<?php

class TransactionStore
{
    public static function empty(): array
    {
        return [
            'activeTransactionId' => '',
            'transactionStartTime' => 0,
            'transactionStartEnergyImport' => 0.0,
            'transactionStartEnergyExport' => 0.0,
            'lastTransactionState' => '',
            'lastIdToken' => '',
            'sessionEnergyImport' => 0.0,
            'sessionEnergyExport' => 0.0,
            'sessionPeakPower' => 0.0,
            'sessionStopReason' => ''
        ];
    }

    public static function fromJson(string $json): array
    {
        $data = json_decode($json, true);
        if (!is_array($data)) {
            return self::empty();
        }
        return array_replace(self::empty(), $data);
    }

    public static function toJson(array $state): string
    {
        return json_encode(array_replace(self::empty(), $state));
    }
}

?>