Add Mail::get_thread() for getting all mails in the same thread as this mail

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

3 files changed, 67 insertions, 0 deletions

diff --git a/lib/domain/libimagmail/Cargo.toml b/lib/domain/libimagmail/Cargo.toml
index 1585dd12..e0b1a891 100644
--- a/lib/domain/libimagmail/Cargo.toml
+++ b/lib/domain/libimagmail/Cargo.toml
@@ -26,6 +26,7 @@ toml-query = "0.9.2"
 mailparse = "0.8.0"
 filters = "0.3.0"
 failure = "0.1.5"
+resiter = "0.4.0"
 serde = "1.0.94"
 serde_derive = "1.0.94"
 
diff --git a/lib/domain/libimagmail/src/lib.rs b/lib/domain/libimagmail/src/lib.rs
index 1a58df0a..3f6ddd3d 100644
--- a/lib/domain/libimagmail/src/lib.rs
+++ b/lib/domain/libimagmail/src/lib.rs
@@ -43,6 +43,7 @@ extern crate toml;
 extern crate toml_query;
 extern crate filters;
 #[macro_use] extern crate failure;
+extern crate resiter;
 extern crate serde;
 #[macro_use] extern crate serde_derive;
 
diff --git a/lib/domain/libimagmail/src/mail.rs b/lib/domain/libimagmail/src/mail.rs
index b33b4f91..bdcee6a2 100644
--- a/lib/domain/libimagmail/src/mail.rs
+++ b/lib/domain/libimagmail/src/mail.rs
@@ -21,6 +21,7 @@ use failure::Fallible as Result;
 use failure::ResultExt;
 use failure::Error;
 use toml_query::read::TomlValueReadExt;
+use resiter::Filter;
 
 use libimagstore::store::Entry;
 use libimagentryutil::isa::Is;
@@ -50,6 +51,7 @@ pub trait Mail : RefFassade + Linkable {
 
     fn neighbors(&self) -> Result<StoreIdIterator>;
     fn get_neighbors<'a>(&self, store: &'a Store) -> Result<MailIterator<'a>>;
+    fn get_thread<'a>(&self, store: &'a Store) -> Result<MailIterator<'a>>;
 
 }
 
@@ -184,6 +186,69 @@ impl Mail for Entry {
                     .into_mail_iterator()
             })
     }
+
+    /// Get the full thread starting from this Mail
+    ///
+    /// This function recursively traverses the linked mails, assumes them all to be in the same
+    /// thread and returns an iterator over all Mails it finds in this way.
+    ///
+    /// # Warning
+    ///
+    /// If a Mail is linked to this mail (even transitively!) but is _not_ in the same thread, it
+    /// is considered to be in the same thread.
+    ///
+    /// This function works recursively. Keep that in mind for large threads. Because it needs to
+    /// collect() internally, it might take a lot of memory for large threads.
+    ///
+    /// # Return value
+    ///
+    /// This function returns an Iterator over StoreIds in the same thread as this mail itself.
+    /// It does not yield any qualification about the distance between a mail in this thread and
+    /// this very mail.
+    ///
+    fn get_thread<'a>(&self, store: &'a Store) -> Result<MailIterator<'a>> {
+        trace!("Getting thread, starting point at: {}", self.get_location());
+        let mut thread = vec![self.get_location().clone()];
+
+        fn traverse<'a>(entry: &'a Entry, thread: &mut Vec<StoreId>, store: &Store) -> Result<()> {
+            // Helper function to get neighbors of a Mail, but filtered
+            fn get_filtered_neighbors<'a>(entry: &'a Entry, skiplist: &[StoreId]) -> Result<Vec<StoreId>> {
+                trace!("Getting filtered neighbors of {}", entry.get_location());
+                entry.neighbors()?.filter_ok(|id| !skiplist.contains(id)).collect()
+            }
+
+            // Get the neighbors, filtered by StoreIds which are already in the thread
+            // Then iterate over them
+            for n in get_filtered_neighbors(entry, thread)? {
+                trace!("Fetching {}", n);
+
+                // Get the FileLockEntry for the StoreId, or fail if it cannot be found
+                let next_entry = store.get(n.clone())?.ok_or_else(|| format_err!("Cannot find {}", n))?;
+
+                // if the FileLockEntry is a Mail
+                if next_entry.is_mail()? {
+                    trace!("{} is a Mail", n);
+                    thread.push(n); // it belongs to the thread
+
+                    // And then traverse further starting from the current Mail
+                    traverse(&next_entry, thread, store)?;
+                }
+            }
+
+            Ok(())
+        }
+
+        trace!("Starting traversing...");
+        traverse(self, &mut thread, store)?;
+        trace!("Finished traversing.");
+        trace!("Found {} entries in thread", thread.len());
+
+        let iter = StoreIdIterator::new(Box::new(thread.into_iter().map(Ok)))
+            .into_get_iter(store)
+            .into_mail_iterator();
+
+        Ok(iter)
+    }
 }
 
 #[derive(Debug)]