From db3425ec96a0f8f72a9aefe55e26a452d4d79895 Mon Sep 17 00:00:00 2001
From: Josh Creek <8179928+jcreek@users.noreply.github.com>
Date: Tue, 8 Oct 2024 19:39:28 +0100
Subject: [PATCH 1/2] feat(#37): Enable tracking credits usage with proof of
 concept test page

---
 src/lib/types/supabase.d.ts                   |  58 +++++++++
 src/lib/utils/supabase/admin.ts               | 116 +++++++++++++++++-
 src/routes/test/test-credits/+page.server.ts  |  18 +++
 src/routes/test/test-credits/+page.svelte     |  93 ++++++++++++++
 src/routes/test/test-credits/+server.ts       |  29 +++++
 .../migrations/20240929120431_add_credits.sql |  35 ++++++
 6 files changed, 348 insertions(+), 1 deletion(-)
 create mode 100644 src/routes/test/test-credits/+page.server.ts
 create mode 100644 src/routes/test/test-credits/+page.svelte
 create mode 100644 src/routes/test/test-credits/+server.ts
 create mode 100644 supabase/migrations/20240929120431_add_credits.sql

diff --git a/src/lib/types/supabase.d.ts b/src/lib/types/supabase.d.ts
index a79afeb..d774c18 100644
--- a/src/lib/types/supabase.d.ts
+++ b/src/lib/types/supabase.d.ts
@@ -34,6 +34,38 @@ export type Database = {
   }
   public: {
     Tables: {
+      credit_transactions: {
+        Row: {
+          created_at: string
+          credits_change: number
+          description: string | null
+          id: string
+          user_id: string
+        }
+        Insert: {
+          created_at?: string
+          credits_change: number
+          description?: string | null
+          id?: string
+          user_id: string
+        }
+        Update: {
+          created_at?: string
+          credits_change?: number
+          description?: string | null
+          id?: string
+          user_id?: string
+        }
+        Relationships: [
+          {
+            foreignKeyName: "credit_transactions_user_id_fkey"
+            columns: ["user_id"]
+            isOneToOne: false
+            referencedRelation: "users"
+            referencedColumns: ["id"]
+          },
+        ]
+      }
       customers: {
         Row: {
           id: string
@@ -268,6 +300,32 @@ export type Database = {
           },
         ]
       }
+      user_credits: {
+        Row: {
+          credits_remaining: number
+          last_updated: string
+          user_id: string
+        }
+        Insert: {
+          credits_remaining?: number
+          last_updated?: string
+          user_id: string
+        }
+        Update: {
+          credits_remaining?: number
+          last_updated?: string
+          user_id?: string
+        }
+        Relationships: [
+          {
+            foreignKeyName: "user_credits_user_id_fkey"
+            columns: ["user_id"]
+            isOneToOne: true
+            referencedRelation: "users"
+            referencedColumns: ["id"]
+          },
+        ]
+      }
       users: {
         Row: {
           id: string
diff --git a/src/lib/utils/supabase/admin.ts b/src/lib/utils/supabase/admin.ts
index 5dafd4f..563b9d2 100644
--- a/src/lib/utils/supabase/admin.ts
+++ b/src/lib/utils/supabase/admin.ts
@@ -298,6 +298,117 @@ const hasProductAccess = async (userId: string, productId: string) => {
 	return false;
 };
 
