package sqlstore

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"

	"github.com/dariuszjaniak/warp/server/internal/storage"
)

// Users is the shared SQL implementation of storage.UserStore.
//
// Unlike the settings store, whose four statements each driver writes in its
// own style, the user store has around thirty. Keeping two copies of them
// differing only in `?` versus `$1` would be a standing invitation to fix a
// bug in one and not the other, so the SQL is written once with `?` and the
// driver supplies a Rebind function. The statements themselves use only
// syntax both engines agree on: ON CONFLICT ... DO UPDATE with `excluded`,
// LIMIT/OFFSET, and comparisons against bound values rather than boolean
// literals.
type Users struct {
	db       *sql.DB
	rebind   func(string) string
	isUnique func(error) bool
}

// NewUsers builds a user store. rebind translates the `?` placeholders into
// the driver's own style, and isUnique recognises its unique-constraint
// error; nil means "no translation" and "never", respectively.
func NewUsers(db *sql.DB, rebind func(string) string, isUnique func(error) bool) *Users {
	if rebind == nil {
		rebind = func(query string) string { return query }
	}
	if isUnique == nil {
		isUnique = func(error) bool { return false }
	}
	return &Users{db: db, rebind: rebind, isUnique: isUnique}
}

// defaultAccountPageSize bounds an admin user listing that asks for no limit,
// so a forgotten ?limit= cannot stream the whole user table.
const defaultAccountPageSize = 100

// maxAccountPageSize caps what a caller may ask for.
const maxAccountPageSize = 1000

// q rebinds a statement for this driver.
func (u *Users) q(query string) string { return u.rebind(query) }

// tx runs fn in a transaction, rolling back on any error. The rollback after
// a successful commit is a no-op, which is why it can be deferred blindly.
func (u *Users) tx(ctx context.Context, fn func(*sql.Tx) error) error {
	tx, err := u.db.BeginTx(ctx, nil)
	if err != nil {
		return fmt.Errorf("begin transaction: %w", err)
	}
	defer func() { _ = tx.Rollback() }()

	if err := fn(tx); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("commit transaction: %w", err)
	}
	return nil
}

const insertAccountSQL = `
	INSERT INTO user_accounts (localpart, password_hash, display_name, admin, created_at_ms)
	VALUES (?, ?, ?, ?, ?)`

// CreateAccount implements storage.UserStore.
//
// Taken localparts are detected by inserting and letting the primary key
// complain, rather than by checking first: the check-then-insert version has
// a race that two simultaneous registrations of the same name would walk
// straight into.
func (u *Users) CreateAccount(ctx context.Context, acc storage.NewAccount) (storage.Account, error) {
	_, err := u.db.ExecContext(ctx, u.q(insertAccountSQL),
		acc.Localpart, acc.PasswordHash, acc.DisplayName, acc.Admin, acc.CreatedAtMS)
	if err != nil {
		if u.isUnique(err) {
			return storage.Account{}, fmt.Errorf("create account %q: %w", acc.Localpart, storage.ErrUserExists)
		}
		return storage.Account{}, fmt.Errorf("create account %q: %w", acc.Localpart, err)
	}
	return storage.Account{
		Localpart:   acc.Localpart,
		DisplayName: acc.DisplayName,
		Admin:       acc.Admin,
		CreatedAtMS: acc.CreatedAtMS,
	}, nil
}

const selectAccountSQL = `
	SELECT localpart, display_name, avatar_url, admin, deactivated, created_at_ms
	FROM user_accounts WHERE localpart = ?`

// Account implements storage.UserStore.
func (u *Users) Account(ctx context.Context, localpart string) (storage.Account, error) {
	var acc storage.Account
	err := u.db.QueryRowContext(ctx, u.q(selectAccountSQL), localpart).Scan(
		&acc.Localpart, &acc.DisplayName, &acc.AvatarURL,
		&acc.Admin, &acc.Deactivated, &acc.CreatedAtMS)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		return storage.Account{}, fmt.Errorf("account %q: %w", localpart, storage.ErrNoSuchUser)
	case err != nil:
		return storage.Account{}, fmt.Errorf("account %q: %w", localpart, err)
	}
	return acc, nil
}

const selectPasswordHashSQL = `SELECT password_hash FROM user_accounts WHERE localpart = ?`

