From f378460553d889cc2a98517c84627ebab2266c75 Mon Sep 17 00:00:00 2001
From: Emil Lerch <emil@lerch.org>
Date: Wed, 22 Jul 2026 07:57:12 -0700
Subject: [PATCH] message thread handling

---
 src/notmuch.zig | 14 ++++++++++++++
 src/root.zig    | 49 ++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/src/notmuch.zig b/src/notmuch.zig
index b554230..791e006 100644
--- a/src/notmuch.zig
+++ b/src/notmuch.zig
@@ -94,6 +94,20 @@ pub const Db = struct {
         if (status != c.NOTMUCH_STATUS_SUCCESS) return error.CouldNotReopenDatabase;
     }
 
+    /// Look up a single message by its exact message-id.
+    ///
+    /// The id must be the bare message-id (no `mid:`/`id:` prefix and no angle
+    /// brackets), exactly as notmuch stores it. Returns null when no message
+    /// has that id. The returned Message owns a notmuch_message_t and must be
+    /// released with Message.deinit.
+    pub fn findMessage(db: Db, message_id: [:0]const u8) !?Message {
+        // SAFETY: out parameter, set by notmuch_database_find_message
+        var msg: ?*c.notmuch_message_t = null;
+        const status = c.notmuch_database_find_message(db.handle, message_id.ptr, &msg);
+        if (status != c.NOTMUCH_STATUS_SUCCESS) return error.CouldNotFindMessage;
+        return if (msg) |m| Message{ .message_handle = m } else null;
+    }
+
     //
     // Execute a query for threads, returning a notmuch_threads_t object
     // which can be used to iterate over the results. The returned threads
diff --git a/src/root.zig b/src/root.zig
index 2e1090d..845ac36 100644
--- a/src/root.zig
+++ b/src/root.zig
@@ -265,17 +265,24 @@ pub const NotmuchDb = struct {
         }
     };
 
+    /// Find a message by its exact id, reopening the snapshot and retrying
+    /// once on failure (mirrors openThreads). Callers must hold self.mutex.
+    fn findMessage(self: *NotmuchDb, message_id: [:0]const u8) !?notmuch.Db.Message {
+        return self.db.findMessage(message_id) catch |first_err| {
+            self.db.reopen() catch return first_err;
+            return self.db.findMessage(message_id);
+        };
+    }
+
     pub fn getMessage(self: *NotmuchDb, message_id: []const u8) !MessageDetail {
-        var query_buf: [1024:0]u8 = undefined;
-        const query_z = try std.fmt.bufPrintZ(&query_buf, "mid:{s}", .{message_id});
-        var thread_iter = try self.openThreads(query_z);
-        defer thread_iter.deinit();
+        const message_id_z = try self.allocator.dupeZ(u8, message_id);
+        defer self.allocator.free(message_id_z);
 
-        const thread = thread_iter.next() orelse return error.MessageNotFound;
-        defer thread.deinit();
-
-        var msg_iter = try thread.getMessages();
-        const notmuch_msg = msg_iter.next() orelse return error.MessageNotFound;
+        // Look the message up by id directly. Previously this searched for the
+        // thread containing the id and returned the thread's first message, so
+        // every message in a reply thread rendered the same body.
+        const notmuch_msg = (try self.findMessage(message_id_z)) orelse return error.MessageNotFound;
+        defer notmuch_msg.deinit();
 
         const filename_z = try self.allocator.dupeZ(u8, notmuch_msg.getFilename());
         defer self.allocator.free(filename_z);
@@ -447,3 +454,27 @@ test "can get message details with content" {
 
     // TODO: Add test with attachment once we have a sample email with attachments
 }
+
+test "getMessage returns the requested message, not the thread's first" {
+    // Regression: getMessage used to search for the *thread* containing the id
+    // and return that thread's first message, so every message in a reply
+    // thread rendered the same (first) body. The fixture has a two-message
+    // thread (mail/Inbox/cur/*.Zthreadtest*): an original and a reply with
+    // distinct bodies. Fetching either id must return THAT message.
+    const allocator = std.testing.allocator;
+    var db = try openNotmuchDb(allocator, "mail", null);
+    defer db.close();
+
+    const orig_id = "zetviel-thread-orig@example.com";
+    const reply_id = "zetviel-thread-reply@example.com";
+
+    const orig = try db.getMessage(orig_id);
+    defer orig.deinit(allocator);
+    try std.testing.expectEqualStrings(orig_id, orig.message_id);
+    try std.testing.expect(std.mem.indexOf(u8, orig.text_content, "UNIQUE-ORIGINAL-BODY-MARKER") != null);
+
+    const reply = try db.getMessage(reply_id);
+    defer reply.deinit(allocator);
+    try std.testing.expectEqualStrings(reply_id, reply.message_id);
+    try std.testing.expect(std.mem.indexOf(u8, reply.text_content, "UNIQUE-REPLY-BODY-MARKER") != null);
+}