docs: Add comprehensive use cases and practical examples

README.md

@@ -55,35 +55,268 @@ yarn lint
 
 ## 🚀 Quick Start
 
+### Minimal Configuration
+
 ```typescript
 import { PinTanClient } from "fints-lib";
 
+// Create a client with minimal required configuration
 const client = new PinTanClient({
-    url: "https://example.com/fints",
-    name: "username",
-    pin: "12345",
-    blz: "12345678",
+    url: "https://banking.example.com/fints",  // Your bank's FinTS URL
+    name: "username",                           // Your banking username
+    pin: "12345",                               // Your banking PIN
+    blz: "12345678",                            // Bank code (BLZ/Bankleitzahl)
 });
 
-// List accounts
+// List all accounts
 const accounts = await client.accounts();
 console.log(accounts);
+```
+
+### CLI Quick Start
+
+```bash
+# Install globally
+npm install -g fints-lib-cli
+
+# List your accounts
+fints-lib list-accounts \
+  --url https://banking.example.com/fints \
+  -n username \
+  -p 12345 \
+  -b 12345678
+```
+
+## 📖 Common Use Cases
+
+### 1. Check Account Balance
+
+```typescript
+import { PinTanClient } from "fints-lib";
+
+const client = new PinTanClient({
+    url: process.env.FINTS_URL,
+    name: process.env.FINTS_USERNAME,
+    pin: process.env.FINTS_PIN,
+    blz: process.env.FINTS_BLZ,
+});
+
+// Get all accounts
+const accounts = await client.accounts();
+
+// Check balance for first account
+const balance = await client.balance(accounts[0]);
+console.log(`Account: ${accounts[0].iban}`);
+console.log(`Balance: ${balance.value.value} ${balance.value.currency}`);
+```
+
+**CLI Example**
+```bash
+fints-lib get-balance \
+  --url https://banking.example.com/fints \
+  -n username -p 12345 -b 12345678 \
+  -i DE89370400440532013000
+```
+
+### 2. Fetch Recent Transactions
+
+```typescript
+import { PinTanClient } from "fints-lib";
+
+const client = new PinTanClient({
+    url: process.env.FINTS_URL,
+    name: process.env.FINTS_USERNAME,
+    pin: process.env.FINTS_PIN,
+    blz: process.env.FINTS_BLZ,
+});
+
+const accounts = await client.accounts();
+
+// Fetch last 30 days of transactions
+const endDate = new Date();
+const startDate = new Date(endDate.getTime() - 30 * 24 * 60 * 60 * 1000);
 
-// Fetch statements
-const startDate = new Date("2024-01-01");
-const endDate = new Date("2024-12-31");
 const statements = await client.statements(accounts[0], startDate, endDate);
-console.log(statements);
+
+// Process transactions
+statements.forEach(statement => {
+    console.log(`Date: ${statement.date}`);
+    statement.transactions.forEach(transaction => {
+        console.log(`  ${transaction.descriptionStructured?.bookingText || 'Transaction'}`);
+        console.log(`  Amount: ${transaction.amount} ${transaction.currency}`);
+        console.log(`  Purpose: ${transaction.purpose || 'N/A'}`);
+    });
+});
 ```
 
