feat: stash composes closed by sidebar trips as drafts

src/app.rs

@@ -15,7 +15,7 @@ use fumi_core::crypto::{unb32, KEY_LEN};
 use fumi_core::store::Store;
 use gtk::prelude::*;
 
-use crate::ops::{self, Folder, OpenedMsg, Row, Snapshot};
+use crate::ops::{self, Draft, Folder, OpenedMsg, Row, Snapshot};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Page {
@@ -273,6 +273,9 @@ pub struct Carrier {
     /// the sidebar's bottom panel; a message selection clears it.
     pub selected_contact: Option<String>,
     pub compose: Option<Compose>,
+    /// Composes set aside by a sidebar trip instead of Cancel, kept in
+    /// the drafts sidecar; the folder only shows once it holds one.
+    pub drafts: Vec<Draft>,
     pub snapshot: Option<Snapshot>,
     pub pin_offer: Option<(Address, [u8; KEY_LEN])>,
     pub backup_text: Option<String>,
@@ -301,6 +304,7 @@ impl Carrier {
             (true, false) => Page::Signup,
             (true, true) => Page::Mail,
         };
+        let drafts = ops::load_drafts(&dir.join("drafts.txt"));
         let app = Carrier {
             marks: ReadMarks::load(dir.join("read.txt")),
             dir,
@@ -330,6 +334,7 @@ impl Carrier {
             open: None,
             selected_contact: None,
             compose: None,
+            drafts,
             snapshot: None,
             pin_offer: None,
             backup_text: None,
@@ -352,6 +357,77 @@ impl Carrier {
         self.dir.join("carrier.key")
     }
 
+    fn drafts_path(&self) -> PathBuf {
+        self.dir.join("drafts.txt")
+    }
+
+    /// Every sidebar trip closes the compose this way: a compose with
+    /// anything in it becomes a draft, an empty one is thrown away, and
+    /// Cancel stays the only way to discard work outright.
+    fn stash_draft(&mut self) {
+        let Some(compose) = self.compose.take() else {
+            return;
+        };
+        if compose.to.trim().is_empty()
+            && compose.subject.trim().is_empty()
+            && compose.body.trim().is_empty()
+        {
+            return;
+        }
+        self.drafts.push(Draft {
+            id: ops::draft_id(),
+            to: compose.to,
+            subject: compose.subject,
+            body: compose.body,
+            reply_to: compose.reply_to,
+            at: fumi_core::store::now(),
+        });
+        ops::save_drafts(&self.drafts_path(), &self.drafts);
+        self.note("draft saved".into());
+    }
+
+    /// Tapping a draft in the folder puts it back in the compose it came
+    /// from, out of the sidecar, so saving it again cannot fork it.
+    fn open_draft(&mut self, id: &str) {
+        let Some(index) = self.drafts.iter().position(|d| d.id == id) else {
+            return;
+        };
+        let draft = self.drafts.remove(index);
+        ops::save_drafts(&self.drafts_path(), &self.drafts);
+        self.compose = Some(Compose {
+            to: draft.to,
+            subject: draft.subject,
+            body: draft.body,
+            reply_to: draft.reply_to,
+        });
+        self.compose_fresh.set(true);
+    }
+
+    /// The current folder's rows, drafts included: drafts carry the
+    /// recipient where mail carries the sender, newest first.
+    pub fn rows(&self) -> Vec<Row> {
+        if self.folder == Folder::Drafts {
+            let mut rows: Vec<Row> = self
+                .drafts
+                .iter()
+                .map(|draft| Row {
+                    id: draft.id.clone(),
+                    from: draft.to.clone(),
+                    subject: draft.subject.clone(),
+                    at: draft.at,
+                    unread: false,
+                })
+                .collect();
+            rows.sort_by_key(|row| -row.at);
+            rows
+        } else {
+            self.lists
+                .get(self.folder as usize)
+                .cloned()
+                .unwrap_or_default()
+        }
+    }
+
     fn note(&mut self, text: String) {
         self.status = Some(text);
         self.status_error = false;
@@ -442,6 +518,7 @@ impl Carrier {
                 self.import_body = text;
             }
             Message::ContactSelected(address) => {
+                self.stash_draft();
                 self.selected_contact = Some(address);
                 self.open = None;
                 self.page = Page::Mail;
@@ -577,6 +654,7 @@ impl Carrier {
                 return vec![PendingOp::Restore { addr }];
             }
             Message::GotoMail(folder) => {
+                self.stash_draft();
                 if self.page == Page::Mail && self.folder == folder {
                     return Vec::new();
                 }
@@ -587,19 +665,24 @@ impl Carrier {
                 return self.refresh().into_iter().collect();
             }
             Message::Goto(page) => {
+                self.stash_draft();
                 self.page = page;
                 self.open = None;
                 self.selected_contact = None;
-                self.compose = None;
                 if page == Page::Mail || page == Page::Contacts || page == Page::Settings {
                     return self.refresh().into_iter().collect();
                 }
             }
             Message::MessageSelected(folder, id) => {
                 self.selected_contact = None;
-                self.select_message(folder, id);
+                if folder == Folder::Drafts {
+                    self.open_draft(&id);
+                } else {
+                    self.select_message(folder, id);
+                }
             }
             Message::FetchPressed => {
+                self.stash_draft();
                 if !self.start("fetching") {
                     return Vec::new();
                 }
@@ -608,6 +691,7 @@ impl Carrier {
                 }];
             }
             Message::ComposePressed => {
+                self.stash_draft();
                 self.compose = Some(Compose {
                     to: String::new(),
                     subject: String::new(),
@@ -970,8 +1054,51 @@ mod tests {
         assert_eq!(app.busy.as_deref(), Some("fetching"));
     }
 
