From 45a2de9401a6855794575ad2aeb288a2a4ba11c8 Mon Sep 17 00:00:00 2001
From: Oliver Deng <oliver.t.deng@gmail.com>
Date: Mon, 3 Nov 2025 23:59:27 -0500
Subject: [PATCH] feat(bfs.py): implement bfs algorithm and appropriate tests

---
 tests/test_algorithms.py        | 24 +++++++++++++++++-------
 waypoint/algorithms/__init__.py |  4 ++--
 waypoint/algorithms/a_star.py   |  5 -----
 waypoint/algorithms/bfs.py      | 24 ++++++++++++++++++++++++
 waypoint/path.py                |  2 +-
 5 files changed, 44 insertions(+), 15 deletions(-)
 delete mode 100644 waypoint/algorithms/a_star.py
 create mode 100644 waypoint/algorithms/bfs.py

diff --git a/tests/test_algorithms.py b/tests/test_algorithms.py
index 8ab3d50..04ade3b 100644
--- a/tests/test_algorithms.py
+++ b/tests/test_algorithms.py
@@ -1,5 +1,5 @@
 import pytest
-from waypoint.algorithms import djikstra, a_star
+from waypoint.algorithms import djikstra, bfs
 from waypoint.path import Path
 
 
@@ -47,12 +47,8 @@ def multiple_paths_graph():
 algorithm_parametrize = pytest.mark.parametrize(
     "algorithm",
     [
-        # pytest.param(bfs, marks=pytest.mark.xfail(reason="BFS not implemented")),
-        pytest.param(
-            djikstra,
-            # marks=pytest.mark.xfail(reason="Dijkstra not implemented"),
-        ),
-        pytest.param(a_star, marks=pytest.mark.xfail(reason="A* not implemented")),
+        pytest.param(djikstra),
+        pytest.param(bfs),
     ],
 )
 
@@ -61,6 +57,13 @@ def multiple_paths_graph():
 @algorithm_parametrize
 class TestAlgorithms:
     def test_simple_path(self, algorithm, simple_graph):
+        if algorithm.__name__ == "bfs":
+            # BFS does not consider weights, so the path may differ
+            result = algorithm(simple_graph, 100, 400)
+            assert result.flights is not None
+            assert result.flights[0] == 100
+            assert result.flights[-1] == 400
+            return
         result = algorithm(simple_graph, 100, 400)
         assert isinstance(result, Path)
         assert result.flights == [100, 200, 300, 400]
@@ -78,6 +81,13 @@ def test_cyclic_path(self, algorithm, cyclic_graph):
         assert result.time <= 7  # Maximum possible path length
 
     def test_multiple_paths(self, algorithm, multiple_paths_graph):
+        if algorithm.__name__ == "bfs":
+            # BFS does not consider weights, so the path may differ
+            result = algorithm(multiple_paths_graph, 100, 400)
+            assert result.flights is not None
+            assert result.flights[0] == 100
+            assert result.flights[-1] == 400
+            return
         result = algorithm(multiple_paths_graph, 100, 400)
         assert result.flights == [100, 300, 400]  # Should find shortest path
         assert result.time == 4
diff --git a/waypoint/algorithms/__init__.py b/waypoint/algorithms/__init__.py
index f8a1d15..2f87fe4 100644
--- a/waypoint/algorithms/__init__.py
+++ b/waypoint/algorithms/__init__.py
@@ -3,6 +3,6 @@
 """
 
 from .djikstra import djikstra
-from .a_star import a_star
+from .bfs import bfs
 
-__all__ = ["djikstra", "a_star"]
+__all__ = ["djikstra", "bfs"]
diff --git a/waypoint/algorithms/a_star.py b/waypoint/algorithms/a_star.py
deleted file mode 100644
index 0825cf9..0000000
--- a/waypoint/algorithms/a_star.py
+++ /dev/null
@@ -1,5 +0,0 @@
-from waypoint.path import Path
-
-
-def a_star(graph: dict[int, dict[int, float]], start: int, destination: int) -> Path:
-    raise NotImplementedError("The A* algorithm is not yet implemented.")
diff --git a/waypoint/algorithms/bfs.py b/waypoint/algorithms/bfs.py
new file mode 100644
index 0000000..feb9730
--- /dev/null
+++ b/waypoint/algorithms/bfs.py
@@ -0,0 +1,24 @@
+from waypoint.path import Path
+
+
+def bfs(graph: dict[int, dict[int, float]], start: int, destination: int) -> Path:
+    visited: set[int] = set()
+    queue: list[tuple[int, float, list[int]]] = [(start, 0, [])]
+
+    while queue:
+        current, time, path = queue.pop(0)
+        current: int
+        time: float
+        path: list[int]
+
+        if current == destination:
+            return Path.from_list(path + [current], time)
+
+        if current not in visited:
+            visited.add(current)
+            neighbors = graph.get(current, {})
+            for neighbor, weight in neighbors.items():
+                if neighbor not in visited:
+                    queue.append((neighbor, time + weight, path + [current]))
+
+    return Path.empty()
diff --git a/waypoint/path.py b/waypoint/path.py
index 95f1791..6ec3aed 100644
--- a/waypoint/path.py
+++ b/waypoint/path.py
@@ -28,7 +28,7 @@ def empty(cls) -> "Path":
         return self
 
     @classmethod
-    def from_list(cls, flights: list[int] | None, time: float = 0.0) -> "Path":
+    def from_list(cls, flights: list[int] | None, time: float) -> "Path":
         """Creates a path from a list of flights and an optional time."""
         self = super().__new__(cls)
         self._flights = flights