-For CLI usage:
+**CLI Example**
+```bash
+# Fetch transactions for a date range
+fints-lib fetch-transactions \
+  --url https://banking.example.com/fints \
+  -n username -p 12345 -b 12345678 \
+  -i DE89370400440532013000 \
+  -s 2024-01-01 -e 2024-12-31 \
+  --json > transactions.json
+```
+
+### 3. SEPA Credit Transfer (Send Money)
+
+```typescript
+import { PinTanClient, TanRequiredError } from "fints-lib";
+
+const client = new PinTanClient({
+    url: process.env.FINTS_URL,
+    name: process.env.FINTS_USERNAME,
+    pin: process.env.FINTS_PIN,
+    blz: process.env.FINTS_BLZ,
+});
+
+const accounts = await client.accounts();
+const myAccount = accounts[0];
+
+// Prepare transfer
+const transfer = {
+    debtorName: "John Doe",
+    creditor: {
+        name: "Recipient Name",
+        iban: "DE44500105175407324931",
+        bic: "INGDDEFFXXX",  // Optional for transfers within SEPA
+    },
+    amount: 50.00,
+    remittanceInformation: "Payment for invoice #12345",
+};
+
+try {
+    // Initiate transfer
+    const result = await client.creditTransfer(myAccount, transfer);
+    console.log("Transfer successful:", result.taskId);
+} catch (error) {
+    if (error instanceof TanRequiredError) {
+        // TAN is required - get TAN from user
+        const tan = "123456";  // Get from user input or TAN app
+
+        const result = await client.completeCreditTransfer(
+            error.dialog,
+            error.transactionReference,
+            tan,
+            error.creditTransferSubmission
+        );
+        console.log("Transfer completed:", result.taskId);
+    } else {
+        throw error;
+    }
+}
+```
+
+**CLI Example**
+```bash
+# Transfer money (will prompt for TAN if required)
+fints-lib submit-credit-transfer \
+  --url https://banking.example.com/fints \
+  -n username -p 12345 -b 12345678 \
+  --account-iban DE89370400440532013000 \
+  --debtor-name "John Doe" \
+  --creditor-name "Recipient Name" \
+  --creditor-iban DE44500105175407324931 \
+  --amount 50.00 \
+  --remittance "Payment for invoice #12345"
+```
+
+### 4. SEPA Direct Debit (Collect Money)
+
+```typescript
+import { PinTanClient, TanRequiredError } from "fints-lib";
+
+const client = new PinTanClient({
+    url: process.env.FINTS_URL,
+    name: process.env.FINTS_USERNAME,
+    pin: process.env.FINTS_PIN,
+    blz: process.env.FINTS_BLZ,
+});
+
+const accounts = await client.accounts();
+const myAccount = accounts[0];
+
+// Prepare direct debit
+const debit = {
+    creditorName: "My Company GmbH",
+    creditorId: "DE98ZZZ09999999999",  // Your SEPA creditor ID
+    debtor: {
+        name: "Customer Name",
+        iban: "DE02120300000000202051",
+    },
+    amount: 99.99,
+    mandateId: "MANDATE-2024-001",
+    mandateSignatureDate: new Date("2024-01-15"),
+    requestedCollectionDate: new Date("2024-12-15"),
+    remittanceInformation: "Monthly subscription fee",
+};
+
+try {
+    const result = await client.directDebit(myAccount, debit);
+    console.log("Direct debit submitted:", result.taskId);
+} catch (error) {
+    if (error instanceof TanRequiredError) {
+        const tan = "123456";  // Get from user
+
+        const result = await client.completeDirectDebit(
+            error.dialog,
+            error.transactionReference,
+            tan,
+            error.directDebitSubmission
+        );
+        console.log("Direct debit completed:", result.taskId);
+    } else {
+        throw error;
+    }
+}
+```
 
+**CLI Example**
 ```bash
-# List accounts
-fints-lib list-accounts --url https://example.com/fints -n username -p 12345 -b 12345678
+fints-lib submit-direct-debit \
+  --url https://banking.example.com/fints \
+  -n username -p 12345 -b 12345678 \
+  --account-iban DE89370400440532013000 \
+  --creditor-name "My Company GmbH" \
+  --creditor-id DE98ZZZ09999999999 \
+  --debtor-name "Customer Name" \
+  --debtor-iban DE02120300000000202051 \
+  --amount 99.99 \
+  --mandate-id MANDATE-2024-001 \
+  --mandate-date 2024-01-15 \
+  --collection-date 2024-12-15 \
+  --remittance "Monthly subscription fee"
+```
 
-# Fetch transactions
-fints-lib fetch-transactions --url https://example.com/fints -n username -p 12345 -b 12345678 -i DE111234567800000001 -s 2024-01-01 -e 2024-12-31
+### 5. List Multiple Accounts and Their Balances
+
+```typescript
+import { PinTanClient } from "fints-lib";
+
+const client = new PinTanClient({
+    url: process.env.FINTS_URL,
+    name: process.env.FINTS_USERNAME,
+    pin: process.env.FINTS_PIN,
+    blz: process.env.FINTS_BLZ,
+});
+
+// Get all accounts with balances
+const accounts = await client.accounts();
+
+for (const account of accounts) {
+    console.log(`\n${account.accountName || 'Account'} (${account.iban})`);
+    console.log(`  Type: ${account.accountType || 'N/A'}`);
+
+    try {
+        const balance = await client.balance(account);
+        console.log(`  Balance: ${balance.value.value} ${balance.value.currency}`);
+        console.log(`  Available: ${balance.availableBalance?.value || 'N/A'}`);
+    } catch (error) {
+        console.log(`  Balance: Unable to fetch`);
+    }
+}
 ```
 
