Add MailStore::thread_root_of()

This patch adds a function to find the root node of a mailthread (as in
In-Reply-To header).

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

2 files changed, 21 insertions, 0 deletions

diff --git a/lib/domain/libimagmail/src/mail.rs b/lib/domain/libimagmail/src/mail.rs
index bdcee6a2..d8e009f0 100644
--- a/lib/domain/libimagmail/src/mail.rs
+++ b/lib/domain/libimagmail/src/mail.rs
@@ -249,6 +249,7 @@ impl Mail for Entry {
 
         Ok(iter)
     }
+
 }
 
 #[derive(Debug)]
diff --git a/lib/domain/libimagmail/src/store.rs b/lib/domain/libimagmail/src/store.rs
index 637dac54..88f49df1 100644
--- a/lib/domain/libimagmail/src/store.rs
+++ b/lib/domain/libimagmail/src/store.rs
@@ -59,6 +59,8 @@ pub trait MailStore<'a> {
 
     fn get_mail(&'a self, mid: MessageId) -> Result<Option<FileLockEntry<'a>>>;
     fn all_mails(&'a self) -> Result<Entries<'a>>;
+
+    fn thread_root_of(&'a self, mid: MessageId, refconfig: &Config) -> Result<Option<FileLockEntry<'a>>>;
 }
 
 impl<'a> MailStore<'a> for Store {
@@ -149,5 +151,23 @@ impl<'a> MailStore<'a> for Store {
     fn all_mails(&'a self) -> Result<Entries<'a>> {
         self.entries()?.in_collection("mail")
     }
+
+    /// Compute the thread root of the thread the Mail belongs to
+    ///
+    /// This function recursively traverses the thread using `Store::get_mail()` and
+    /// `Mail::get_in_reply_to()` to find the root of the thread (The mail that is not a reply to
+    /// any other mail).
+    ///
+    fn thread_root_of(&'a self, mid: MessageId, refconfig: &Config) -> Result<Option<FileLockEntry<'a>>> {
+        if let Some(entry) = self.get_mail(mid)? {
+            if let Some(parent_mid) = entry.get_in_reply_to(refconfig)? {
+                self.thread_root_of(parent_mid, refconfig)
+            } else {
+                Ok(Some(entry))
+            }
+        } else {
+            Ok(None)
+        }
+    }
 }