[geary/wip/search-cleanup: 7/9] Clean up ImapDB.Account.search_async and related methods

[Michael Gratton <mjog src gnome org>]

commit 489f62e2fc6b5a1d03a23cd2f388014c86090f84
Author: Michael Gratton <mike vee net>
Date:   Mon Feb 4 23:09:55 2019 +1100

    Clean up ImapDB.Account.search_async and related methods
    
    Make result stripping methods operate on the same collection so it's
    easier to follow what is happening, and less objects need to be created
    (especially when not stripping greedy stemming results).

 src/engine/imap-db/imap-db-account.vala | 193 +++++++++++++++++---------------
 1 file changed, 101 insertions(+), 92 deletions(-)
---
diff --git a/src/engine/imap-db/imap-db-account.vala b/src/engine/imap-db/imap-db-account.vala
index d221af52..56613066 100644
--- a/src/engine/imap-db/imap-db-account.vala
+++ b/src/engine/imap-db/imap-db-account.vala
@@ -1092,7 +1092,8 @@ private class Geary.ImapDB.Account : BaseObject {
         Gee.Collection<Geary.EmailIdentifier>? search_ids = null, Cancellable? cancellable = null)
         throws Error {
 
-        debug("Search: %s", q.to_string());
+        debug("Search terms, offset/limit: %s %d/%d",
+              q.to_string(), offset, limit);
 
         check_open();
         ImapDB.SearchQuery query = check_search_query(q);
@@ -1121,28 +1122,11 @@ private class Geary.ImapDB.Account : BaseObject {
 
         // Do this outside of transaction to catch invalid search ids up-front
         string? search_ids_sql = get_search_ids_sql(search_ids);
-        
-        // for some searches, results are stripped if they're too "greedy", but this requires
-        // examining the matched text, which has an expense to fetch, so avoid doing so unless
-        // necessary
-        bool strip_results = true;
-        
-        // HORIZON strategy is configured in such a way to allow all stemmed variants to match,
-        // so don't do any stripping in that case
-        //
-        // If any of the search terms is exact-match (no prefix matching) or none have stemmed
-        // variants, then don't do stripping of "greedy" stemmed matching (because in both cases,
-        // there are none)
-        if (query.strategy == Geary.SearchQuery.Strategy.HORIZON)
-            strip_results = false;
-        else if (traverse<SearchTerm>(query.get_all_terms()).any(term => term.stemmed == null || 
term.is_exact))
-            strip_results = false;
 
-        debug(strip_results ? "Stripping results..." : "Not stripping results...");
+        bool strip_greedy = should_strip_greedy_results(query);
+        Gee.Set<EmailIdentifier> matching_ids = new Gee.HashSet<EmailIdentifier>();
+        Gee.Map<EmailIdentifier,Gee.Set<string>>? search_matches = null;
 
