feat(plugins): discover packages and persist state

app-instance/backend/beaver/plugins/hashing.py

@@ -0,0 +1,78 @@
+"""Canonical hashing for plugin skill trees."""
+
+from __future__ import annotations
+
+import hashlib
+import os
+from pathlib import Path
+
+from .models import PluginSkillFileDigest, PluginSkillTreeDigest
+
+IGNORED_METADATA_FILENAMES = {"version.json", "upstream.json"}
+
+
+def hash_plugin_skill_tree(root: str | Path) -> PluginSkillTreeDigest:
+    skill_root = Path(root)
+    if not skill_root.is_dir():
+        raise ValueError(f"Plugin skill root is not a directory: {skill_root}")
+    skill_file = skill_root / "SKILL.md"
+    if not skill_file.is_file() or skill_file.is_symlink():
+        raise ValueError("Plugin skill tree must contain a regular SKILL.md")
+
+    file_digests: list[PluginSkillFileDigest] = []
+    tree_hasher = hashlib.sha256()
+    for path in _iter_regular_files(skill_root):
+        relative = path.relative_to(skill_root).as_posix()
+        data = path.read_bytes()
+        executable = _is_executable(path)
+        content_hash = _sha256(data)
+        file_digests.append(
+            PluginSkillFileDigest(
+                path=relative,
+                size=len(data),
+                executable=executable,
+                content_hash=content_hash,
+            )
+        )
+        _update_field(tree_hasher, relative.encode("utf-8"))
+        _update_field(tree_hasher, str(len(data)).encode("ascii"))
+        _update_field(tree_hasher, b"1" if executable else b"0")
+        _update_field(tree_hasher, data)
+
+    skill_content = skill_file.read_text(encoding="utf-8").replace("\r\n", "\n").replace("\r", "\n")
+    return PluginSkillTreeDigest(
+        skill_content_hash=_sha256(skill_content.encode("utf-8")),
+        skill_tree_hash=f"sha256:{tree_hasher.hexdigest()}",
+        files=tuple(file_digests),
+    )
+
+
+def _iter_regular_files(root: Path) -> list[Path]:
+    results: list[Path] = []
+    for path in sorted(root.rglob("*"), key=lambda item: item.relative_to(root).as_posix()):
+        relative = path.relative_to(root)
+        if any(part in {"", ".", ".."} for part in relative.parts):
+            raise ValueError(f"Invalid path in plugin skill tree: {relative.as_posix()}")
+        if path.is_symlink():
+            raise ValueError(f"Plugin skill tree contains a symlink: {relative.as_posix()}")
+        if path.is_dir():
+            continue
+        if not path.is_file():
+            raise ValueError(f"Plugin skill tree contains a non-regular file: {relative.as_posix()}")
+        if len(relative.parts) == 1 and relative.name in IGNORED_METADATA_FILENAMES:
+            continue
+        results.append(path)
+    return results
+
+
+def _is_executable(path: Path) -> bool:
+    return bool(path.stat().st_mode & (os.X_OK | 0o111))
+
+
+def _sha256(data: bytes) -> str:
+    return f"sha256:{hashlib.sha256(data).hexdigest()}"
+
+
+def _update_field(hasher: "hashlib._Hash", data: bytes) -> None:
+    hasher.update(len(data).to_bytes(8, "big"))
+    hasher.update(data)