[balsa] mailbox-local: Fetch threading info when needed

[Peter Bloomfield <peterb src gnome org>]

commit 12853d44547df6805df98751b64f36873de83ed4
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Fri Jan 31 11:53:52 2020 -0500

    mailbox-local: Fetch threading info when needed
    
    Add missing_info and missing_parent members to ThreadingInfo,
    and use them to decide when complete rethreading is needed.
    
    * libbalsa/mailbox_local.c (lbml_info_setup): initialize them to FALSE;
      (lbml_thread_messages): if both are TRUE, we must fetch
        threading info for all messages, in case the parent is present
        but has not been seen;
      (lbml_set_parent): set missing_info if the info is missing;
      (lbml_find_parent): set missing_paarent if the message has
        references but no parent was found.

 ChangeLog                | 16 ++++++++++++++++
 libbalsa/mailbox_local.c | 28 +++++++++++++++++++++++++---
 2 files changed, 41 insertions(+), 3 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 731c794a5..28502f266 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2020-01-31  Peter Bloomfield  <pbloomfield bellsouth net>
+
+       mailbox-local: Fetch threading info when needed
+
+       Add missing_info and missing_parent members to ThreadingInfo,
+       and use them to decide when complete rethreading is needed.
+
+       * libbalsa/mailbox_local.c (lbml_info_setup): initialize them to
+       FALSE;
+       (lbml_thread_messages): if both are TRUE, we must fetch
+       threading info for all messages, in case the parent is present
+       but has not been seen;
+       (lbml_set_parent): set missing_info if the info is missing;
+       (lbml_find_parent): set missing_paarent if the message has
+       references but no parent was found.
+
 2020-01-30  Peter Bloomfield  <pbloomfield bellsouth net>
 
        Move messages-loaded from LibBalsaMailbox to LibBalsaMailboxLocal
diff --git a/libbalsa/mailbox_local.c b/libbalsa/mailbox_local.c
index a64a2fbe6..3ffa5579c 100644
--- a/libbalsa/mailbox_local.c
+++ b/libbalsa/mailbox_local.c
@@ -1499,7 +1499,8 @@ struct _ThreadingInfo {
     GNode *root;
     GHashTable *id_table;
     GHashTable *subject_table;
-    LibBalsaMailboxThreadingType type;
+    gboolean missing_info;
+    gboolean missing_parent;
 };
 typedef struct _ThreadingInfo ThreadingInfo;
 
@@ -1525,6 +1526,8 @@ lbml_info_setup(LibBalsaMailbox * mailbox, ThreadingInfo * ti)
     ti->root = g_node_new(libbalsa_mailbox_get_msg_tree(mailbox));
     ti->id_table = g_hash_table_new(g_str_hash, g_str_equal);
     ti->subject_table = NULL;
+    ti->missing_info = FALSE;
+    ti->missing_parent = FALSE;
 }
 
 static void
@@ -1577,6 +1580,12 @@ lbml_thread_messages(LibBalsaMailbox * mailbox, gboolean subject_gather)
 #endif                         /* MAKE_EMPTY_CONTAINER_FOR_MISSING_PARENT */
 
     lbml_info_free(&ti);
+
+    if (ti.missing_parent && ti.missing_info) {
+        /* We need to completely rethread.
+         * If any new info is found, a rethreading will be scheduled. */
+        libbalsa_mailbox_prepare_threading(mailbox, 0);
+    }
 }
 
 static LibBalsaMailboxLocalInfo *
@@ -1625,8 +1634,11 @@ lbml_set_parent(GNode * msg_node, ThreadingInfo * ti)
 
     info = lbml_get_info(msg_node, ti);
 
-    if (!info) /* FIXME assert this? */
+    if (info == NULL) {
+        /* We may not need the info; just note that it is missing. */
+        ti->missing_info = TRUE;
        return FALSE;
+    }
 
     node = lbml_insert_node(msg_node, info, ti);
 
@@ -1699,13 +1711,16 @@ lbml_find_parent(LibBalsaMailboxLocalInfo * info, ThreadingInfo * ti)
     GNode *parent = ti->root;
     GList *reference;
     GHashTable *id_table = ti->id_table;
+    gboolean has_real_parent = FALSE;
 
     for (reference = info->refs_for_threading; reference;
         reference = reference->next) {
        gchar *id = reference->data;
        GNode *foo = g_hash_table_lookup(id_table, id);
 
-       if (foo == NULL) {
+       if (foo != NULL) {
+            has_real_parent = TRUE;
+        } else {
            foo = g_node_new(NULL);
            g_hash_table_insert(id_table, id, foo);
        }
@@ -1717,6 +1732,13 @@ lbml_find_parent(LibBalsaMailboxLocalInfo * info, ThreadingInfo * ti)
 
        parent = foo;
     }
+
+    if (info->refs_for_threading != NULL && !has_real_parent) {
+        /* This message appears to have a parent, but we did not find
+         * it. */
+        ti->missing_parent = TRUE;
+    }
+
     return parent;
 }