Simplify interface for testing

day2/day2_sample.py

@@ -8,7 +8,6 @@ A report (one line of space-separated integers) is safe if:
 
 Usage:
   python day2/aoc_2024_day2.py input.txt
-  cat input.txt | python day2/aoc_2024_day2.py
 """
 
 import argparse
@@ -59,13 +58,14 @@ class Report:
         return True
 
 
-def parse_reports(lines):
+def parse_reports(path):
     reports = []
-    for raw in lines:
-        line = raw.strip()
-        if not line:
-            continue
-        reports.append(Report.from_line(line))
+    with open(path, "r", encoding="utf-8") as f:
+        for raw in f:
+            line = raw.strip()
+            if not line:
+                continue
+            reports.append(Report.from_line(line))
     return reports
 
 
@@ -77,17 +77,25 @@ def count_safe(reports):
     return safe_count
 
 
-def main():
-    parser = argparse.ArgumentParser("CLI to read sample files.")
-    parser.add_argument("input", help="Input file path (defaults to stdin). Use '-' for stdin.")
-    
-    args = parser.parse_args()
-    reports = parse_reports(args.input)
+def count_safe_in_file(path):
+    return count_safe(parse_reports(path))
 
-    print(count_safe(reports))
+
+def main(argv=None):
+    parser = argparse.ArgumentParser("CLI to read sample files.")
+    parser.add_argument(
+        "input",
+        help="Input file path.",
+    )
+
+    args = parser.parse_args(argv)
+    return count_safe_in_file(args.input)
+
+
+def cli(argv=None):
+    print(main(argv))
     return 0
 
 
 if __name__ == "__main__":
-    main()
-
+    raise SystemExit(cli())