// PasswordHash implements storage.UserStore.
func (u *Users) PasswordHash(ctx context.Context, localpart string) (string, error) {
	var hash string
	err := u.db.QueryRowContext(ctx, u.q(selectPasswordHashSQL), localpart).Scan(&hash)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		return "", fmt.Errorf("password for %q: %w", localpart, storage.ErrNoSuchUser)
	case err != nil:
		return "", fmt.Errorf("password for %q: %w", localpart, err)
	}
	return hash, nil
}

// SetPasswordHash implements storage.UserStore.
func (u *Users) SetPasswordHash(ctx context.Context, localpart, hash string) error {
	return u.updateAccount(ctx, localpart,
		`UPDATE user_accounts SET password_hash = ? WHERE localpart = ?`, hash)
}

// SetAdmin implements storage.UserStore.
func (u *Users) SetAdmin(ctx context.Context, localpart string, admin bool) error {
	return u.updateAccount(ctx, localpart,
		`UPDATE user_accounts SET admin = ? WHERE localpart = ?`, admin)
}

// SetDisplayName implements storage.UserStore.
func (u *Users) SetDisplayName(ctx context.Context, localpart, displayName string) error {
	return u.updateAccount(ctx, localpart,
		`UPDATE user_accounts SET display_name = ? WHERE localpart = ?`, displayName)
}

// SetAvatarURL implements storage.UserStore.
func (u *Users) SetAvatarURL(ctx context.Context, localpart, avatarURL string) error {
	return u.updateAccount(ctx, localpart,
		`UPDATE user_accounts SET avatar_url = ? WHERE localpart = ?`, avatarURL)
}

// updateAccount runs a single-column update and turns "nothing changed" into
// ErrNoSuchUser, so callers do not have to look the account up first.
func (u *Users) updateAccount(ctx context.Context, localpart, query string, value any) error {
	res, err := u.db.ExecContext(ctx, u.q(query), value, localpart)
	if err != nil {
		return fmt.Errorf("update account %q: %w", localpart, err)
	}
	affected, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("update account %q: %w", localpart, err)
	}
	if affected == 0 {
		return fmt.Errorf("update account %q: %w", localpart, storage.ErrNoSuchUser)
	}
	return nil
}

// likeEscape is the escape character the search patterns use.
//
// It is deliberately not a backslash: a backslash in a SQL string literal
// means different things depending on PostgreSQL's standard_conforming_
// strings setting, and "!" means exactly one thing everywhere.
const likeEscape = '!'

const (
	countAccountsSQL = `
		SELECT COUNT(*) FROM user_accounts
		WHERE LOWER(localpart) LIKE ? ESCAPE '!' OR LOWER(display_name) LIKE ? ESCAPE '!'`

	listAccountsSQL = `
		SELECT localpart, display_name, avatar_url, admin, deactivated, created_at_ms
		FROM user_accounts
		WHERE LOWER(localpart) LIKE ? ESCAPE '!' OR LOWER(display_name) LIKE ? ESCAPE '!'
		ORDER BY localpart
		LIMIT ? OFFSET ?`
)

