<?php

namespace ChargeForms\Includes;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Gateway-agnostic "what does this form's total add up to" — extracted out
 * of Stripe_Gateway when PayPal became a second gateway, since this is the
 * anti-tampering authority BOTH gateways depend on (RestApi's order/intent
 * creation and SubmissionHandler::verify_payment()'s post-payment check both
 * need to recompute the exact same number from the form's own stored field
 * config, independent of which processor actually took the payment). There
 * must be exactly one implementation of this, not one per gateway.
 */
class Commerce_Calculator {

	/**
	 * Recomputes a form's total from its OWN stored field config. The only
	 * part a submitter can influence is a Custom Amount field's value (a
	 * donation-style amount is supposed to be visitor-chosen, floored at the
	 * field's configured minimum) — a Payment Item's price always comes from
	 * the form's saved configuration, never from the request. That split is
	 * what stops a tampered client from paying less than a fixed-price item
	 * actually costs.
	 */
	public static function calculate_total( array $form, array $submitted_values ) {
		$summary = self::calculate_commerce_summary( $form['fields'] ?? [], $submitted_values );
		return round( $summary['total'], 2 );
	}

	public static function calculate_commerce_summary( array $fields, array $submitted_values ) {
		$subtotal  = 0.0;
		$shipping  = 0.0;
		$tax_rates = [];
		$discounts = [];

		foreach ( $fields as $field ) {
			if ( ! empty( $field['children'] ) && is_array( $field['children'] ) ) {
				$child_summary = self::calculate_commerce_summary( $field['children'], $submitted_values );
				$subtotal += $child_summary['subtotal'];
				$shipping += $child_summary['shipping'];
				$tax_rates = array_merge( $tax_rates, $child_summary['tax_rates'] );
				$discounts = array_merge( $discounts, $child_summary['discounts'] );
				continue;
			}

			$type = $field['type'] ?? '';
			if ( 'payment_item' === $type ) {
				$subtotal += (float) ( $field['amount'] ?? 0 );
			} elseif ( 'custom_amount' === $type ) {
				$min       = (float) ( $field['minAmount'] ?? 0 );
				$submitted = (float) ( $submitted_values[ $field['id'] ] ?? 0 );
				$subtotal += max( $min, $submitted );
			} elseif ( 'product' === $type || 'price' === $type ) {
				$subtotal += (float) ( $field['price'] ?? 0 );
			} elseif ( 'quantity' === $type ) {
				$qty = (float) ( $submitted_values[ $field['id'] ] ?? ( $field['default'] ?? ( $field['min'] ?? 0 ) ) );
				$min = isset( $field['min'] ) ? (float) $field['min'] : null;
				$max = isset( $field['max'] ) ? (float) $field['max'] : null;
				if ( null !== $min ) {
					$qty = max( $min, $qty );
				}
				if ( null !== $max ) {
					$qty = min( $max, $qty );
				}
				$subtotal += $qty * (float) ( $field['unitPrice'] ?? 0 );
			} elseif ( 'shipping' === $type ) {
				$chosen = (string) ( $submitted_values[ $field['id'] ] ?? '' );
				foreach ( $field['shippingOptions'] ?? [] as $option ) {
					if ( $chosen === (string) ( $option['label'] ?? '' ) ) {
						$shipping += (float) ( $option['cost'] ?? 0 );
						break;
					}
				}
			} elseif ( 'tax' === $type ) {
				$tax_rates[] = (float) ( $field['rate'] ?? 0 );
			} elseif ( 'discount' === $type ) {
				$discounts[] = [
					'type'  => $field['discountType'] ?? 'fixed',
					'value' => (float) ( $field['discountValue'] ?? 0 ),
				];
			}
		}

		$tax_total = 0.0;
		foreach ( $tax_rates as $rate ) {
			$tax_total += $subtotal * ( $rate / 100 );
		}

		$discount_total = 0.0;
		foreach ( $discounts as $discount ) {
			$discount_total += 'percent' === $discount['type'] ? $subtotal * ( $discount['value'] / 100 ) : $discount['value'];
		}

		return [
			'subtotal'  => $subtotal,
			'shipping'  => $shipping,
			'tax_rates' => $tax_rates,
			'discounts' => $discounts,
			'total'     => max( 0, $subtotal + $shipping + $tax_total - $discount_total ),
		];
	}

	/**
	 * The one place that walks a form's field tree looking for its Payment
	 * Method field — shared by RestApi::create_subscription() (needs the
	 * field's billingType/billingInterval/trialDays config before starting
	 * a subscription) and SubmissionHandler (needs the same config to know
	 * which verify_*() path to take). Recursive, unlike the private,
	 * top-level-only version SubmissionHandler had before this — a Payment
	 * Method field nested inside a Section/Row/Column previously would
	 * silently never be found by that check; this fixes that as a side
	 * effect of not duplicating the walk a second time, not as a separate
	 * change. Returns the first payment_method field found, or null.
	 */
	public static function find_payment_method_field( array $fields ) {
		foreach ( $fields as $field ) {
			if ( 'payment_method' === ( $field['type'] ?? '' ) ) {
				return $field;
			}
			if ( ! empty( $field['children'] ) && is_array( $field['children'] ) ) {
				$found = self::find_payment_method_field( $field['children'] );
				if ( $found ) {
					return $found;
				}
			}
		}
		return null;
	}
}