<?php
require_once __DIR__ . '/db.php';

session_start();

function formatCurrency(float $amount): string {
    return '$' . number_format($amount, 2);
}

function generateToken(): string {
    return bin2hex(random_bytes(20));
}

/**
 * Work weeks run Friday-Thursday (Sat/Sun excluded entirely, not tracked).
 * Returns the Friday date (Y-m-d) that the given date's work week belongs to.
 */
function getWeekStart(string $dateStr): string {
    $d = new DateTime($dateStr);
    $dow = (int) $d->format('N'); // 1=Mon ... 5=Fri, 6=Sat, 7=Sun
    if ($dow === 5) {
        // Friday itself
        return $d->format('Y-m-d');
    } elseif ($dow === 6) {
        // Saturday - previous day is Friday
        $d->modify('-1 day');
        return $d->format('Y-m-d');
    } elseif ($dow === 7) {
        // Sunday - 2 days back is Friday
        $d->modify('-2 days');
        return $d->format('Y-m-d');
    } else {
        // Mon(1)->Fri is 3 days prior; Tue(2)->4; Wed(3)->5; Thu(4)->6
        $daysBack = $dow + 2;
        $d->modify("-{$daysBack} days");
        return $d->format('Y-m-d');
    }
}

/**
 * Returns the 5 workdate strings (Y-m-d) for the week starting on $weekStart (a Friday),
 * in order: Friday, Monday, Tuesday, Wednesday, Thursday.
 */
function getWeekDates(string $weekStart): array {
    $fri = new DateTime($weekStart);
    $dates = [$fri->format('Y-m-d')];
    $d = clone $fri;
    $d->modify('+3 days'); // Monday
    for ($i = 0; $i < 4; $i++) {
        $dates[] = $d->format('Y-m-d');
        $d->modify('+1 day');
    }
    return $dates;
}

function dayLabel(string $dateStr): string {
    $d = new DateTime($dateStr);
    return $d->format('D, M j');
}

function currentWeekStart(): string {
    return getWeekStart(date('Y-m-d'));
}

function nextWeekStart(string $weekStart): string {
    $d = new DateTime($weekStart);
    $d->modify('+7 days');
    return $d->format('Y-m-d');
}

/**
 * Compute the dollar amount owed for a set of day_entries rows.
 */
function calcOwed(array $entries): float {
    $total = 0.0;
    foreach ($entries as $e) {
        if ($e['status'] === 'full') $total += FULL_DAY_RATE;
        elseif ($e['status'] === 'half') $total += HALF_DAY_RATE;
    }
    return $total;
}

function e(string $s): string {
    return htmlspecialchars($s, ENT_QUOTES, 'UTF-8');
}

/**
 * Validates a Y-m-d date string strictly (rejects malformed input that
 * would otherwise throw when passed to `new DateTime()`).
 */
function isValidDateStr(?string $s): bool {
    if (!$s) return false;
    $d = DateTime::createFromFormat('Y-m-d', $s);
    return $d !== false && $d->format('Y-m-d') === $s;
}