// ListAccounts implements storage.UserStore.
//
// The search is a LOWER(...) LIKE rather than ILIKE, which is PostgreSQL
// only, and the pattern is escaped so that searching for "_" does not
// quietly match every single-character name.
func (u *Users) ListAccounts(ctx context.Context, filter storage.AccountFilter) ([]storage.Account, int, error) {
	pattern := likeContains(filter.Search)

	limit := filter.Limit
	switch {
	case limit <= 0:
		limit = defaultAccountPageSize
	case limit > maxAccountPageSize:
		limit = maxAccountPageSize
	}
	offset := max(filter.Offset, 0)

	var total int
	if err := u.db.QueryRowContext(ctx, u.q(countAccountsSQL), pattern, pattern).Scan(&total); err != nil {
		return nil, 0, fmt.Errorf("count accounts: %w", err)
	}

	rows, err := u.db.QueryContext(ctx, u.q(listAccountsSQL), pattern, pattern, limit, offset)
	if err != nil {
		return nil, 0, fmt.Errorf("list accounts: %w", err)
	}
	defer rows.Close()

	accounts := []storage.Account{}
	for rows.Next() {
		var acc storage.Account
		if err := rows.Scan(&acc.Localpart, &acc.DisplayName, &acc.AvatarURL,
			&acc.Admin, &acc.Deactivated, &acc.CreatedAtMS); err != nil {
			return nil, 0, fmt.Errorf("scan account: %w", err)
		}
		accounts = append(accounts, acc)
	}
	if err := rows.Err(); err != nil {
		return nil, 0, fmt.Errorf("list accounts: %w", err)
	}
	return accounts, total, nil
}

// likeContains turns a search term into a LIKE pattern matching it
// anywhere, escaping the two wildcards and the escape character itself. The
// statements using it declare ESCAPE explicitly, because SQLite has no
// default escape character at all.
func likeContains(search string) string {
	search = strings.ToLower(strings.TrimSpace(search))
	var b strings.Builder
	b.Grow(len(search) + 2)
	b.WriteByte('%')
	for _, r := range search {
		if r == '%' || r == '_' || r == likeEscape {
			b.WriteByte(likeEscape)
		}
		b.WriteRune(r)
	}
	b.WriteByte('%')
	return b.String()
}

const statsSQL = `
	SELECT
		(SELECT COUNT(*) FROM user_accounts),
		(SELECT COUNT(*) FROM user_accounts WHERE admin = ?),
		(SELECT COUNT(*) FROM user_accounts WHERE deactivated = ?),
		(SELECT COUNT(*) FROM user_devices)`

// Stats implements storage.UserStore.
func (u *Users) Stats(ctx context.Context) (storage.Stats, error) {
	var s storage.Stats
	// The flags are compared against bound values rather than TRUE, which
	// SQLite only learned in 3.23 and which PostgreSQL spells differently
	// from an integer.
	err := u.db.QueryRowContext(ctx, u.q(statsSQL), true, true).
		Scan(&s.Users, &s.Admins, &s.Deactivated, &s.Devices)
	if err != nil {
		return storage.Stats{}, fmt.Errorf("user stats: %w", err)
	}
	return s, nil
}

const (
	selectDeviceForUpdateSQL = `
		SELECT display_name, created_at_ms FROM user_devices
		WHERE localpart = ? AND device_id = ?`

	insertDeviceSQL = `
		INSERT INTO user_devices
			(localpart, device_id, display_name, created_at_ms, last_seen_ms, last_seen_ip, user_agent)
		VALUES (?, ?, ?, ?, ?, ?, ?)`

	touchDeviceSQL = `
		UPDATE user_devices SET last_seen_ms = ?, last_seen_ip = ?, user_agent = ?
		WHERE localpart = ? AND device_id = ?`

	deleteDeviceTokensSQL = `DELETE FROM user_access_tokens WHERE localpart = ? AND device_id = ?`

	deleteDeviceRefreshTokensSQL = `DELETE FROM user_refresh_tokens WHERE localpart = ? AND device_id = ?`

	insertAccessTokenSQL = `
		INSERT INTO user_access_tokens (token_hash, localpart, device_id, created_at_ms, expires_at_ms)
		VALUES (?, ?, ?, ?, ?)`

	insertRefreshTokenSQL = `
		INSERT INTO user_refresh_tokens (token_hash, localpart, device_id, created_at_ms, expires_at_ms)
		VALUES (?, ?, ?, ?, ?)`

	accountExistsSQL = `SELECT 1 FROM user_accounts WHERE localpart = ?`
)

