<?php

declare(strict_types=1);

namespace App\Form\ParticipantFieldHandler\Condition;

use App\Form\Model\BookingDtoInterface;

/**
 * Condition that evaluates participant age against specified range criteria.
 *
 * This condition checks if a participant's age (calculated from their date of birth)
 * falls within, outside, or meets specific age criteria. It's commonly used to
 * enable/disable fields based on age restrictions for services, legal requirements,
 * or business rules.
 *
 * Age Calculation:
 * - Uses participant's dateOfBirth property to calculate current age
 * - Handles null dates gracefully (condition fails if no birth date)
 * - Age is calculated as of today's date when condition is evaluated
 *
 * Range Types:
 * - Minimum age: participant must be at least X years old
 * - Maximum age: participant must be under X years old
 * - Age range: participant must be between X and Y years old
 * - Exact age: participant must be exactly X years old
 */
class AgeRangeCondition implements FieldConditionInterface
{
    /**
     * Creates a new age range condition.
     *
     * @param int|null $minAge Minimum required age (inclusive), null for no minimum
     * @param int|null $maxAge Maximum allowed age (inclusive), null for no maximum
     */
    public function __construct(
        private readonly ?int $minAge = null,
        private readonly ?int $maxAge = null,
    ) {
        if (null === $minAge && null === $maxAge) {
            throw new \InvalidArgumentException('At least one of minAge or maxAge must be specified');
        }

        if (null !== $minAge && null !== $maxAge && $minAge > $maxAge) {
            throw new \InvalidArgumentException('Minimum age cannot be greater than maximum age');
        }
    }

    /**
     * Evaluates if the participant's age meets the specified criteria.
     *
     * Calculates the participant's current age from their date of birth and
     * checks if it falls within the configured age range. Returns false if
     * the participant has no date of birth set.
     *
     * @param BookingDtoInterface  $bookingDto       The current booking data (create or edit)
     * @param int                  $participantIndex The index of the participant being evaluated
     * @param array<string, mixed> $formData         Current form data (unused for age conditions)
     *
     * @return bool True if the participant's age meets the criteria, false otherwise
     */
    public function evaluate(BookingDtoInterface $bookingDto, int $participantIndex, array $formData): bool
    {
        $participant = $bookingDto->getParticipant($participantIndex);

        if (null === $participant || null === $participant->dateOfBirth) {
            return false;
        }

        $age = $this->calculateAge($participant->dateOfBirth);

        // Check minimum age requirement
        if (null !== $this->minAge && $age < $this->minAge) {
            return false;
        }

        // Check maximum age requirement
        if (null !== $this->maxAge && $age > $this->maxAge) {
            return false;
        }

        return true;
    }

    /**
     * Returns field names that affect age calculation.
     *
     * The age condition depends on the participant's date of birth field.
     * When this field changes, any conditions based on age should be re-evaluated.
     *
     * @return string[] Array containing 'dateOfBirth' field name
     */
    public function getDependentFields(): array
    {
        return ['dateOfBirth'];
    }

    /**
     * Returns a human-readable description of the age criteria.
     *
     * Generates a descriptive string explaining the age requirements,
     * useful for debugging and understanding condition logic.
     *
     * @return string Description of the age range criteria
     */
    public function getDescription(): string
    {
        if (null !== $this->minAge && null !== $this->maxAge) {
            if ($this->minAge === $this->maxAge) {
                return sprintf('Participant must be exactly %d years old', $this->minAge);
            }

            return sprintf('Participant must be between %d and %d years old', $this->minAge, $this->maxAge);
        }

        if (null !== $this->minAge) {
            return sprintf('Participant must be at least %d years old', $this->minAge);
        }

        return sprintf('Participant must be under %d years old', $this->maxAge + 1);
    }

    /**
     * Calculates age in years from a date of birth.
     *
     * Uses DateTimeImmutable to ensure immutable date calculations and
     * handles the calculation accurately accounting for leap years and
     * exact birth date anniversaries.
     *
     * @param \DateTimeImmutable $dateOfBirth The participant's date of birth
     *
     * @return int The calculated age in complete years
     */
    private function calculateAge(\DateTimeImmutable $dateOfBirth): int
    {
        $today = new \DateTimeImmutable();

        return (int) $dateOfBirth->diff($today)->y;
    }
}