Implemented initial DLPak design

Implemented DLPak design with zip storage, DLPak consists of two files,
a manifest.json which provides details on the signals, time of recording
and currently blank comment field and data.csv which stores all the
signals as csv with the nanosecond timestamp and indexed against the
signal id

src/dynalab_core/__init__.py

@@ -2,6 +2,8 @@
 # Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+
+from datetime import datetime, timezone
 import logging
 from queue import Empty, Queue
 import threading
@@ -13,6 +15,7 @@ from uuid import UUID
 from dynalab_core.buffer import ValueBuffer
 from dynalab_core.config import CoreConfig
 from dynalab_core.constants import CORE_VERSION
+from dynalab_core.dlpak import DLPak
 from dynalab_core.errors import CoreStateMismatchError
 from dynalab_core.protocols.endpoint import ConnectorRegistry
 from dynalab_core.protocols.common import VersionDescriptor
@@ -34,6 +37,8 @@ class Core:
         )
         self._recording = threading.Event()
         self._recording_buffer = ValueBuffer()
+        self._recording_timestamp: datetime = datetime.now(timezone.utc)
+        self._processing_buffer: DLPak | None = None
         self._core_version: VersionDescriptor = CORE_VERSION
         self._stop_event: threading.Event = threading.Event()
         self._core_config: CoreConfig = config
@@ -106,11 +111,18 @@ class Core:
 
     def start_recording(self) -> None:
         self._recording_buffer.clear()
+        self._recording_timestamp = datetime.now(timezone.utc)
         self._recording.set()
 
     def stop_recording(self) -> None:
         self._recording.clear()
-        self._recording_buffer.export_csv("output.csv")
+        self._processing_buffer = DLPak()
+        self._processing_buffer.set_data(self._recording_buffer)
+        self._processing_buffer.set_manifest(
+            self._recording_timestamp,
+            self._connector_registry.get_all_signal_descriptors(),
+        )
+        self._processing_buffer.write("./", "output")
 
     def get_signal_descriptor(self, signal_id: UUID) -> SignalDescriptor | None:
         return self._connector_registry.get_signal_descriptor(signal_id)

src/dynalab_core/buffer.py

@@ -4,6 +4,7 @@
 
 from collections import defaultdict
 import csv
+import io
 from pathlib import Path
 from threading import Lock
 from uuid import UUID
@@ -22,11 +23,15 @@ class ValueBuffer:
         with self._lock:
             self._samples.clear()
 
+    def get_signal_ids(self) -> list[UUID]:
+        with self._lock:
+            return list({signal_id for _, signal_id, _ in self._samples})
+
     def __len__(self) -> int:
         with self._lock:
             return len(self._samples)
 
-    def export_csv(self, path: str | Path) -> None:
+    def export_csv(self) -> str:
         with self._lock:
             samples = list(self._samples)
 
@@ -39,8 +44,9 @@ class ValueBuffer:
 
         ordered_signal_ids = sorted(signal_ids, key=str)
 
-        with Path(path).open(mode="w", newline="", encoding="utf-8") as file:
-            writer = csv.writer(file)
+        output = io.StringIO(newline="")
+
+        writer = csv.writer(output)
 
         writer.writerow(
             ["timestamp_ns", *(str(signal_id) for signal_id in ordered_signal_ids)]
@@ -58,3 +64,5 @@ class ValueBuffer:
                     ),
                 ]
             )
+
+        return output.getvalue()

src/dynalab_core/dlpak.py

@@ -0,0 +1,67 @@
+# Copyright (C) 2026 Hector van der Aa <hector@h3cx.dev>
+# Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Literal
+from zipfile import ZIP_DEFLATED, ZipFile
+
+from pydantic import BaseModel, Field
+
+from dynalab_core.buffer import ValueBuffer
+from dynalab_core.errors import DLPakNoDataError
+from dynalab_core.protocols.packets.handshake import SignalDescriptor
+
+
+class RecordManifest(BaseModel):
+    timestamp: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+    signals: list[SignalDescriptor] = Field(default_factory=list)
+    comments: str = ""
+
+
+class DLPak:
+    def __init__(self) -> None:
+        self._dir: Path | None = None
+        self._filename: str | None = None
+        self._savetype: Literal["zip", "folder"] = "zip"
+        self._data: ValueBuffer | None = None
+        self._manifest: RecordManifest | None = None
+
+    def set_data(self, data: ValueBuffer) -> None:
+        self._data = data
+
+    def set_manifest(
+        self, timestamp: datetime, all_signals: list[SignalDescriptor]
+    ) -> None:
+        if self._data is None:
+            raise DLPakNoDataError
+
+        data_signal_ids = self._data.get_signal_ids()
+
+        manifest_signals: list[SignalDescriptor] = []
+
+        for signal in all_signals:
+            if signal.id in data_signal_ids:
+                manifest_signals.append(signal)
+
+        self._manifest = RecordManifest(
+            timestamp=timestamp, signals=manifest_signals, comments=""
+        )
+
+    def write(self, dir: str | Path, filename: str) -> None:
+        output_dir = Path(dir)
+
+        if output_dir.is_file():
+            output_dir = output_dir.parent
+
+        file_path = Path(filename)
+
+        if file_path.suffix.lower() != ".dlpak":
+            file_path = file_path.with_suffix(".dlpak")
+
+        output_path = output_dir / file_path
+
+        with ZipFile(output_path, mode="w", compression=ZIP_DEFLATED) as archive:
+            archive.writestr("manifest.json", self._manifest.model_dump_json(indent=2))
+            archive.writestr("data.csv", self._data.export_csv())

src/dynalab_core/errors.py

@@ -9,3 +9,12 @@ class CoreError(Exception):
 
 class CoreStateMismatchError(CoreError):
     """DynaLab Core state error."""
+
+
+# DLPak error declarations
+class DLPakError(Exception):
+    """DLPak error."""
+
+
+class DLPakNoDataError(DLPakError):
+    """DLPak no data error."""