// CreateSession implements storage.UserStore.
//
// Logging in on a device ID that already exists keeps the device — and its
// display name, because initial_device_display_name only applies to a device
// being created — but revokes the tokens it held, which is what the spec
// requires.
func (u *Users) CreateSession(ctx context.Context, s storage.NewSession) (storage.Device, error) {
	device := storage.Device{
		Localpart:   s.Localpart,
		ID:          s.DeviceID,
		DisplayName: s.DisplayName,
		CreatedAtMS: s.CreatedAtMS,
		LastSeenMS:  s.CreatedAtMS,
		LastSeenIP:  s.LastSeenIP,
		UserAgent:   s.UserAgent,
	}

	err := u.tx(ctx, func(tx *sql.Tx) error {
		var exists int
		switch err := tx.QueryRowContext(ctx, u.q(accountExistsSQL), s.Localpart).Scan(&exists); {
		case errors.Is(err, sql.ErrNoRows):
			return fmt.Errorf("create session for %q: %w", s.Localpart, storage.ErrNoSuchUser)
		case err != nil:
			return fmt.Errorf("create session for %q: %w", s.Localpart, err)
		}

		var existingName string
		var existingCreated int64
		err := tx.QueryRowContext(ctx, u.q(selectDeviceForUpdateSQL), s.Localpart, s.DeviceID).
			Scan(&existingName, &existingCreated)
		switch {
		case errors.Is(err, sql.ErrNoRows):
			if _, err := tx.ExecContext(ctx, u.q(insertDeviceSQL),
				s.Localpart, s.DeviceID, s.DisplayName, s.CreatedAtMS,
				s.CreatedAtMS, s.LastSeenIP, s.UserAgent); err != nil {
				return fmt.Errorf("create device %q: %w", s.DeviceID, err)
			}
		case err != nil:
			return fmt.Errorf("read device %q: %w", s.DeviceID, err)
		default:
			device.DisplayName = existingName
			device.CreatedAtMS = existingCreated
			if _, err := tx.ExecContext(ctx, u.q(touchDeviceSQL),
				s.CreatedAtMS, s.LastSeenIP, s.UserAgent, s.Localpart, s.DeviceID); err != nil {
				return fmt.Errorf("update device %q: %w", s.DeviceID, err)
			}
			for _, query := range []string{deleteDeviceTokensSQL, deleteDeviceRefreshTokensSQL} {
				if _, err := tx.ExecContext(ctx, u.q(query), s.Localpart, s.DeviceID); err != nil {
					return fmt.Errorf("revoke tokens of device %q: %w", s.DeviceID, err)
				}
			}
		}

		if _, err := tx.ExecContext(ctx, u.q(insertAccessTokenSQL),
			s.AccessTokenHash, s.Localpart, s.DeviceID,
			s.CreatedAtMS, s.AccessTokenExpiresAtMS); err != nil {
			return fmt.Errorf("store access token: %w", err)
		}
		if s.RefreshTokenHash != "" {
			if _, err := tx.ExecContext(ctx, u.q(insertRefreshTokenSQL),
				s.RefreshTokenHash, s.Localpart, s.DeviceID,
				s.CreatedAtMS, s.RefreshTokenExpiresAtMS); err != nil {
				return fmt.Errorf("store refresh token: %w", err)
			}
		}
		return nil
	})
	if err != nil {
		return storage.Device{}, err
	}
	return device, nil
}

const (
	selectRefreshTokenSQL = `
		SELECT localpart, device_id, expires_at_ms FROM user_refresh_tokens WHERE token_hash = ?`

	deleteRefreshTokenSQL = `DELETE FROM user_refresh_tokens WHERE token_hash = ?`

	selectAccountFlagsSQL = `SELECT admin, deactivated FROM user_accounts WHERE localpart = ?`
)

