Add Expenses app

A UI based on [Budget Zen](https://github.com/BrunoBernardino/budgetzen-web) but slightly updated and adjusted for bewCloud. It also features a chart with available money and spent by budgets.

This is useful for envelope-based budgeting.

routes/api/expenses/add-budget.tsx

@@ -0,0 +1,57 @@
+import { Handlers } from 'fresh/server.ts';
+
+import { Budget, FreshContextState } from '/lib/types.ts';
+import { createBudget, getBudgets } from '/lib/data/expenses.ts';
+
+interface Data {}
+
+export interface RequestBody {
+  name: string;
+  month: string;
+  value: number;
+  currentMonth: string;
+}
+
+export interface ResponseBody {
+  success: boolean;
+  newBudgets: Budget[];
+}
+
+export const handler: Handlers<Data, FreshContextState> = {
+  async POST(request, context) {
+    if (!context.state.user) {
+      return new Response('Unauthorized', { status: 401 });
+    }
+
+    const requestBody = await request.clone().json() as RequestBody;
+
+    if (
+      !requestBody.name || !requestBody.month || !requestBody.month.match(/^\d{4}-\d{2}$/) || !requestBody.value ||
+      Number.isNaN(requestBody.value) || !requestBody.currentMonth || !requestBody.currentMonth.match(/^\d{4}-\d{2}$/)
+    ) {
+      return new Response('Bad request', { status: 400 });
+    }
+
+    try {
+      const newBudget = await createBudget(
+        context.state.user.id,
+        requestBody.name,
+        requestBody.month,
+        requestBody.value,
+      );
+
+      if (!newBudget) {
+        throw new Error('Failed to add budget!');
+      }
+    } catch (error) {
+      console.error(error);
+      return new Response(`${error}`, { status: 500 });
+    }
+
+    const newBudgets = await getBudgets(context.state.user.id, requestBody.currentMonth);
+
+    const responseBody: ResponseBody = { success: true, newBudgets };
+
+    return new Response(JSON.stringify(responseBody));
+  },
+};