From d3250f2c5936ba7de128ef7a5592ae3c0757c74f Mon Sep 17 00:00:00 2001
From: Matthew Somerville <matthew@mysociety.org>
Date: Tue, 11 Jun 2024 17:20:25 +0100
Subject: [PATCH] Improve plan downgrade behaviour.

Use the new Subscription Schedules so that downgrade will only apply
from the next billing period.
---
 classes/Subscription.php                      | 93 ++++++++++++++-----
 .../html/api/subscription_detail.php          |  4 +
 2 files changed, 72 insertions(+), 25 deletions(-)

diff --git a/classes/Subscription.php b/classes/Subscription.php
index 8d428163da..e18b6c020b 100644
--- a/classes/Subscription.php
+++ b/classes/Subscription.php
@@ -12,6 +12,7 @@ class Subscription {
     public $has_payment_data = false;
 
     private static $plans = ['twfy-1k', 'twfy-5k', 'twfy-10k', 'twfy-0k'];
+    private static $prices = [2000, 5000, 10000, 30000];
 
     public function __construct($arg) {
         # User ID
@@ -62,6 +63,7 @@ public function __construct($arg) {
                     'customer.default_source',
                     'customer.invoice_settings.default_payment_method',
                     'latest_invoice.payment_intent',
+                    'schedule.phases.items.plan',
                 ],
             ]);
         } catch (\Stripe\Exception\InvalidRequestException $e) {
@@ -98,33 +100,74 @@ private function update_subscription($form_data) {
             $this->update_payment_method($form_data['payment_method']);
         }
 
-        # Update Stripe subscription
-        $args = [
-            'payment_behavior' => 'allow_incomplete',
-            'plan' => $form_data['plan'],
-            'metadata' => $form_data['metadata'],
-            'cancel_at_period_end' => false, # Needed in Stripe 2018-02-28
-        ];
-        if ($form_data['coupon']) {
-            $args['coupon'] = $form_data['coupon'];
-        } elseif ($this->stripe->discount) {
-            $args['coupon'] = '';
+        foreach ($this::$plans as $i => $plan) {
+            if ($plan == $form_data['plan']) {
+                $new_price = $this::$prices[$i];
+                if ($form_data['coupon'] == 'charitable100') {
+                    $new_price = 0;
+                } elseif ($form_data['coupon'] == 'charitable50') {
+                    $new_price /= 2;
+                }
+            }
+            if ($plan == $this->stripe->plan->id) {
+                $old_price = $this::$prices[$i];
+                if ($this->stripe->discount && ($coupon = $this->stripe->discount->coupon)) {
+                    if ($coupon->percent_off == 100) {
+                        $old_price = 0;
+                    } elseif ($coupon->percent_off == 50) {
+                        $old_price /= 2;
+                    }
+                }
+            }
         }
-        \Stripe\Subscription::update($this->stripe->id, $args);
 
-        # Attempt immediate payment on the upgrade
-        try {
-            $invoice = \Stripe\Invoice::create([
-                'customer' => $this->stripe->customer,
-                'subscription' => $this->stripe,
-                'tax_rates': [STRIPE_TAX_RATE],
-            ]);
-            $invoice->finalizeInvoice();
-            $invoice->pay();
-        } catch (\Stripe\Exception\InvalidRequestException $e) {
-            # No invoice created if nothing to pay
-        } catch (\Stripe\Exception\CardException $e) {
-            # A source may still require 3DS... Stripe will have sent an email :-/
+       if ($old_price >= $new_price) {
+            if ($this->stripe->schedule) {
+                \Stripe\SubscriptionSchedule::release($this->stripe->schedule);
+            }
+            $schedule = \Stripe\SubscriptionSchedule::create(['from_subscription' => $this->stripe->id]);
+            $phases = [
+                {
+                    'items' => [['price' => $schedule->phases[0]->items[0]->price]],
+                    'start_date' => $schedule->phases[0]->start_date,
+                    'end_date' => $schedule->phases[0]->end_date,
+                    'proration_behavior' => 'none',
+                    'default_tax_rates' => [STRIPE_TAX_RATE],
+                },
+                {
+                    'items' => [['price' => $form_data['plan']]],
+                    'iterations' => 1,
+                    'metadata' => $form_data['metadata'],
+                    'proration_behavior' => 'none',
+                    'default_tax_rates' => [STRIPE_TAX_RATE],
+                },
+            ];
+            if ($schedule->phases[0]->discounts && $schedule->phases[0]->discounts[0]->coupon) {
+                $phases[0]['discounts'] = [['coupon' => $schedule->phases[0]->discounts[0]->coupon]];
+            }
+            if ($form_data['coupon']) {
+                $phases[1]['coupon'] = $form_data['coupon'];
+            }
+            \Stripe\SubscriptionSchedule::update($schedule->id, ['phases' => $phases]);
+        }
+
+        if ($old_price < $new_price) {
+            $args = [
+                'payment_behavior' => 'allow_incomplete',
+                'plan' => $form_data['plan'],
+                'metadata' => $form_data['metadata'],
+                'cancel_at_period_end' => false, # Needed in Stripe 2018-02-28
+                'proration_behavior': 'always_invoice',
+            ];
+            if ($form_data['coupon']) {
+                $args['coupon'] = $form_data['coupon'];
+            } elseif ($this->stripe->discount) {
+                $args['coupon'] = '';
+            }
+            if ($this->stripe->schedule) {
+                stripe.SubscriptionSchedule.release(self.object.schedule)
+            }
+            \Stripe\Subscription::update($this->stripe->id, $args);
         }
     }
 
diff --git a/www/includes/easyparliament/templates/html/api/subscription_detail.php b/www/includes/easyparliament/templates/html/api/subscription_detail.php
index bdbe9e22be..a0f0faf22f 100644
--- a/www/includes/easyparliament/templates/html/api/subscription_detail.php
+++ b/www/includes/easyparliament/templates/html/api/subscription_detail.php
@@ -40,6 +40,10 @@
             <?php } ?>
             </p>
 
+            <?php if ($subscription->stripe->schedule->phases[1] && $subscription->stripe->schedule->phases[1]->items[0]->plan->nickname != $subscription->stripe->plan->nickname ?>
+                 <p>You are switching to <strong><?php $subscription->stripe->schedule->phases[1]->items[0]->plan->nickname ?></strong> at the end of your current period.</p>
+            <?php } ?>
+
             <?php if ($subscription->stripe->discount && $subscription->stripe->discount->end) { ?>
                 <p>Your discount will expire on <?= $subscription->stripe->discount->end ?>.</p>
             <?php } ?>