lib.FileContext: Support attaching data filters

- Add optional in_pipe and out_pipe parameters to __init__()

 - Add a add_proc_filter() method

Add possibilites to attach input / output pipes to a FileContext
instance. Data will be passed through the input pipe between ._get()
and .get(), and through the output pipe between .put() and _put().

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

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

@@ -3,7 +3,8 @@
 from __future__ import annotations
 
 import abc, re
-from typing import TYPE_CHECKING
+from enum import Enum, auto
+from typing import TYPE_CHECKING, Self
 from functools import cached_property, cache
 
 if TYPE_CHECKING:
@@ -11,16 +12,31 @@ if TYPE_CHECKING:
 
 from .log import *
 from .base import Input, InputMode, Result, StatResult
+from .ProcFilter import ProcPipeline
 
 class FileContext(abc.ABC):
 
-    def __init__(self, uri: str, interactive: bool|None=None, verbose_default=False, chroot: bool=False):
+    class Direction(Enum):
+        In = auto()
+        Out = auto()
+
+    def __init__(
+            self,
+            uri: str,
+            interactive: bool|None = None,
+            verbose_default = False,
+            chroot: bool = False,
+            in_pipe: ProcPipeline|None = None,
+            out_pipe: ProcPipeline|None = None,
+        ):
         self.__uri = uri
         self.__id, self.__root = self.split_uri(uri)
         self.__chroot = chroot
         self.__interactive = interactive
         self.__verbose_default = verbose_default
         self.__log_name: str|None = None
+        self.__in_pipe = in_pipe
+        self.__out_pipe = out_pipe
         assert verbose_default is not None
 
     async def __aenter__(self):
@@ -30,6 +46,19 @@ class FileContext(abc.ABC):
     async def __aexit__(self, exc_type, exc, tb):
         await self.close()
 
+    def __pipe(self, d: Direction):
+        match d:
+            case self.Direction.In:
+                if not self.__in_pipe:
+                    self.__in_pipe = ProcPipeline()
+                return self.__in_pipe
+            case self.Direction.Out:
+                if not self.__out_pipe:
+                    self.__out_pipe = ProcPipeline()
+                return self.__out_pipe
+            case _:
+                raise Exception(f'Invalid pipe direction "{str(d)}"')
+
     def _chroot(self, path: str) -> str:
         if not self.__chroot:
             return path
@@ -39,6 +68,9 @@ class FileContext(abc.ABC):
             return self.__root + path
         return self.__root + '/' + path
 
+    def add_proc_filter(self, d: Direction, proc_filter: ProcFilter):
+        self.__pipe(d).append(proc_filter)
+
     async def _open(self) -> None:
         pass
 
@@ -121,7 +153,14 @@ class FileContext(abc.ABC):
         group: str|None=None,
         mode: str|None=None,
     ) -> Result:
-        return await self._get(self._chroot(path), wd=wd, throw=throw, verbose=verbose, title=title)
+        ret = await self._get(
+            self._chroot(path),
+            wd = wd,
+            throw = throw,
+            verbose = verbose,
+            title = title,
+        )
+        return await self.__in_pipe.run(ret) if self.__in_pipe else ret
 
     async def _put(
         self,
@@ -152,8 +191,20 @@ class FileContext(abc.ABC):
         atomic: bool = False
     ) -> Result:
         mode_str = None if mode is None else oct(mode).replace('0o', '0')
-        return await self._put(self._chroot(path), content, wd=wd, throw=throw, verbose=verbose,
-                               title=title, owner=owner, group=group, mode=mode_str, atomic=atomic)
+        if self.__out_pipe is not None:
+            content = self.__out_pipe.run(content).stdout
+        return await self._put(
+            self._chroot(path),
+            content,
+            wd = wd,
+            throw = throw,
+            verbose = verbose,
+            title = title,
+            owner = owner,
+            group = group,
+            mode = mode_str,
+            atomic = atomic,
+        )
 
     async def _unlink(self, path: str) -> None:
         raise NotImplementedError(f'{self.log_name}: unlink("{path}") is not implemented')