README

Sequence is an opinionated model for generating sequences of unique integers.

Description

This model was designed to extract and make explicit the requirement that some models need to have auto-incrementing behavior. It originated from a project that required MySQL-style auto-incrementing fields.

Installation

Install the project with Composer:

composer require simensen/sequence

Usage

Sequence

The Sequence<T> Interface

The Sequence<T> interface represents the state of an incrementing numeric value.

Calling a Sequence's next(): T method will return the next value. The core expectations for the next value:

• The next value SHOULD be a number (int)
• The next value SHOULD be unique to the sequence

Additional Sequences (see below for Sequences) may provide additional guarantees.

Sequence Configuration

Attributes are provided to facilitate commonly needed Sequence configuration without introducing these concepts through the public interfaces.

Connection

Used to configure the connection name used by the sequence.

CurrentValueColumn

Used to configure the column or field name that contains the sequence's current value.

DefaultStartValue

Used to configure the start value of a sequence.

Name

Used to configure the name of the sequence.

NameColumn

Used to configure the column or field that contains the sequence's name.

Table

Used to configure the table or document name that contains the sequence.

NumericSequence

The NumericSequence abstract class can be used when a native int will suffice.

use Simensen\Sequence\NumericSequence;

#[Connection('accounting_db')]
#[Table('invoice_number_sequence')]
final readonly class InvoiceNumber extends NumericSequence
{
}

CastedSequence

The CastedSequence<T> abstract class can be used when a model wraps the native int with a value object of type T. The transformation from int to type T is facilitated by a cast(int $next): T method.

use Simensen\Sequence\CastedSequence;

/**
 * @extends CastedSequence<PartId>
 */
#[Table('part_id_seq')]
final readonly class PartIdSequence extends CastedSequence
{
    protected function cast(int $next): PartId
    {
        return PartId::fromInt($next);
    }
}

Sequences

The Sequences interface provides the bridge between a Sequence and its underlying persistence infrastructure.

Calling a Sequences' nextValueForSequence($sequenceClassName): int method will return the next value for the specified $sequenceClassName. The core expectations for the next value:

• The Sequences MAY require additional configuration
  • The Sequences MAY introduce additional Sequence Configuration attributes
• The Sequences SHOULD read and map the Sequence Configuration attributes where possible
  • An in-memory implementation may not care about Column, Connection, or Table
  • A database-backed implementation may care about Column, Connection, or Table
• The next value SHOULD be a number (int)
• The next value SHOULD be unique to at least the sequence

Additional Sequences may provide additional guarantees.

GlobalInMemorySequences

This Sequences implementation is useful for testing. It generates unique next values using the same underlying value for every type of Sequence<T>.

use Simensen\Sequence\Sequences\Adapter\GlobalInMemorySequences;

$sequences = new GlobalInMemorySequences();

$userIdSequence = new UserIdSequence($sequences);
$serviceIdSequence = new ServiceIdSequence($sequences);

$userIdSequence->next(); // 1
$userIdSequence->next(); // 2

$serviceIdSequence->next(); // 3

$userIdSequence->next(); // 4

ClassBasedInMemorySequences

This Sequences implementation is useful for testing. It generates unique next values using a different underlying value for every type of Sequence<T>.

use Simensen\Sequence\Sequences\Adapter\ClassBasedInMemorySequences;

$sequences = new ClassBasedInMemorySequences();

$userIdSequence = new UserIdSequence($sequences);
$serviceIdSequence = new ServiceIdSequence($sequences);

$userIdSequence->next(); // 1
$userIdSequence->next(); // 2

$serviceIdSequence->next(); // 1

$userIdSequence->next(); // 3

CurrentValueManagement

The CurrentValueManagement interface exposes additional functionality for Sequences to manage aspects of Sequence's current value.

registerPotentialCurrentValueForSequence

Useful for backfilling sequence-related data. This method sets the current value to the specified value only if it is a larger value than the existing current value.

This method is called with a Sequence<T> class name and a potential current value.

If the Sequence<T> does not have a current value yet, the default start value is used for the current value.

If the potential current value is greater than the current value for the Sequence<T>, the potential current value becomes the new current value.

Otherwise, there is no change to the current value.

forceSetCurrentValueForSequence

Useful in testing. This method sets the current value to the specified value regardless of the existing current value.

This method is called with a Sequence<T> class name and a value.

The current value for the Sequence<T> is always set to the new value.

License

This project is licensed under the MIT License. See the LICENSE file for more details on terms and conditions.

Feel free to use and contribute to the project under these terms!