Merge pull request #6 from acedanger/feature/1-add-api-endpoints

Feature/1 add api endpoints
2025-12-05 22:50:12 -08:00 · 2025-04-24 12:23:31 -04:00
parent 5fc02e1a9e e4b608fb0a
commit da35b7d994
26 changed files with 3889 additions and 103 deletions
--- a/.astro/content-assets.mjs
+++ b/.astro/content-assets.mjs
@@ -1 +0,0 @@
-export default new Map();
--- a/.astro/content-modules.mjs
+++ b/.astro/content-modules.mjs
@@ -1 +0,0 @@
-export default new Map();
--- a/.astro/data-store.json
+++ b/.astro/data-store.json
@@ -1 +0,0 @@
-[["Map",1,2],"meta::meta",["Map",3,4,5,6],"astro-version","5.7.5","astro-config-digest","{\"root\":{},\"srcDir\":{},\"publicDir\":{},\"outDir\":{},\"cacheDir\":{},\"compressHTML\":true,\"base\":\"/\",\"trailingSlash\":\"ignore\",\"output\":\"static\",\"scopedStyleStrategy\":\"attribute\",\"build\":{\"format\":\"directory\",\"client\":{},\"server\":{},\"assets\":\"_astro\",\"serverEntry\":\"entry.mjs\",\"redirects\":true,\"inlineStylesheets\":\"auto\",\"concurrency\":1},\"server\":{\"open\":false,\"host\":false,\"port\":4321,\"streaming\":true,\"allowedHosts\":[]},\"redirects\":{},\"image\":{\"endpoint\":{\"route\":\"/_image\"},\"service\":{\"entrypoint\":\"astro/assets/services/sharp\",\"config\":{}},\"domains\":[],\"remotePatterns\":[]},\"devToolbar\":{\"enabled\":true},\"markdown\":{\"syntaxHighlight\":{\"type\":\"shiki\",\"excludeLangs\":[\"math\"]},\"shikiConfig\":{\"langs\":[],\"langAlias\":{},\"theme\":\"github-dark\",\"themes\":{},\"wrap\":false,\"transformers\":[]},\"remarkPlugins\":[],\"rehypePlugins\":[],\"remarkRehype\":{},\"gfm\":true,\"smartypants\":true},\"security\":{\"checkOrigin\":true},\"env\":{\"schema\":{},\"validateSecrets\":false},\"experimental\":{\"clientPrerender\":false,\"contentIntellisense\":false,\"responsiveImages\":false,\"headingIdCompat\":false,\"preserveScriptOrder\":false},\"legacy\":{\"collections\":false}}"]
--- a/.astro/settings.json
+++ b/.astro/settings.json
@@ -1,5 +0,0 @@
-{
-	"_variables": {
-		"lastUpdateCheck": 1745454555490
-	}
-}
--- a/.astro/types.d.ts
+++ b/.astro/types.d.ts
@@ -1,2 +0,0 @@
-/// <reference types="astro/client" />
-/// <reference path="content.d.ts" />
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -9,7 +9,7 @@ This project is a web user interface (UI) for a CRUD (Create, Read, Update, Dele
 *   **Framework:** Astro (latest version)
 *   **Language:** TypeScript, JavaScript (client-side scripts), HTML, CSS
 *   **Styling:** Plain CSS (`src/styles/global.css`)
-*   **Data:** Currently using in-memory arrays. **The goal is to eventually integrate with a backend API.**
+*   **Data:** Using Astro's built-in API routes in `src/pages/api/` with a temporary in-memory store (`src/data/store.ts`). **The goal is to eventually replace the in-memory store with a persistent database.**

 ## Current State & Key Features

@@ -17,7 +17,18 @@ This project is a web user interface (UI) for a CRUD (Create, Read, Update, Dele
    *   **Sidebar:** (`src/components/Sidebar.astro`) Contains account selection dropdown and a collapsible section for adding new transactions. Includes an account summary section.
    *   **Main Content:** (`src/components/MainContent.astro`) Displays the header with the current account name and the transaction list.
 *   **Components:** Separate Astro components exist for major UI sections (Sidebar, MainContent, TransactionTable, AddTransactionForm, AccountSummary).
-*   **Data Loading:** Currently using empty arrays for accounts and transactions, initialized in `src/pages/index.astro`.
+*   **API Integration:** 
+    *   API routes structure implemented in `src/pages/api/`
+    *   Temporary data store in `src/data/store.ts`
+    *   All API endpoints implemented and ready to use:
+        *   GET /api/accounts - List all accounts
+        *   GET /api/accounts/:id - Get single account details
+        *   GET /api/accounts/:id/transactions - Get transactions for an account
+        *   POST /api/transactions - Create new transaction
+        *   PUT /api/transactions/:id - Update existing transaction
+        *   DELETE /api/transactions/:id - Delete transaction
+    *   Error handling and validation included
+    *   Prepared for future database integration with modular store design
 *   **Account Switching:** Selecting an account from the dropdown in the sidebar correctly updates the Main Content area (header, transaction table) and the Account Summary section using client-side JavaScript (`<script>` tag in `index.astro`).
 *   **Collapsible Form:** The "Add Transaction" section in the sidebar (`src/components/AddTransactionForm.astro`) can be expanded and collapsed using client-side JavaScript (`<script>` tag in `AddTransactionForm.astro`).
 *   **Basic Formatting:** Utility functions (`src/utils.ts`) exist for formatting currency and dates, used both server-side and client-side (mirrored in `index.astro` script).
@@ -26,8 +37,13 @@ This project is a web user interface (UI) for a CRUD (Create, Read, Update, Dele
 ## File Structure Overview

 *   `src/components/`: Reusable UI components.
+*   `src/data/`: Data store and persistence layer.
 *   `src/layouts/`: Base page layout(s).
-*   `src/pages/`: Astro pages (routes). `index.astro` is the main page.
+*   `src/pages/`: Astro pages and API routes.
+    *   `index.astro`: Main page
+    *   `api/`: Backend API endpoints
+        *   `accounts/`: Account-related endpoints
+        *   `transactions/`: Transaction-related endpoints
 *   `src/styles/`: Global CSS styles.
 *   `src/types.ts`: TypeScript type definitions.
 *   `src/utils.ts`: Utility functions (formatting, etc.).
@@ -35,10 +51,9 @@ This project is a web user interface (UI) for a CRUD (Create, Read, Update, Dele

 ## Next Steps & TODOs

-1.  **Backend API Integration:**
-    *   Define the expected API endpoints (e.g., `GET /api/accounts`, `GET /api/accounts/:id/transactions`, `POST /api/transactions`, `PUT /api/transactions/:id`, `DELETE /api/transactions/:id`).
-    *   Replace static JSON data fetching in `index.astro` with `fetch` calls to the backend API during server-side rendering (or potentially client-side, depending on strategy).
-    *   Update client-side logic to interact with the API for CRUD operations.
+1.  **Complete API Implementation:**
+    *   Add error handling and validation
+    *   Prepare for future database integration
 2.  **Implement Create Functionality:**
    *   Add client-side JavaScript to the `AddTransactionForm.astro` component (or enhance the script in `index.astro`) to handle form submission.
    *   Prevent default form submission.
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 # build output
 dist/
 .output/
+.astro/

