417 lines
13 KiB
Go
417 lines
13 KiB
Go
// GoToSocial
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// Copyright (C) GoToSocial Authors admin@gotosocial.org
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// SPDX-License-Identifier: AGPL-3.0-or-later
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package timeline
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import (
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"container/list"
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"context"
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"errors"
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"time"
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"codeberg.org/gruf/go-kv"
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"github.com/superseriousbusiness/gotosocial/internal/db"
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"github.com/superseriousbusiness/gotosocial/internal/gtserror"
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"github.com/superseriousbusiness/gotosocial/internal/id"
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"github.com/superseriousbusiness/gotosocial/internal/log"
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)
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func (t *timeline) LastGot() time.Time {
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t.Lock()
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defer t.Unlock()
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return t.lastGot
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}
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func (t *timeline) Get(ctx context.Context, amount int, maxID string, sinceID string, minID string, prepareNext bool) ([]Preparable, error) {
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l := log.WithContext(ctx).
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WithFields(kv.Fields{
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{"accountID", t.timelineID},
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{"amount", amount},
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{"maxID", maxID},
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{"sinceID", sinceID},
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{"minID", minID},
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}...)
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l.Trace("entering get and updating t.lastGot")
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// Regardless of what happens below, update the
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// last time Get was called for this timeline.
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t.Lock()
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t.lastGot = time.Now()
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t.Unlock()
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var (
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items []Preparable
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err error
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)
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switch {
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case maxID == "" && sinceID == "" && minID == "":
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// No params are defined so just fetch from the top.
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// This is equivalent to a user starting to view
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// their timeline from newest -> older posts.
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items, err = t.getXBetweenIDs(ctx, amount, id.Highest, id.Lowest, true)
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// Cache expected next query to speed up scrolling.
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// Assume the user will be scrolling downwards from
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// the final ID in items.
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if prepareNext && err == nil && len(items) != 0 {
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nextMaxID := items[len(items)-1].GetID()
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t.prepareNextQuery(amount, nextMaxID, "", "")
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}
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case maxID != "" && sinceID == "" && minID == "":
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// Only maxID is defined, so fetch from maxID onwards.
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// This is equivalent to a user paging further down
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// their timeline from newer -> older posts.
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items, err = t.getXBetweenIDs(ctx, amount, maxID, id.Lowest, true)
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// Cache expected next query to speed up scrolling.
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// Assume the user will be scrolling downwards from
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// the final ID in items.
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if prepareNext && err == nil && len(items) != 0 {
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nextMaxID := items[len(items)-1].GetID()
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t.prepareNextQuery(amount, nextMaxID, "", "")
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}
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// In the next cases, maxID is defined, and so are
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// either sinceID or minID. This is equivalent to
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// a user opening an in-progress timeline and asking
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// for a slice of posts somewhere in the middle, or
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// trying to "fill in the blanks" between two points,
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// paging either up or down.
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case maxID != "" && sinceID != "":
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items, err = t.getXBetweenIDs(ctx, amount, maxID, sinceID, true)
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// Cache expected next query to speed up scrolling.
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// We can assume the caller is scrolling downwards.
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// Guess id.Lowest as sinceID, since we don't actually
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// know what the next sinceID would be.
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if prepareNext && err == nil && len(items) != 0 {
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nextMaxID := items[len(items)-1].GetID()
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t.prepareNextQuery(amount, nextMaxID, id.Lowest, "")
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}
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case maxID != "" && minID != "":
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items, err = t.getXBetweenIDs(ctx, amount, maxID, minID, false)
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// Cache expected next query to speed up scrolling.
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// We can assume the caller is scrolling upwards.
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// Guess id.Highest as maxID, since we don't actually
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// know what the next maxID would be.
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if prepareNext && err == nil && len(items) != 0 {
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prevMinID := items[0].GetID()
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t.prepareNextQuery(amount, id.Highest, "", prevMinID)
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}
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// In the final cases, maxID is not defined, but
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// either sinceID or minID are. This is equivalent to
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// a user either "pulling up" at the top of their timeline
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// to refresh it and check if newer posts have come in, or
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// trying to scroll upwards from an old post to see what
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// they missed since then.
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//
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// In these calls, we use the highest possible ulid as
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// behindID because we don't have a cap for newest that
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// we're interested in.
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case maxID == "" && sinceID != "":
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items, err = t.getXBetweenIDs(ctx, amount, id.Highest, sinceID, true)
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// We can't cache an expected next query for this one,
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// since presumably the caller is at the top of their
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// timeline already.