-    /// The store is committed envelope by envelope, so a tick mid-fetch
-    /// sees a message that the running fetch has already verified.
+    /// A compose closed by any sidebar trip becomes a draft in the
+    /// sidecar; Cancel stays the only way to throw work away.
+    #[test]
+    fn sidebar_trips_stash_the_compose_as_a_draft() {
+        let mut app = app();
+        app.handle(Message::ComposePressed);
+        app.handle(Message::ComposeToChanged("alice@example.org".into()));
+        app.handle(Message::ComposeSubjectChanged("half written".into()));
+        app.handle(Message::ComposeBodyChanged("still typing".into()));
+
+        // The same folder the compose was opened over still closes it.
+        app.folder = Folder::Inbox;
+        app.page = Page::Mail;
+        app.handle(Message::GotoMail(Folder::Inbox));
+        assert!(app.compose.is_none());
+        assert_eq!(app.drafts.len(), 1);
+        assert!(app.dir.join("drafts.txt").exists());
+        let draft = app.drafts[0].clone();
+        assert_eq!(draft.to, "alice@example.org");
+        assert_eq!(draft.subject, "half written");
+        app.folder = Folder::Drafts;
+        assert_eq!(app.rows()[0].id, draft.id);
+
+        // Opening the draft moves it back into the compose, out of the
+        // sidecar, so saving it again cannot fork it.
+        app.handle(Message::MessageSelected(Folder::Drafts, draft.id.clone()));
+        assert!(app.compose.is_some());
+        assert!(app.drafts.is_empty());
+        assert_eq!(app.compose.as_ref().unwrap().subject, "half written");
+
+        // Write while editing stashes the draft being edited first, and the
+        // fresh empty compose a trip then discards adds nothing.
+        app.handle(Message::ComposePressed);
+        assert_eq!(app.drafts.len(), 1);
+        app.handle(Message::GotoMail(Folder::Sent));
+        assert!(app.compose.is_none());
+        assert_eq!(app.drafts.len(), 1);
+
+        // An empty compose discarded by a trip leaves no draft behind.
+        app.drafts.clear();
+        app.handle(Message::ComposePressed);
+        app.handle(Message::GotoMail(Folder::Sent));
+        assert!(app.drafts.is_empty());
+    }
+
     #[test]
     fn fetch_tick_lists_mail_as_it_lands() {
         use fumi_core::message::{build_frontmatter, message_id, seal};

src/demo.rs

@@ -219,6 +219,19 @@ fn plant(dir: &Path) -> Result<(), String> {
     // pre-marked read rows, so unread dots have both states to show
     std::fs::write(dir.join("read.txt"), read_ids.join("\n") + "\n").map_err(|e| e.to_string())?;
 
+    // one sample draft, so the drafts folder has a row to show
+    crate::ops::save_drafts(
+        &dir.join("drafts.txt"),
+        &[crate::ops::Draft {
+            id: "0000000000000000".into(),
+            to: "grace@example.org".into(),
+            subject: "Re: quarterly infrastructure review".into(),
+            body: "started a reply, will finish it after the review call".into(),
+            reply_to: None,
+            at: now() - 3 * 3600,
+        }],
+    );
+
     let _ = b32(&pk);
     Ok(())
 }

src/ops.rs

@@ -78,12 +78,15 @@ pub fn snapshot(
     })
 }
 
-/// The three folders, in sidebar order.
+/// The sidebar's folders, in its order. Drafts is carrier's own folder:
+/// it has no table in the sealed store, its rows come from the drafts
+/// sidecar, and it only appears in the sidebar once it holds one.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Folder {
     Inbox,
     Requests,
     Sent,
+    Drafts,
 }
 
 impl Folder {
@@ -94,10 +97,110 @@ impl Folder {
             Folder::Inbox => "inbox",
             Folder::Requests => "requests",
             Folder::Sent => "sent",
+            // Never reached: `handle` routes draft selection away from
+            // the store before any table lookup happens.
+            Folder::Drafts => "drafts",
         }
     }
 }
 