 # dependencies
 node_modules/
@@ -23,3 +24,6 @@ pnpm-debug.log*
 .vscode/
 *.swp
 *.swo
+
+# Test coverage
+coverage/
--- a/astro.config.mjs
+++ b/astro.config.mjs
@@ -1,5 +1,7 @@
 // @ts-check
-import { defineConfig } from 'astro/config';
+import { defineConfig } from "astro/config";

 // https://astro.build/config
-export default defineConfig({});
+export default defineConfig({
+  output: "server",
+});
--- a/package-lock.json
+++ b/package-lock.json
--- a/package.json
+++ b/package.json
@@ -6,9 +6,17 @@
    "dev": "astro dev",
    "build": "astro build",
    "preview": "astro preview",
-    "astro": "astro"
+    "astro": "astro",
+    "test": "vitest",
+    "test:coverage": "vitest run --coverage"
  },
  "dependencies": {
    "astro": "^5.7.5"
+  },
+  "devDependencies": {
+    "@types/supertest": "^2.0.12",
+    "@vitest/coverage-v8": "^0.34.6",
+    "supertest": "^6.3.3",
+    "vitest": "^0.34.3"
  }
 }
--- a/src/components/AddTransactionForm.astro
+++ b/src/components/AddTransactionForm.astro
@@ -1,5 +1,10 @@
 ---
-// This component needs client-side JS for the toggle
+// TODO: Enhance form validation and submission
+// - Add more robust client-side validation
+// - Implement better error message display
+// - Add loading states during submission
+// - Consider adding form reset confirmation if there are unsaved changes
+// This component handles both creating and editing transactions
 ---
 <section class="add-transaction-section">
    <button
@@ -10,42 +15,287 @@
    >
        Add Transaction +
    </button>
-    <form id="add-transaction-form" class="collapsible-form collapsed">
-        <h4>New Transaction</h4>
+    <form id="add-transaction-form" class="collapsible-form collapsed" novalidate>
+        <h4 id="form-title">New Transaction</h4>
+        <div id="form-error" class="error-message hidden"></div>
+        <input type="hidden" id="txn-id" name="id">
        <div class="form-group">
            <label for="txn-date">Date</label>
            <input type="date" id="txn-date" name="date" required>
        </div>
        <div class="form-group">
            <label for="txn-description">Description</label>
-            <input type="text" id="txn-description" name="description" required placeholder="e.g. Groceries">
+            <input type="text" id="txn-description" name="description" required minlength="2" maxlength="100" placeholder="e.g. Groceries">
        </div>
        <div class="form-group">
            <label for="txn-amount">Amount</label>
            <input type="number" id="txn-amount" name="amount" step="0.01" required placeholder="e.g. -25.50 or 1200.00">
+            <small class="help-text">Use negative numbers for expenses (e.g., -50.00)</small>
+        </div>
+        <div class="button-group">
+            <button type="submit" id="submit-btn" class="form-submit-btn">Save Transaction</button>
+            <button type="button" id="cancel-btn" class="cancel-btn hidden">Cancel</button>
        </div>
-        <!-- In a real app, prevent default and use JS to submit -->
-        <button type="submit">Save</button>
    </form>
 </section>

-<script>
-    // Script to handle the collapsible form toggle
-    const toggleBtn = document.getElementById('toggle-form-btn');
-    const form = document.getElementById('add-transaction-form');
+<style>
+.error-message {
+    background-color: #f8d7da;
+    border: 1px solid #f5c6cb;
+    color: #721c24;
+    padding: 8px 12px;
+    margin-bottom: 15px;
+    border-radius: 4px;
+    font-size: 0.9em;
+}
+.hidden {
+    display: none;
+}
+.help-text {
+    color: #666;
+    font-size: 0.8em;
+    margin-top: 4px;
+    display: block;
+}
+.button-group {
+    display: flex;
+    gap: 10px;
+    margin-top: 15px;
+}
+.cancel-btn {
+    background-color: #6c757d;
+    color: white;
+    padding: 8px 15px;
+    border: none;
+    border-radius: 3px;
+    cursor: pointer;
+}
+.cancel-btn:hover {
+    background-color: #5a6268;
+}
+.form-submit-btn.loading {
+    background-color: #ccc;
+    cursor: not-allowed;
+}
+</style>

