[feature] Conversations API (#3013)

* Implement conversations API

* Sort and page conversations by last status ID

* Appease linter

* Fix deleting conversations and statuses

* Refactor to make migrations automatic

* Lint

* Update tests post-merge

* Fixes from live-fire testing

* Linter caught a format problem

* Refactor tests, fix cache

* Negative test for non-DMs

* Run conversations advanced migration on testrig startup as well as regular server startup

* Document (lack of) side effects of API method for deleting a conversation

* Make not-found check less nested for readability

* Rename PutConversation to UpsertConversation

* Use util.Ptr instead of IIFE

* Reduce cache used by conversations

* Remove unnecessary TableExpr/ColumnExpr

* Use struct tags for both unique constraints on Conversation

* Make it clear how paging with GetDirectStatusIDsBatch should be used

* Let conversation paging skip conversations it can't render

* Use Bun NewDropTable

* Convert delete raw query to Bun

* Convert update raw query to Bun

* Convert latestConversationStatusesTempTable raw query partially to Bun

* Convert conversationStatusesTempTable raw query partially to Bun

* Rename field used to store result of MaxDirectStatusID

* Move advanced migrations to their own tiny processor

* Catch up util function name with main

* Remove json.… wrappers

* Remove redundant check

* Combine error checks

* Replace map with slice of structs

* Address processor/type converter comments

- Add context info for errors
- Extract some common processor code into shared methods
- Move conversation eligibility check ahead of populating conversation

* Add error context when dropping temp tables

1 files changed, 85 insertions, 0 deletions

diff --git a/internal/processing/conversations/migrate_test.go b/internal/processing/conversations/migrate_test.go
new file mode 100644
index 000000000..b625e59ba
--- /dev/null
+++ b/internal/processing/conversations/migrate_test.go
@@ -0,0 +1,85 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package conversations_test
+
+import (
+	"context"
+
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/db/bundb"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+)
+
+// Test that we can migrate DMs to conversations.
+// This test assumes that we're using the standard test fixtures, which contain some conversation-eligible DMs.
+func (suite *ConversationsTestSuite) TestMigrateDMsToConversations() {
+	advancedMigrationID := "20240611190733_add_conversations"
+	ctx := context.Background()
+	rawDB := (suite.db).(*bundb.DBService).DB()
+
+	// Precondition: we shouldn't have any conversations yet.
+	numConversations := 0
+	if err := rawDB.NewSelect().
+		Model((*gtsmodel.Conversation)(nil)).
+		ColumnExpr("COUNT(*)").
+		Scan(ctx, &numConversations); // nocollapse
+	err != nil {
+		suite.FailNow(err.Error())
+	}
+	suite.Zero(numConversations)
+
+	// Precondition: there is no record of the conversations advanced migration.
+	_, err := suite.db.GetAdvancedMigration(ctx, advancedMigrationID)
+	suite.ErrorIs(err, db.ErrNoEntries)
+
+	// Run the migration, which should not fail.
+	if err := suite.conversationsProcessor.MigrateDMsToConversations(ctx); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	// We should now have some conversations.
+	if err := rawDB.NewSelect().
+		Model((*gtsmodel.Conversation)(nil)).
+		ColumnExpr("COUNT(*)").
+		Scan(ctx, &numConversations); // nocollapse
+	err != nil {
+		suite.FailNow(err.Error())
+	}
+	suite.NotZero(numConversations)
+
+	// The advanced migration should now be marked as finished.
+	advancedMigration, err := suite.db.GetAdvancedMigration(ctx, advancedMigrationID)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+	if suite.NotNil(advancedMigration) && suite.NotNil(advancedMigration.Finished) {
+		suite.True(*advancedMigration.Finished)
+	}
+
+	// Run the migration again, which should not fail.
+	if err := suite.conversationsProcessor.MigrateDMsToConversations(ctx); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	// However, it shouldn't have done anything, so the advanced migration should not have been updated.
+	advancedMigration2, err := suite.db.GetAdvancedMigration(ctx, advancedMigrationID)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+	suite.Equal(advancedMigration.UpdatedAt, advancedMigration2.UpdatedAt)
+}