lib.ProcFilter: Add module

Add the ProcFilter module, containing the following classes:

  - ProcFilter:

    Abstract base class defining a run(data: bytes) -> Result method,
    allowing to do arbitrary data manipulation in subclasses.

  - ProcFilterIdenty

    A ProcFilter specialization which passes through the input
    unchanged.

  - ProcPipeline

    A container for multiple chained ProcFilter classes

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ProcFilter.py

@@ -0,0 +1,44 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+import abc
+
+from .base import Result
+
+if TYPE_CHECKING:
+    from typing import Iterable
+
+class ProcFilter(abc.ABC):
+
+    @abc.abstractmethod
+    async def _run(self, data: bytes) -> Result:
+        raise NotImplementedError()
+
+    async def run(self, data: bytes) -> Result:
+        return await self._run(data)
+
+class ProcFilterIdentity(ProcFilter):
+
+    async def _run(self, data: bytes) -> Result:
+        return Result(data, None, 0)
+
+class ProcPipeline:
+
+    def __init__(self, f: Iterable[ProcFilter]|ProcFilter = []) -> None:
+        self.__filters: list[ProcFilter] = []
+        self.append(f)
+
+    def append(self, f: ProcFilter|Iterable[ProcFilter]) -> None:
+        if not isinstance(f, ProcFilter):
+            for e in f:
+                self.append(e)
+            return
+        self.__filters.append(f)
+
+    async def run(self, data: bytes|Result) -> Result:
+        ret = data if isinstance(data, Result) else Result(data, None, 0)
+        for f in self.__filters:
+            ret = await f.run(ret.stdout)
+        return ret