refactor(string): split utilities by responsibility

app/domain/episode.py

@@ -0,0 +1,39 @@
+"""剧集编号列表的业务显示规则。"""
+
+from typing import List
+
+
+def compact_numbers(numbers: List[int]) -> str:
+    """把连续剧集编号压缩为逗号分隔的数字区间。"""
+    numbers.sort()
+    result = []
+    start = numbers[0]
+    end = numbers[0]
+    for number in numbers[1:]:
+        if number == end + 1:
+            end = number
+            continue
+        result.append(str(start) if start == end else f"{start}-{end}")
+        start = end = number
+    result.append(str(start) if start == end else f"{start}-{end}")
+    return ",".join(result)
+
+
+def format_ranges(numbers: List[int]) -> str:
+    """把剧集编号格式化为带 E 前缀和中文顿号的连续区间。"""
+    if not numbers:
+        return ""
+    if len(numbers) == 1:
+        return f"E{numbers[0]:02d}"
+    numbers.sort()
+    ranges = []
+    start = numbers[0]
+    end = numbers[0]
+    for number in numbers[1:]:
+        if number == end + 1:
+            end = number
+            continue
+        ranges.append(f"E{start:02d}" if start == end else f"E{start:02d}-E{end:02d}")
+        start = end = number
+    ranges.append(f"E{start:02d}" if start == end else f"E{start:02d}-E{end:02d}")
+    return "、".join(ranges)