-        Gee.Set<ImapDB.EmailIdentifier> unstripped_ids = new Gee.HashSet<ImapDB.EmailIdentifier>();
-        Gee.Map<ImapDB.EmailIdentifier, Gee.Set<string>>? search_results = null;
-        
         yield db.exec_transaction_async(Db.TransactionType.RO, (cx) => {
             string blacklisted_ids_sql = do_get_blacklisted_message_ids_sql(
                 folder_blacklist, cx, cancellable);
@@ -1198,47 +1182,38 @@ private class Geary.ImapDB.Account : BaseObject {
                 int64 internaldate_time_t = result.int64_at(1);
                 DateTime? internaldate = (internaldate_time_t == -1
                     ? null : new DateTime.from_unix_local(internaldate_time_t));
-                
+
                 ImapDB.EmailIdentifier id = new ImapDB.SearchEmailIdentifier(message_id, internaldate);
-                
-                unstripped_ids.add(id);
+                matching_ids.add(id);
                 id_map.set(message_id, id);
-                
+
                 result.next(cancellable);
             }
-            
-            if (!strip_results)
-                return Db.TransactionOutcome.DONE;
-            
-            search_results = do_get_search_matches(cx, query, id_map, cancellable);
-            
+
+
+            if (strip_greedy && !id_map.is_empty) {
+                search_matches = do_get_search_matches(
+                    cx, query, id_map, cancellable
+                );
+            }
+
             return Db.TransactionOutcome.DONE;
         }, cancellable);
-        
-        if (unstripped_ids == null || unstripped_ids.size == 0)
-            return null;
-        
-        // at this point, there should be some "full" search results to strip from
-        if (strip_results)
-            assert(search_results != null && search_results.size > 0);
-        
+
+        debug("Matching emails found: %d", matching_ids.size);
+
         if (!removal_conditions.is_empty) {
-            if (!strip_results) {
-                search_results = new Gee.HashMap<ImapDB.EmailIdentifier, Gee.Set<string>>();
-                foreach (ImapDB.EmailIdentifier id in unstripped_ids)
-                    search_results.set(id, new Gee.HashSet<string>());
-            }
-            yield remove_results(query, search_results, removal_conditions, cancellable);
-            if (!strip_results)
-                return search_results.size == 0 ? null : search_results.keys;
+            yield strip_removal_conditions(
+                query, matching_ids, removal_conditions, cancellable
+            );
         }
-        
-        if (!strip_results)
-            return unstripped_ids;
-        
-        strip_greedy_results(query, search_results);
-        
-        return search_results.size == 0 ? null : search_results.keys;
+
+        if (strip_greedy && search_matches != null) {
+            strip_greedy_results(query, matching_ids, search_matches);
+        }
+
+        debug("Final search matches: %d", matching_ids.size);
+        return matching_ids.is_empty ? null : matching_ids;
     }
 
     private Gee.Map<Geary.NamedFlag, bool> get_removal_conditions(ImapDB.SearchQuery query) {
@@ -1258,18 +1233,21 @@ private class Geary.ImapDB.Account : BaseObject {
         return removal_conditions;
     }
 
