feat(core): define managed tabular file contract

src/govoplan_core/core/files.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from collections.abc import Mapping
 from dataclasses import dataclass, field
+from datetime import datetime
 from typing import Protocol, runtime_checkable
 
 from govoplan_core.core.access import ResourceAccessExplanationProvider
@@ -10,6 +11,48 @@ from govoplan_core.core.access import ResourceAccessExplanationProvider
 CAPABILITY_FILES_ACCESS = "files.access"
 CAPABILITY_FILES_ARTIFACT_STORE = "files.artifact_store"
 CAPABILITY_FILES_POSTBOX_REFERENCES = "files.postbox_references"
+CAPABILITY_FILES_TABULAR_CONTENT = "files.tabular_content"
+
+
+class ManagedTabularFileError(ValueError):
+    """Stable base error for exact-version managed tabular file access."""
+
+
+class ManagedTabularFileNotFoundError(ManagedTabularFileError):
+    pass
+
+
+class ManagedTabularFileAccessError(ManagedTabularFileError):
+    pass
+
+
+class ManagedTabularFileUnavailableError(ManagedTabularFileError):
+    pass
+
+
+class ManagedTabularFileValidationError(ManagedTabularFileError):
+    pass
+
+
+@dataclass(frozen=True, slots=True)
+class ManagedTabularFile:
+    """Authorized metadata for one immutable managed file version."""
+
+    file_asset_id: str
+    file_version_id: str
+    filename: str
+    display_path: str
+    content_type: str | None
+    size_bytes: int
+    sha256: str
+    updated_at: datetime | None = None
+    current_version: bool = True
+
+
+@dataclass(frozen=True, slots=True)
+class ManagedTabularFileContent:
+    file: ManagedTabularFile
+    payload: bytes
 
 
 @dataclass(frozen=True, slots=True)
@@ -91,6 +134,39 @@ class PostboxFileReferenceProvider(Protocol):
     ) -> tuple[PostboxFileReferenceRef, ...]: ...
 
 
+@runtime_checkable
+class ManagedTabularFileProvider(Protocol):
+    """List and open authorized CSV/XLSX content without exposing Files internals."""
+
+    def list_tabular_files(
+        self,
+        session: object,
+        principal: object,
+        *,
+        query: str = "",
+        limit: int = 100,
+    ) -> tuple[ManagedTabularFile, ...]: ...
+
+    def get_tabular_file(
+        self,
+        session: object,
+        principal: object,
+        *,
+        file_asset_id: str,
+        file_version_id: str | None = None,
+    ) -> ManagedTabularFile | None: ...
+
+    def read_tabular_file(
+        self,
+        session: object,
+        principal: object,
+        *,
+        file_asset_id: str,
+        file_version_id: str,
+        max_bytes: int,
+    ) -> ManagedTabularFileContent: ...
+
+
 def postbox_file_reference_provider(
     registry: object | None,
 ) -> PostboxFileReferenceProvider | None:
@@ -107,3 +183,46 @@ def postbox_file_reference_provider(
             "PostboxFileReferenceProvider"
         )
     return provider
+
+
+def managed_tabular_file_provider(
+    registry: object | None,
+) -> ManagedTabularFileProvider | None:
+    if (
+        registry is None
+        or not hasattr(registry, "has_capability")
+        or not registry.has_capability(CAPABILITY_FILES_TABULAR_CONTENT)
+    ):
+        return None
+    provider = registry.require_capability(CAPABILITY_FILES_TABULAR_CONTENT)
+    if not isinstance(provider, ManagedTabularFileProvider):
+        raise TypeError(
+            "files.tabular_content provider does not implement "
+            "ManagedTabularFileProvider"
+        )
+    return provider
+
+
+__all__ = [
+    "CAPABILITY_FILES_ACCESS",
+    "CAPABILITY_FILES_ARTIFACT_STORE",
+    "CAPABILITY_FILES_POSTBOX_REFERENCES",
+    "CAPABILITY_FILES_TABULAR_CONTENT",
+    "FileAccessProvider",
+    "ManagedArtifactRef",
+    "ManagedArtifactStore",
+    "ManagedArtifactWriteRequest",
+    "ManagedTabularFile",
+    "ManagedTabularFileAccessError",
+    "ManagedTabularFileContent",
+    "ManagedTabularFileError",
+    "ManagedTabularFileNotFoundError",
+    "ManagedTabularFileProvider",
+    "ManagedTabularFileUnavailableError",
+    "ManagedTabularFileValidationError",
+    "PostboxFileReferenceProvider",
+    "PostboxFileReferenceRef",
+    "PostboxFileReferenceRequest",
+    "managed_tabular_file_provider",
+    "postbox_file_reference_provider",
+]