/*
   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 db

import (
	"context"
	"crypto/rand"
	"crypto/rsa"
	"errors"
	"fmt"
	"net"
	"net/mail"
	"regexp"
	"strings"
	"time"

	"github.com/go-fed/activity/pub"
	"github.com/go-pg/pg/extra/pgdebug"
	"github.com/go-pg/pg/v10"
	"github.com/go-pg/pg/v10/orm"
	"github.com/google/uuid"
	"github.com/sirupsen/logrus"
	"github.com/superseriousbusiness/gotosocial/internal/config"
	"github.com/superseriousbusiness/gotosocial/internal/db/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/util"
	"golang.org/x/crypto/bcrypt"
)

// postgresService satisfies the DB interface
type postgresService struct {
	config       *config.Config
	conn         *pg.DB
	log          *logrus.Entry
	cancel       context.CancelFunc
	federationDB pub.Database
}

// newPostgresService returns a postgresService derived from the provided config, which implements the go-fed DB interface.
// Under the hood, it uses https://github.com/go-pg/pg to create and maintain a database connection.
func newPostgresService(ctx context.Context, c *config.Config, log *logrus.Entry) (DB, error) {
	opts, err := derivePGOptions(c)
	if err != nil {
		return nil, fmt.Errorf("could not create postgres service: %s", err)
	}
	log.Debugf("using pg options: %+v", opts)

	// create a connection
	pgCtx, cancel := context.WithCancel(ctx)
	conn := pg.Connect(opts).WithContext(pgCtx)

	// this will break the logfmt format we normally log in,
	// since we can't choose where pg outputs to and it defaults to
	// stdout. So use this option with care!
	if log.Logger.GetLevel() >= logrus.TraceLevel {
		conn.AddQueryHook(pgdebug.DebugHook{
			// Print all queries.
			Verbose: true,
		})
	}

	// actually *begin* the connection so that we can tell if the db is there and listening
	if err := conn.Ping(ctx); err != nil {
		cancel()
		return nil, fmt.Errorf("db connection error: %s", err)
	}

	// print out discovered postgres version
	var version string
	if _, err = conn.QueryOneContext(ctx, pg.Scan(&version), "SELECT version()"); err != nil {
		cancel()
		return nil, fmt.Errorf("db connection error: %s", err)
	}
	log.Infof("connected to postgres version: %s", version)

	ps := &postgresService{
		config: c,
		conn:   conn,
		log:    log,
		cancel: cancel,
	}

	federatingDB := newFederatingDB(ps, c)
	ps.federationDB = federatingDB

	// we can confidently return this useable postgres service now
	return ps, nil
}

/*
	HANDY STUFF
*/

// derivePGOptions takes an application config and returns either a ready-to-use *pg.Options
// with sensible defaults, or an error if it's not satisfied by the provided config.
func derivePGOptions(c *config.Config) (*pg.Options, error) {
	if strings.ToUpper(c.DBConfig.Type) != dbTypePostgres {
		return nil, fmt.Errorf("expected db type of %s but got %s", dbTypePostgres, c.DBConfig.Type)
	}

	// validate port
	if c.DBConfig.Port == 0 {
		return nil, errors.New("no port set")
	}

	// validate address
	if c.DBConfig.Address == "" {
		return nil, errors.New("no address set")
	}

	ipv4Regex := regexp.MustCompile(`^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$`)
	hostnameRegex := regexp.MustCompile(`^(?:[a-z0-9]+(?:-[a-z0-9]+)*\.)+[a-z]{2,}$`)
	if !hostnameRegex.MatchString(c.DBConfig.Address) && !ipv4Regex.MatchString(c.DBConfig.Address) && c.DBConfig.Address != "localhost" {
		return nil, fmt.Errorf("address %s was neither an ipv4 address nor a valid hostname", c.DBConfig.Address)
	}

	// validate username
	if c.DBConfig.User == "" {
		return nil, errors.New("no user set")
	}

	// validate that there's a password
	if c.DBConfig.Password == "" {
		return nil, errors.New("no password set")
	}

	// validate database
	if c.DBConfig.Database == "" {
		return nil, errors.New("no database set")
	}

