Treat ListSharee as access table

This is so that multiple users can be paired with a single list.

In the future, we may want to reconsider list deletion behavior to simply remove a user's access and only delete it when no one has access.

We may also want the user deletion Lambda to use the list deletion Lambda when it is created.

Lambdas/Lists/ListShare/src/ListSharePOST.java

@@ -0,0 +1,11 @@
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+
+import java.util.Map;
+
+public class ListSharePOST implements RequestHandler<Map<String,Object>, Object> {
+
+    public Object handleRequest(Map<String, Object> inputMap, Context unfilled) {
+        return BasicHandler.handleRequest(inputMap, unfilled, ListSharer.class);
+    }
+}

Lambdas/Lists/ListShare/src/ListSharer.java

@@ -0,0 +1,68 @@
+import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
+import com.amazonaws.services.lambda.model.InvokeRequest;
+import com.amazonaws.services.lambda.model.InvokeResult;
+
+import java.security.AccessControlException;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.HashMap;
+import java.util.InputMismatchException;
+import java.util.Map;
+
+public class ListSharer implements CallHandler {
+
+    private Connection connection;
+    private String cognitoID;
+
+    public ListSharer(Connection connection, String cognitoID) {
+        this.connection = connection;
+        this.cognitoID = cognitoID;
+    }
+
+    final private String CHECK_ACCESS = "SELECT * from ListSharee WHERE listID = ? AND userID = ?;";
+    final private String SHARE_LIST = "INSERT INTO ListSharee(listID, userID) VALUES(?, ?);";
+
+    public Object conductAction(Map<String, Object> bodyMap, HashMap<String, String> queryString, String cognitoID) throws SQLException {
+        PreparedStatement checkAccess = connection.prepareStatement(CHECK_ACCESS);
+        Integer listID = Integer.parseInt(bodyMap.get("listID").toString());
+        checkAccess.setInt(1, listID);
+        checkAccess.setString(2, cognitoID);
+        ResultSet checkAccessRS = checkAccess.executeQuery();
+        if (!checkAccessRS.next()) {
+            throw new AccessControlException("The requesting user does not have access to the requested list");
+        }
+        InvokeRequest invokeRequest = new InvokeRequest();
+        invokeRequest.setFunctionName("UserGET");
+        invokeRequest.setPayload("{" +
+                "  \"body\": {" +
+                "      \"emailToCheck\": \"" + bodyMap.get("shareWith").toString() + "\"" +
+                "  }," +
+                "  \"params\": {" +
+                "      \"querystring\": {" +
+                "      }" +
+                "  }," +
+                "  \"context\": {" +
+                "    \"sub\": \"not used\"" +
+                "  }" +
+                "}");
+        InvokeResult invokeResult = AWSLambdaClientBuilder.defaultClient().invoke(invokeRequest);
+        if (invokeResult.getStatusCode() != 200) {
+            throw new InputMismatchException("Could not find specified user to share with");
+        }
+        String shareWithSub = new String(invokeResult.getPayload().array()).replace("\"", "");
+        checkAccess.setString(2, shareWithSub);
+        checkAccessRS = checkAccess.executeQuery();
+        if (checkAccessRS.next()) {
+            throw new InputMismatchException("The specified user already has access");
+        }
+
+        PreparedStatement shareList = connection.prepareStatement(SHARE_LIST);
+        shareList.setInt(1, listID);
+        shareList.setString(2, shareWithSub);
+        shareList.executeUpdate();
+        connection.commit();
+        return null;
+    }
+}