+<script>
+    // --- DOM Elements ---
+    const toggleBtn = document.getElementById('toggle-form-btn');
+    const form = document.getElementById('add-transaction-form') as HTMLFormElement;
+    const formTitle = document.getElementById('form-title');
+    const errorDiv = document.getElementById('form-error');
+    const accountSelect = document.getElementById('account-select') as HTMLSelectElement;
+    const cancelBtn = document.getElementById('cancel-btn');
+    const submitBtn = document.getElementById('submit-btn');
+    const txnIdInput = document.getElementById('txn-id') as HTMLInputElement;
+    const dateInput = document.getElementById('txn-date') as HTMLInputElement;
+
+    let isEditMode = false;
+    let isSubmitting = false;
+
+    // Set default date to today
+    if (dateInput) {
+        dateInput.value = new Date().toISOString().split('T')[0];
+    }
+
+    // --- Helper Functions ---
+    function showError(message: string) {
+        if (errorDiv) {
+            errorDiv.textContent = message;
+            errorDiv.classList.remove('hidden');
+        }
+    }
+
+    function hideError() {
+        if (errorDiv) {
+            errorDiv.classList.add('hidden');
+        }
+    }
+
+    function clearForm() {
+        if (form) {
+            form.reset();
+            // Reset date to today
+            if (dateInput) {
+                dateInput.value = new Date().toISOString().split('T')[0];
+            }
+            // Reset edit mode
+            setEditMode(false);
+            // Clear any errors
+            hideError();
+        }
+    }
+
+    function setEditMode(enabled: boolean) {
+        isEditMode = enabled;
+        if (formTitle) formTitle.textContent = enabled ? 'Edit Transaction' : 'New Transaction';
+        if (submitBtn) submitBtn.textContent = enabled ? 'Update Transaction' : 'Save Transaction';
+        if (cancelBtn) cancelBtn.classList.toggle('hidden', !enabled);
+        if (toggleBtn) toggleBtn.classList.toggle('hidden', enabled);
+    }
+
+    function setLoading(enabled: boolean) {
+        isSubmitting = enabled;
+        if (submitBtn) {
+            const button = submitBtn as HTMLButtonElement;
+            button.classList.toggle('loading', enabled);
+            button.disabled = enabled;
+        }
+    }
+
+    function validateForm() {
+        if (!form) return null;
+        
+        const formData = new FormData(form);
+        const errors: string[] = [];
+
+        // Check required fields
+        const description = formData.get('description') as string;
+        const amount = formData.get('amount') as string;
+        const date = formData.get('date');
+
+        if (!description || description.trim().length < 2) {
+            errors.push('Description must be at least 2 characters long');
+        }
+
+        if (!amount) {
+            errors.push('Amount is required');
+        } else {
+            const amountNum = parseFloat(amount);
+            if (isNaN(amountNum)) {
+                errors.push('Amount must be a valid number');
+            } else if (amountNum === 0) {
+                errors.push('Amount cannot be zero');
+            }
+        }
+
+        if (!date) {
+            errors.push('Date is required');
+        } else {
+            const dateObj = new Date(date as string);
+            if (isNaN(dateObj.getTime())) {
+                errors.push('Invalid date format');
+            }
+        }
+
+        return errors.length > 0 ? errors : null;
+    }
+
+    // --- Form Toggle ---
    if (toggleBtn && form) {
        toggleBtn.addEventListener('click', () => {
            const isExpanded = toggleBtn.getAttribute('aria-expanded') === 'true';
            toggleBtn.setAttribute('aria-expanded', String(!isExpanded));
            form.classList.toggle('collapsed');
            toggleBtn.textContent = isExpanded ? 'Add Transaction +' : 'Hide Form -';
-            // Optional: Focus first input when opening
            if (!isExpanded) {
                form.querySelector('input')?.focus();
            }
+            hideError();
        });
-    } else {
-        console.error("Toggle button or form not found");
    }
+
+    // Cancel button handler
+    if (cancelBtn) {
+        cancelBtn.addEventListener('click', () => {
+            clearForm();
+            form?.classList.add('collapsed');
+        });
+    }
+
+    // --- Form Submission ---
+    if (form) {
+        form.addEventListener('submit', async (e) => {
+            e.preventDefault();
+            hideError();
+
+            if (isSubmitting) return;
+
+            // Validate form
+            const errors = validateForm();
+            if (errors) {
+                showError(errors.join('. '));
+                return;
+            }
+
+            setLoading(true);
+
+            try {
+                const formData = new FormData(form);
+                const currentAccountId = accountSelect?.value;
+
+                if (!currentAccountId) {
+                    throw new Error('No account selected');
+                }
+
+                const amount = parseFloat(formData.get('amount') as string);
+                const transaction = {
+                    accountId: currentAccountId,
+                    date: formData.get('date'),
+                    description: (formData.get('description') as string).trim(),
+                    amount: amount
+                };
+
+                const transactionId = txnIdInput.value;
+                const method = transactionId ? 'PUT' : 'POST';
+                const url = transactionId 
+                    ? `/api/transactions/${transactionId}`
+                    : '/api/transactions';
+
+                const response = await fetch(url, {
+                    method,
+                    headers: {
+                        'Content-Type': 'application/json'
+                    },
+                    body: JSON.stringify(transaction)
+                });
+
+                if (!response.ok) {
+                    const error = await response.json();
+                    throw new Error(error.error || `Failed to ${isEditMode ? 'update' : 'create'} transaction`);
+                }
+
+                // Transaction saved successfully
+                const savedTransaction = await response.json();
+
+                // Update UI
+                const eventName = isEditMode ? 'transactionUpdated' : 'transactionCreated';
+                document.dispatchEvent(new CustomEvent(eventName, {
+                    detail: { transaction: savedTransaction }
+                }));
+
+                // Clear and collapse form
+                clearForm();
+                form.classList.add('collapsed');
+                if (toggleBtn) {
+                    toggleBtn.setAttribute('aria-expanded', 'false');
+                    toggleBtn.textContent = 'Add Transaction +';
+                }
+
+            } catch (error) {
+                showError(error instanceof Error ? error.message : 'An unexpected error occurred');
+            } finally {
+                setLoading(false);
+            }
+        });
+    }
+
+    // --- Edit Transaction Handler ---
+    document.addEventListener('editTransaction', ((event: CustomEvent) => {
+        const transaction = event.detail.transaction;
+        if (!form || !transaction) return;
+
+        // Populate form
+        txnIdInput.value = transaction.id;
+        if (dateInput) dateInput.value = transaction.date;
+        (form.querySelector('#txn-description') as HTMLInputElement).value = transaction.description;
+        (form.querySelector('#txn-amount') as HTMLInputElement).value = transaction.amount.toString();
+
+        // Show form in edit mode
+        setEditMode(true);
+        form.classList.remove('collapsed');
+        form.querySelector('input')?.focus();
+    }) as EventListener);
 </script>
--- a/src/components/TransactionTable.astro
+++ b/src/components/TransactionTable.astro
@@ -10,8 +10,16 @@ const { transactions } = Astro.props;

 // Sort transactions by date descending for display
 const sortedTransactions = [...transactions].sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime());
+
+// TODO: UI/UX Improvements
+// - Add sorting functionality for all columns
+// - Implement pagination for large transaction lists
+// - Add transaction filtering capabilities
+// - Implement row hover actions
+// - Add transaction details expansion/collapse
+// - Consider adding bulk actions (delete, categorize)
 ---
-<section class="transaction-list">
+<section class="transaction-list" id="transaction-section">
    <table id="transaction-table">
        <thead>
            <tr>
@@ -30,8 +38,8 @@ const sortedTransactions = [...transactions].sort((a, b) => new Date(b.date).get
                        {formatCurrency(txn.amount)}
                    </td>
                    <td>
-                        <button class="action-btn edit-btn" title="Edit transaction (not implemented)">Edit</button>
-                        <button class="action-btn delete-btn" title="Delete transaction (not implemented)">Delete</button>
+                        <button class="action-btn edit-btn" title="Edit transaction">Edit</button>
+                        <button class="action-btn delete-btn" title="Delete transaction">Delete</button>
                    </td>
                </tr>
            ))}
--- a/src/data/store.ts
+++ b/src/data/store.ts
@@ -0,0 +1,57 @@
+// TODO: Database Integration & Persistence
+// - Implement database schema design
+// - Add database connection pooling
+// - Implement data migration strategy
+// - Add database backup and recovery plans
+// - Implement data validation layer
+// - Add transaction logging
+// - Implement audit trail
+// - Add data archival strategy
+
+import type { Account, Transaction } from "../types";
+
+// TODO: Replace in-memory store with persistent database
+// - Implement database connection and configuration
+// - Create database schema for accounts and transactions
+// - Add migration system for schema changes
+// - Update all CRUD operations to use database instead of arrays
+
+// Temporary in-memory store for development
+export const accounts: Account[] = [
+  {
+    id: "1",
+    name: "Checking Account",
+    last4: "4321",
+    balance: 2500.0,
+  },
+  {
+    id: "2",
+    name: "Savings Account",
+    last4: "8765",
+    balance: 10000.0,
+  },
+];
+
+export const transactions: Transaction[] = [
+  {
+    id: "1",
+    accountId: "1",
+    date: "2025-04-20",
+    description: "Grocery Store",
+    amount: -75.5,
+  },
+  {
+    id: "2",
+    accountId: "1",
+    date: "2025-04-21",
+    description: "Salary Deposit",
+    amount: 3000.0,
+  },
+  {
+    id: "3",
+    accountId: "2",
+    date: "2025-04-22",
+    description: "Transfer to Savings",
+    amount: 500.0,
+  },
+];
--- a/src/layouts/BaseLayout.astro
+++ b/src/layouts/BaseLayout.astro
@@ -3,6 +3,15 @@ interface Props {
 	title: string;
 }