	// We can rely on the pg library we're using to set
	// sensible defaults for everything we don't set here.
	options := &pg.Options{
		Addr:            fmt.Sprintf("%s:%d", c.DBConfig.Address, c.DBConfig.Port),
		User:            c.DBConfig.User,
		Password:        c.DBConfig.Password,
		Database:        c.DBConfig.Database,
		ApplicationName: c.ApplicationName,
	}

	return options, nil
}

/*
	FEDERATION FUNCTIONALITY
*/

func (ps *postgresService) Federation() pub.Database {
	return ps.federationDB
}

/*
	BASIC DB FUNCTIONALITY
*/

func (ps *postgresService) CreateTable(i interface{}) error {
	return ps.conn.Model(i).CreateTable(&orm.CreateTableOptions{
		IfNotExists: true,
	})
}

func (ps *postgresService) DropTable(i interface{}) error {
	return ps.conn.Model(i).DropTable(&orm.DropTableOptions{
		IfExists: true,
	})
}

func (ps *postgresService) Stop(ctx context.Context) error {
	ps.log.Info("closing db connection")
	if err := ps.conn.Close(); err != nil {
		// only cancel if there's a problem closing the db
		ps.cancel()
		return err
	}
	return nil
}

func (ps *postgresService) IsHealthy(ctx context.Context) error {
	return ps.conn.Ping(ctx)
}

func (ps *postgresService) CreateSchema(ctx context.Context) error {
	models := []interface{}{
		(*gtsmodel.Account)(nil),
		(*gtsmodel.Status)(nil),
		(*gtsmodel.User)(nil),
	}
	ps.log.Info("creating db schema")

	for _, model := range models {
		err := ps.conn.Model(model).CreateTable(&orm.CreateTableOptions{
			IfNotExists: true,
		})
		if err != nil {
			return err
		}
	}

	ps.log.Info("db schema created")
	return nil
}

func (ps *postgresService) GetByID(id string, i interface{}) error {
	if err := ps.conn.Model(i).Where("id = ?", id).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err

	}
	return nil
}

func (ps *postgresService) GetWhere(key string, value interface{}, i interface{}) error {
	if err := ps.conn.Model(i).Where("? = ?", pg.Safe(key), value).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

// func (ps *postgresService) GetWhereMany(i interface{}, where ...model.Where) error {
// 	return nil
// }

func (ps *postgresService) GetAll(i interface{}) error {
	if err := ps.conn.Model(i).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) Put(i interface{}) error {
	_, err := ps.conn.Model(i).Insert(i)
	return err
}

func (ps *postgresService) Upsert(i interface{}, conflictColumn string) error {
	if _, err := ps.conn.Model(i).OnConflict(fmt.Sprintf("(%s) DO UPDATE", conflictColumn)).Insert(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) UpdateByID(id string, i interface{}) error {
	if _, err := ps.conn.Model(i).Where("id = ?", id).OnConflict("(id) DO UPDATE").Insert(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) UpdateOneByID(id string, key string, value interface{}, i interface{}) error {
	_, err := ps.conn.Model(i).Set("? = ?", pg.Safe(key), value).Where("id = ?", id).Update()
	return err
}

func (ps *postgresService) DeleteByID(id string, i interface{}) error {
	if _, err := ps.conn.Model(i).Where("id = ?", id).Delete(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) DeleteWhere(key string, value interface{}, i interface{}) error {
	if _, err := ps.conn.Model(i).Where("? = ?", pg.Safe(key), value).Delete(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

/*
	HANDY SHORTCUTS
*/

func (ps *postgresService) CreateInstanceAccount() error {
	username := ps.config.Host
	instanceAccount := &gtsmodel.Account{
		Username: username,
	}
	inserted, err := ps.conn.Model(instanceAccount).Where("username = ?", username).SelectOrInsert()
	if err != nil {
		return err
	}
	if inserted {
		ps.log.Infof("created instance account %s with id %s", username, instanceAccount.ID)
	} else {
		ps.log.Infof("instance account %s already exists with id %s", username, instanceAccount.ID)
	}
	return nil
}