+/// A compose set aside instead of sent, kept beside the store like the read
+/// marks — it is plaintext by nature until it is sealed on the way out.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Draft {
+    pub id: String,
+    pub to: String,
+    pub subject: String,
+    pub body: String,
+    /// The message this draft replies to, as 64 hex characters.
+    pub reply_to: Option<String>,
+    pub at: i64,
+}
+
+/// A fresh draft id: 8 random bytes as hex, unique within the sidecar.
+pub fn draft_id() -> String {
+    use rand_core::RngCore;
+    let mut bytes = [0u8; 8];
+    rand_core::OsRng.fill_bytes(&mut bytes);
+    bytes.iter().map(|b| format!("{b:02x}")).collect()
+}
+
+/// One line per field, with backslash escapes so no field can break the
+/// line format: `\` becomes `\\`, a newline `\n`, a carriage return `\r`.
+fn line(text: &str) -> String {
+    text.replace('\\', "\\\\")
+        .replace('\n', "\\n")
+        .replace('\r', "\\r")
+}
+
+fn unline(text: &str) -> String {
+    let mut out = String::with_capacity(text.len());
+    let mut chars = text.chars();
+    while let Some(c) = chars.next() {
+        if c == '\\' {
+            match chars.next() {
+                Some('n') => out.push('\n'),
+                Some('r') => out.push('\r'),
+                Some(other) => out.push(other),
+                None => out.push('\\'),
+            }
+        } else {
+            out.push(c);
+        }
+    }
+    out
+}
+
+/// Four lines per draft: header, to, subject, body. The whole file is
+/// rewritten on every change, which a handful of drafts makes honest.
+pub fn save_drafts(path: &Path, drafts: &[Draft]) {
+    let mut text = String::new();
+    for draft in drafts {
+        let reply_to = draft.reply_to.as_deref().unwrap_or("-");
+        use std::fmt::Write;
+        let _ = writeln!(text, "draft {} {} {}", draft.id, draft.at, reply_to);
+        let _ = writeln!(text, "{}", line(&draft.to));
+        let _ = writeln!(text, "{}", line(&draft.subject));
+        let _ = writeln!(text, "{}", line(&draft.body));
+    }
+    let _ = std::fs::write(path, text);
+}
+
+/// Reads the drafts sidecar; a missing or torn tail only costs the
+/// incomplete record at the end.
+pub fn load_drafts(path: &Path) -> Vec<Draft> {
+    let text = std::fs::read_to_string(path).unwrap_or_default();
+    let lines: Vec<&str> = text.lines().collect();
+    let mut drafts = Vec::new();
+    for record in lines.chunks(4) {
+        let [header, to, subject, body] = record else {
+            break;
+        };
+        let mut parts = header.split_whitespace();
+        let (Some("draft"), Some(id), Some(at), reply_to) =
+            (parts.next(), parts.next(), parts.next(), parts.next())
+        else {
+            break;
+        };
+        let Ok(at) = at.parse::<i64>() else {
+            break;
+        };
+        let id = id.to_string();
+        drafts.push(Draft {
+            id,
+            to: unline(to),
+            subject: unline(subject),
+            body: unline(body),
+            reply_to: match reply_to {
+                None | Some("-") => None,
+                Some(other) => Some(other.to_string()),
+            },
+            at,
+        });
+    }
+    drafts
+}
+
 fn explain(e: Error) -> String {
     e.to_string()
 }
@@ -535,6 +638,38 @@ mod tests {
     use fumi_core::message::{build_frontmatter, message_id, seal};
     use fumi_core::store::now;
 
