added index_of_with_escape function

src/pwo/__init__.py

@@ -9,6 +9,7 @@ from .private import (
     classproperty,
     AsyncQueueIterator,
     aenumerate,
+    index_of_with_escape
 )
 from .maybe import Maybe
 from .notification import TopicManager, Subscriber
@@ -28,5 +29,6 @@ __all__ = [
     'Subscriber',
     'AsyncQueueIterator',
     'aenumerate',
-    'Try'
+    'Try',
+    'index_of_with_escape'
 ]

src/pwo/private.py

@@ -252,3 +252,32 @@ class aenumerate[T](AsyncIterator[Tuple[int, T]]):
         val = await self._ait.__anext__()
         self._i += 1
         return self._i, val
+
+
+def index_of_with_escape(haystack: str, needle: str, escape: str, begin: int, end: int = 0) -> int:
+    result = -1
+    cursor = begin
+    if end == 0:
+        end = len(haystack)
+    escape_count = 0
+
+    while cursor < end:
+        c = haystack[cursor]
+
+        if escape_count > 0:
+            escape_count -= 1
+            if c == escape:
+                result = -1
+        elif escape_count == 0:
+            if c == escape:
+                escape_count += 1
+            if c == needle:
+                result = cursor
+
+        if result >= 0 and escape_count == 0:
+            break
+
+        cursor += 1
+
+    return result
+

tests/test_private.py

@@ -1,6 +1,6 @@
 import unittest
 
-from pwo import retry, async_retry, async_test, AsyncQueueIterator, aenumerate
+from pwo import retry, async_retry, async_test, AsyncQueueIterator, aenumerate, index_of_with_escape
 from asyncio import Queue
 
 
@@ -93,3 +93,35 @@ class PrivateTest(unittest.TestCase):
         self.assertEqual(queue_size, processed)
 
 
+class TestIndexOfWithEscape(unittest.TestCase):
+
+    def run_test_case(self, haystack, needle, escape, expected_solution):
+        solution = []
+        i = 0
+        while True:
+            i = index_of_with_escape(haystack, needle, escape, i, len(haystack))
+            if i < 0:
+                break
+            solution.append(i)
+            i += 1
+        self.assertEqual(solution, expected_solution)
+
+    def test_simple(self):
+        self.run_test_case(" dsds $sdsa \\$dfivbdsf \\\\$sdgsga", '$', '\\', [6, 25])
+
+    def test_simple2(self):
+        self.run_test_case("asdasd$$vdfv$", '$', '$', [12])
+
+    def test_no_needle(self):
+        self.run_test_case("asdasd$$vdfv$", '#', '\\', [])
+
+    def test_escaped_needle(self):
+        self.run_test_case("asdasd$$vdfv$#sdfs", '#', '$', [])
+
+    def test_not_escaped_needle(self):
+        self.run_test_case("asdasd$$#vdfv$#sdfs", '#', '$', [8])
+
+    def test_special_case(self):
+        self.run_test_case("\n${sys:user.home}${env:HOME}", ':', '\\', [6, 22])
+
+