func (ps *postgresService) GetAccountByUserID(userID string, account *gtsmodel.Account) error {
	user := &gtsmodel.User{
		ID: userID,
	}
	if err := ps.conn.Model(user).Where("id = ?", userID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	if err := ps.conn.Model(account).Where("id = ?", user.AccountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetFollowRequestsForAccountID(accountID string, followRequests *[]gtsmodel.FollowRequest) error {
	if err := ps.conn.Model(followRequests).Where("target_account_id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetFollowingByAccountID(accountID string, following *[]gtsmodel.Follow) error {
	if err := ps.conn.Model(following).Where("account_id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetFollowersByAccountID(accountID string, followers *[]gtsmodel.Follow) error {
	if err := ps.conn.Model(followers).Where("target_account_id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetStatusesByAccountID(accountID string, statuses *[]gtsmodel.Status) error {
	if err := ps.conn.Model(statuses).Where("account_id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetStatusesByTimeDescending(accountID string, statuses *[]gtsmodel.Status, limit int) error {
	q := ps.conn.Model(statuses).Order("created_at DESC")
	if limit != 0 {
		q = q.Limit(limit)
	}
	if accountID != "" {
		q = q.Where("account_id = ?", accountID)
	}
	if err := q.Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetLastStatusForAccountID(accountID string, status *gtsmodel.Status) error {
	if err := ps.conn.Model(status).Order("created_at DESC").Limit(1).Where("account_id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil

}

func (ps *postgresService) IsUsernameAvailable(username string) error {
	// if no error we fail because it means we found something
	// if error but it's not pg.ErrNoRows then we fail
	// if err is pg.ErrNoRows we're good, we found nothing so continue
	if err := ps.conn.Model(&gtsmodel.Account{}).Where("username = ?", username).Where("domain = ?", nil).Select(); err == nil {
		return fmt.Errorf("username %s already in use", username)
	} else if err != pg.ErrNoRows {
		return fmt.Errorf("db error: %s", err)
	}
	return nil
}

func (ps *postgresService) IsEmailAvailable(email string) error {
	// parse the domain from the email
	m, err := mail.ParseAddress(email)
	if err != nil {
		return fmt.Errorf("error parsing email address %s: %s", email, err)
	}
	domain := strings.Split(m.Address, "@")[1] // domain will always be the second part after @

	// check if the email domain is blocked
	if err := ps.conn.Model(&gtsmodel.EmailDomainBlock{}).Where("domain = ?", domain).Select(); err == nil {
		// fail because we found something
		return fmt.Errorf("email domain %s is blocked", domain)
	} else if err != pg.ErrNoRows {
		// fail because we got an unexpected error
		return fmt.Errorf("db error: %s", err)
	}

	// check if this email is associated with a user already
	if err := ps.conn.Model(&gtsmodel.User{}).Where("email = ?", email).WhereOr("unconfirmed_email = ?", email).Select(); err == nil {
		// fail because we found something
		return fmt.Errorf("email %s already in use", email)
	} else if err != pg.ErrNoRows {
		// fail because we got an unexpected error
		return fmt.Errorf("db error: %s", err)
	}
	return nil
}

func (ps *postgresService) NewSignup(username string, reason string, requireApproval bool, email string, password string, signUpIP net.IP, locale string, appID string) (*gtsmodel.User, error) {
	key, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		ps.log.Errorf("error creating new rsa key: %s", err)
		return nil, err
	}

	uris := util.GenerateURIs(username, ps.config.Protocol, ps.config.Host)

	a := &gtsmodel.Account{
		Username:              username,
		DisplayName:           username,
		Reason:                reason,
		URL:                   uris.UserURL,
		PrivateKey:            key,
		PublicKey:             &key.PublicKey,
		ActorType:             gtsmodel.ActivityStreamsPerson,
		URI:                   uris.UserURI,
		InboxURL:              uris.InboxURI,
		OutboxURL:             uris.OutboxURI,
		FollowersURL:          uris.FollowersURI,
		FeaturedCollectionURL: uris.CollectionURI,
	}
	if _, err = ps.conn.Model(a).Insert(); err != nil {
		return nil, err
	}