+const validateInput = (userId: string, credits: number, description: string) => {
+	if (!userId) throw new Error('User ID is required');
+	if (credits <= 0) throw new Error('Credits must be greater than zero');
+	if (!description) throw new Error('Description is required');
+};
+
+const logCreditTransaction = async (userId: string, creditsChange: number, description: string) => {
+	const { error } = await supabaseAdmin.from('credit_transactions').insert({
+		user_id: userId,
+		credits_change: creditsChange,
+		description,
+		created_at: new Date().toISOString()
+	});
+
+	if (error) {
+		throw new Error(`Error logging credit transaction: ${error.message}`);
+	}
+};
+
+const updateUserCredits = async (userId: string, creditsChange: number, description: string) => {
+	validateInput(userId, Math.abs(creditsChange), description);
+
+	const { data: creditData, error: fetchError } = await supabaseAdmin
+		.from('user_credits')
+		.select('credits_remaining, last_updated')
+		.eq('user_id', userId)
+		.single();
+
+	if (fetchError) {
+		throw new Error(`Error fetching credits: ${fetchError.message}`);
+	}
+
+	const newCreditTotal = (creditData?.credits_remaining || 0) + creditsChange;
+
+	if (newCreditTotal < 0) {
+		throw new Error('Insufficient credits');
+	}
+
+	const { error: upsertError } = await supabaseAdmin
+		.from('user_credits')
+		.upsert(
+			{
+				user_id: userId,
+				credits_remaining: newCreditTotal,
+				last_updated: new Date().toISOString()
+			},
+			{
+				onConflict: 'user_id'
+			}
+		)
+		.eq('last_updated', creditData?.last_updated); // Optimistic concurrency control
+
+	if (upsertError) {
+		throw new Error(`Error updating credits: ${upsertError.message}`);
+	}
+
+	await logCreditTransaction(userId, creditsChange, description);
+
+	console.log(
+		`${creditsChange > 0 ? 'Added' : 'Deducted'} ${Math.abs(creditsChange)} credits to user [${userId}]`
+	);
+};
+
+const addCredits = async (userId: string, creditsToAdd: number, description: string) => {
+	try {
+		await updateUserCredits(userId, creditsToAdd, description);
+	} catch (error) {
+		console.error(error);
+	}
+};
+
+const deductCredits = async (userId: string, creditsToDeduct: number, description: string) => {
+	try {
+		await updateUserCredits(userId, -creditsToDeduct, description);
+	} catch (error) {
+		console.error(error);
+	}
+};
+
+const getUserCredits = async (userId: string) => {
+	if (!userId) throw new Error('User ID is required');
+
+	// Fetch the user's credits from the user_credits table
+	const { data: creditData, error } = await supabaseAdmin
+		.from('user_credits')
+		.select('credits_remaining')
+		.eq('user_id', userId)
+		.single();
+
+	if (error && error.code !== 'PGRST116') {
+		// Code 'PGRST116' represents no rows found
+		throw new Error(`Error fetching credits: ${error.message}`);
+	}
+
+	if (!creditData) {
+		// If no row exists in the user_credits table, insert a new row for the user
+		const { error: insertError } = await supabaseAdmin.from('user_credits').insert({
+			user_id: userId,
+			credits_remaining: 0
+		});
+
+		if (insertError) {
+			throw new Error(`Error creating user credits: ${insertError.message}`);
+		}
+
+		return 0;
+	}
+
+	return creditData.credits_remaining;
+};
+
 export {
 	upsertProductRecord,
 	upsertPriceRecord,
@@ -306,5 +417,8 @@ export {
 	createOrRetrieveCustomer,
 	manageSubscriptionStatusChange,
 	recordProductPurchase,
-	hasProductAccess
+	hasProductAccess,
+	addCredits,
+	deductCredits,
+	getUserCredits
 };
diff --git a/src/routes/test/test-credits/+page.server.ts b/src/routes/test/test-credits/+page.server.ts
new file mode 100644
index 0000000..3f79606
--- /dev/null
+++ b/src/routes/test/test-credits/+page.server.ts
@@ -0,0 +1,18 @@
+import { redirect } from '@sveltejs/kit';
+import type { PageServerLoad } from './$types';
+
+export const load: PageServerLoad = async ({ locals: { supabase, safeGetSession } }) => {
+	const { session } = await safeGetSession();
+
+	if (!session) {
+		redirect(303, '/');
+	}
+
+	const { data: user } = await supabase
+		.from('users')
+		.select(`name, id`)
+		.eq('id', session.user.id)
+		.single();
+
+	return { session, user };
+};
diff --git a/src/routes/test/test-credits/+page.svelte b/src/routes/test/test-credits/+page.svelte
new file mode 100644
index 0000000..c4363a1
--- /dev/null
+++ b/src/routes/test/test-credits/+page.svelte
@@ -0,0 +1,93 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import { writable } from 'svelte/store';
+
+	export let data;
+
+	let { session, supabase, user } = data;
+	$: ({ session, supabase, user } = data);
+
+	const credits = writable<number>(0);
+	let errorMessage: string = '';
+
+	onMount(async () => {
+		try {
+			const pageUserId = user?.id;
+			if (pageUserId) {
+				const response = await fetch('/test/test-credits', {
+					method: 'POST',
+					headers: { 'Content-Type': 'application/json' },
+					body: JSON.stringify({ action: 'getUserCredits', userId: pageUserId })
+				});
+				if (!response.ok) throw new Error('Failed to fetch credits');
+				const { credits: fetchedCredits } = await response.json();
+				credits.set(fetchedCredits);
+			}
+		} catch (error) {
+			errorMessage = error.message;
+		}
+	});
+
+	const addCredits = async () => {
+		try {