// RefreshSession implements storage.UserStore.
//
// The spent refresh token and the access token it had minted both go away
// immediately. The spec allows keeping the old access token alive for a grace
// period; refusing it at once is the stricter reading and means a stolen
// token stops working the moment the real client refreshes.
func (u *Users) RefreshSession(ctx context.Context, r storage.RefreshedSession) (storage.TokenInfo, error) {
	var info storage.TokenInfo

	err := u.tx(ctx, func(tx *sql.Tx) error {
		var expiresAt int64
		err := tx.QueryRowContext(ctx, u.q(selectRefreshTokenSQL), r.RefreshTokenHash).
			Scan(&info.Localpart, &info.DeviceID, &expiresAt)
		switch {
		case errors.Is(err, sql.ErrNoRows):
			return fmt.Errorf("refresh token: %w", storage.ErrNoSuchToken)
		case err != nil:
			return fmt.Errorf("refresh token: %w", err)
		}
		if expiresAt != 0 && expiresAt <= r.RefreshedAtMS {
			// Clean the dead token up on the way past; nothing else sweeps.
			if _, err := tx.ExecContext(ctx, u.q(deleteRefreshTokenSQL), r.RefreshTokenHash); err != nil {
				return fmt.Errorf("delete expired refresh token: %w", err)
			}
			return fmt.Errorf("refresh token has expired: %w", storage.ErrNoSuchToken)
		}

		if _, err := tx.ExecContext(ctx, u.q(deleteRefreshTokenSQL), r.RefreshTokenHash); err != nil {
			return fmt.Errorf("spend refresh token: %w", err)
		}
		if _, err := tx.ExecContext(ctx, u.q(deleteDeviceTokensSQL), info.Localpart, info.DeviceID); err != nil {
			return fmt.Errorf("revoke previous access token: %w", err)
		}
		if _, err := tx.ExecContext(ctx, u.q(insertAccessTokenSQL),
			r.NewAccessTokenHash, info.Localpart, info.DeviceID,
			r.RefreshedAtMS, r.AccessTokenExpiresAtMS); err != nil {
			return fmt.Errorf("store access token: %w", err)
		}
		if r.NewRefreshTokenHash != "" {
			if _, err := tx.ExecContext(ctx, u.q(insertRefreshTokenSQL),
				r.NewRefreshTokenHash, info.Localpart, info.DeviceID,
				r.RefreshedAtMS, r.RefreshTokenExpiresAtMS); err != nil {
				return fmt.Errorf("store refresh token: %w", err)
			}
		}

		if err := tx.QueryRowContext(ctx, u.q(selectAccountFlagsSQL), info.Localpart).
			Scan(&info.Admin, &info.Deactivated); err != nil {
			return fmt.Errorf("read account %q: %w", info.Localpart, err)
		}
		info.ExpiresAtMS = r.AccessTokenExpiresAtMS
		return nil
	})
	if err != nil {
		return storage.TokenInfo{}, err
	}
	return info, nil
}

const selectTokenInfoSQL = `
	SELECT t.localpart, t.device_id, t.expires_at_ms, a.admin, a.deactivated
	FROM user_access_tokens t
	JOIN user_accounts a ON a.localpart = t.localpart
	WHERE t.token_hash = ?`

// TokenInfo implements storage.UserStore.
func (u *Users) TokenInfo(ctx context.Context, tokenHash string) (storage.TokenInfo, error) {
	var info storage.TokenInfo
	err := u.db.QueryRowContext(ctx, u.q(selectTokenInfoSQL), tokenHash).Scan(
		&info.Localpart, &info.DeviceID, &info.ExpiresAtMS, &info.Admin, &info.Deactivated)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		return storage.TokenInfo{}, storage.ErrNoSuchToken
	case err != nil:
		return storage.TokenInfo{}, fmt.Errorf("look up access token: %w", err)
	}
	return info, nil
}