	pw, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return nil, fmt.Errorf("error hashing password: %s", err)
	}
	u := &gtsmodel.User{
		AccountID:              a.ID,
		EncryptedPassword:      string(pw),
		SignUpIP:               signUpIP,
		Locale:                 locale,
		UnconfirmedEmail:       email,
		CreatedByApplicationID: appID,
		Approved:               !requireApproval, // if we don't require moderator approval, just pre-approve the user
	}
	if _, err = ps.conn.Model(u).Insert(); err != nil {
		return nil, err
	}

	return u, nil
}

func (ps *postgresService) SetHeaderOrAvatarForAccountID(mediaAttachment *gtsmodel.MediaAttachment, accountID string) error {
	if mediaAttachment.Avatar && mediaAttachment.Header {
		return errors.New("one media attachment cannot be both header and avatar")
	}

	var headerOrAVI string
	if mediaAttachment.Avatar {
		headerOrAVI = "avatar"
	} else if mediaAttachment.Header {
		headerOrAVI = "header"
	} else {
		return errors.New("given media attachment was neither a header nor an avatar")
	}

	// TODO: there are probably more side effects here that need to be handled
	if _, err := ps.conn.Model(mediaAttachment).OnConflict("(id) DO UPDATE").Insert(); err != nil {
		return err
	}

	if _, err := ps.conn.Model(&gtsmodel.Account{}).Set(fmt.Sprintf("%s_media_attachment_id = ?", headerOrAVI), mediaAttachment.ID).Where("id = ?", accountID).Update(); err != nil {
		return err
	}
	return nil
}

func (ps *postgresService) GetHeaderForAccountID(header *gtsmodel.MediaAttachment, accountID string) error {
	acct := &gtsmodel.Account{}
	if err := ps.conn.Model(acct).Where("id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}

	if acct.HeaderMediaAttachmentID == "" {
		return ErrNoEntries{}
	}

	if err := ps.conn.Model(header).Where("id = ?", acct.HeaderMediaAttachmentID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) GetAvatarForAccountID(avatar *gtsmodel.MediaAttachment, accountID string) error {
	acct := &gtsmodel.Account{}
	if err := ps.conn.Model(acct).Where("id = ?", accountID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}

	if acct.AvatarMediaAttachmentID == "" {
		return ErrNoEntries{}
	}

	if err := ps.conn.Model(avatar).Where("id = ?", acct.AvatarMediaAttachmentID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return ErrNoEntries{}
		}
		return err
	}
	return nil
}

func (ps *postgresService) Blocked(account1 string, account2 string) (bool, error) {
	var blocked bool
	if err := ps.conn.Model(&gtsmodel.Block{}).
		Where("account_id = ?", account1).Where("target_account_id = ?", account2).
		WhereOr("target_account_id = ?", account1).Where("account_id = ?", account2).
		Select(); err != nil {
		if err == pg.ErrNoRows {
			blocked = false
			return blocked, nil
		} else {
			return blocked, err
		}
	}
	blocked = true
	return blocked, nil
}

func (ps *postgresService) StatusVisible(targetStatus *gtsmodel.Status, targetAccount *gtsmodel.Account, requestingAccount *gtsmodel.Account, relevantAccounts *gtsmodel.RelevantAccounts) (bool, error) {
	l := ps.log.WithField("func", "StatusVisible")

	// if target account is suspended then don't show the status
	if !targetAccount.SuspendedAt.IsZero() {
		l.Debug("target account suspended at is not zero")
		return false, nil
	}

	// if the target user doesn't exist (anymore) then the status also shouldn't be visible
	targetUser := &gtsmodel.User{}
	if err := ps.conn.Model(targetUser).Where("account_id = ?", targetAccount.ID).Select(); err != nil {
		l.Debug("target user could not be selected")
		if err == pg.ErrNoRows {
			return false, ErrNoEntries{}
		} else {
			return false, err
		}
	}

	// if target user is disabled, not yet approved, or not confirmed then don't show the status
	// (although in the latter two cases it's unlikely they posted a status yet anyway, but you never know!)
	if targetUser.Disabled || !targetUser.Approved || targetUser.ConfirmedAt.IsZero() {
		l.Debug("target user is disabled, not approved, or not confirmed")
		return false, nil
	}

