<?php

namespace App\Models;

use InvalidArgumentException;

/**
 * PHP port of app/Controllers/financial_aid_formula.py
 */
class FinancialAidEstimateModel
{
    private const FEDERAL_POVERTY_BASE = 15960.0;
    private const FEDERAL_POVERTY_STEP = 5680.0;
    private const MASSACHUSETTS_COST_FACTOR = 1.05757;
    private const PROTECTED_INCOME_MULTIPLIER = 2.0;
    private const DISCRETIONARY_CONTRIBUTION_RATE = 0.10;

    public function estimatedAid(float $totalBalance, int $householdSize, float $householdIncome): float
    {
        if ($householdSize < 1) {
            throw new InvalidArgumentException('household_size must be at least 1');
        }
        if ($totalBalance < 0 || $householdIncome < 0) {
            throw new InvalidArgumentException('balance and income cannot be negative');
        }

        $federalPovertyLevel = self::FEDERAL_POVERTY_BASE + (self::FEDERAL_POVERTY_STEP * ($householdSize - 1));
        $adjustedNeedThreshold = $federalPovertyLevel * self::MASSACHUSETTS_COST_FACTOR;
        $protectedIncome = self::PROTECTED_INCOME_MULTIPLIER * $adjustedNeedThreshold;
        $discretionaryIncome = max(0.0, $householdIncome - $protectedIncome);
        $expectedContribution = self::DISCRETIONARY_CONTRIBUTION_RATE * $discretionaryIncome;
        $estimated = $totalBalance - $expectedContribution;

        return round(max(0.0, min($totalBalance, $estimated)), 2);
    }

    public function finalRebate(
        float $totalBalance,
        int $householdSize,
        float $householdIncome,
        float $amountRequested
    ): float {
        if ($amountRequested < 0) {
            throw new InvalidArgumentException('amount_requested cannot be negative');
        }

        $estimated = $this->estimatedAid($totalBalance, $householdSize, $householdIncome);

        return min($estimated, $amountRequested, $totalBalance);
    }
}