// TouchDevice implements storage.UserStore. A device that has gone away
// between authenticating and recording the visit is not an error: the
// request is being answered either way.
func (u *Users) TouchDevice(ctx context.Context, localpart, deviceID, ip, userAgent string, seenAtMS int64) error {
	if _, err := u.db.ExecContext(ctx, u.q(touchDeviceSQL),
		seenAtMS, ip, userAgent, localpart, deviceID); err != nil {
		return fmt.Errorf("touch device %q: %w", deviceID, err)
	}
	return nil
}

const (
	selectDeviceSQL = `
		SELECT localpart, device_id, display_name, created_at_ms, last_seen_ms, last_seen_ip, user_agent
		FROM user_devices WHERE localpart = ? AND device_id = ?`

	selectDevicesSQL = `
		SELECT localpart, device_id, display_name, created_at_ms, last_seen_ms, last_seen_ip, user_agent
		FROM user_devices WHERE localpart = ? ORDER BY device_id`

	updateDeviceDisplayNameSQL = `
		UPDATE user_devices SET display_name = ? WHERE localpart = ? AND device_id = ?`
)

// Device implements storage.UserStore.
func (u *Users) Device(ctx context.Context, localpart, deviceID string) (storage.Device, error) {
	var d storage.Device
	err := u.db.QueryRowContext(ctx, u.q(selectDeviceSQL), localpart, deviceID).Scan(
		&d.Localpart, &d.ID, &d.DisplayName, &d.CreatedAtMS,
		&d.LastSeenMS, &d.LastSeenIP, &d.UserAgent)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		return storage.Device{}, fmt.Errorf("device %q: %w", deviceID, storage.ErrNoSuchDevice)
	case err != nil:
		return storage.Device{}, fmt.Errorf("device %q: %w", deviceID, err)
	}
	return d, nil
}

// Devices implements storage.UserStore.
func (u *Users) Devices(ctx context.Context, localpart string) ([]storage.Device, error) {
	rows, err := u.db.QueryContext(ctx, u.q(selectDevicesSQL), localpart)
	if err != nil {
		return nil, fmt.Errorf("list devices of %q: %w", localpart, err)
	}
	defer rows.Close()

	devices := []storage.Device{}
	for rows.Next() {
		var d storage.Device
		if err := rows.Scan(&d.Localpart, &d.ID, &d.DisplayName, &d.CreatedAtMS,
			&d.LastSeenMS, &d.LastSeenIP, &d.UserAgent); err != nil {
			return nil, fmt.Errorf("scan device: %w", err)
		}
		devices = append(devices, d)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("list devices of %q: %w", localpart, err)
	}
	return devices, nil
}

// SetDeviceDisplayName implements storage.UserStore.
func (u *Users) SetDeviceDisplayName(ctx context.Context, localpart, deviceID, displayName string) error {
	res, err := u.db.ExecContext(ctx, u.q(updateDeviceDisplayNameSQL), displayName, localpart, deviceID)
	if err != nil {
		return fmt.Errorf("rename device %q: %w", deviceID, err)
	}
	affected, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("rename device %q: %w", deviceID, err)
	}
	if affected == 0 {
		return fmt.Errorf("rename device %q: %w", deviceID, storage.ErrNoSuchDevice)
	}
	return nil
}

// DeleteDevices implements storage.UserStore.
//
// Tokens are deleted explicitly rather than left to ON DELETE CASCADE: SQLite
// only enforces foreign keys when the connection asks it to, so relying on
// the cascade would make revocation depend on a DSN pragma.
func (u *Users) DeleteDevices(ctx context.Context, localpart string, deviceIDs []string) (int, error) {
	if len(deviceIDs) == 0 {
		return 0, nil
	}
	args := make([]any, 0, len(deviceIDs)+1)
	args = append(args, localpart)
	for _, id := range deviceIDs {
		args = append(args, id)
	}
	in := "(" + strings.TrimSuffix(strings.Repeat("?,", len(deviceIDs)), ",") + ")"