-    private async void remove_results(ImapDB.SearchQuery query,
-        Gee.Map<ImapDB.EmailIdentifier, Gee.Set<string>> search_results,
-        Gee.Map<Geary.NamedFlag, bool> removal_conditions, Cancellable? cancellable = null) {
-        Geary.Email.Field required_fields = Geary.Email.Field.FLAGS;
-        Gee.MapIterator<ImapDB.EmailIdentifier, Gee.Set<string>> iter = search_results.map_iterator();
+    // Strip out from the given collection any email that matches the
+    // given removal conditions
+    private async void strip_removal_conditions(ImapDB.SearchQuery query,
+                                                Gee.Collection<EmailIdentifier> matches,
+                                                Gee.Map<Geary.NamedFlag, bool> conditions,
+                                                GLib.Cancellable? cancellable = null) {
+        Email.Field required_fields = Geary.Email.Field.FLAGS;
+        Gee.Iterator<EmailIdentifier> iter = matches.iterator();
         while (iter.next()) {
             try {
-                ImapDB.EmailIdentifier id = iter.get_key();
+                ImapDB.EmailIdentifier id = iter.get();
                 Geary.Email email = yield fetch_email_async(id, required_fields, cancellable);
-                foreach (Geary.NamedFlag flag in removal_conditions.keys)
-                    if (email.email_flags.contains(flag) == removal_conditions.get(flag)) {
-                        iter.unset();
+                foreach (Geary.NamedFlag flag in conditions.keys)
+                    if (email.email_flags.contains(flag) == conditions.get(flag)) {
+                        iter.remove();
                         break;
                     }
             } catch (Error e) {
@@ -1277,51 +1255,82 @@ private class Geary.ImapDB.Account : BaseObject {
             }
         }
     }
-    
-    // Strip out search results that only contain a hit due to "greedy" matching of the stemmed
-    // variants on all search terms
-    private void strip_greedy_results(ImapDB.SearchQuery query,
-        Gee.Map<ImapDB.EmailIdentifier, Gee.Set<string>> search_results) {
-        int prestripped_results = search_results.size;
-        Gee.MapIterator<ImapDB.EmailIdentifier, Gee.Set<string>> iter = search_results.map_iterator();
+
+    // For some searches, results are stripped if they're too
+    // "greedy", but this requires examining the matched text, which
+    // has an expense to fetch, so avoid doing so unless necessary
+    private bool should_strip_greedy_results(SearchQuery query) {
+        // HORIZON strategy is configured in such a way to allow all
+        // stemmed variants to match, so don't do any stripping in
+        // that case
+        //
+        // If any of the search terms is exact-match (no prefix
+        // matching) or none have stemmed variants, then don't do
+        // stripping of "greedy" stemmed matching (because in both
+        // cases, there are none)
+
+        bool strip_results = true;
+        if (query.strategy == Geary.SearchQuery.Strategy.HORIZON)
+            strip_results = false;
+        else if (traverse<SearchTerm>(query.get_all_terms()).any(
+                     term => term.stemmed == null || term.is_exact)) {
+            strip_results = false;
+        }
+        return strip_results;
+    }
+
+    // Strip out from the given collection of matching ids and results
+    // for any search results that only contain a hit due to "greedy"
+    // matching of the stemmed variants on all search terms.
+    private void strip_greedy_results(SearchQuery query,
+                                      Gee.Collection<EmailIdentifier> matches,
+                                      Gee.Map<EmailIdentifier,Gee.Set<string>> results) {
+        int prestripped_results = matches.size;
+        Gee.Iterator<EmailIdentifier> iter = matches.iterator();
         while (iter.next()) {
             // For each matched string in this message, retain the message in the search results
             // if it prefix-matches any of the straight-up parsed terms or matches a stemmed
             // variant (with only max. difference in their lengths allowed, i.e. not a "greedy"
             // match)
+            EmailIdentifier id = iter.get();
             bool good_match_found = false;
-            foreach (string match in iter.get_value()) {
-                foreach (SearchTerm term in query.get_all_terms()) {
-                    // if prefix-matches parsed term, then don't strip
-                    if (match.has_prefix(term.parsed)) {
-                        good_match_found = true;
-                        
-                        break;
-                    }
-                    
-                    // if prefix-matches stemmed term w/o doing so greedily, then don't strip
-                    if (term.stemmed != null && match.has_prefix(term.stemmed)) {
-                        int diff = match.length - term.stemmed.length;
-                        if (diff <= query.max_difference_match_stem_lengths) {
+            Gee.Set<string>? result = results.get(id);
+            if (result != null) {
+                foreach (string match in result) {
+                    foreach (SearchTerm term in query.get_all_terms()) {
+                        // if prefix-matches parsed term, then don't strip
+                        if (match.has_prefix(term.parsed)) {
                             good_match_found = true;
-                            
                             break;
                         }
+
+                        // if prefix-matches stemmed term w/o doing so
+                        // greedily, then don't strip
+                        if (term.stemmed != null && match.has_prefix(term.stemmed)) {
+                            int diff = match.length - term.stemmed.length;
+                            if (diff <= query.max_difference_match_stem_lengths) {
+                                good_match_found = true;
+                                break;
+                            }
+                        }
                     }
                 }
-                
-                if (good_match_found)
+
+                if (good_match_found) {
                     break;
+                }
+            }
+
+            if (!good_match_found) {
+                iter.remove();
+                matches.remove(id);
             }
-            
-            if (!good_match_found)
-                iter.unset();
         }
-        
+
         debug("Stripped %d emails from search for [%s] due to greedy stem matching",
-            prestripped_results - search_results.size, query.raw);
+              prestripped_results - matches.size, query.raw);
     }
-    
+
     public async Gee.Set<string>? get_search_matches_async(Geary.SearchQuery q,
         Gee.Collection<ImapDB.EmailIdentifier> ids, Cancellable? cancellable = null) throws Error {
         check_open();