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FrequencyGenerator.php
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FrequencyGenerator.php
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<?php
namespace Eris\Generator;
use Eris\Generator;
use Eris\Generators;
use InvalidArgumentException;
use Eris\Random\RandomRange;
/**
* @return FrequencyGenerator
*/
function frequency(/*$frequencyAndGenerator, $frequencyAndGenerator, ...*/)
{
return call_user_func_array(
[Generators::class, 'frequency'],
func_get_args()
);
}
/**
* @psalm-template T
* @template-implements Generator<Generator<T>>
*/
class FrequencyGenerator implements Generator
{
private $generators;
public function __construct(array $generatorsWithFrequency)
{
if (empty($generatorsWithFrequency)) {
throw new InvalidArgumentException(
'Cannot choose from an empty array of generators'
);
}
$this->generators = array_reduce(
$generatorsWithFrequency,
function ($generators, $generatorWithFrequency) {
list($frequency, $generator) = $generatorWithFrequency;
$frequency = $this->ensureIsFrequency($generatorWithFrequency[0]);
$generator = ensureIsGenerator($generatorWithFrequency[1]);
if ($frequency > 0) {
$generators[] = [
'generator' => $generator,
'frequency' => $frequency,
];
}
return $generators;
},
[]
);
}
public function __invoke($size, RandomRange $rand)
{
list($index, $generator) = $this->pickFrom($this->generators, $rand);
$originalValue = $generator->__invoke($size, $rand);
return GeneratedValueSingle::fromValueAndInput(
$originalValue->unbox(),
[
'value' => $originalValue,
'generator' => $index,
],
'frequency'
);
}
public function shrink(GeneratedValue $element)
{
$input = $element->input();
$originalGeneratorIndex = $input['generator'];
$shrinkedValue = $this->generators[$originalGeneratorIndex]['generator']->shrink($input['value']);
// TODO: take advantage of multiple shrinking
return GeneratedValueSingle::fromValueAndInput(
$shrinkedValue->unbox(),
[
'value' => $shrinkedValue,
'generator' => $originalGeneratorIndex,
],
'frequency'
);
}
/**
* @return array two elements: index and Generator object
*/
private function pickFrom($generators, RandomRange $rand)
{
$acc = 0;
$frequencies = $this->frequenciesFrom($generators);
$random = $rand->rand(1, array_sum($frequencies));
foreach ($generators as $index => $generator) {
$acc += $generator['frequency'];
if ($random <= $acc) {
return [$index, $generator['generator']];
}
}
throw new \Exception(
'Unable to pick a generator with frequencies: ' . var_export($frequencies, true)
);
}
private function frequenciesFrom($generators)
{
return array_map(
function ($generatorWithFrequency) {
return $generatorWithFrequency['frequency'];
},
$generators
);
}
private function ensureIsFrequency($frequency)
{
if (!is_int($frequency) || $frequency < 0) {
throw new InvalidArgumentException(
'Frequency must be an integer greater or equal than 0, given: ' . var_export($frequency, true)
);
}
return $frequency;
}
}

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FrequencyGenerator.php (3 KB)

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