GoToSocial/internal/timeline/timeline.go

/*
   GoToSocial
   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org

   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 timeline

import (
	"context"
	"sync"
	"time"

	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/typeutils"
	"github.com/superseriousbusiness/gotosocial/internal/visibility"
)

const boostReinsertionDepth = 50

// Timeline represents a timeline for one account, and contains indexed and prepared posts.
type Timeline interface {
	/*
		RETRIEVAL FUNCTIONS
	*/

	// Get returns an amount of statuses with the given parameters.
	// If prepareNext is true, then the next predicted query will be prepared already in a goroutine,
	// to make the next call to Get faster.
	Get(ctx context.Context, amount int, maxID string, sinceID string, minID string, prepareNext bool) ([]*apimodel.Status, error)
	// GetXFromTop returns x amount of posts from the top of the timeline, from newest to oldest.
	GetXFromTop(ctx context.Context, amount int) ([]*apimodel.Status, error)
	// GetXBehindID returns x amount of posts from the given id onwards, from newest to oldest.
	// This will NOT include the status with the given ID.
	//
	// This corresponds to an api call to /timelines/home?max_id=WHATEVER
	GetXBehindID(ctx context.Context, amount int, fromID string, attempts *int) ([]*apimodel.Status, error)
	// GetXBeforeID returns x amount of posts up to the given id, from newest to oldest.
	// This will NOT include the status with the given ID.
	//
	// This corresponds to an api call to /timelines/home?since_id=WHATEVER
	GetXBeforeID(ctx context.Context, amount int, sinceID string, startFromTop bool) ([]*apimodel.Status, error)
	// GetXBetweenID returns x amount of posts from the given maxID, up to the given id, from newest to oldest.
	// This will NOT include the status with the given IDs.
	//
	// This corresponds to an api call to /timelines/home?since_id=WHATEVER&max_id=WHATEVER_ELSE
	GetXBetweenID(ctx context.Context, amount int, maxID string, sinceID string) ([]*apimodel.Status, error)

	/*
		INDEXING FUNCTIONS
	*/

	// IndexOne puts a status into the timeline at the appropriate place according to its 'createdAt' property.
	//
	// The returned bool indicates whether or not the status was actually inserted into the timeline. This will be false
	// if the status is a boost and the original post or another boost of it already exists < boostReinsertionDepth back in the timeline.
	IndexOne(ctx context.Context, statusCreatedAt time.Time, statusID string, boostOfID string, accountID string, boostOfAccountID string) (bool, error)

	// OldestIndexedPostID returns the id of the rearmost (ie., the oldest) indexed post, or an error if something goes wrong.
	// If nothing goes wrong but there's no oldest post, an empty string will be returned so make sure to check for this.
	OldestIndexedPostID(ctx context.Context) (string, error)
	// NewestIndexedPostID returns the id of the frontmost (ie., the newest) indexed post, or an error if something goes wrong.
	// If nothing goes wrong but there's no newest post, an empty string will be returned so make sure to check for this.
	NewestIndexedPostID(ctx context.Context) (string, error)

	IndexBefore(ctx context.Context, statusID string, include bool, amount int) error
	IndexBehind(ctx context.Context, statusID string, include bool, amount int) error

	/*
		PREPARATION FUNCTIONS
	*/

	// PrepareXFromTop instructs the timeline to prepare x amount of posts from the top of the timeline.
	PrepareFromTop(ctx context.Context, amount int) error
	// PrepareBehind instructs the timeline to prepare the next amount of entries for serialization, from position onwards.
	// If include is true, then the given status ID will also be prepared, otherwise only entries behind it will be prepared.
	PrepareBehind(ctx context.Context, statusID string, amount int) error
	// IndexOne puts a status into the timeline at the appropriate place according to its 'createdAt' property,
	// and then immediately prepares it.
	//
	// The returned bool indicates whether or not the status was actually inserted into the timeline. This will be false
	// if the status is a boost and the original post or another boost of it already exists < boostReinsertionDepth back in the timeline.
	IndexAndPrepareOne(ctx context.Context, statusCreatedAt time.Time, statusID string, boostOfID string, accountID string, boostOfAccountID string) (bool, error)
	// OldestPreparedPostID returns the id of the rearmost (ie., the oldest) prepared post, or an error if something goes wrong.
	// If nothing goes wrong but there's no oldest post, an empty string will be returned so make sure to check for this.
	OldestPreparedPostID(ctx context.Context) (string, error)

	/*
		INFO FUNCTIONS
	*/

	// ActualPostIndexLength returns the actual length of the post index at this point in time.
	PostIndexLength(ctx context.Context) int

	/*
		UTILITY FUNCTIONS
	*/

	// Reset instructs the timeline to reset to its base state -- cache only the minimum amount of posts.
	Reset() error
	// Remove removes a status from both the index and prepared posts.
	//
	// If a status has multiple entries in a timeline, they will all be removed.
	//
	// The returned int indicates the amount of entries that were removed.
	Remove(ctx context.Context, statusID string) (int, error)
	// RemoveAllBy removes all statuses by the given accountID, from both the index and prepared posts.
	//
	// The returned int indicates the amount of entries that were removed.
	RemoveAllBy(ctx context.Context, accountID string) (int, error)
}

// timeline fulfils the Timeline interface
type timeline struct {
	postIndex     *postIndex
	preparedPosts *preparedPosts
	accountID     string
	account       *gtsmodel.Account
	db            db.DB
	filter        visibility.Filter
	tc            typeutils.TypeConverter
	sync.Mutex
}

// NewTimeline returns a new Timeline for the given account ID
func NewTimeline(ctx context.Context, accountID string, db db.DB, typeConverter typeutils.TypeConverter) (Timeline, error) {
	timelineOwnerAccount := &gtsmodel.Account{}
	if err := db.GetByID(ctx, accountID, timelineOwnerAccount); err != nil {
		return nil, err
	}

	return &timeline{
		postIndex:     &postIndex{},
		preparedPosts: &preparedPosts{},
		accountID:     accountID,
		account:       timelineOwnerAccount,
		db:            db,
		filter:        visibility.NewFilter(db),
		tc:            typeConverter,
	}, nil
}

func (t *timeline) Reset() error {
	return nil
}

func (t *timeline) PostIndexLength(ctx context.Context) int {
	if t.postIndex == nil || t.postIndex.data == nil {
		return 0
	}

	return t.postIndex.data.Len()
}