Add First Version Of Workflow Layer Codes

workflow/task.py

@@ -0,0 +1,113 @@
+from __future__ import annotations
+from abc import ABC, abstractmethod
+from typing import Any, Dict, List, Optional
+from datetime import datetime
+from enum import Enum
+
+
+class Status(Enum):
+    PENDING = "pending"
+    READY = "ready"
+    RUNNING = "running"
+    PAUSED = "paused"
+    STOPPED = "stopped"
+    COMPLETED = "completed"
+    FAILED = "failed"
+
+
+class TaskEvent(Enum):
+    BEFORE_RUN = "before_run"
+    STATUS_CHANGED = "status_changed"
+    ERROR = "error"
+    COMPLETED = "completed"           
+
+
+class TaskEventListener:
+    def handle(self, event: TaskEvent, task: "Task", payload: Optional[Any] = None):
+        pass
+
+    def handle_log(self, task: "Task", message: str):
+        pass
+
+
+class ExecutionContext:
+    def __init__(self):
+        self._assets: Dict[str, Any] = {}
+
+    def put_asset(self, key: str, value: Any):
+        self._assets[key] = value
+
+    def get_asset(self, key: str, default: Any = None):
+        return self._assets.get(key, default)
+
+    def snapshot(self):
+        return dict(self._assets)
+
+
+class Task(ABC):
+    def __init__(self, name: str):
+        self._name = name
+
+        # execution dependencies (DAG edges)
+        self._parents: List["Task"] = []
+
+        # structural parent in workflow tree (Composite hierarchy)
+        self._parent_task: Optional["Task"] = None
+
+        self._status: Status = Status.PENDING
+        self._listeners: List[TaskEventListener] = []
+        self._timestamps: Dict[str, datetime] = {}
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def parents(self):
+        return self._parents
+
+    def add_parent(self, parent: "Task"):
+        if parent not in self._parents:
+            self._parents.append(parent)
+
+    def set_parent_task(self, parent: "Task"):
+        self._parent_task = parent
+
+    # Events / Logging / Status
+    def add_listener(self, listener: TaskEventListener):
+        self._listeners.append(listener)
+
+    def _emit(self, event: TaskEvent, payload: Optional[Any] = None):
+        for listener in self._listeners:
+            listener.handle(event, self, payload)
+
+    def log(self, message: str):
+        for listener in self._listeners:
+            listener.handle_log(self, message)
+
+    def _set_status(self, new_status: Status):
+        old_status = self._status
+        self._status = new_status
+
+        if new_status == Status.RUNNING:
+            self._timestamps["start"] = datetime.now()
+
+        if new_status in (Status.COMPLETED, Status.FAILED, Status.STOPPED):
+            self._timestamps["end"] = datetime.now()
+
+        if old_status != new_status:
+            self._emit(TaskEvent.STATUS_CHANGED, {"from": old_status, "to": new_status})
+
+    def get_status(self):
+        return self._status
+
+    def get_timestamps(self):
+        return dict(self._timestamps)
+
+    # Abstract execution
+    @abstractmethod
+    def run(self, context: ExecutionContext):
+        pass
+
+    def __repr__(self):
+        return f"<Task {self.name}>"