+// TODO: Accessibility Improvements
+// - Add ARIA landmarks for main regions
+// - Implement keyboard navigation
+// - Add skip navigation links
+// - Ensure proper heading hierarchy
+// - Add focus management for modals/dialogs
+// - Implement proper announcements for dynamic content
+// - Add high contrast theme support
+
 const { title } = Astro.props;
 ---
 <!doctype html>
--- a/src/pages/api/accounts/[id]/index.ts
+++ b/src/pages/api/accounts/[id]/index.ts
@@ -0,0 +1,22 @@
+import type { APIRoute } from "astro";
+import { accounts } from "../../../../data/store";
+
+export const GET: APIRoute = async ({ params }) => {
+  const account = accounts.find((a) => a.id === params.id);
+
+  if (!account) {
+    return new Response(JSON.stringify({ error: "Account not found" }), {
+      status: 404,
+      headers: {
+        "Content-Type": "application/json",
+      },
+    });
+  }
+
+  return new Response(JSON.stringify(account), {
+    status: 200,
+    headers: {
+      "Content-Type": "application/json",
+    },
+  });
+};
--- a/src/pages/api/accounts/[id]/transactions/index.ts
+++ b/src/pages/api/accounts/[id]/transactions/index.ts
@@ -0,0 +1,15 @@
+import type { APIRoute } from "astro";
+import { transactions } from "../../../../../data/store";
+
+export const GET: APIRoute = async ({ params }) => {
+  const accountTransactions = transactions.filter(
+    (t) => t.accountId === params.id
+  );
+
+  return new Response(JSON.stringify(accountTransactions), {
+    status: 200,
+    headers: {
+      "Content-Type": "application/json",
+    },
+  });
+};
--- a/src/pages/api/accounts/index.ts
+++ b/src/pages/api/accounts/index.ts
@@ -0,0 +1,11 @@
+import type { APIRoute } from "astro";
+import { accounts } from "../../../data/store";
+
+export const GET: APIRoute = async () => {
+  return new Response(JSON.stringify(accounts), {
+    status: 200,
+    headers: {
+      "Content-Type": "application/json",
+    },
+  });
+};
--- a/src/pages/api/transactions/[id]/index.ts
+++ b/src/pages/api/transactions/[id]/index.ts
@@ -0,0 +1,126 @@
+import type { APIRoute } from "astro";
+import { transactions, accounts } from "../../../../data/store";
+import type { Transaction } from "../../../../types";
+
+export const PUT: APIRoute = async ({ request, params }) => {
+  const { id } = params;
+
+  if (!id) {
+    return new Response(
+      JSON.stringify({ error: "Transaction ID is required" }),
+      {
+        status: 400,
+        headers: { "Content-Type": "application/json" },
+      }
+    );
+  }
+
+  try {
+    const updates = (await request.json()) as Partial<Transaction>;
+    const transactionIndex = transactions.findIndex((t) => t.id === id);
+
+    if (transactionIndex === -1) {
+      return new Response(JSON.stringify({ error: "Transaction not found" }), {
+        status: 404,
+        headers: { "Content-Type": "application/json" },
+      });
+    }
+
+    const oldTransaction = transactions[transactionIndex];
+
+    // Get the old account first
+    const oldAccount = accounts.find((a) => a.id === oldTransaction.accountId);
+    if (!oldAccount) {
+      return new Response(JSON.stringify({ error: "Account not found" }), {
+        status: 404,
+        headers: { "Content-Type": "application/json" },
+      });
+    }
+
+    // If account is changing, validate new account exists
+    let newAccount = oldAccount;
+    if (updates.accountId && updates.accountId !== oldTransaction.accountId) {
+      const foundAccount = accounts.find((a) => a.id === updates.accountId);
+      if (!foundAccount) {
+        return new Response(JSON.stringify({ error: "Account not found" }), {
+          status: 404,
+          headers: { "Content-Type": "application/json" },
+        });
+      }
+      newAccount = foundAccount;
+    }
+
+    // First, remove the old transaction's effect on the old account
+    oldAccount.balance -= oldTransaction.amount;
+
+    // Create updated transaction
+    const updatedTransaction: Transaction = {
+      ...oldTransaction,
+      ...updates,
+      id: id, // Ensure ID doesn't change
+    };
+
+    // Then add the new transaction's effect to the appropriate account
+    if (newAccount === oldAccount) {
+      // If same account, just add the new amount
+      oldAccount.balance += updatedTransaction.amount;
+    } else {
+      // If different account, add to the new account
+      newAccount.balance += updatedTransaction.amount;
+    }
+
+    // Update transaction in array
+    transactions[transactionIndex] = updatedTransaction;
+
+    return new Response(JSON.stringify(updatedTransaction), {
+      status: 200,
+      headers: { "Content-Type": "application/json" },
+    });
+  } catch (error) {
+    return new Response(JSON.stringify({ error: "Invalid request body" }), {
+      status: 400,
+      headers: { "Content-Type": "application/json" },
+    });
+  }
+};
+
+export const DELETE: APIRoute = async ({ params }) => {
+  const { id } = params;
+
+  if (!id) {
+    return new Response(
+      JSON.stringify({ error: "Transaction ID is required" }),
+      {
+        status: 400,
+        headers: { "Content-Type": "application/json" },
+      }
+    );
+  }
+
+  const transactionIndex = transactions.findIndex((t) => t.id === id);
+
+  if (transactionIndex === -1) {
+    return new Response(JSON.stringify({ error: "Transaction not found" }), {
+      status: 404,
+      headers: { "Content-Type": "application/json" },
+    });
+  }
+
+  const transaction = transactions[transactionIndex];
+  const account = accounts.find((a) => a.id === transaction.accountId);
+
+  if (!account) {
+    return new Response(JSON.stringify({ error: "Account not found" }), {
+      status: 404,
+      headers: { "Content-Type": "application/json" },
+    });
+  }
+
+  // Update account balance
+  account.balance -= transaction.amount;
+
+  // Remove transaction from array
+  transactions.splice(transactionIndex, 1);
+
+  return new Response(null, { status: 204 });
+};
--- a/src/pages/api/transactions/index.ts
+++ b/src/pages/api/transactions/index.ts
@@ -0,0 +1,79 @@
+/**
+ * TODO: Security Improvements
+ * - Add input validation and sanitization
+ * - Implement rate limiting for API endpoints
+ * - Add request authentication
+ * - Implement CSRF protection
+ * - Add request logging and monitoring
+ * - Implement secure session management
+ * - Add API versioning
+ * - Set up proper CORS configuration
+ */
+
+import type { APIRoute } from "astro";
+import { transactions, accounts } from "../../../data/store";
+import type { Transaction } from "../../../types";
+
+/**
+ * TODO: API Improvements
+ * - Add request rate limiting
+ * - Implement proper API authentication
+ * - Add input sanitization
+ * - Implement request validation middleware
+ * - Add API versioning
+ * - Consider implementing GraphQL for more flexible queries
+ * - Add proper logging and monitoring
+ */
+
+export const POST: APIRoute = async ({ request }) => {
+  try {
+    const transaction = (await request.json()) as Omit<Transaction, "id">;
+
+    // Validate required fields
+    if (
+      !transaction.accountId ||
+      !transaction.date ||
+      !transaction.description ||
+      transaction.amount === undefined
+    ) {
+      return new Response(
+        JSON.stringify({ error: "Missing required fields" }),
+        {
+          status: 400,
+          headers: { "Content-Type": "application/json" },
+        }
+      );
+    }
+
+    // Validate account exists
+    const account = accounts.find((a) => a.id === transaction.accountId);
+    if (!account) {
+      return new Response(JSON.stringify({ error: "Account not found" }), {
+        status: 404,
+        headers: { "Content-Type": "application/json" },
+      });
+    }
+
+    // Create new transaction with generated ID
+    const newTransaction: Transaction = {
+      ...transaction,
+      id: (transactions.length + 1).toString(), // Simple ID generation for demo
+    };
+
+    // Update account balance
+    account.balance += transaction.amount;
+
+    // Add to transactions array
+    transactions.push(newTransaction);
+
+    return new Response(JSON.stringify(newTransaction), {
+      status: 201,
+      headers: { "Content-Type": "application/json" },
+    });
+  } catch (error) {
+    return new Response(JSON.stringify({ error: "Invalid request body" }), {
+      status: 400,
+      headers: { "Content-Type": "application/json" },
+    });
+  }
+};
--- a/src/pages/index.astro
+++ b/src/pages/index.astro
@@ -3,21 +3,48 @@ import BaseLayout from '../layouts/BaseLayout.astro';
 import Sidebar from '../components/Sidebar.astro';
 import MainContent from '../components/MainContent.astro';
 import type { Account, Transaction } from '../types';
-import { formatCurrency, formatDate } from '../utils';

-// Initialize with empty arrays until API integration
-const accounts: Account[] = [];
-const allTransactions: Transaction[] = [];
+// Fetch accounts from API
+const accountsResponse = await fetch('http://localhost:4321/api/accounts');
+const accounts: Account[] = await accountsResponse.json();

-// Create an empty initial account
-const initialAccount: Account = {
+// Initialize with first account or empty account if none exist
+const initialAccount: Account = accounts[0] || {
    id: '',
    name: 'No accounts available',
    last4: '0000',
    balance: 0
 };
-const initialTransactions: Transaction[] = [];
+
+// Fetch initial transactions if we have an account
+let initialTransactions: Transaction[] = [];
+if (initialAccount.id) {
+    const transactionsResponse = await fetch(`http://localhost:4321/api/accounts/${initialAccount.id}/transactions`);
+    initialTransactions = await transactionsResponse.json();
+}
 ---
+
+<!--
+TODO: State Management Improvements
+- Consider implementing Nano Stores for better state management
+- Add more robust error handling and user feedback
+- Implement loading states for all async operations
+- Add offline support with data synchronization
+- Consider implementing optimistic updates for better UX
+-->
+
+<!--
+TODO: Performance & Monitoring
+- Implement client-side error tracking
+- Add performance metrics collection
+- Set up monitoring for API response times
+- Implement request caching strategy
+- Add lazy loading for transaction history
+- Optimize bundle size
+- Add performance budgets
+- Implement progressive loading
+-->
+
 <BaseLayout title="Bank Transactions Dashboard">
    <div class="dashboard-layout">
        <Sidebar accounts={accounts} initialAccount={initialAccount} />
@@ -25,52 +52,116 @@ const initialTransactions: Transaction[] = [];
    </div>
 </BaseLayout>

-<script define:vars={{ allAccounts: accounts, allTransactions }}>
-    // Client-side script to handle account switching and updating the UI
+<script>
+    // Import types for client-side script
+    type Transaction = import('../types').Transaction;
+    type Account = import('../types').Account;
+    type TransactionEventDetail = import('../types/events').TransactionEventDetail;

    // --- DOM Elements ---
-    const accountSelect = document.getElementById('account-select');
+    const accountSelect = document.getElementById('account-select') as HTMLSelectElement;
    const currentAccountNameSpan = document.getElementById('current-account-name');
    const accountBalanceSpan = document.getElementById('account-balance');
    const transactionTableBody = document.getElementById('transaction-table-body');
+    const transactionSection = document.getElementById('transaction-section');

-    // --- Helper Functions (mirror utils.ts for client-side use) ---
-    function formatCurrency(amount) {
+    // --- Helper Functions ---
+    function formatCurrency(amount: number): string {
        return new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(amount);
    }

-    function formatDate(dateString) {
-        const date = new Date(dateString + 'T00:00:00'); // Ensure local date
+    function formatDate(dateString: string): string {
+        const date = new Date(dateString + 'T00:00:00');
        return new Intl.DateTimeFormat('en-US', { year: 'numeric', month: 'short', day: 'numeric' }).format(date);
    }

+    async function fetchAccountTransactions(accountId: string): Promise<Transaction[]> {
+        try {
+            const response = await fetch(`/api/accounts/${accountId}/transactions`);
+            if (!response.ok) throw new Error('Failed to fetch transactions');
+            return await response.json();
+        } catch (error) {
+            console.error('Error fetching transactions:', error);
+            return [];
+        }
+    }
+
+    async function fetchAccountDetails(accountId: string): Promise<Account | null> {
+        try {
+            const response = await fetch(`/api/accounts/${accountId}`);
+            if (!response.ok) throw new Error('Failed to fetch account details');
+            return await response.json();
+        } catch (error) {
+            console.error('Error fetching account:', error);
+            return null;
+        }
+    }
+
    // --- Update UI Function ---
-    function updateUIForAccount(accountId) {
-        console.log("Updating UI for account:", accountId); // Debug log
+    async function updateUIForAccount(accountId: string): Promise<void> {
+        console.log("Updating UI for account:", accountId);