+    #[test]
+    fn drafts_round_trip_through_the_sidecar() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("drafts.txt");
+        let drafts = vec![
+            Draft {
+                id: draft_id(),
+                to: "smol://alice@example.org/KEY".into(),
+                subject: "line breaks\nand \\backslashes\r".into(),
+                body: "a draft\n\nwith paragraphs\nand a \\ literal".into(),
+                reply_to: Some("ab".repeat(32)),
+                at: now(),
+            },
+            Draft {
+                id: draft_id(),
+                to: "bob@example.org".into(),
+                subject: "no reply".into(),
+                body: String::new(),
+                reply_to: None,
+                at: now(),
+            },
+        ];
+        save_drafts(&path, &drafts);
+        assert_eq!(load_drafts(&path), drafts);
+
+        // A torn tail costs only its own incomplete record.
+        let text = std::fs::read_to_string(&path).unwrap();
+        let torn = text.lines().take(6).collect::<Vec<_>>().join("\n") + "\n";
+        std::fs::write(&path, torn).unwrap();
+        assert_eq!(load_drafts(&path).len(), 1);
+    }
+
     fn master() -> [u8; KEY_LEN] {
         let mut seed = [0u8; KEY_LEN];
         for (i, b) in seed.iter_mut().enumerate() {

src/view.rs

@@ -183,6 +183,8 @@ pub struct CarrierWidgets {
     // sidebar top: actions and destinations
     folders: gtk::ListBox,
     folder_counts: Vec<gtk::Label>,
+    /// The Drafts row, hidden until the folder holds one.
+    drafts_nav: gtk::ListBoxRow,
     settings_nav: gtk::ListBox,
     fetch_button: gtk::Button,
     write_button: gtk::Button,
@@ -303,12 +305,21 @@ impl CarrierWidgets {
             nav_row("folder-download-symbolic", "Inbox"),
             nav_row("contact-new-symbolic", "Requests"),
             nav_row("mail-send-symbolic", "Sent"),
+            nav_row("document-edit-symbolic", "Drafts"),
         ];
         let mut folder_counts = Vec::new();
-        for (row, count) in folder_rows {
+        let mut drafts_nav = None;
+        for (index, (row, count)) in folder_rows.into_iter().enumerate() {
+            // The drafts folder is carrier's own: it stays out of the
+            // sidebar until a compose has been set aside into it.
+            if index == 3 {
+                row.set_visible(false);
+                drafts_nav = Some(row.clone());
+            }
             folders.append(&row);
             folder_counts.push(count);
         }
+        let drafts_nav = drafts_nav.expect("four folder rows");
         sidebar_top.append(&folders);
 
         // Settings closes the top panel, pinned to its bottom. It is its
@@ -782,6 +793,7 @@ impl CarrierWidgets {
                 0 => Folder::Inbox,
                 1 => Folder::Requests,
                 2 => Folder::Sent,
+                3 => Folder::Drafts,
                 _ => return,
             };
             folder_sender.input(Message::GotoMail(folder));
@@ -804,6 +816,7 @@ impl CarrierWidgets {
                     "0" => Folder::Inbox,
                     "1" => Folder::Requests,
                     "2" => Folder::Sent,
+                    "3" => Folder::Drafts,
                     _ => return,
                 };
                 mail_sender.input(Message::MessageSelected(folder, id.to_string()));
@@ -902,6 +915,7 @@ impl CarrierWidgets {
             toolbar,
             folders,
             folder_counts,
+            drafts_nav,
             settings_nav,
             fetch_button,
             write_button,
@@ -1158,7 +1172,13 @@ fn render(model: &Carrier, w: &mut CarrierWidgets, sender: &ComponentSender<Carr
             .map(|rows| rows.iter().filter(|r| r.unread).count())
             .unwrap_or(0)
     };
-    for (count, value) in w.folder_counts.iter().zip([unread(0), unread(1), 0]) {
+    let draft_count = model.drafts.len();
+    w.drafts_nav.set_visible(draft_count > 0);
+    for (count, value) in w
+        .folder_counts
+        .iter()
+        .zip([unread(0), unread(1), 0, draft_count])
+    {
         count.set_text(&value.to_string());
         count.set_visible(value > 0);
     }
@@ -1198,11 +1218,7 @@ fn render(model: &Carrier, w: &mut CarrierWidgets, sender: &ComponentSender<Carr
 
     // Mail list.
     clear_list(&w.mail_list);
-    let rows = model
-        .lists
-        .get(model.folder as usize)
-        .cloned()
-        .unwrap_or_default();
+    let rows = model.rows();
     let (icon, title, description) = match model.folder {
         Folder::Inbox => (
             "mail-read-symbolic",
@@ -1219,6 +1235,11 @@ fn render(model: &Carrier, w: &mut CarrierWidgets, sender: &ComponentSender<Carr
             "Nothing sent yet",
             "Messages you send keep a sealed copy here.",
         ),
+        Folder::Drafts => (
+            "document-edit-symbolic",
+            "No drafts",
+            "A compose closed from the sidebar is kept here.",
+        ),
     };
     w.list_empty.set_icon_name(Some(icon));
     w.list_empty.set_title(title);