From a3a0a150a8440393e40b1518ee4d8a02aeb7ac5f Mon Sep 17 00:00:00 2001
From: Sven Heidemann <sven.heidemann@sh-edraft.de>
Date: Tue, 27 Jul 2021 11:29:52 +0200
Subject: [PATCH] Added element at query

---
 src/cpl_query/_extension/iterable.py    |  7 +++++++
 src/cpl_query/_query/element_at.py      | 25 +++++++++++++++++++++++++
 src/cpl_query/exceptions.py             |  1 +
 src/cpl_query/extension/iterable_abc.py |  6 ++++++
 src/cpl_query/tests/query_test.py       |  9 +++++++++
 5 files changed, 48 insertions(+)
 create mode 100644 src/cpl_query/_query/element_at.py

diff --git a/src/cpl_query/_extension/iterable.py b/src/cpl_query/_extension/iterable.py
index 2361fe67..cb0f868e 100644
--- a/src/cpl_query/_extension/iterable.py
+++ b/src/cpl_query/_extension/iterable.py
@@ -8,6 +8,7 @@ from .._query.avg import avg_query
 from .._query.contains import contains_query
 from .._query.count import count_query
 from .._query.distinct import distinct_query
+from .._query.element_at import element_at_query, element_at_or_default_query
 from .._query.first import first_or_default_query, first_query
 from .._query.for_each import for_each_query
 from .._query.order_by import order_by_query, order_by_descending_query
@@ -41,6 +42,12 @@ class Iterable(IterableABC):
         res.__class__ = Iterable
         return res
 
+    def element_at(self, index: int) -> any:
+        return element_at_query(self, index)
+
+    def element_at_or_default(self, index: int) -> Optional[any]:
+        return element_at_or_default_query(self, index)
+
     def first(self) -> any:
         return first_query(self)
 
diff --git a/src/cpl_query/_query/element_at.py b/src/cpl_query/_query/element_at.py
new file mode 100644
index 00000000..67bd514c
--- /dev/null
+++ b/src/cpl_query/_query/element_at.py
@@ -0,0 +1,25 @@
+from cpl_query.exceptions import ArgumentNoneException, ExceptionArgument
+from cpl_query.extension.iterable_abc import IterableABC
+
+
+def element_at_query(_list: IterableABC, _index: int) -> any:
+    if _list is None:
+        raise ArgumentNoneException(ExceptionArgument.list)
+
+    if _index is None:
+        raise ArgumentNoneException(ExceptionArgument.index)
+
+    return _list[_index]
+
+
+def element_at_or_default_query(_list: IterableABC, _index: int) -> any:
+    if _list is None:
+        raise ArgumentNoneException(ExceptionArgument.list)
+
+    if _index is None:
+        raise ArgumentNoneException(ExceptionArgument.index)
+
+    try:
+        return _list[_index]
+    except IndexError:
+        return None
diff --git a/src/cpl_query/exceptions.py b/src/cpl_query/exceptions.py
index c9694221..1b6e550d 100644
--- a/src/cpl_query/exceptions.py
+++ b/src/cpl_query/exceptions.py
@@ -7,6 +7,7 @@ class ExceptionArgument(Enum):
     func = 'func'
     type = 'type'
     value = 'value'
+    index = 'index'
 
 
 # exceptions
diff --git a/src/cpl_query/extension/iterable_abc.py b/src/cpl_query/extension/iterable_abc.py
index bd031833..28cb188b 100644
--- a/src/cpl_query/extension/iterable_abc.py
+++ b/src/cpl_query/extension/iterable_abc.py
@@ -26,6 +26,12 @@ class IterableABC(ABC, list):
     @abstractmethod
     def distinct(self, func: Callable) -> 'IterableABC': pass
 
+    @abstractmethod
+    def element_at(self, index: int) -> any: pass
+
+    @abstractmethod
+    def element_at_or_default(self, index: int) -> Optional[any]: pass
+
     @abstractmethod
     def first(self) -> any: pass
 
diff --git a/src/cpl_query/tests/query_test.py b/src/cpl_query/tests/query_test.py
index 9a187f3e..2481f60e 100644
--- a/src/cpl_query/tests/query_test.py
+++ b/src/cpl_query/tests/query_test.py
@@ -91,6 +91,15 @@ class QueryTest(unittest.TestCase):
         res = self._tests.distinct(lambda u: u.address.nr).where(lambda u: u.address.nr == 5)
         self.assertEqual(1, len(res))
 
+    def test_element_at(self):
+        index = randint(0, len(self._tests) - 1)
+        self.assertEqual(self._tests[index], self._tests.element_at(index))
+
+    def test_element_at_or_default(self):
+        index = randint(0, len(self._tests) - 1)
+        self.assertEqual(self._tests[index], self._tests.element_at_or_default(index))
+        self.assertIsNone(self._tests.element_at_or_default(len(self._tests)))
+
     def test_first(self):
         results = []
         for user in self._tests: