<?php

/**
 * Server-side rules shared by the documents that carry priced lines: sales
 * orders, purchase orders, quotations and purchase requests.
 *
 * The pages enforce the same limits, but only in JavaScript, so a request sent
 * straight to the engine could store a 150% tax rate, a negative price or a
 * line total that does not match quantity × price. Everything here throws a
 * plain Exception, which the engines already report back as the alert text.
 */
class DocumentValidator
{
    const MAX_TAX_RATE   = 100;
    // Far above any real unit price, low enough to stop a slipped keystroke
    // (or a crafted request) from booking billions.
    const MAX_UNIT_PRICE = 999999999.99;
    const MAX_QUANTITY   = 999999999.9999;
    const MIN_QUANTITY   = 0.0001;

    /**
     * Validate the lines and return them with total_price and tax_amount
     * recomputed, using the same formula as the pages:
     *   total = quantity × unit_price, tax = total × tax_rate / 100 (4 dp).
     */
    public static function normaliseLines(array $items, string $doc_label = 'Document'): array
    {
        $out = [];
        foreach (array_values($items) as $i => $item) {
            if (!is_array($item)) {
                throw new Exception("{$doc_label} line #" . ($i + 1) . " is not valid.");
            }
            $name  = trim((string)($item['product_name'] ?? '')) ?: trim((string)($item['product_sku'] ?? ''));
            $label = 'Line #' . ($i + 1) . ($name !== '' ? " ({$name})" : '');

            $qty   = self::number($item['quantity'] ?? 0, "{$label}: quantity");
            $price = self::number($item['unit_price'] ?? $item['price'] ?? 0, "{$label}: unit price");
            $rate  = self::number($item['tax_rate'] ?? 0, "{$label}: tax rate");

            $qty = round($qty, 4);
            if ($qty < self::MIN_QUANTITY) {
                throw new Exception("{$label}: quantity must be greater than zero.");
            }
            if ($qty > self::MAX_QUANTITY) {
                throw new Exception("{$label}: quantity is too large.");
            }
            if ($price < 0) {
                throw new Exception("{$label}: unit price cannot be negative.");
            }
            if ($price > self::MAX_UNIT_PRICE) {
                throw new Exception("{$label}: unit price cannot exceed " . number_format(self::MAX_UNIT_PRICE, 2) . ".");
            }
            if ($rate < 0 || $rate > self::MAX_TAX_RATE) {
                throw new Exception("{$label}: tax rate must be between 0 and " . self::MAX_TAX_RATE . "%.");
            }

            $total = round($qty * $price, 4);
            $item['quantity']    = $qty;
            $item['unit_price']  = round($price, 4);
            $item['tax_rate']    = round($rate, 2);
            $item['total_price'] = $total;
            $item['tax_amount']  = round($total * $item['tax_rate'] / 100, 4);
            $out[] = $item;
        }
        return $out;
    }

    /** Header amounts (discount, shipping fee): numeric and never negative. */
    public static function amount($value, string $label): float
    {
        $n = self::number($value, $label);
        if ($n < 0) {
            throw new Exception("{$label} cannot be negative.");
        }
        if ($n > self::MAX_UNIT_PRICE * 1000) {
            throw new Exception("{$label} is too large.");
        }
        return $n;
    }

    /** A discount larger than the goods would turn the document negative. */
    public static function discount($value, float $subtotal): float
    {
        $discount = self::amount($value, 'Discount');
        if ($discount > $subtotal + 0.00005) {
            throw new Exception('Discount cannot exceed the subtotal.');
        }
        return $discount;
    }

    public static function requireId($value, string $message): int
    {
        $id = (int)$value;
        if ($id <= 0) {
            throw new Exception($message);
        }
        return $id;
    }

    /**
     * A department is mandatory once the company uses departments. A company
     * that has never defined one keeps saving with "No Department".
     */
    public static function requireDepartment(PDO $pdo, int $company_id, $value): int
    {
        $id = (int)$value;
        if ($id > 0) {
            $sth = $pdo->prepare("SELECT COUNT(*) FROM md_department WHERE company_id = :cid AND id = :id");
            $sth->execute([':cid' => $company_id, ':id' => $id]);
            if ((int)$sth->fetchColumn() === 0) {
                throw new Exception('The selected department does not exist.');
            }
            return $id;
        }
        $sth = $pdo->prepare("SELECT COUNT(*) FROM md_department WHERE company_id = :cid AND status = 1");
        $sth->execute([':cid' => $company_id]);
        if ((int)$sth->fetchColumn() > 0) {
            throw new Exception('Department is required.');
        }
        return 0;
    }

    private static function number($value, string $label): float
    {
        if ($value === '' || $value === null) return 0.0;
        if (!is_numeric($value) || !is_finite((float)$value)) {
            throw new Exception("{$label} must be a number.");
        }
        return (float)$value;
    }
}