-        const selectedAccount = allAccounts.find(acc => acc.id === accountId);
-        const accountTransactions = allTransactions
-            .filter(txn => txn.accountId === accountId)
-            .sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime()); // Sort desc
+        if (transactionSection) {
+            transactionSection.classList.add('loading');
+        }

-        if (!selectedAccount || !transactionTableBody || !currentAccountNameSpan || !accountBalanceSpan) {
-            console.error("Required UI elements not found!");
+        try {
+            // Fetch latest account details and transactions
+            const [account, transactions] = await Promise.all([
+                fetchAccountDetails(accountId),
+                fetchAccountTransactions(accountId)
+            ]);
+
+            if (!account || !transactionTableBody || !currentAccountNameSpan || !accountBalanceSpan) {
+                console.error("Required data or UI elements not found!");
                return;
            }

            // Update header
-        currentAccountNameSpan.textContent = `${selectedAccount.name} (***${selectedAccount.last4})`;
+            currentAccountNameSpan.textContent = `${account.name} (***${account.last4})`;

            // Update summary
-        accountBalanceSpan.textContent = formatCurrency(selectedAccount.balance);
+            accountBalanceSpan.textContent = formatCurrency(account.balance);

            // Update table
-        transactionTableBody.innerHTML = ''; // Clear existing rows
+            updateTransactionTable(transactions);
+        } catch (error) {
+            console.error('Error updating UI:', error);
+            if (transactionTableBody) {
+                transactionTableBody.innerHTML = `
+                    <tr>
+                        <td colspan="4" style="text-align: center; color: #dc3545;">
+                            Failed to load transactions. Please try again.
+                        </td>
+                    </tr>`;
+            }
+        } finally {
+            if (transactionSection) {
+                transactionSection.classList.remove('loading');
+            }
+        }
+    }

-        if (accountTransactions.length === 0) {
-            transactionTableBody.innerHTML = `<tr><td colspan="4" style="text-align: center; font-style: italic; color: #777;">No transactions found for this account.</td></tr>`;
-        } else {
-            accountTransactions.forEach(txn => {
+    function updateTransactionTable(transactions: Transaction[]): void {
+        if (!transactionTableBody) return;
+
+        const sortedTransactions = [...transactions].sort((a, b) => 
+            new Date(b.date).getTime() - new Date(a.date).getTime()
+        );
+
+        transactionTableBody.innerHTML = '';
+
+        if (sortedTransactions.length === 0) {
+            transactionTableBody.innerHTML = `
+                <tr>
+                    <td colspan="4" style="text-align: center; font-style: italic; color: #777;">
+                        No transactions found for this account.
+                    </td>
+                </tr>`;
+            return;
+        }
+
+        sortedTransactions.forEach(txn => {
            const row = document.createElement('tr');
            row.setAttribute('data-txn-id', txn.id);
            row.innerHTML = `
@@ -80,29 +171,115 @@ const initialTransactions: Transaction[] = [];
                    ${formatCurrency(txn.amount)}
                </td>
                <td>
-                        <button class="action-btn edit-btn" title="Edit transaction (not implemented)">Edit</button>
-                        <button class="action-btn delete-btn" title="Delete transaction (not implemented)">Delete</button>
+                    <button class="action-btn edit-btn" title="Edit transaction">Edit</button>
+                    <button class="action-btn delete-btn" title="Delete transaction">Delete</button>
                </td>
            `;
            transactionTableBody.appendChild(row);
        });
-        }
+
+        setupTransactionButtons();
    }

-    // --- Event Listener ---
-    if (accountSelect) {
-        accountSelect.addEventListener('change', (event) => {
-            const selectedAccountId = event.target.value;
-            updateUIForAccount(selectedAccountId);
+    function setupTransactionButtons(): void {
+        const transactionRows = transactionTableBody?.querySelectorAll('tr[data-txn-id]');
+        transactionRows?.forEach(row => {
+            const txnId = row.getAttribute('data-txn-id');
+            if (!txnId) return;
+
+            // Delete button handler
+            const deleteBtn = row.querySelector('.delete-btn');
+            deleteBtn?.addEventListener('click', () => handleDeleteTransaction(txnId));
+
+            // Edit button handler
+            const editBtn = row.querySelector('.edit-btn');
+            editBtn?.addEventListener('click', () => handleEditTransaction(txnId));
        });
-    } else {
-        console.error("Account select element not found");
    }

-    // --- Initial Load (Optional but good practice) ---
-    // The page already renders the initial state server-side,
-    // so no need to call updateUIForAccount() immediately unless
-    // there's a chance the JS loads before initial render completes fully.
-    // console.log("Account switcher script loaded.");
+    // --- Transaction Actions ---
+    async function handleDeleteTransaction(txnId: string): Promise<void> {
+        if (!confirm('Are you sure you want to delete this transaction?')) {
+            return;
+        }

