#20 Add transaction type

financer-common/src/main/java/de/financer/model/Transaction.java

@@ -39,6 +39,8 @@ public class Transaction {
     // the inline expense history chart and the expense/income/liability chart
     // No UI to set the flag as its use is only for very special cases
     private boolean expenseNeutral;
+    @Enumerated(EnumType.STRING)
+    private TransactionType transactionType;
 
     public Long getId() {
         return id;
@@ -123,4 +125,12 @@ public class Transaction {
     public void setExpenseNeutral(boolean expenseNeutral) {
         this.expenseNeutral = expenseNeutral;
     }
+
+    public TransactionType getTransactionType() {
+        return transactionType;
+    }
+
+    public void setTransactionType(TransactionType transactionType) {
+        this.transactionType = transactionType;
+    }
 }

financer-common/src/main/java/de/financer/model/TransactionType.java

@@ -0,0 +1,51 @@
+package de.financer.model;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * This enum specifies constants that specify the type of a transaction. Actual specification which type is used when
+ * is implemented in <code>financer-server#RuleService</code>
+ */
+public enum TransactionType {
+    /**
+     * Specifies that a transaction swaps money from one asset account (e.g. {@link AccountType#BANK BANK})
+     * to another one (e.g. {@link AccountType#CASH CASH})
+     */
+    ASSET_SWAP,
+
+    /**
+     * Specifies that a transaction captured the process of buying something
+     */
+    EXPENSE,
+
+    /**
+     * Specifies that a transaction was made to pay back a liability
+     */
+    LIABILITY,
+
+    /**
+     * Specifies a transaction that increases the assets
+     */
+    INCOME,
+
+    /**
+     * Specifies that a transaction was used to book the starting amount to a liability account.
+     */
+    START_LIABILITY;
+
+    /**
+     * This method validates whether the given string represents a valid transaction type.
+     *
+     * @param type to check
+     * @return whether the given type represents a valid transaction type
+     */
+    public static boolean isValidType(String type) {
+        return Arrays.stream(TransactionType.values()).anyMatch((accountType) -> accountType.name().equals(type));
+    }
+
+    public static List<String> valueList() {
+        return Arrays.stream(TransactionType.values()).map(TransactionType::name).collect(Collectors.toList());
+    }
+}