	// If requesting account is nil, that means whoever requested the status didn't auth, or their auth failed.
	// In this case, we can still serve the status if it's public, otherwise we definitely shouldn't.
	if requestingAccount == nil {

		if targetStatus.Visibility == gtsmodel.VisibilityPublic {
			return true, nil
		}
		l.Debug("requesting account is nil but the target status isn't public")
		return false, nil
	}

	// if requesting account is suspended then don't show the status -- although they probably shouldn't have gotten
	// this far (ie., been authed) in the first place: this is just for safety.
	if !requestingAccount.SuspendedAt.IsZero() {
		l.Debug("requesting account is suspended")
		return false, nil
	}

	// check if we have a local account -- if so we can check the user for that account in the DB
	if requestingAccount.Domain == "" {
		requestingUser := &gtsmodel.User{}
		if err := ps.conn.Model(requestingUser).Where("account_id = ?", requestingAccount.ID).Select(); err != nil {
			// if the requesting account is local but doesn't have a corresponding user in the db this is a problem
			if err == pg.ErrNoRows {
				l.Debug("requesting account is local but there's no corresponding user")
				return false, nil
			} else {
				l.Debugf("requesting account is local but there was an error getting the corresponding user: %s", err)
				return false, err
			}
		}
		// okay, user exists, so make sure it has full privileges/is confirmed/approved
		if requestingUser.Disabled || !requestingUser.Approved || requestingUser.ConfirmedAt.IsZero() {
			l.Debug("requesting account is local but corresponding user is either disabled, not approved, or not confirmed")
			return false, nil
		}
	}

	// if the target status belongs to the requesting account, they should always be able to view it at this point
	if targetStatus.AccountID == requestingAccount.ID {
		return true, nil
	}

	// At this point we have a populated targetAccount, targetStatus, and requestingAccount, so we can check for blocks and whathaveyou
	// First check if a block exists directly between the target account (which authored the status) and the requesting account.
	if blocked, err := ps.Blocked(targetAccount.ID, requestingAccount.ID); err != nil {
		l.Debugf("something went wrong figuring out if the accounts have a block: %s", err)
		return false, err
	} else if blocked {
		// don't allow the status to be viewed if a block exists in *either* direction between these two accounts, no creepy stalking please
		l.Debug("a block exists between requesting account and target account")
		return false, nil
	}

	// check other accounts mentioned/boosted by/replied to by the status, if they exist
	if relevantAccounts != nil {
		// status replies to account id
		if relevantAccounts.ReplyToAccount != nil {
			if blocked, err := ps.Blocked(relevantAccounts.ReplyToAccount.ID, requestingAccount.ID); err != nil {
				return false, err
			} else if blocked {
				return false, nil
			}
		}

		// status boosts accounts id
		if relevantAccounts.BoostedAccount != nil {
			if blocked, err := ps.Blocked(relevantAccounts.BoostedAccount.ID, requestingAccount.ID); err != nil {
				return false, err
			} else if blocked {
				return false, nil
			}
		}

		// status boosts a reply to account id
		if relevantAccounts.BoostedReplyToAccount != nil {
			if blocked, err := ps.Blocked(relevantAccounts.BoostedReplyToAccount.ID, requestingAccount.ID); err != nil {
				return false, err
			} else if blocked {
				return false, nil
			}
		}

		// status mentions accounts
		for _, a := range relevantAccounts.MentionedAccounts {
			if blocked, err := ps.Blocked(a.ID, requestingAccount.ID); err != nil {
				return false, err
			} else if blocked {
				return false, nil
			}
		}
	}

	// at this point we know neither account blocks the other, or another account mentioned or otherwise referred to in the status
	// that means it's now just a matter of checking the visibility settings of the status itself
	switch targetStatus.Visibility {
	case gtsmodel.VisibilityPublic, gtsmodel.VisibilityUnlocked:
		// no problem here, just return OK
		return true, nil
	case gtsmodel.VisibilityFollowersOnly:
		// check one-way follow
		follows, err := ps.Follows(requestingAccount, targetAccount)
		if err != nil {
			return false, err
		}
		if !follows {
			return false, nil
		}
		return true, nil
	case gtsmodel.VisibilityMutualsOnly:
		// check mutual follow
		mutuals, err := ps.Mutuals(requestingAccount, targetAccount)
		if err != nil {
			return false, err
		}
		if !mutuals {
			return false, nil
		}
		return true, nil
	case gtsmodel.VisibilityDirect:
		// make sure the requesting account is mentioned in the status
		for _, menchie := range targetStatus.Mentions {
			if menchie == requestingAccount.ID {
				return true, nil // yep it's mentioned!
			}
		}
		return false, nil // it's not mentioned -_-
	}

