69 lines
1.7 KiB
Go
69 lines
1.7 KiB
Go
package database
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import (
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"database/sql"
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"encoding/json"
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"errors"
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)
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// Atomically check the lock status of a state and lock it if unlocked. Returns
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// true if the function locked the state, otherwise returns false and the lock
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// parameter is updated to the value of the existing lock
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func (db *DB) SetLockOrGetExistingLock(name string, lock any) (bool, error) {
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tx, err := db.Begin()
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if err != nil {
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return false, err
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}
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defer func() {
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if err != nil {
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_ = tx.Rollback()
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}
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}()
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var lockData []byte
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if err = tx.QueryRowContext(db.ctx, `SELECT lock FROM states WHERE name = ?;`, name).Scan(&lockData); err != nil {
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if errors.Is(err, sql.ErrNoRows) {
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if lockData, err = json.Marshal(lock); err != nil {
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return false, err
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}
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_, err = tx.ExecContext(db.ctx,
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`INSERT INTO states(name, lock) VALUES (:name, json(:lock))`,
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sql.Named("lock", lockData),
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sql.Named("name", name),
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)
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if err != nil {
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return false, err
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}
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err = tx.Commit()
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return true, err
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} else {
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return false, err
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}
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}
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if lockData != nil {
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_ = tx.Rollback()
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err = json.Unmarshal(lockData, lock)
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return false, err
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}
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if lockData, err = json.Marshal(lock); err != nil {
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return false, err
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}
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_, err = tx.ExecContext(db.ctx, `UPDATE states SET lock = json(?) WHERE name = ?;`, lockData, name)
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if err != nil {
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return false, err
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}
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err = tx.Commit()
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return true, err
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}
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func (db *DB) Unlock(name, lock any) (bool, error) {
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data, err := json.Marshal(lock)
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if err != nil {
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return false, err
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}
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result, err := db.Exec(`UPDATE states SET lock = NULL WHERE name = ? and lock = json(?);`, name, data)
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if err != nil {
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return false, err
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}
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n, err := result.RowsAffected()
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return n == 1, err
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}
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