From 2de079a5d33212c3a7a0122e5121773364650cf6 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Fri, 24 Apr 2020 11:35:31 +0000
Subject: [PATCH] Add a few Transform combinators

---
 PFERD/transform.py | 140 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 139 insertions(+), 1 deletion(-)

diff --git a/PFERD/transform.py b/PFERD/transform.py
index f72c342..bce7ee5 100644
--- a/PFERD/transform.py
+++ b/PFERD/transform.py
@@ -5,9 +5,10 @@ only files whose names match a regex, or renaming files from one numbering
 scheme to another.
 """
 
+import re
 from dataclasses import dataclass
 from pathlib import PurePath
-from typing import Callable, List, Optional, TypeVar
+from typing import Callable, List, Optional, Tuple, TypeVar, Union
 
 Transform = Callable[[PurePath], Optional[PurePath]]
 
@@ -39,3 +40,140 @@ def apply_transform(
             transformable.path = new_path
             result.append(transformable)
     return result
+
+# Utility types and functions
+
+PathLike = Union[PurePath, str, Tuple[str, ...]]
+
+def _path(pathlike: PathLike) -> PurePath:
+    if isinstance(pathlike, tuple):
+        return PurePath(*pathlike)
+    return PurePath(pathlike)
+
+Regex = Union[str, re.Pattern]
+
+def _pattern(regex: Regex) -> re.Pattern:
+    if isinstance(regex, re.Pattern):
+        return regex
+    return re.compile(regex)
+
+# Transform combinators
+
+def attempt(*args: Transform) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        for transform in args:
+            if result := transform(path):
+                return result
+        return None
+    return inner
+
+def optionally(transform: Transform) -> Transform:
+    return attempt(transform, lambda path: path)
+
+def do(*args: Transform) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        current = path
+        for transform in args:
+            if result := transform(current):
+                current = result
+            else:
+                return None
+        return current
+    return inner
+
+def predicate(pred: Callable[[PurePath], bool]) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if pred(path):
+            return path
+        return None
+    return inner
+
+def glob(pattern: str) -> Transform:
+    return predicate(lambda path: path.match(pattern))
+
+def move_dir(source_dir: PathLike, target_dir: PathLike) -> Transform:
+    source_path = _path(source_dir)
+    target_path = _path(target_dir)
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if source_path in path.parents:
+            return target_path / path.relative_to(source_path)
+        return None
+    return inner
+
+def move(source: PathLike, target: PathLike) -> Transform:
+    source_path = _path(source)
+    target_path = _path(target)
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if path == source_path:
+            return target_path
+        return None
+    return inner
+
+def rename(source: str, target: str) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if path.name == source:
+            return path.with_name(target)
+        return None
+    return inner
+
+def re_move(regex: Regex, target: str) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if match := _pattern(regex).fullmatch(str(path)):
+            groups = [match.group(0)]
+            groups.extend(match.groups())
+            return PurePath(target.format(*groups))
+        return None
+    return inner
+
+def re_rename(regex: Regex, target: str) -> Transform:
+    def inner(path: PurePath) -> Optional[PurePath]:
+        if match := _pattern(regex).fullmatch(path.name):
+            groups = [match.group(0)]
+            groups.extend(match.groups())
+            return path.with_name(target.format(*groups))
+        return None
+    return inner
+
+# def match(regex: Union[str, re.Pattern]) -> Transform:
+#     pattern: re.Pattern
+#     if isinstance(regex, str):
+#         pattern = re.compile(regex)
+#     else:
+#         pattern = regex
+
+#     return predicate(lambda path: bool(pattern.match(path.name)))
+
+# def full_match(regex: Union[str, re.Pattern]) -> Transform:
+#     pattern: re.Pattern
+#     if isinstance(regex, str):
+#         pattern = re.compile(regex)
+#     else:
+#         pattern = regex
+
+#     return predicate(lambda path: bool(pattern.match(str(path))))
+
+# def zoom(
+#         selector: Callable[[PurePath], Optional[Tuple[PurePath, PurePath]]],
+#         actor: Callable[[PurePath], Transform],
+# ) -> Transform:
+#     def inner(path: PurePath) -> Optional[PurePath]:
+#         if selected := selector(path):
+#             base, relative = selected
+#             return actor(base)(relative)
+#         return None
+#     return inner
+
+# def move_from(source: PurePath, target: PurePath) -> Transform:
+#     return zoom(
+#         lambda path: (source, path.relative_to(source)) if source in path.parents else None,
+#         lambda _: lambda path: target / path,
+#     )
+
+# re_move(r"Übungsmaterial/Blätter/(\d+).pdf", "Blätter/Blatt{1:02}.pdf")
+# re_rename(r"(\d+).pdf", "Blatt{1:02}.pdf")
+
+# def at(at_path: PurePath) -> Transform:
+#     return predicate(lambda path: path == at_path)
+
+# def inside(inside_path: PurePath) -> Transform:
+#     return predicate(lambda path: inside_path in path.parents)