+        if (transactionSection) {
+            transactionSection.classList.add('loading');
+        }
+
+        try {
+            const response = await fetch(`/api/transactions/${txnId}`, {
+                method: 'DELETE'
+            });
+
+            if (!response.ok) {
+                const error = await response.json();
+                throw new Error(error.error || 'Failed to delete transaction');
+            }
+
+            // Refresh the current account view
+            const currentAccountId = accountSelect?.value;
+            if (currentAccountId) {
+                await updateUIForAccount(currentAccountId);
+            }
+        } catch (error) {
+            alert(error instanceof Error ? error.message : 'Failed to delete transaction');
+        } finally {
+            if (transactionSection) {
+                transactionSection.classList.remove('loading');
+            }
+        }
+    }
+
+    async function handleEditTransaction(txnId: string): Promise<void> {
+        try {
+            // Find transaction in current transactions list
+            const currentAccountId = accountSelect?.value;
+            if (!currentAccountId) return;
+            
+            const transactions = await fetchAccountTransactions(currentAccountId);
+            const transaction = transactions.find(t => t.id === txnId);
+            
+            if (!transaction) {
+                throw new Error('Transaction not found');
+            }
+
+            // Trigger edit mode in form
+            document.dispatchEvent(new CustomEvent<TransactionEventDetail>('editTransaction', {
+                detail: { transaction }
+            }));
+
+        } catch (error) {
+            alert(error instanceof Error ? error.message : 'Failed to load transaction for editing');
+        }
+    }
+
+    // --- Event Listeners ---
+    if (accountSelect) {
+        accountSelect.addEventListener('change', (event: Event) => {
+            const target = event.target as HTMLSelectElement;
+            updateUIForAccount(target.value);
+        });
+    }
+
+    // Listen for transaction events
+    document.addEventListener('transactionCreated', ((event: CustomEvent<TransactionEventDetail>) => {
+        const currentAccountId = accountSelect?.value;
+        if (currentAccountId) {
+            updateUIForAccount(currentAccountId);
+        }
+    }) as EventListener);
+
+    document.addEventListener('transactionUpdated', ((event: CustomEvent<TransactionEventDetail>) => {
+        const currentAccountId = accountSelect?.value;
+        if (currentAccountId) {
+            updateUIForAccount(currentAccountId);
+        }
+    }) as EventListener);
+
+    // Initial load with transactions if available
+    const initialAccountId = accountSelect?.value;
+    if (initialAccountId) {
+        updateUIForAccount(initialAccountId);
+    }
 </script>
--- a/src/styles/global.css
+++ b/src/styles/global.css
@@ -232,3 +232,48 @@ tbody tr:hover {
    padding: 20px;
  }
 }
+
+/* Loading States */
+.loading {
+  opacity: 0.6;
+  pointer-events: none;
+  position: relative;
+}
+
+.loading::after {
+  content: "";
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  width: 1.5em;
+  height: 1.5em;
+  margin: -0.75em 0 0 -0.75em;
+  border: 3px solid rgba(0, 123, 255, 0.2);
+  border-top-color: #007bff;
+  border-radius: 50%;
+  animation: spinner 0.6s linear infinite;
+}
+
+@keyframes spinner {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
+.form-submit-btn {
+  position: relative;
+  min-width: 100px;
+}
+
+.form-submit-btn.loading {
+  padding-right: 35px;
+}
+
+.form-submit-btn.loading::after {
+  width: 1em;
+  height: 1em;
+  margin: -0.5em 0 0 0;
+  left: auto;
+  right: 10px;
+  border-width: 2px;
+}
--- a/src/test/accounts.test.ts
+++ b/src/test/accounts.test.ts
@@ -0,0 +1,65 @@
+import { describe, it, expect } from "vitest";
+import { GET as listAccounts } from "../pages/api/accounts/index";
+import { GET as getAccount } from "../pages/api/accounts/[id]/index";
+import { GET as listTransactions } from "../pages/api/accounts/[id]/transactions/index";
+import { createMockAPIContext } from "./setup";
+
+describe("Accounts API", () => {
+  describe("GET /api/accounts", () => {
+    it("should return all accounts", async () => {
+      const response = await listAccounts(createMockAPIContext() as any);
+      const accounts = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(accounts).toHaveLength(2);
+      expect(accounts[0]).toHaveProperty("id", "1");
+      expect(accounts[1]).toHaveProperty("id", "2");
+    });
+  });
+
+  describe("GET /api/accounts/:id", () => {
+    it("should return a specific account", async () => {
+      const response = await getAccount(
+        createMockAPIContext({ params: { id: "1" } }) as any
+      );
+      const account = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(account).toHaveProperty("id", "1");
+      expect(account).toHaveProperty("name", "Test Checking");
+    });
+
+    it("should return 404 for non-existent account", async () => {
+      const response = await getAccount(
+        createMockAPIContext({ params: { id: "999" } }) as any
+      );
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+    });
+  });
+
+  describe("GET /api/accounts/:id/transactions", () => {
+    it("should return transactions for an account", async () => {
+      const response = await listTransactions(
+        createMockAPIContext({ params: { id: "1" } }) as any
+      );
+      const transactions = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(transactions).toHaveLength(1);
+      expect(transactions[0]).toHaveProperty("accountId", "1");
+    });
+
+    it("should return empty array for account with no transactions", async () => {
+      const response = await listTransactions(
+        createMockAPIContext({ params: { id: "999" } }) as any
+      );
+      const transactions = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(transactions).toHaveLength(0);
+    });
+  });
+});
--- a/src/test/setup.ts
+++ b/src/test/setup.ts
@@ -0,0 +1,67 @@
+import { beforeEach } from "vitest";
+import { accounts, transactions } from "../data/store";
+import type { APIContext } from "astro";
+
+// Create a mock APIContext factory
+export function createMockAPIContext<
+  T extends Record<string, string> = Record<string, string>
+>({ params = {} as T } = {}): Partial<APIContext> {
+  return {
+    params,
+    props: {},
+    request: new Request("http://localhost:4321"),
+    site: new URL("http://localhost:4321"),
+    generator: "test",
+    url: new URL("http://localhost:4321"),
+    clientAddress: "127.0.0.1",
+    cookies: new Headers() as any, // Cast Headers to cookies as we don't need cookie functionality in tests
+    redirect: () => new Response(),
+    locals: {},
+    preferredLocale: undefined,
+    preferredLocaleList: [],
+    currentLocale: undefined,
+    routePattern: "/api/[...path]",
+    originPathname: "/api",
+    getActionResult: () => undefined,
+    isPrerendered: false,
+  };
+}
+
+// Reset test data before each test
+beforeEach(() => {
+  // Reset accounts to initial state
+  accounts.length = 0;
+  accounts.push(
+    {
+      id: "1",
+      name: "Test Checking",
+      last4: "1234",
+      balance: 1000.0,
+    },
+    {
+      id: "2",
+      name: "Test Savings",
+      last4: "5678",
+      balance: 5000.0,
+    }
+  );
+
+  // Reset transactions to initial state
+  transactions.length = 0;
+  transactions.push(
+    {
+      id: "1",
+      accountId: "1",
+      date: "2025-04-24",
+      description: "Test Transaction 1",
+      amount: -50.0,
+    },
+    {
+      id: "2",
+      accountId: "2",
+      date: "2025-04-24",
+      description: "Test Transaction 2",
+      amount: 100.0,
+    }
+  );
+});
--- a/src/test/transactions.test.ts
+++ b/src/test/transactions.test.ts
@@ -0,0 +1,332 @@
+// TODO: Testing Improvements
+// - Add integration tests for API endpoints
+// - Add end-to-end tests with Playwright/Cypress
+// - Add performance testing
+// - Add accessibility testing with axe-core
+// - Add visual regression testing
+// - Add load testing for API endpoints
+// - Implement test data factories
+
+import { describe, it, expect } from "vitest";
+import { POST as createTransaction } from "../pages/api/transactions/index";
+import {
+  PUT as updateTransaction,
+  DELETE as deleteTransaction,
+} from "../pages/api/transactions/[id]/index";
+import { accounts, transactions } from "../data/store";
+import type { Transaction } from "../types";
+import { createMockAPIContext } from "./setup";
+
+describe("Transactions API", () => {
+  describe("POST /api/transactions", () => {
+    it("should create a new transaction", async () => {
+      const initialBalance = accounts[0].balance;
+      const newTransaction = {
+        accountId: "1",
+        date: "2025-04-24",
+        description: "Test New Transaction",
+        amount: -25.0,
+      };
+
+      const ctx = createMockAPIContext() as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(newTransaction),