	return false, errors.New("reached the end of StatusVisible with no result")
}

func (ps *postgresService) Follows(sourceAccount *gtsmodel.Account, targetAccount *gtsmodel.Account) (bool, error) {
	return ps.conn.Model(&gtsmodel.Follow{}).Where("account_id = ?", sourceAccount.ID).Where("target_account_id = ?", targetAccount.ID).Exists()
}

func (ps *postgresService) Mutuals(account1 *gtsmodel.Account, account2 *gtsmodel.Account) (bool, error) {
	// make sure account 1 follows account 2
	f1, err := ps.conn.Model(&gtsmodel.Follow{}).Where("account_id = ?", account1.ID).Where("target_account_id = ?", account2.ID).Exists()
	if err != nil {
		if err == pg.ErrNoRows {
			return false, nil
		} else {
			return false, err
		}
	}

	// make sure account 2 follows account 1
	f2, err := ps.conn.Model(&gtsmodel.Follow{}).Where("account_id = ?", account2.ID).Where("target_account_id = ?", account1.ID).Exists()
	if err != nil {
		if err == pg.ErrNoRows {
			return false, nil
		} else {
			return false, err
		}
	}

	return f1 && f2, nil
}

func (ps *postgresService) PullRelevantAccountsFromStatus(targetStatus *gtsmodel.Status) (*gtsmodel.RelevantAccounts, error) {
	accounts := &gtsmodel.RelevantAccounts{
		MentionedAccounts: []*gtsmodel.Account{},
	}

	// get the replied to account from the status and add it to the pile
	if targetStatus.InReplyToAccountID != "" {
		repliedToAccount := &gtsmodel.Account{}
		if err := ps.conn.Model(repliedToAccount).Where("id = ?", targetStatus.InReplyToAccountID).Select(); err != nil {
			return accounts, err
		}
		accounts.ReplyToAccount = repliedToAccount
	}

	// get the boosted account from the status and add it to the pile
	if targetStatus.BoostOfID != "" {
		// retrieve the boosted status first
		boostedStatus := &gtsmodel.Status{}
		if err := ps.conn.Model(boostedStatus).Where("id = ?", targetStatus.BoostOfID).Select(); err != nil {
			return accounts, err
		}
		boostedAccount := &gtsmodel.Account{}
		if err := ps.conn.Model(boostedAccount).Where("id = ?", boostedStatus.AccountID).Select(); err != nil {
			return accounts, err
		}
		accounts.BoostedAccount = boostedAccount

		// the boosted status might be a reply to another account so we should get that too
		if boostedStatus.InReplyToAccountID != "" {
			boostedStatusRepliedToAccount := &gtsmodel.Account{}
			if err := ps.conn.Model(boostedStatusRepliedToAccount).Where("id = ?", boostedStatus.InReplyToAccountID).Select(); err != nil {
				return accounts, err
			}
			accounts.BoostedReplyToAccount = boostedStatusRepliedToAccount
		}
	}

	// now get all accounts with IDs that are mentioned in the status
	for _, mentionedAccountID := range targetStatus.Mentions {
		mentionedAccount := &gtsmodel.Account{}
		if err := ps.conn.Model(mentionedAccount).Where("id = ?", mentionedAccountID).Select(); err != nil {
			return accounts, err
		}
		accounts.MentionedAccounts = append(accounts.MentionedAccounts, mentionedAccount)
	}

	return accounts, nil
}

func (ps *postgresService) GetReplyCountForStatus(status *gtsmodel.Status) (int, error) {
	return ps.conn.Model(&gtsmodel.Status{}).Where("in_reply_to_id = ?", status.ID).Count()
}

func (ps *postgresService) GetReblogCountForStatus(status *gtsmodel.Status) (int, error) {
	return ps.conn.Model(&gtsmodel.Status{}).Where("boost_of_id = ?", status.ID).Count()
}

