[feature] Add List functionality (#1802)

* start working on lists

* further list work

* test list db functions nicely

* more work on lists

* peepoopeepoo

* poke

* start list timeline func

* we're getting there lads

* couldn't be me working on stuff... could it?

* hook up handlers

* fiddling

* weeee

* woah

* screaming, pissing

* fix streaming being a whiny baby

* lint, small test fix, swagger

* tidying up, testing

* fucked! by the linter

* move timelines to state like a boss

* add timeline start to tests using state

* invalidate lists

1 files changed, 151 insertions, 0 deletions

diff --git a/internal/processing/list/updateentries.go b/internal/processing/list/updateentries.go
new file mode 100644
index 000000000..6dcb951a7
--- /dev/null
+++ b/internal/processing/list/updateentries.go
@@ -0,0 +1,151 @@
+// 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 list
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/id"
+)
+
+// AddToList adds targetAccountIDs to the given list, if valid.
+func (p *Processor) AddToList(ctx context.Context, account *gtsmodel.Account, listID string, targetAccountIDs []string) gtserror.WithCode {
+	// Ensure this list exists + account owns it.
+	list, errWithCode := p.getList(ctx, account.ID, listID)
+	if errWithCode != nil {
+		return errWithCode
+	}
+
+	// Pre-assemble list of entries to add. We *could* add these
+	// one by one as we iterate through accountIDs, but according
+	// to the Mastodon API we should only add them all once we know
+	// they're all valid, no partial updates.
+	listEntries := make([]*gtsmodel.ListEntry, 0, len(targetAccountIDs))
+
+	// Check each targetAccountID is valid.
+	//   - Follow must exist.
+	//   - Follow must not already be in the given list.
+	for _, targetAccountID := range targetAccountIDs {
+		// Ensure follow exists.
+		follow, err := p.state.DB.GetFollow(ctx, account.ID, targetAccountID)
+		if err != nil {
+			if errors.Is(err, db.ErrNoEntries) {
+				err = fmt.Errorf("you do not follow account %s", targetAccountID)
+				return gtserror.NewErrorNotFound(err, err.Error())
+			}
+			return gtserror.NewErrorInternalError(err)
+		}
+
+		// Ensure followID not already in list.
+		// This particular call to isInList will
+		// never error, so just check entryID.
+		entryID, _ := isInList(
+			list,
+			follow.ID,
+			func(listEntry *gtsmodel.ListEntry) (string, error) {
+				// Looking for the listEntry follow ID.
+				return listEntry.FollowID, nil
+			},
+		)
+
+		// Empty entryID means entry with given
+		// followID wasn't found in the list.
+		if entryID != "" {
+			err = fmt.Errorf("account with id %s is already in list %s with entryID %s", targetAccountID, listID, entryID)
+			return gtserror.NewErrorUnprocessableEntity(err, err.Error())
+		}
+
+		// Entry wasn't in the list, we can add it.
+		listEntries = append(listEntries, &gtsmodel.ListEntry{
+			ID:       id.NewULID(),
+			ListID:   listID,
+			FollowID: follow.ID,
+		})
+	}
+
+	// If we get to here we can assume all
+	// entries are valid, so try to add them.
+	if err := p.state.DB.PutListEntries(ctx, listEntries); err != nil {
+		if errors.Is(err, db.ErrAlreadyExists) {
+			err = fmt.Errorf("one or more errors inserting list entries: %w", err)
+			return gtserror.NewErrorUnprocessableEntity(err, err.Error())
+		}
+		return gtserror.NewErrorInternalError(err)
+	}
+
+	return nil
+}
+
+// RemoveFromList removes targetAccountIDs from the given list, if valid.
+func (p *Processor) RemoveFromList(ctx context.Context, account *gtsmodel.Account, listID string, targetAccountIDs []string) gtserror.WithCode {
+	// Ensure this list exists + account owns it.
+	list, errWithCode := p.getList(ctx, account.ID, listID)
+	if errWithCode != nil {
+		return errWithCode
+	}
+
+	// For each targetAccountID, we want to check if
+	// a follow with that targetAccountID is in the
+	// given list. If it is in there, we want to remove
+	// it from the list.
+	for _, targetAccountID := range targetAccountIDs {
+		// Check if targetAccountID is
+		// on a follow in the list.
+		entryID, err := isInList(
+			list,
+			targetAccountID,
+			func(listEntry *gtsmodel.ListEntry) (string, error) {
+				// We need the follow so populate this
+				// entry, if it's not already populated.
+				if err := p.state.DB.PopulateListEntry(ctx, listEntry); err != nil {
+					return "", err
+				}
+
+				// Looking for the list entry targetAccountID.
+				return listEntry.Follow.TargetAccountID, nil
+			},
+		)
+
+		// Error may be returned here if there was an issue
+		// populating the list entry. We only return on proper
+		// DB errors, we can just skip no entry errors.
+		if err != nil && !errors.Is(err, db.ErrNoEntries) {
+			err = fmt.Errorf("error checking if targetAccountID %s was in list %s: %w", targetAccountID, listID, err)
+			return gtserror.NewErrorInternalError(err)
+		}
+
+		if entryID == "" {
+			// There was an errNoEntries or targetAccount
+			// wasn't in this list anyway, so we can skip it.
+			continue
+		}
+
+		// TargetAccount was in the list, remove the entry.
+		if err := p.state.DB.DeleteListEntry(ctx, entryID); err != nil && !errors.Is(err, db.ErrNoEntries) {
+			err = fmt.Errorf("error removing list entry %s from list %s: %w", entryID, listID, err)
+			return gtserror.NewErrorInternalError(err)
+		}
+	}
+
+	return nil
+}