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case maxID == "" && minID != "":
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items, err = t.getXBetweenIDs(ctx, amount, id.Highest, minID, false)
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// Cache expected next query to speed up scrolling.
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// We can assume the caller is scrolling upwards.
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// Guess id.Highest as maxID, since we don't actually
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// know what the next maxID would be.
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if prepareNext && err == nil && len(items) != 0 {
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prevMinID := items[0].GetID()
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t.prepareNextQuery(amount, id.Highest, "", prevMinID)
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}
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default:
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err = gtserror.New("switch statement exhausted with no results")
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}
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return items, err
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}
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// getXBetweenIDs returns x amount of items somewhere between (not including) the given IDs.
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//
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// If frontToBack is true, items will be served paging down from behindID.
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// This corresponds to an api call to /timelines/home?max_id=WHATEVER&since_id=WHATEVER
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//
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// If frontToBack is false, items will be served paging up from beforeID.
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// This corresponds to an api call to /timelines/home?max_id=WHATEVER&min_id=WHATEVER
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func (t *timeline) getXBetweenIDs(ctx context.Context, amount int, behindID string, beforeID string, frontToBack bool) ([]Preparable, error) {
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l := log.
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WithContext(ctx).
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WithFields(kv.Fields{
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{"amount", amount},
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{"behindID", behindID},
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{"beforeID", beforeID},
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{"frontToBack", frontToBack},
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}...)
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l.Trace("entering getXBetweenID")
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// Assume length we need to return.
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items := make([]Preparable, 0, amount)
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if beforeID >= behindID {
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// This is an impossible situation, we
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// can't serve anything between these.
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return items, nil
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}
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// Try to ensure we have enough items prepared.
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if err := t.prepareXBetweenIDs(ctx, amount, behindID, beforeID, frontToBack); err != nil {
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// An error here doesn't necessarily mean we
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// can't serve anything, so log + keep going.
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l.Debugf("error calling prepareXBetweenIDs: %s", err)
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}
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var (
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beforeIDMark *list.Element
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served int
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// Our behavior while ranging through the
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// list changes depending on if we're
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// going front-to-back or back-to-front.
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//
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// To avoid checking which one we're doing
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// in each loop iteration, define our range
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// function here outside the loop.
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//
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// The bool indicates to the caller whether
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// iteration should continue (true) or stop
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// (false).
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rangeF func(e *list.Element) (bool, error)
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// If we get certain errors on entries as we're
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// looking through, we might want to cheekily
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// remove their elements from the timeline.
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// Everything added to this slice will be removed.
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removeElements = []*list.Element{}
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)
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defer func() {
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for _, e := range removeElements {
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t.items.data.Remove(e)
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}
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}()
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if frontToBack {
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// We're going front-to-back, which means we
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// don't need to look for a mark per se, we
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// just keep serving items until we've reached
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// a point where the items are out of the range
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// we're interested in.
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rangeF = func(e *list.Element) (bool, error) {
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entry := e.Value.(*indexedItemsEntry) //nolint:forcetypeassert
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if entry.itemID >= behindID {
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// ID of this item is too high,
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// just keep iterating.
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l.Trace("item is too new, continuing")
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return true, nil
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}
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if entry.itemID <= beforeID {
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// We've gone as far as we can through
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// the list and reached entries that are
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// now too old for us, stop here.
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l.Trace("reached older items, breaking")
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return false, nil
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}
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l.Trace("entry is just right")
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if entry.prepared == nil {
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// Whoops, this entry isn't prepared yet; some
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// race condition? That's OK, we can do it now.
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prepared, err := t.prepareFunction(ctx, t.timelineID, entry.itemID)
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if err != nil {
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if errors.Is(err, db.ErrNoEntries) {
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// ErrNoEntries means something has been deleted,
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// so we'll likely not be able to ever prepare this.
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// This means we can remove it and skip past it.
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l.Debugf("db.ErrNoEntries while trying to prepare %s; will remove from timeline", entry.itemID)
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removeElements = append(removeElements, e)
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return true, nil
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}
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// We've got a proper db error.
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err = gtserror.Newf("db error while trying to prepare %s: %w", entry.itemID, err)
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return false, err
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}
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entry.prepared = prepared
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}
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items = append(items, entry.prepared)
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served++
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return served < amount, nil
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}
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} else {
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// Iterate through the list from the top, until
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// we reach an item with id smaller than beforeID;
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// ie., an item OLDER than beforeID. At that point,
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// we can stop looking because we're not interested
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// in older entries.