func (ps *postgresService) GetFaveCountForStatus(status *gtsmodel.Status) (int, error) {
	return ps.conn.Model(&gtsmodel.StatusFave{}).Where("status_id = ?", status.ID).Count()
}

func (ps *postgresService) StatusFavedBy(status *gtsmodel.Status, accountID string) (bool, error) {
	return ps.conn.Model(&gtsmodel.StatusFave{}).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Exists()
}

func (ps *postgresService) StatusRebloggedBy(status *gtsmodel.Status, accountID string) (bool, error) {
	return ps.conn.Model(&gtsmodel.Status{}).Where("boost_of_id = ?", status.ID).Where("account_id = ?", accountID).Exists()
}

func (ps *postgresService) StatusMutedBy(status *gtsmodel.Status, accountID string) (bool, error) {
	return ps.conn.Model(&gtsmodel.StatusMute{}).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Exists()
}

func (ps *postgresService) StatusBookmarkedBy(status *gtsmodel.Status, accountID string) (bool, error) {
	return ps.conn.Model(&gtsmodel.StatusBookmark{}).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Exists()
}

func (ps *postgresService) StatusPinnedBy(status *gtsmodel.Status, accountID string) (bool, error) {
	return ps.conn.Model(&gtsmodel.StatusPin{}).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Exists()
}

func (ps *postgresService) FaveStatus(status *gtsmodel.Status, accountID string) (*gtsmodel.StatusFave, error) {
	// first check if a fave already exists, we can just return if so
	existingFave := &gtsmodel.StatusFave{}
	err := ps.conn.Model(existingFave).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Select()
	if err == nil {
		// fave already exists so just return nothing at all
		return nil, nil
	}

	// an error occurred so it might exist or not, we don't know
	if err != pg.ErrNoRows {
		return nil, err
	}

	// it doesn't exist so create it
	newFave := &gtsmodel.StatusFave{
		AccountID:       accountID,
		TargetAccountID: status.AccountID,
		StatusID:        status.ID,
	}
	if _, err = ps.conn.Model(newFave).Insert(); err != nil {
		return nil, err
	}

	return newFave, nil
}

func (ps *postgresService) UnfaveStatus(status *gtsmodel.Status, accountID string) (*gtsmodel.StatusFave, error) {
	// if a fave doesn't exist, we don't need to do anything
	existingFave := &gtsmodel.StatusFave{}
	err := ps.conn.Model(existingFave).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Select()
	// the fave doesn't exist so return nothing at all
	if err == pg.ErrNoRows {
		return nil, nil
	}

	// an error occurred so it might exist or not, we don't know
	if err != nil && err != pg.ErrNoRows {
		return nil, err
	}

	// the fave exists so remove it
	if _, err = ps.conn.Model(&gtsmodel.StatusFave{}).Where("status_id = ?", status.ID).Where("account_id = ?", accountID).Delete(); err != nil {
		return nil, err
	}

	return existingFave, nil
}

func (ps *postgresService) WhoFavedStatus(status *gtsmodel.Status) ([]*gtsmodel.Account, error) {
	accounts := []*gtsmodel.Account{}

	faves := []*gtsmodel.StatusFave{}
	if err := ps.conn.Model(&faves).Where("status_id = ?", status.ID).Select(); err != nil {
		if err == pg.ErrNoRows {
			return accounts, nil // no rows just means nobody has faved this status, so that's fine
		}
		return nil, err // an actual error has occurred
	}

	for _, f := range faves {
		acc := &gtsmodel.Account{}
		if err := ps.conn.Model(acc).Where("id = ?", f.AccountID).Select(); err != nil {
			if err == pg.ErrNoRows {
				continue // the account doesn't exist for some reason??? but this isn't the place to worry about that so just skip it
			}
			return nil, err // an actual error has occurred
		}
		accounts = append(accounts, acc)
	}
	return accounts, nil
}

/*
	CONVERSION FUNCTIONS
*/

func (ps *postgresService) MentionStringsToMentions(targetAccounts []string, originAccountID string, statusID string) ([]*gtsmodel.Mention, error) {
	menchies := []*gtsmodel.Mention{}
	for _, a := range targetAccounts {
		// A mentioned account looks like "@test@example.org" or just "@test" for a local account
		// -- we can guarantee this from the regex that targetAccounts should have been derived from.
		// But we still need to do a bit of fiddling to get what we need here -- the username and domain (if given).

