Configuration: Fix currency fallback

Previously, it would always use fallback currency for child fees.

Also add a test that demonstrates the issue – the `overridden` category would use `GBP` instead of `USD`.

Author: jtojnar

app/Model/Configuration/Category.php

@@ -40,7 +40,7 @@ public static function from(
 		Fees $parentFees,
 		DateTimeInterface $eventDate,
 	): self {
-		$fees = Fees::from($category['fees'] ?? [], $parentFees);
+		$fees = Fees::from("categories.$key", $category['fees'] ?? [], $parentFees);
 		if ($fees->person === null) {
 			throw new InvalidConfigurationException("No person fee set for category “{$key}”");
 		}

app/Model/Configuration/CategoryGroup.php

@@ -27,7 +27,7 @@ public static function from(
 		Fees $parentFees,
 		DateTimeInterface $eventDate,
 	): self {
-		$fees = Fees::from($group['fees'] ?? [], $parentFees);
+		$fees = Fees::from("categories.$key", $group['fees'] ?? [], $parentFees);
 
 		if (!isset($group['categories']) || !\is_array($group['categories']) || \count($group['categories']) === 0) {
 			throw new InvalidConfigurationException("Category group #{$key} lacks categories");

app/Model/Configuration/Entries.php

@@ -45,7 +45,7 @@ public static function from(
 		array $entries,
 	): self {
 		$allLocales = $entries['supportedLocales'] ?? ['en', 'cs'];
-		$fees = Fees::from($entries['fees'] ?? []);
+		$fees = Fees::fromRoot($entries['fees'] ?? []);
 		$eventDate = $entries['eventDate'];
 		$minMembers = $entries['minMembers'] ?? 0;
 		$personFieldsRaw = Helpers::ensureFields('person', $entries['fields']['person'] ?? []);

app/Model/Configuration/Fees.php

@@ -14,12 +14,28 @@ public function __construct(
 	) {
 	}
 
-	public static function from(array $fees, ?self $parentFees = null): self {
-		$currency = $parentFees?->currency ?? new Currency($fees['currency'] ?? 'CZK');
+	/**
+	 * @param array<mixed> $fees
+	 */
+	public static function fromRoot(array $fees): self {
+		$currencyCode = Helpers::ensureNonEmptyString('fees.currency', $fees['currency'] ?? 'CZK');
+		$currency = new Currency($currencyCode);
 
 		return new self(
 			currency: $currency,
-			person: isset($fees['person']) ? new Money($fees['person'] * 100, $currency) : $parentFees?->person,
+			person: isset($fees['person']) ? new Money($fees['person'] * 100, $currency) : null,
+		);
+	}
+
+	/**
+	 * @param array<mixed> $fees
+	 */
+	public static function from(string $context, array $fees, self $parentFees): self {
+		$currency = isset($fees['currency']) ? new Currency(Helpers::ensureNonEmptyString("$context.fees.currency", $fees['currency'])) : $parentFees->currency;
+
+		return new self(
+			currency: $currency,
+			person: isset($fees['person']) ? new Money($fees['person'] * 100, $currency) : $parentFees->person,
 		);
 	}
 }

app/Model/Configuration/Helpers.php

@@ -141,6 +141,21 @@ public static function ensureIntMaybe(string $context, mixed $value): ?int {
 		return $value;
 	}
 
+	/**
+	 * @return non-empty-string
+	 */
+	public static function ensureNonEmptyString(string $context, mixed $value): string {
+		if (!\is_string($value)) {
+			throw new InvalidConfigurationException("Expected string for {$context}.");
+		}
+
+		if ($value === '') {
+			throw new InvalidConfigurationException("Expected non-empty string for {$context}.");
+		}
+
+		return $value;
+	}
+
 	public static function ensureStringMaybe(string $context, mixed $value): ?string {
 		if ($value === null) {
 			return $value;

tests/Model/Configuration/BasicReadTest.phpt

@@ -115,6 +115,31 @@ class BasicReadTest extends TestCase {
 		Assert::equal(new Money(20_00, new Currency('CZK')), $entries->categories->allCategories['inherited']->fees->person);
 	}
 
+	public function testFlatCategoriesFeesWithCurrency(): void {
+		$entries = Entries::from([
+			'eventDate' => new DateTimeImmutable('2050-12-07'),
+			'fees' => [
+				'person' => 20,
+				'currency' => 'GBP',
+			],
+			'categories' => [
+				'overridden' => [
+					'fees' => [
+						'currency' => 'USD',
+						'person' => 10,
+					],
+				],
+				'inherited' => [
+					'fees' => [
+						'person' => 30,
+					],
+				],
+			],
+		]);
+		Assert::equal(new Money(10_00, new Currency('USD')), $entries->categories->allCategories['overridden']->fees->person);
+		Assert::equal(new Money(30_00, new Currency('GBP')), $entries->categories->allCategories['inherited']->fees->person);
+	}
+
 	public function testNestedCategoriesFees(): void {
 		$entries = Entries::from([
 			'eventDate' => new DateTimeImmutable('2050-12-07'),