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rangeF = func(e *list.Element) (bool, error) {
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// Move the mark back one place each loop.
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beforeIDMark = e
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//nolint:forcetypeassert
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if entry := e.Value.(*indexedItemsEntry); entry.itemID <= beforeID {
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// We've gone as far as we can through
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// the list and reached entries that are
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// now too old for us, stop here.
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l.Trace("reached older items, breaking")
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return false, nil
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}
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return true, nil
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}
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}
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// Iterate through the list until the function
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// we defined above instructs us to stop.
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for e := t.items.data.Front(); e != nil; e = e.Next() {
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keepGoing, err := rangeF(e)
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if err != nil {
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return nil, err
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}
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if !keepGoing {
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break
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}
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}
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if frontToBack || beforeIDMark == nil {
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// If we're serving front to back, then
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// items should be populated by now. If
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// we're serving back to front but didn't
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// find any items newer than beforeID,
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// we can just return empty items.
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return items, nil
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}
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// We're serving back to front, so iterate upwards
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// towards the front of the list from the mark we found,
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// until we either get to the front, serve enough
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// items, or reach behindID.
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//
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// To preserve ordering, we need to reverse the slice
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// when we're finished.
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for e := beforeIDMark; e != nil; e = e.Prev() {
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entry := e.Value.(*indexedItemsEntry) //nolint:forcetypeassert
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if entry.itemID == beforeID {
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// Don't include the beforeID
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// entry itself, just continue.
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l.Trace("entry item ID is equal to beforeID, skipping")
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continue
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}
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if entry.itemID >= behindID {
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// We've reached items that are
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// newer than what we're looking
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// for, just stop here.
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l.Trace("reached newer items, breaking")
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break
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}
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if entry.prepared == nil {
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// Whoops, this entry isn't prepared yet; some
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// race condition? That's OK, we can do it now.
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prepared, err := t.prepareFunction(ctx, t.timelineID, entry.itemID)
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if err != nil {
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if errors.Is(err, db.ErrNoEntries) {
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// ErrNoEntries means something has been deleted,
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// so we'll likely not be able to ever prepare this.
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// This means we can remove it and skip past it.
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l.Debugf("db.ErrNoEntries while trying to prepare %s; will remove from timeline", entry.itemID)
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removeElements = append(removeElements, e)
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continue
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}
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// We've got a proper db error.
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err = gtserror.Newf("db error while trying to prepare %s: %w", entry.itemID, err)
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return nil, err
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}
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entry.prepared = prepared
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}
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items = append(items, entry.prepared)
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served++
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if served >= amount {
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break
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}
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}
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// Reverse order of items.
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// https://zchee.github.io/golang-wiki/SliceTricks/#reversing
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for l, r := 0, len(items)-1; l < r; l, r = l+1, r-1 {
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items[l], items[r] = items[r], items[l]
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}
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return items, nil
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}
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func (t *timeline) prepareNextQuery(amount int, maxID string, sinceID string, minID string) {
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var (
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// We explicitly use context.Background() rather than
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// accepting a context param because we don't want this
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// to stop/break when the calling context finishes.
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ctx = context.Background()
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err error
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)
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// Always perform this async so caller doesn't have to wait.
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go func() {
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switch {
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case maxID == "" && sinceID == "" && minID == "":
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err = t.prepareXBetweenIDs(ctx, amount, id.Highest, id.Lowest, true)
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case maxID != "" && sinceID == "" && minID == "":
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err = t.prepareXBetweenIDs(ctx, amount, maxID, id.Lowest, true)
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case maxID != "" && sinceID != "":
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err = t.prepareXBetweenIDs(ctx, amount, maxID, sinceID, true)
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case maxID != "" && minID != "":
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err = t.prepareXBetweenIDs(ctx, amount, maxID, minID, false)
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case maxID == "" && sinceID != "":
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err = t.prepareXBetweenIDs(ctx, amount, id.Highest, sinceID, true)
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case maxID == "" && minID != "":
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err = t.prepareXBetweenIDs(ctx, amount, id.Highest, minID, false)
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default:
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err = gtserror.New("switch statement exhausted with no results")
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}
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if err != nil {
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log.
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WithContext(ctx).
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WithFields(kv.Fields{
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{"amount", amount},
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{"maxID", maxID},
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{"sinceID", sinceID},
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{"minID", minID},
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}...).
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Warnf("error preparing next query: %s", err)
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}
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}()
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}
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