+			const response = await fetch('/test/test-credits', {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify({
+					action: 'addCredits',
+					userId: user?.id,
+					credits: 10,
+					description: 'Test add credits'
+				})
+			});
+			if (!response.ok) throw new Error('Failed to add credits');
+			const { credits: updatedCredits } = await response.json();
+			credits.set(updatedCredits);
+		} catch (error) {
+			errorMessage = error.message;
+		}
+	};
+
+	const deductCredits = async () => {
+		try {
+			const response = await fetch('/test/test-credits', {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify({
+					action: 'deductCredits',
+					userId: user?.id,
+					credits: 5,
+					description: 'Test deduct credits'
+				})
+			});
+			if (!response.ok) throw new Error('Failed to deduct credits');
+			const { credits: updatedCredits } = await response.json();
+			credits.set(updatedCredits);
+		} catch (error) {
+			errorMessage = error.message;
+		}
+	};
+</script>
+
+<main>
+	<h1>Credits Management for User: {user?.id}</h1>
+	<p>Credits Remaining: {$credits}</p>
+	{#if errorMessage}
+		<p style="color: red;">{errorMessage}</p>
+	{/if}
+
+	<button on:click={addCredits}>Add 10 Credits</button>
+	<button on:click={deductCredits}>Deduct 5 Credits</button>
+</main>
+
+<style>
+	main {
+		text-align: center;
+		padding: 2rem;
+	}
+	button {
+		margin: 0.5rem;
+		padding: 0.5rem 1rem;
+		cursor: pointer;
+	}
+</style>
diff --git a/src/routes/test/test-credits/+server.ts b/src/routes/test/test-credits/+server.ts
new file mode 100644
index 0000000..5949f67
--- /dev/null
+++ b/src/routes/test/test-credits/+server.ts
@@ -0,0 +1,29 @@
+import { json } from '@sveltejs/kit';
+import { addCredits, deductCredits, getUserCredits } from '$lib/utils/supabase/admin';
+
+export const POST = async ({ request }) => {
+	const { action, userId, credits, description } = await request.json();
+
+	if (!userId) {
+		return json({ success: false, error: 'User ID is required' }, { status: 400 });
+	}
+
+	try {
+		if (action === 'addCredits') {
+			await addCredits(userId, credits, description);
+			const updatedCredits = await getUserCredits(userId);
+			return json({ success: true, credits: updatedCredits });
+		} else if (action === 'deductCredits') {
+			await deductCredits(userId, credits, description);
+			const updatedCredits = await getUserCredits(userId);
+			return json({ success: true, credits: updatedCredits });
+		} else if (action === 'getUserCredits') {
+			const fetchedCredits = await getUserCredits(userId);
+			return json({ success: true, credits: fetchedCredits });
+		} else {
+			return json({ success: false, error: 'Invalid action' }, { status: 400 });
+		}
+	} catch (error) {
+		return json({ success: false, error: error.message }, { status: 500 });
+	}
+};
diff --git a/supabase/migrations/20240929120431_add_credits.sql b/supabase/migrations/20240929120431_add_credits.sql
new file mode 100644
index 0000000..44680d4
--- /dev/null
+++ b/supabase/migrations/20240929120431_add_credits.sql
@@ -0,0 +1,35 @@
+create table user_credits (
+  user_id uuid references auth.users not null primary key,
+  credits_remaining integer not null default 0,
+  last_updated timestamp with time zone not null default now()
+);
+
+alter table user_credits enable row level security;
+
+create policy "Can view own credits." on user_credits
+  for select using (auth.uid() = user_id);
+
+-- Uncomment and modify the update policy if allowing users to modify their own credits
+-- create policy "Can update own credits." on user_credits
+--   for update using (auth.uid() = user_id);
+
+create table credit_transactions (
+  id uuid default uuid_generate_v4() primary key,
+  user_id uuid references auth.users not null,
+  credits_change integer not null,
+  description text,
+  created_at timestamp with time zone not null default now()
+);
+
+alter table credit_transactions enable row level security;
+
+create policy "Can view own transactions." on credit_transactions
+  for select using (auth.uid() = user_id);
+
+-- Adding indexing to improve query performance
+create index on user_credits (user_id);
+create index on credit_transactions (user_id);
+
+-- Adding a check constraint to enforce data integrity
+alter table credit_transactions
+add constraint check_credits_change_nonzero check (credits_change <> 0);

From 5d83c79b9737d1817251625a413d1fad79c3eb8b Mon Sep 17 00:00:00 2001
From: Josh Creek <8179928+jcreek@users.noreply.github.com>
Date: Tue, 8 Oct 2024 19:41:08 +0100
Subject: [PATCH 2/2] docs(#37): Add testing notes

---
 README.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/README.md b/README.md
index 62a8574..66416fb 100644
--- a/README.md
+++ b/README.md
@@ -55,3 +55,7 @@ Please see the Issues tab for `enhancement` tagged issues.
 ## [Database setup](/docs/database-setup.md)
 
 ## [Stripe webhook event listening](/docs/stripe-setup.md)
+
+## Testing the example credits management system
+
+There is an example system in this project for being able to manage credits that are sold to users. To test this system you can visit the `http://localhost:5173/test/test-credits` route. This will allow you to add credits to a user and then spend them by clicking the buttons on the page, and will show the user's credit balance updating in real time.