tanken: cleanup code

* Add type annotations
* Use meaningfull variable names
* Add doc-strings
* Remove she-bang line from non-executable file

2 files changed, 31 insertions, 19 deletions

diff --git a/geldschieberbot.py b/geldschieberbot.py
index ff285db..f21b7d6 100644
--- a/geldschieberbot.py
+++ b/geldschieberbot.py
@@ -620,6 +620,8 @@ def _tanken(sender, args, msg) -> dict[str, str]:
     if err:
         return {'err': err}
 
+    assert parts
+
     output = ""
     change = [args]
     for pname, values in parts.items():
diff --git a/tanken.py b/tanken.py
index b19fb53..2c65c73 100644
--- a/tanken.py
+++ b/tanken.py
@@ -1,47 +1,57 @@
-#!/bin/env python3
+"""Utilities to support splitting fuel and car maintainance costs"""
+
+import typing as T
+
+PassengerResult = dict[str, int]
+Results = dict[str, PassengerResult]
+TankenFailure = T.Tuple[None, str]
+TankenSuccess = T.Tuple[Results, None]
+TankenResult = T.Union[TankenSuccess, TankenFailure]
 
 
 # cost should be given in cents
-def tanken(drives, cost, service_charge=0):
+def tanken(_drives: list[str], cost: int, service_charge=0) -> TankenResult:
+    """calculate costs per passange for one tank load"""
     passengers = {}
     distance = 0.
-    drives = [d.split(' ') for d in drives]
+    drives = [d.split(' ') for d in _drives]
 
-    for d in drives:
+    for drive in drives:
         try:
-            d[0] = int(d[0])
+            drive_distance = int(drive[0])
         except (IndexError, ValueError):
             return None, "Lines have to start with the driven distance!"
 
         # calculate overall distance
-        distance += d[0]
+        distance += drive_distance
 
         # collect distances per passenger
-        for p in d[1:]:
-            if p not in passengers:
-                passengers[p] = {
-                    "distance": d[0],
+        for passenger in drive[1:]:
+            if passenger not in passengers:
+                passengers[passenger] = {
+                    "distance": drive_distance,
                     "cost": 0,
                     "service_charge": 0
                 }
             else:
-                passengers[p]["distance"] += d[0]
+                passengers[passenger]["distance"] += drive_distance
 
     # calculate cost per kilometer
     if distance <= 0:
         return None, "Driven distance must be greater than 0!"
 
-    c = cost / distance
+    c_km = cost / distance
 
-    for d in drives:
+    for drive in drives:
+        drive_distance = int(drive[0])
         # calculate cost per drive split among passengers
-        c_d = int(c * d[0] / (len(d) - 1))
-        for p in d[1:]:
-            passengers[p]["cost"] += c_d
+        c_d = int(c_km * drive_distance / (len(drive) - 1))
+        for passenger in drive[1:]:
+            passengers[passenger]["cost"] += c_d
 
         # calculate service charge per drive split among passengers
-        sc_d = int(service_charge * d[0] / (len(d) - 1))
-        for p in d[1:]:
-            passengers[p]["service_charge"] += sc_d
+        sc_d = int(service_charge * drive_distance / (len(drive) - 1))
+        for passenger in drive[1:]:
+            passengers[passenger]["service_charge"] += sc_d
 
     return passengers, None