 > Before using any FinTS library you have to register your application with Die Deutsche Kreditwirtschaft in order to get your registration number. Note that this process can take several weeks. First you receive your registration number after a couple days, but then you have to wait anywhere between 0 and 8+ weeks for the registration to reach your bank's server. If you have multiple banks, it probably reaches them at different times.
@@ -135,6 +368,86 @@ const badClient = new PinTanClient({
 
 If you discover a security vulnerability, please report it privately via GitHub's "Security" tab instead of opening a public issue.
 
+## 💡 Tips and Troubleshooting
+
+### Finding Your Bank's FinTS URL
+
+You can find your bank's FinTS endpoint URL in this community database:
+- [FinTS Institute Database](https://github.com/jhermsmeier/fints-institute-db)
+
+### Common Issues
+
+**Authentication Errors:**
+- Verify your username, PIN, and BLZ are correct
+- Some banks require you to enable FinTS/HBCI access in your online banking settings
+- Check if your bank requires registration (see registration note below)
+
+**TAN Requirements:**
+- Many operations (transfers, direct debits) require TAN authentication
+- Use try-catch with `TanRequiredError` to handle TAN challenges properly
+- Some banks require TAN even for login - handle with `completeLogin()`
+
+**Timeout Issues:**
+- Increase the timeout value in client configuration:
+  ```typescript
+  const client = new PinTanClient({
+      // ... other config
+      timeout: 60000,  // 60 seconds
+      maxRetries: 5,
+  });
+  ```
+
+**Date Range Queries:**
+- Not all banks support all date ranges - some limit how far back you can query
+- Use shorter date ranges if you experience timeouts or errors
+
+### Best Practices
+
+1. **Always use environment variables for credentials:**
+   ```typescript
+   const client = new PinTanClient({
+       url: process.env.FINTS_URL,
+       name: process.env.FINTS_USERNAME,
+       pin: process.env.FINTS_PIN,
+       blz: process.env.FINTS_BLZ,
+   });
+   ```
+
+2. **Enable debug mode during development:**
+   ```typescript
+   const client = new PinTanClient({
+       // ... credentials
+       debug: process.env.NODE_ENV === 'development',
+   });
+   ```
+
+3. **Handle errors gracefully:**
+   ```typescript
+   import { FinTSError, TanRequiredError, PinError } from "fints-lib";
+
+   try {
+       const accounts = await client.accounts();
+   } catch (error) {
+       if (error instanceof TanRequiredError) {
+           // Handle TAN requirement
+       } else if (error instanceof PinError) {
+           // Handle PIN error
+       } else if (error instanceof FinTSError) {
+           console.error(`FinTS Error [${error.code}]: ${error.message}`);
+       }
+   }
+   ```
+
+4. **Close dialogs when done:**
+   ```typescript
+   const dialog = await client.startDialog();
+   try {
+       // ... perform operations
+   } finally {
+       await dialog.end();
+   }
+   ```
+
 ## Mentions
 
 FinTS is a complex and old format and this library wouldn't have been possible without the great work of: