Add Geary.Account::list_local_email_async

Add new method and implementation to support breaking search folder
impl out of the ImapDb package.

src/engine/api/geary-account.vala

@@ -425,6 +425,22 @@ public abstract class Geary.Account : BaseObject, Logging.Source {
     public abstract async Geary.Email local_fetch_email_async(Geary.EmailIdentifier email_id,
         Geary.Email.Field required_fields, Cancellable? cancellable = null) throws Error;
 
+    /**
+     * Return a collection of email with the given identifiers.
+     *
+     * The returned collection will be in the same order as the
+     * natural ordering of the given identifiers.
+     *
+     * Throws {@link EngineError.NOT_FOUND} if any email is not found
+     * and {@link EngineError.INCOMPLETE_MESSAGE} if the fields aren't
+     * available.
+     */
+    public abstract async Gee.List<Email> list_local_email_async(
+        Gee.Collection<EmailIdentifier> ids,
+        Email.Field required_fields,
+        GLib.Cancellable? cancellable = null
+    ) throws GLib.Error;
+
     /**
      * Create a new {@link SearchQuery} for this {@link Account}.
      *

src/engine/imap-db/imap-db-account.vala

@@ -804,6 +804,48 @@ private class Geary.ImapDB.Account : BaseObject {
         return search_matches;
     }
 
+    public async Gee.List<Email>? list_email(Gee.Collection<EmailIdentifier> ids,
+                                             Email.Field required_fields,
+                                             GLib.Cancellable? cancellable = null)
+    throws GLib.Error {
+        check_open();
+
+        var results = new Gee.ArrayList<Email>();
+        yield db.exec_transaction_async(Db.TransactionType.RO, (cx) => {
+                foreach (var id in ids) {
+                    // TODO: once we have a way of deleting messages, we won't be able
+                    // to assume that a row id will point to the same email outside of
+                    // transactions, because SQLite will reuse row ids.
+                    Geary.Email.Field db_fields;
+                    MessageRow row = Geary.ImapDB.Folder.do_fetch_message_row(
+                        cx, id.message_id, required_fields, out db_fields, cancellable
+                    );
+                    if (!row.fields.fulfills(required_fields)) {
+                        throw new EngineError.INCOMPLETE_MESSAGE(
+                            "Message %s only fulfills %Xh fields (required: %Xh)",
+                            id.to_string(), row.fields, required_fields
+                        );
+                    }
+
+                    Email email = row.to_email(id);
+                    Attachment.add_attachments(
+                        cx,
+                        this.db.attachments_path,
+                        email,
+                        id.message_id,
+                        cancellable
+                    );
+
+                    results.add(email);
+                }
+                return Db.TransactionOutcome.DONE;
+            },
+            cancellable
+        );
+
+        return results;
+    }
+
     public async Geary.Email fetch_email_async(ImapDB.EmailIdentifier email_id,
         Geary.Email.Field required_fields, Cancellable? cancellable = null) throws Error {
         check_open();

src/engine/imap-engine/imap-engine-generic-account.vala

@@ -512,6 +512,16 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.Account {
         return (Gee.Collection<ImapDB.EmailIdentifier>) ids;
     }
 
+    /** {@inheritDoc} */
+    public override async SearchQuery new_search_query(string query,
+                                                       SearchQuery.Strategy strategy,
+                                                       GLib.Cancellable? cancellable)
+        throws GLib.Error {
+        return yield new ImapDB.SearchQuery(
+            this, local, query, strategy, cancellable
+        );
+    }
+
     public override async Gee.MultiMap<Geary.Email, Geary.FolderPath?>? local_search_message_id_async(
         Geary.RFC822.MessageID message_id, Geary.Email.Field requested_fields, bool partial_ok,
         Gee.Collection<Geary.FolderPath?>? folder_blacklist, Geary.EmailFlags? flag_blacklist,
@@ -526,12 +536,13 @@ private abstract class Geary.ImapEngine.GenericAccount : Geary.Account {
     }
 
     /** {@inheritDoc} */
-    public override async SearchQuery new_search_query(string query,
-                                                       SearchQuery.Strategy strategy,
-                                                       GLib.Cancellable? cancellable)
-        throws GLib.Error {
-        return yield new ImapDB.SearchQuery(
-            this, local, query, strategy, cancellable
+    public override async Gee.List<Email> list_local_email_async(
+        Gee.Collection<EmailIdentifier> ids,
+        Email.Field required_fields,
+        GLib.Cancellable? cancellable = null
+    ) throws GLib.Error {
+        return yield local.list_email(
+            check_ids(ids), required_fields, cancellable
         );
     }