Proxies and Dummy Services
##########################

.. highlight:: php

Proxies and Dummy Services are defined in the core library, ``peso/core``.

ChainService
============

``\Peso\Core\Services\ChainService($service1, $service2, ...)``

Chain service allows you to request data from several sources::

    <?php

    use Peso\Core\Services\ChainService;
    use Peso\Peso\CurrencyConverter;
    use Peso\Services\CzechNationalBankService;
    use Peso\Services\EuropeanCentralBankService;

    $converter = new CurrencyConverter(new ChainService(
        new EuropeanCentralBankService(),
        new CzechNationalBankService(),
    ));

    // ECB doesn't know that
    echo $converter->convertOnDate('1.20', 'USD', 'CZK', 2, '2025-06-13'); // 25.88

.. _builtin_reversible:

ReversibleService
=================

``\Peso\Core\Services\ReversibleService``

.. warning::
    Values returned by a Reversible Service are calculated and therefore informational only.
    Never use them for precise conversions.

In case a service defines only a single base or quote currency,
Reversible Service can make it bi-directional by calculating a reverse value::

    <?php

    use Peso\Core\Services\ReversibleService;
    use Peso\Peso\CurrencyConverter;
    use Peso\Services\EuropeanCentralBankService;

    $converter = new CurrencyConverter(
        new ReversibleService(new EuropeanCentralBankService())
    );

    echo $converter->convertOnDate('123.45', 'USD', 'EUR', 2, '2025-06-13'); // 107.24

IndirectExchangeService
=======================

``\Peso\Core\Services\IndirectExchangeService``

.. warning::
    Values returned by an Indirect Exchange Service are calculated and therefore informational only.
    Never use them for precise conversions.

In case a service defines only conversion rates back and forth for a single currency,
Indirect Exchange Service can make it every-to-every by using the selected currency as an intermediary::

    <?php

    use Peso\Core\Services\IndirectExchangeService;
    use Peso\Core\Services\ReversibleService;
    use Peso\Peso\CurrencyConverter;
    use Peso\Services\EuropeanCentralBankService;

    $converter = new CurrencyConverter(
        new IndirectExchangeService(
            new ReversibleService( // To and from EUR
                new EuropeanCentralBankService(), // Only EUR base
            ),
            'EUR',
        ),
    );

    // USD -> EUR -> PLN
    echo $converter->convertOnDate('123.45', 'USD', 'PLN', 2, '2025-06-13'); // 458.38

ArrayService
------------

``\Peso\Core\Services\ArrayService($currentRates = [], $historicalRates = [])``

Array Service holds static exchange rates::

    <?php

    use Peso\Core\Services\ArrayService;
    use Peso\Peso\CurrencyConverter;

    $service = new ArrayService(
        currentRates: [
            // Base Currencies
            'EUR' => [
                // Quote => rate
                'USD' => '1.12',
            ],
        ],
        historicalRates: [
            // Y-m-d dates
            '2025-06-13' => [
                // Base Currencies
                'EUR' => [
                    // Quote => rate
                    'USD' => '1.09',
                ],
            ],
        ]
    );
    $converter = new CurrencyConverter($service);

    echo
        $converter->convert('150.00', 'EUR', 'USD', 2), PHP_EOL, // 168.00
        $converter->convertOnDate('150.00', 'EUR', 'USD', 2, '2025-06-13'), PHP_EOL; // 163.50

NullService
-----------

``\Peso\Core\Services\NullService``

Null Service fails every request, may be useful for testing purposes::

    <?php

    use Peso\Core\Services\NullService;
    use Peso\Peso\CurrencyConverter;

    $converter = new CurrencyConverter(new NullService());

    // Peso\Core\Exceptions\RequestNotSupportedException
    $converter->convert('100', 'USD', 'EUR', 2);