n\
+MIME-Version: 1.0\r\n\
+Content-Type: multipart/alternative; boundary=XYZ\r\n\
+\r\n\
+--XYZ\r\n\
+Content-Type: text/plain; charset=utf-8\r\n\
+Content-Transfer-Encoding: quoted-printable\r\n\
+\r\n\
+Hola, =C2=BFtodo bien?\r\n\
+--XYZ\r\n\
+Content-Type: text/html; charset=utf-8\r\n\
+Content-Transfer-Encoding: base64\r\n\
+\r\n\
+PGI+SG9sYTwvYj4=\r\n\
+--XYZ--\r\n";
+
+    #[test]
+    fn header_summary_reads_basic_fields() {
+        let h = parse_header_summary(PLAIN);
+        assert_eq!(h.from.as_deref(), Some("Alice <alice@example.com>"));
+        assert_eq!(h.subject.as_deref(), Some("Hello"));
+        assert_eq!(h.date.as_deref(), Some("Fri, 17 Jul 2026 10:00:00 -0300"));
+    }
+
+    #[test]
+    fn header_summary_decodes_rfc2047() {
+        let h = parse_header_summary(MULTIPART);
+        assert_eq!(h.from.as_deref(), Some("María <maria@example.com>"));
+        assert_eq!(h.subject.as_deref(), Some("Hola 🚀"));
+    }
+
+    #[test]
+    fn garbage_headers_yield_empty_summary() {
+        assert_eq!(
+            parse_header_summary(b"\xff\xfe\x00"),
+            HeaderSummary::default()
+        );
+    }
+
+    #[test]
+    fn plain_body_is_extracted() {
+        let mail = mailparse::parse_mail(PLAIN).unwrap();
+        assert_eq!(
+            extract_body(&mail, false).unwrap().trim(),
+            "Just checking in."
+        );
+    }
+
+    #[test]
+    fn multipart_prefers_plain_and_decodes_qp() {
+        let mail = mailparse::parse_mail(MULTIPART).unwrap();
+        assert_eq!(
+            extract_body(&mail, false).unwrap().trim(),
+            "Hola, ¿todo bien?"
+        );
+    }
+
+    #[test]
+    fn html_flag_prefers_html_and_decodes_base64() {
+        let mail = mailparse::parse_mail(MULTIPART).unwrap();
+        assert_eq!(extract_body(&mail, true).unwrap().trim(), "<b>Hola</b>");
+    }
+
+    #[test]
+    fn html_only_message_falls_back_when_plain_requested() {
+        let raw = b"Content-Type: text/html\r\n\r\n<p>hi</p>\r\n";
+        let mail = mailparse::parse_mail(raw).unwrap();
+        assert_eq!(extract_body(&mail, false).unwrap().trim(), "<p>hi</p>");
+    }
+}