	var deleted int
	err := u.tx(ctx, func(tx *sql.Tx) error {
		for _, table := range []string{"user_access_tokens", "user_refresh_tokens"} {
			query := "DELETE FROM " + table + " WHERE localpart = ? AND device_id IN " + in
			if _, err := tx.ExecContext(ctx, u.q(query), args...); err != nil {
				return fmt.Errorf("revoke tokens: %w", err)
			}
		}
		res, err := tx.ExecContext(ctx,
			u.q("DELETE FROM user_devices WHERE localpart = ? AND device_id IN "+in), args...)
		if err != nil {
			return fmt.Errorf("delete devices: %w", err)
		}
		affected, err := res.RowsAffected()
		if err != nil {
			return fmt.Errorf("delete devices: %w", err)
		}
		deleted = int(affected)
		return nil
	})
	return deleted, err
}

// DeleteAllDevices implements storage.UserStore.
func (u *Users) DeleteAllDevices(ctx context.Context, localpart string) (int, error) {
	var deleted int
	err := u.tx(ctx, func(tx *sql.Tx) error {
		for _, table := range []string{"user_access_tokens", "user_refresh_tokens"} {
			if _, err := tx.ExecContext(ctx,
				u.q("DELETE FROM "+table+" WHERE localpart = ?"), localpart); err != nil {
				return fmt.Errorf("revoke tokens of %q: %w", localpart, err)
			}
		}
		res, err := tx.ExecContext(ctx,
			u.q("DELETE FROM user_devices WHERE localpart = ?"), localpart)
		if err != nil {
			return fmt.Errorf("delete devices of %q: %w", localpart, err)
		}
		affected, err := res.RowsAffected()
		if err != nil {
			return fmt.Errorf("delete devices of %q: %w", localpart, err)
		}
		deleted = int(affected)
		return nil
	})
	return deleted, err
}

const (
	selectAccountDataSQL = `
		SELECT content FROM user_account_data
		WHERE localpart = ? AND room_id = ? AND data_type = ?`

	upsertAccountDataSQL = `
		INSERT INTO user_account_data (localpart, room_id, data_type, content, stream_pos)
		VALUES (?, ?, ?, ?, ?)
		ON CONFLICT (localpart, room_id, data_type)
		DO UPDATE SET content = excluded.content, stream_pos = excluded.stream_pos`
)

// AccountData implements storage.UserStore.
func (u *Users) AccountData(ctx context.Context, localpart, roomID, dataType string) ([]byte, error) {
	var content string
	err := u.db.QueryRowContext(ctx, u.q(selectAccountDataSQL), localpart, roomID, dataType).Scan(&content)
	switch {
	case errors.Is(err, sql.ErrNoRows):
		return nil, fmt.Errorf("account data %q: %w", dataType, storage.ErrNoSuchAccountData)
	case err != nil:
		return nil, fmt.Errorf("account data %q: %w", dataType, err)
	}
	return []byte(content), nil
}

// SetAccountData implements storage.UserStore. The content is stored as text
// rather than a JSON column type: the two engines disagree on what JSON
// normalisation does, and account data has to come back out byte for byte.
//
// The write also stamps the row with a position in the account data stream,
// taken inside the same transaction as the write itself. Account data is
// one of the streams /sync reports, and a position assigned separately
// would either be visible before the content it describes or after it — in
// the second case a client would be told the stream had moved and then find
// the old value.
func (u *Users) SetAccountData(ctx context.Context, localpart, roomID, dataType string, content []byte) error {
	err := u.tx(ctx, func(tx *sql.Tx) error {
		pos, err := nextSequence(ctx, tx, u.q, syncSequences, seqAccountData)
		if err != nil {
			return err
		}
		if _, err := tx.ExecContext(ctx, u.q(upsertAccountDataSQL),
			localpart, roomID, dataType, string(content), pos); err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("set account data %q: %w", dataType, err)
	}
	return nil
}

// Compile-time proof that the shared implementation satisfies the interface.
var _ storage.UserStore = (*Users)(nil)