Policy Pattern Generator

Creates Policy pattern infrastructure for encapsulating business rules and authorization logic.

When to Use

Scenario	Example
Authorization checks	Can user cancel order?
Business rule validation	Is discount applicable?
Complex conditions	Multiple rules combined
Auditable decisions	Log why access denied

Component Characteristics

PolicyInterface

• Single responsibility rule
• Returns authorization result
• Provides denial reasons

Policy Implementation

• Encapsulates one business rule
• Stateless evaluation
• Composable with other policies

PolicyResult

• Success/failure status
• Denial reasons
• Metadata for logging

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Generation Process

Step 1: Generate Shared Components

Path: src/Domain/Shared/Policy/

1. PolicyResult.php — Result value object with and/or composition
2. CompositionMode.php — Enum for AllMustPass/AnyMustPass

Step 2: Generate Policy Interface

Path: src/Domain/{BoundedContext}/Policy/

1. {Name}PolicyInterface.php — Policy contract

Step 3: Generate Concrete Policies

Path: src/Domain/{BoundedContext}/Policy/

1. {Rule1}Policy.php — First rule implementation
2. {Rule2}Policy.php — Second rule implementation
3. {Name}Policy.php — Composite policy combining rules

Step 4: Generate Exception

Path: src/Domain/Shared/Exception/

1. PolicyViolationException.php — Exception with policy context

Step 5: Generate Tests

1. {Rule}PolicyTest.php — Individual rule tests
2. {Name}PolicyTest.php — Composite policy tests
3. PolicyResultTest.php — Result composition tests

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File Placement

Component	Path
Policy Interface	src/Domain/{BoundedContext}/Policy/
Policy Implementation	src/Domain/{BoundedContext}/Policy/
PolicyResult	src/Domain/Shared/Policy/
Exception	src/Domain/Shared/Exception/
Unit Tests	tests/Unit/Domain/{BoundedContext}/Policy/

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Naming Conventions

Component	Pattern	Example
Interface	{Name}PolicyInterface	OrderCancellationPolicyInterface
Implementation	{Rule}Policy	OrderOwnershipPolicy
Composite	{Name}Policy	OrderCancellationPolicy
Result	PolicyResult	PolicyResult
Exception	PolicyViolationException	PolicyViolationException
Test	{ClassName}Test	OrderOwnershipPolicyTest

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Quick Template Reference

PolicyInterface

interface {Name}PolicyInterface
{
    public function evaluate({SubjectType} $subject, {ResourceType} $resource): PolicyResult;
    public function getRuleName(): string;
}

PolicyResult

final readonly class PolicyResult
{
    public static function allow(): self;
    public static function deny(string $reason, array $metadata = []): self;
    public function isAllowed(): bool;
    public function isDenied(): bool;
    public function and(self $other): self; // Both must pass
    public function or(self $other): self;  // Either can pass
}

Policy Implementation

final readonly class {Rule}Policy implements {Name}PolicyInterface
{
    public function evaluate({Subject} $subject, {Resource} $resource): PolicyResult
    {
        if ({condition}) {
            return PolicyResult::allow();
        }
        return PolicyResult::deny('{reason}', ['context' => 'data']);
    }

    public function getRuleName(): string
    {
        return '{rule_name}';
    }
}

Composite Policy

final readonly class {Name}Policy implements {Name}PolicyInterface
{
    public function evaluate({Subject} $subject, {Resource} $resource): PolicyResult
    {
        return $this->rule1Policy->evaluate($subject, $resource)
            ->and($this->rule2Policy->evaluate($subject, $resource))
            ->and($this->rule3Policy->evaluate($subject, $resource));
    }
}

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Usage Example

// In UseCase
$result = $this->cancellationPolicy->evaluate($user, $order);

if ($result->isDenied()) {
    throw new PolicyViolationException(
        $this->cancellationPolicy->getRuleName(),
        $result->getReason(),
        $result->metadata
    );
}

$order->cancel($reason);

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Anti-patterns to Avoid

Anti-pattern	Problem	Solution
Side Effects	Policy modifies state	Keep evaluation pure
Boolean Returns	No denial reason	Use PolicyResult
Fat Policies	Too many rules	Split into composable policies
Hardcoded Values	Can't configure	Inject thresholds
No Logging Context	Can't debug	Include metadata

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References

For complete PHP templates and examples, see:

• references/templates.md — Policy, composite, result templates
• references/examples.md — Order cancellation policies and tests