		// 1.  trim off the first @
		t := strings.TrimPrefix(a, "@")

		// 2. split the username and domain
		s := strings.Split(t, "@")

		// 3. if it's length 1 it's a local account, length 2 means remote, anything else means something is wrong
		var local bool
		switch len(s) {
		case 1:
			local = true
		case 2:
			local = false
		default:
			return nil, fmt.Errorf("mentioned account format '%s' was not valid", a)
		}

		var username, domain string
		username = s[0]
		if !local {
			domain = s[1]
		}

		// 4. check we now have a proper username and domain
		if username == "" || (!local && domain == "") {
			return nil, fmt.Errorf("username or domain for '%s' was nil", a)
		}

		// okay we're good now, we can start pulling accounts out of the database
		mentionedAccount := &gtsmodel.Account{}
		var err error
		if local {
			// local user -- should have a null domain
			err = ps.conn.Model(mentionedAccount).Where("username = ?", username).Where("? IS NULL", pg.Ident("domain")).Select()
		} else {
			// remote user -- should have domain defined
			err = ps.conn.Model(mentionedAccount).Where("username = ?", username).Where("? = ?", pg.Ident("domain"), domain).Select()
		}

		if err != nil {
			if err == pg.ErrNoRows {
				// no result found for this username/domain so just don't include it as a mencho and carry on about our business
				ps.log.Debugf("no account found with username '%s' and domain '%s', skipping it", username, domain)
				continue
			}
			// a serious error has happened so bail
			return nil, fmt.Errorf("error getting account with username '%s' and domain '%s': %s", username, domain, err)
		}

		// id, createdAt and updatedAt will be populated by the db, so we have everything we need!
		menchies = append(menchies, &gtsmodel.Mention{
			StatusID:        statusID,
			OriginAccountID: originAccountID,
			TargetAccountID: mentionedAccount.ID,
		})
	}
	return menchies, nil
}

func (ps *postgresService) TagStringsToTags(tags []string, originAccountID string, statusID string) ([]*gtsmodel.Tag, error) {
	newTags := []*gtsmodel.Tag{}
	for _, t := range tags {
		tag := &gtsmodel.Tag{}
		// we can use selectorinsert here to create the new tag if it doesn't exist already
		// inserted will be true if this is a new tag we just created
		if err := ps.conn.Model(tag).Where("name = ?", t).Select(); err != nil {
			if err == pg.ErrNoRows {
				// tag doesn't exist yet so populate it
				tag.ID = uuid.NewString()
				tag.Name = t
				tag.FirstSeenFromAccountID = originAccountID
				tag.CreatedAt = time.Now()
				tag.UpdatedAt = time.Now()
				tag.Useable = true
				tag.Listable = true
			} else {
				return nil, fmt.Errorf("error getting tag with name %s: %s", t, err)
			}
		}

		// bail already if the tag isn't useable
		if !tag.Useable {
			continue
		}
		tag.LastStatusAt = time.Now()
		newTags = append(newTags, tag)
	}
	return newTags, nil
}

func (ps *postgresService) EmojiStringsToEmojis(emojis []string, originAccountID string, statusID string) ([]*gtsmodel.Emoji, error) {
	newEmojis := []*gtsmodel.Emoji{}
	for _, e := range emojis {
		emoji := &gtsmodel.Emoji{}
		err := ps.conn.Model(emoji).Where("shortcode = ?", e).Where("visible_in_picker = true").Where("disabled = false").Select()
		if err != nil {
			if err == pg.ErrNoRows {
				// no result found for this username/domain so just don't include it as an emoji and carry on about our business
				ps.log.Debugf("no emoji found with shortcode %s, skipping it", e)
				continue
			}
			// a serious error has happened so bail
			return nil, fmt.Errorf("error getting emoji with shortcode %s: %s", e, err)
		}
		newEmojis = append(newEmojis, emoji)
	}
	return newEmojis, nil
}