feat: set up modularized version of project with testing

src/timesheets/utils.py

@@ -0,0 +1,44 @@
+import re
+from datetime import date
+
+
+def parse_duration(duration_str: str) -> float:
+    """Convert HH:MM duration string to decimal hours."""
+    duration_str = duration_str.strip()
+    match = re.match(r"^(\d+):(\d{2})$", duration_str)
+    if not match:
+        raise ValueError(f"Invalid duration format: {duration_str!r}")
+    return int(match.group(1)) + int(match.group(2)) / 60.0
+
+
+def duration_from_start_end(start_str: str, end_str: str) -> float:
+    """Calculate duration in decimal hours from two HH:MM time strings."""
+
+    def to_minutes(t: str) -> int:
+        match = re.match(r"^(\d+):(\d{2})$", t.strip())
+        if not match:
+            raise ValueError(f"Invalid time format: {t!r}")
+        return int(match.group(1)) * 60 + int(match.group(2))
+
+    start_minutes = to_minutes(start_str)
+    end_minutes = to_minutes(end_str)
+    if end_minutes < start_minutes:
+        end_minutes += 24 * 60  # midnight rollover
+    return (end_minutes - start_minutes) / 60.0
+
+
+def decimal_to_hhmm(hours: float) -> str:
+    """Convert decimal hours to a HH:MM string."""
+    total_minutes = round(hours * 60)
+    h, m = divmod(total_minutes, 60)
+    return f"{h:02d}:{m:02d}"
+
+
+def strip_markdown_link(text: str) -> str:
+    """Strip markdown link syntax [label](url), keeping only the label."""
+    return re.sub(r"\[([^\]]+)\]\([^)]*\)", r"\1", text)
+
+
+def format_date(d: date) -> str:
+    """Format date as DD/MM/YY."""
+    return d.strftime("%d/%m/%y")