+      });
+
+      const response = await createTransaction(ctx);
+      const result = await response.json();
+
+      expect(response.status).toBe(201);
+      expect(result).toHaveProperty("id");
+      expect(result.description).toBe(newTransaction.description);
+      expect(accounts[0].balance).toBe(initialBalance + newTransaction.amount);
+    });
+
+    it("should reject transaction with missing fields", async () => {
+      const invalidTransaction = {
+        accountId: "1",
+        // Missing required fields
+      };
+
+      const ctx = createMockAPIContext() as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(invalidTransaction),
+      });
+
+      const response = await createTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(error).toHaveProperty("error", "Missing required fields");
+    });
+
+    it("should reject transaction with invalid account", async () => {
+      const invalidTransaction = {
+        accountId: "999",
+        date: "2025-04-24",
+        description: "Invalid Account Test",
+        amount: 100,
+      };
+
+      const ctx = createMockAPIContext() as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(invalidTransaction),
+      });
+
+      const response = await createTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+    });
+
+    it("should reject invalid request body", async () => {
+      const ctx = createMockAPIContext() as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: "invalid json",
+      });
+
+      const response = await createTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(error).toHaveProperty("error", "Invalid request body");
+    });
+  });
+
+  describe("PUT /api/transactions/:id", () => {
+    it("should update an existing transaction", async () => {
+      const initialBalance = accounts[0].balance;
+      const originalAmount = transactions[0].amount;
+      const updates = {
+        description: "Updated Description",
+        amount: -75.0,
+      };
+
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(updates),
+      });
+
+      const response = await updateTransaction(ctx);
+      const result = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(result.description).toBe(updates.description);
+      expect(result.amount).toBe(updates.amount);
+      expect(accounts[0].balance).toBe(
+        initialBalance - originalAmount + updates.amount
+      );
+    });
+
+    it("should reject update with invalid request body", async () => {
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: "invalid json",
+      });
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(error).toHaveProperty("error", "Invalid request body");
+    });
+
+    it("should reject update for non-existent transaction", async () => {
+      const ctx = createMockAPIContext({ params: { id: "999" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/999", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ description: "Test" }),
+      });
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Transaction not found");
+    });
+
+    it("should reject update for non-existent account", async () => {
+      // First update the transaction to point to a non-existent account
+      transactions[0].accountId = "999";
+
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ amount: -100 }),
+      });
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+
+      // Reset account ID for other tests
+      transactions[0].accountId = "1";
+    });
+
+    it("should handle account balance updates correctly when switching accounts", async () => {
+      // Create initial state
+      const oldAccount = accounts[0];
+      const newAccount = accounts[1];
+      const initialOldBalance = oldAccount.balance;
+      const initialNewBalance = newAccount.balance;
+      const oldTransaction = transactions.find((t) => t.id === "1");
+      if (!oldTransaction) throw new Error("Test transaction not found");
+
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          accountId: newAccount.id,
+          amount: -100,
+        }),
+      });
+
+      const response = await updateTransaction(ctx);
+      const result = await response.json();
+
+      expect(response.status).toBe(200);
+      expect(result.accountId).toBe(newAccount.id);
+
+      // Old account should have the old amount removed
+      expect(oldAccount.balance).toBe(
+        initialOldBalance + Math.abs(oldTransaction.amount)
+      );
+
+      // New account should have the new amount added
+      expect(newAccount.balance).toBe(initialNewBalance - 100);
+    });
+
+    it("should reject update without transaction ID", async () => {
+      const ctx = createMockAPIContext() as any;
+      ctx.request = new Request(
+        "http://localhost:4321/api/transactions/undefined",
+        {
+          method: "PUT",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ description: "Test" }),
+        }
+      );
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(error).toHaveProperty("error", "Transaction ID is required");
+    });
+
+    it("should reject update when old account is missing", async () => {
+      // Store current accounts and clear the array
+      const savedAccounts = [...accounts];
+      accounts.length = 0;
+
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ amount: -100 }),
+      });
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+
+      // Restore accounts
+      accounts.push(...savedAccounts);
+    });
+
+    it("should reject update when new account doesn't exist", async () => {
+      const ctx = createMockAPIContext({ params: { id: "1" } }) as any;
+      ctx.request = new Request("http://localhost:4321/api/transactions/1", {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          accountId: "999", // Non-existent account
+          amount: -100,
+        }),
+      });
+
+      const response = await updateTransaction(ctx);
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+    });
+  });
+
+  describe("DELETE /api/transactions/:id", () => {
+    it("should delete a transaction", async () => {
+      const initialBalance = accounts[0].balance;
+      const transactionAmount = transactions[0].amount;
+      const initialCount = transactions.length;
+
+      const response = await deleteTransaction(
+        createMockAPIContext({ params: { id: "1" } }) as any
+      );
+
+      expect(response.status).toBe(204);
+      expect(transactions).toHaveLength(initialCount - 1);
+      expect(accounts[0].balance).toBe(initialBalance - transactionAmount);
+    });
+
+    it("should reject delete without transaction ID", async () => {
+      const response = await deleteTransaction(createMockAPIContext() as any);
+
+      const error = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(error).toHaveProperty("error", "Transaction ID is required");
+    });
+
+    it("should return 404 for non-existent transaction", async () => {
+      const response = await deleteTransaction(
+        createMockAPIContext({ params: { id: "999" } }) as any
+      );
+
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Transaction not found");
+    });
+
+    it("should handle deletion with non-existent account", async () => {
+      // Create a transaction then remove its account
+      const testTransaction: Transaction = {
+        id: "test-delete",
+        accountId: "test-account",
+        date: "2025-04-24",
+        description: "Test Delete",
+        amount: 100,
+      };
+      transactions.push(testTransaction);
+
+      const response = await deleteTransaction(
+        createMockAPIContext({ params: { id: "test-delete" } }) as any
+      );
+
+      const error = await response.json();
+
+      expect(response.status).toBe(404);
+      expect(error).toHaveProperty("error", "Account not found");
+    });
+  });
+});
--- a/src/types/events.ts
+++ b/src/types/events.ts
@@ -0,0 +1,13 @@
+import type { Transaction } from "../types";
+
+export interface TransactionEventDetail {
+  transaction: Transaction;
+}
+
+declare global {
+  interface WindowEventMap {
+    transactionCreated: CustomEvent<TransactionEventDetail>;
+    transactionUpdated: CustomEvent<TransactionEventDetail>;
+    editTransaction: CustomEvent<TransactionEventDetail>;
+  }
+}
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -0,0 +1,21 @@
+/// <reference types="vitest" />
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    // Increase timeout for slower CI environments
+    testTimeout: 10000,
+    // Use the setup file we created
+    setupFiles: ["./src/test/setup.ts"],
+    // Ensure we're using the right environment
+    environment: "node",
+    // Only include test files
+    include: ["src/test/**/*.{test,spec}.{ts,js}"],
+    // Configure coverage collection
+    coverage: {
+      provider: "v8",
+      reporter: ["text", "json", "html"],
+      exclude: ["node_modules/", "src/test/**/*", "**/*.d.ts"],
+    },
+  },
+});
				`@@ -1 +0,0 @@`
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