Asset Management Module
This module implements an asset manager that provides methods for storing, updating, deleting, and receiving assets for the FreeCAD CAM workbench.
Goals of the asset manager
While currently the AssetManager has no UI yet, the plan is to add one.
The ultimate vision for the asset manager is to provide a unified UI that can download assets from arbitrary sources, such as online databases, Git repositories, and also local storage. It should also allow for copying between these storages, effectively allowing for publishing assets.
Essentially, something similar to what Blender has:
What are assets in CAM?
Assets are arbitrary data, such as FreeCAD models, Tools, and many more. Specifically in the context of CAM, assets are:
- Tool bit libraries
- Tool bits
- Tool bit shape files
- Tool bit shape icons
- Machines
- Fixtures
- Post processors
- ...
Assets have dependencies: For example, a ToolBitLibrary requires ToolBits, and a ToolBit requires a ToolBitShape (which is a FreeCAD model).
Challenges
In the current codebase, CAM objects are monoliths that handle everything: in-memory data, serialization, deserialization, storage. They are tightly coupled to files, and make assumptions about how other objects are stored.
Examples:
- Tool bits have "File" attributes that they use to collect dependencies such as ToolBit files and shape files.
- It also writes directly to the disk.
- GuiToolBit performs serialization directly in UI functions.
- ToolBits could not be created without an active document.
As the code base grows, separation of concerns becomes more important. Managing dependencies between asset becomes a hassle if every object tries to resolve them in their own way.
Solution
The main effort went into two key areas:
-
The generic AssetManager:
- Manages storage while existing FreeCAD tool library file structures retained
- Manages dependencies including detection of cyclic dependencies, deep vs. shallow fetching
- Manages threading for asynchronous storage, while FreeCAD objects are assembled in the main UI thread
- Defining a generic asset interface that classes can implement to become "storable"
-
Refactoring existing CAM objects for clear separation of concerns:
- View: Should handle user interface only. Existing file system access methods were removed.
- Object Model: In-memory representation of an object, for example a ToolBit, Icon, or a ToolBitShape. By giving all classes
from_bytes()andto_bytes()methods; the objects no longer need to handle storage themselves. - Storage: Persisting an object to a file system, database system, or API. This is now handled by the AssetManager
- Serialization A serialization protocol needs to be defined. This will allow for better import/export mechanisms in the future
FreeCAD is now fully usable with the changes in place. Work remains to be done on the serializers.
Asset Manager API usage example
import pathlib
from typing import Any, Mapping, List, Type
from Path.Tool.assets import AssetManager, FileStore, AssetUri, Asset
# Define a simple Material class implementing the Asset interface
class Material(Asset):
asset_type: str = "material"
def __init__(self, name: str):
self.name = name
def get_id() -> str:
return self.name.lower().replace(" ", "-")
@classmethod
def dependencies(cls, data: bytes) -> List[AssetUri]:
return []
@classmethod
def from_bytes(cls, data: bytes, id: str, dependencies: Optional[Mapping[AssetUri, Asset]]) -> Material:
return cls(data.decode('utf-8'))
def to_bytes(self) -> bytes:
return self.name.encode('utf-8')
manager = AssetManager()
# Register FileStore and the simple asset class
manager.register_store(FileStore("local", pathlib.Path("/tmp/assets")))
manager.register_asset(Material)
# Create and get an asset
asset_uri = manager.add(Material("Copper"))
print(f"Stored with URI: {asset_uri}")
retrieved_asset = manager.get(asset_uri)
print(f"Retrieved: {retrieved_asset}")
The Serializer Protocol
The serializer protocol defines how assets are converted to and from bytes and how their dependencies are identified. This separation of concerns allows assets to be stored and retrieved independently of their specific serialization format.
The core components of the protocol are the Asset
and AssetSerializer classes.
-
The
Assetclass represents an asset object in memory. It provides methods liketo_bytes()andfrom_bytes()which delegate the actual serialization and deserialization to anAssetSerializerinstance. It also has anextract_dependencies()method that uses the serializer to find dependencies within the raw asset data. -
The
AssetSerializeris an abstract base class that defines the interface for serializers. Concrete implementations ofAssetSerializerare responsible for the specific logic of converting an asset object to bytes (serialize()), converting bytes back to an asset object (deserialize()), and extracting dependency URIs from the raw byte data (extract_dependencies()).
This design allows the AssetManager to work with various asset types and serialization formats
by simply registering the appropriate AssetSerializer
for each asset type.
Class diagram
classDiagram
direction LR
%% -------------- Asset Manager Module --------------
note for AssetManager "AssetUri structure:
<asset_type>:\//<asset_id>[/<version>]<br/>
Examples:
material:\//1234567/1
toolbitshape:\//endmill/1
material:\//aluminium-6012/2"
class AssetManager["AssetManager
<small>Creates, assembles or deletes assets from URIs</small>"] {
stores: Mapping[str, AssetStore] // maps protocol to store
register_store(store: AssetStore, cacheable: bool = False)
register_asset(asset_class: Type[Asset], serializer: Type[AssetSerializer])
get(uri: AssetUri | str, store: str = "local", depth: Optional[int] = None) Any
get_raw(uri: AssetUri | str, store: str = "local") bytes
add(obj: Asset, store: str = "local") AssetUri
add_raw(asset_type: str, asset_id: str, data: bytes, store: str = "local") AssetUri
delete(uri: AssetUri | str, store: str = "local")
is_empty(asset_type: str | None = None, store: str = "local") bool
list_assets(asset_type: str | None = None, limit: int | None = None, offset: int | None = None, store: str = "local") List[AssetUri]
list_versions(uri: AssetUri | str, store: str = "local") List[AssetUri]
get_bulk(uris: Sequence[AssetUri | str], store: str = "local", depth: Optional[int] = None) List[Any]
fetch(asset_type: str | None = None, limit: int | None = None, offset: int | None = None, store: str = "local", depth: Optional[int] = None) List[Asset]
}
class AssetStore["AssetStore
<small>Stores/Retrieves assets as raw bytes</small>"] {
<<abstract>>
async get(uri: AssetUri) bytes
async count_assets(asset_type: str | None = None) int
async delete(uri: AssetUri)
async create(asset_type: str, asset_id: str, data: bytes) AssetUri
async update(uri: AssetUri, data: bytes) AssetUri
async list_assets(asset_type: str | None, limit: int | None, offset: int | None) List[AssetUri]
async list_versions(uri: AssetUri) List[AssetUri]
async is_empty(asset_type: str | None = None) bool
}
AssetStore *-- AssetManager: has many
class FileStore["FileStore
<small>Stores/Retrieves versioned assets as directories/files</small>"] {
__init__(name: str, filepath: pathlib.Path)
set_dir(new_dir: pathlib.Path)
async get(uri: AssetUri) bytes
async delete(uri: AssetUri)
async create(asset_type: str, asset_id: str, data: bytes) AssetUri
async update(uri: AssetUri, data: bytes) AssetUri
async list_assets(asset_type: str | None, limit: int | None, offset: int | None) List[AssetUri]
async list_versions(uri: AssetUri) List[AssetUri]
async is_empty(asset_type: str | None = None) bool
}
FileStore <|-- AssetStore: is
class MemoryStore["MemoryStore
<small>In-memory store, mostly for testing/demonstration</small>"] {
__init__(name: str)
async get(uri: AssetUri) bytes
async delete(uri: AssetUri)
async create(asset_type: str, asset_id: str, data: bytes) AssetUri
async update(uri: AssetUri, data: bytes) AssetUri
async list_assets(asset_type: str | None, limit: int | None, offset: int | None) List[AssetUri]
async list_versions(uri: AssetUri) List[AssetUri]
async is_empty(asset_type: str | None) bool
dump(print: bool) Dict | None
}
MemoryStore <|-- AssetStore: is
class AssetSerializer["AssetSerializer<br/><small>Abstract base class for asset serializers</small>"] {
<<abstract>>
for_class: Type[Asset]
extensions: Tuple[str]
mime_type: str
extract_dependencies(data: bytes) List[AssetUri]
serialize(asset: Asset) bytes
deserialize(data: bytes, id: str, dependencies: Optional[Mapping[AssetUri, Asset]]) Asset
}
AssetSerializer *-- AssetManager: has many
Asset --> AssetSerializer: uses
class Asset["Asset<br/><small>Common interface for all asset types</small>"] {
<<abstract>>
asset_type: str // type of the asset type, e.g., toolbit
get_id() str // Returns a unique ID of the asset
to_bytes(serializer: AssetSerializer) bytes
from_bytes(data: bytes, id: str, dependencies: Optional[Mapping[AssetUri, Asset]], serializer: Type[AssetSerializer]) Asset
extract_dependencies(data: bytes, serializer: Type[AssetSerializer]) List[AssetUri] // Extracts dependency URIs from bytes
}
Asset *-- AssetManager: creates
namespace AssetManagerModule {
class AssetManager
class AssetStore
class FileStore
class MemoryStore
class AssetSerializer
class Asset
}
%% -------------- CAM Module (as an example) --------------
class ToolBitShape["ToolBitShape<br/><small>for assets with type toolbitshape</small>"] {
<<Asset>>
asset_type: str = "toolbitshape"
get_id() str // Returns a unique ID
from_bytes(data: bytes, id: str, dependencies: Dict[AssetUri, Asset]) ToolBitShape
to_bytes(obj: ToolBitShape) bytes
dependencies(data: bytes) List[AssetUri]
}
ToolBitShape ..|> Asset: is
class ToolBit["ToolBit<br/><small>for assets with type toolbit</small>"] {
<<Asset>>
asset_type: str = "toolbit"
get_id() str // Returns a unique ID
from_bytes(data: bytes, id: str, dependencies: Dict[AssetUri, Asset]) ToolBit
to_bytes(obj: ToolBit) bytes
dependencies(data: bytes) List[AssetUri]
}
ToolBit ..|> Asset: is
ToolBit --> ToolBitShape: has
namespace CAMModule {
class ToolBitShape
class ToolBit
}
%% -------------- Materials Module (as an example) --------------
class Material["Material<br/><small>for assets with type material</small>"] {
<<Asset>>
asset_type: str = "material"
get_id() str // Returns a unique ID
dependencies(data: bytes) List[AssetUri]
from_bytes(data: bytes, id: str, dependencies: Dict[AssetUri, Asset]) Material
to_bytes(obj: Material) bytes
}
Material ..|> Asset: is
namespace MaterialModule {
class Material
class Material
}
UI Helpers
The ui directory contains helper modules for the asset manager's user interface.
-
filedialog.py: Provides file dialogs for importing and exporting assets. -
util.py: Contains general utility functions used within the asset manager UI.
What's next
Shorter term
- Improving the integration of serializers. Ideally the asset manager could help here too: We can define a common serializer protocol for all assets. It could then become the central point for imports and exports.
Potential future extensions (longer term)
-
Adding a AssetManager UI, to allow for browsing and searching stores for all kinds of assets (Machines, Fixtures, Libraries, Tools, Shapes, Post Processors, ...) from all kings of sources (online DB, git repository, etc.).
-
Adding a GitStore, to connect to things like the FreeCAD library.
-
Adding an HttpStore for connectivity to online databases.