[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

internal/processing/account/lists.go

@@ -0,0 +1,107 @@
+// 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 account
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+var noLists = make([]*apimodel.List, 0)
+
+// ListsGet returns all lists owned by requestingAccount, which contain a follow for targetAccountID.
+func (p *Processor) ListsGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string) ([]*apimodel.List, gtserror.WithCode) {
+	targetAccount, err := p.state.DB.GetAccountByID(ctx, targetAccountID)
+	if err != nil {
+		if errors.Is(err, db.ErrNoEntries) {
+			return nil, gtserror.NewErrorNotFound(errors.New("account not found"))
+		}
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("db error: %w", err))
+	}
+
+	visible, err := p.filter.AccountVisible(ctx, requestingAccount, targetAccount)
+	if err != nil {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("db error: %w", err))
+	}
+
+	if !visible {
+		return nil, gtserror.NewErrorNotFound(errors.New("account not found"))
+	}
+
+	// Requester has to follow targetAccount
+	// for them to be in any of their lists.
+	follow, err := p.state.DB.GetFollow(
+		// Don't populate follow.
+		gtscontext.SetBarebones(ctx),
+		requestingAccount.ID,
+		targetAccountID,
+	)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("db error: %w", err))
+	}
+
+	if follow == nil {
+		return noLists, nil // by definition we know they're in no lists
+	}
+
+	listEntries, err := p.state.DB.GetListEntriesForFollowID(
+		// Don't populate entries.
+		gtscontext.SetBarebones(ctx),
+		follow.ID,
+	)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		return nil, gtserror.NewErrorInternalError(fmt.Errorf("db error: %w", err))
+	}
+
+	count := len(listEntries)
+	if count == 0 {
+		return noLists, nil
+	}
+
+	apiLists := make([]*apimodel.List, 0, count)
+	for _, listEntry := range listEntries {
+		list, err := p.state.DB.GetListByID(
+			// Don't populate list.
+			gtscontext.SetBarebones(ctx),
+			listEntry.ListID,
+		)
+
+		if err != nil {
+			log.Debugf(ctx, "skipping list %s due to error %q", listEntry.ListID, err)
+			continue
+		}
+
+		apiList, err := p.tc.ListToAPIList(ctx, list)
+		if err != nil {
+			log.Debugf(ctx, "skipping list %s due to error %q", listEntry.ListID, err)
+			continue
+		}
+
+		apiLists = append(apiLists, apiList)
+	}
+
+	return apiLists, nil
+}