Add load_kernels method to MetaKernel object (!41)

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 [new]: https://juigitlab.esac.esa.int/datalab/moon-coverage/-/compare/0.12.0...main
 
 ### Added
-- `TourConfig` and `Trajectory` object can now be used to load the SPICE pool directly with the `load_kernels()` method ([!41](https://juigitlab.esac.esa.int/datalab/moon-coverage/-/merge_requests/41)).
+- `TourConfig`, `Trajectory` and `MetaKernel` objects can now be used to load the SPICE pool directly with the `load_kernels()` method ([!41](https://juigitlab.esac.esa.int/datalab/moon-coverage/-/merge_requests/41)).
 
 
 [Release 0.12.0 - 2022/10/31][0.12.0]

docs/spice/mk.md

@@ -138,7 +138,15 @@ MetaKernel(
 
 ## Load the kernels
 
-The `MetaKernel` object can be used with [`spiceypy.furnsh()`](https://spiceypy.readthedocs.io/en/main/documentation.html#spiceypy.spiceypy.furnsh) to load its kernels list into the SPICE pool.
+Similarly to [`TourConfig`](../trajectory/spacecraft/tour_config.md#spice-pool-content) and [`Trajectory`](../api/trajectory.md#trajectory) objects, you can load the kernels in a `MetaKernel` at initialization (with `load_kernels=True` attribute) or later on with the `.load_kernels()` function:
+
+```{code-cell}
+MetaKernel('metakernel.tm', kernels='kernels', load_kernels=True)
+# or
+mk.load_kernels()
+```
+
+The `MetaKernel` object can also be used with [`spiceypy.furnsh()`](https://spiceypy.readthedocs.io/en/main/documentation.html#spiceypy.spiceypy.furnsh) to load its kernels list into the SPICE pool.
 
 __However__, contrary to a regular metakernel, the tool will create a temporary copy of the metakernel on the fly with an edited set of `PATH_VALUES`. The original metakernel is kept untouched, the new file is stored in the system temporary folder. This allow the tool to redefined the location of the kernels at runtime (which was not possible with the default SPICE toolkit).
 

docs/trajectory/spacecraft/tour_config.md

@@ -193,10 +193,11 @@ tour.load_kernels()
 ```
 
 This method could be very handy if you need to switch between different set of kernels.
-It is also available on [`Trajectory`](../../api/trajectory.md#trajectory) objects as well:
+It is also available on [`Trajectory`](../../api/trajectory.md#trajectory) and [`MetaKernel`](../../spice/mk.md) objects as well:
 
 ```python
 traj.load_kernels()
+mk.load_kernels()
 ```
 
 :::

src/moon_coverage/spice/abc.py

+"""Abstract base class module."""
+
+
+class ABCMetaKernel:
+    """Abstract base class for MetaKernel objects.
+
+    See Also
+    --------
+    moon_coverage.spice.metakernel.MetaKernel
+
+    """

src/moon_coverage/spice/metakernel.py

@@ -12,14 +12,16 @@ from multiprocessing import Pool
 from pathlib import Path
 from tempfile import NamedTemporaryFile
 
+from .abc import ABCMetaKernel
 from .kernel import format_data, kernel_parser
+from .pool import SpicePool, log_spice_pool
 from ..misc import wget
 
 
 KERNEL_MAX_LENGTH = 255
 
 
-class MetaKernel:
+class MetaKernel(ABCMetaKernel):
     """Metakernel object.
 
     Parameters
@@ -35,6 +37,9 @@ class MetaKernel:
         You can provide an integer to choose which one you want to use.
         This value is not required if all the kernel are present locally (it is only
         used to download the missing kernels).
+    load_kernels: bool, optional
+        Load the kernels listed in the metakernel into the SPICE pool.
+        If other kernels are present in the SPICE pool, they will be flushed.
     **kwargs: dict, optional
         Path key(s) and value(s) to be substituted in ``KERNELS_TO_LOAD``.
 
@@ -53,7 +58,7 @@ class MetaKernel:
     """
     _tmp_mk = None
 
-    def __init__(self, mk, download=False, remote=0, **kwargs):
+    def __init__(self, mk, download=False, remote=0, load_kernels=False, **kwargs):
         self.__content, self.data = None, None
         self.fname = mk
         self.remote = remote
@@ -63,6 +68,9 @@ class MetaKernel:
         else:
             self.check(download=download)
 
+        if load_kernels:
+            self.load_kernels()
+
     def __str__(self):
         return self.fname.name
 
@@ -287,6 +295,20 @@ class MetaKernel:
             with Pool() as p:
                 p.starmap(wget, set(missing))  # SET => avoid duplicates
 
+    def load_kernels(self):
+        """Load the kernels listed in the metakernel into the SPICE pool.
+
+        Note
+        ----
+        If the SPICE pool already contains these kernels, nothing will append.
+        If not, the pool is flushed and only the metakernels kernels are reloaded.
+
+        """
+        if SpicePool != SpicePool.hash(self):
+            log_spice_pool.info(
+                'The content of the pool changed -> the metakernel will be reloaded.')
+            SpicePool.add(self, purge=True)
+
 
 class MissingKernel(FileNotFoundError):
     """Missing kernel locally."""

src/moon_coverage/spice/pool.py

@@ -6,8 +6,8 @@ import numpy as np
 
 import spiceypy as sp
 
+from .abc import ABCMetaKernel as MetaKernel
 from .kernel import get_item
-from .metakernel import MetaKernel
 from .references import SpiceRef
 from .times import tdb, utc
 from ..misc import depreciated, logger
@@ -130,8 +130,14 @@ class MetaSpicePool(type):
         if kernel not in cls:
             raise ValueError(f'Kernel `{kernel}` is not in the pool.')
 
-        log_spice_pool.debug('Remove %s', kernel)
-        sp.unload(kernel)
+        if isinstance(kernel, MetaKernel):
+            mk_hash = hash(kernel)
+            for key, value in cls.MK_HASH.items():
+                if value == mk_hash and key in cls.kernels:
+                    cls.remove(key)
+        else:
+            log_spice_pool.debug('Remove %s', kernel)
+            sp.unload(kernel)
 
     def purge(cls):
         """Purge the pool from all its content."""

tests/spice/test_metakernel.py

@@ -7,6 +7,7 @@ from pytest import fixture, raises
 
 import moon_coverage.spice.metakernel as _metakernel
 from moon_coverage import MetaKernel
+from moon_coverage.spice import SpicePool, debug_spice_pool
 from moon_coverage.spice.metakernel import MissingKernel, MissingKernelsRemote
 
 
@@ -329,3 +330,41 @@ def test_metakernel_duplicate_download(monkeypatch, mock_mk_content):
         'https://example.org/baz.bc',
         'https://example.org/foo.bc',
     ]
+
+
+def test_metakernel_load_kernels(caplog):
+    """Test MetaKernel kernels loader."""
+    debug_spice_pool(True)
+    SpicePool.purge()
+    caplog.clear()
+
+    mk = MetaKernel(KERNELS + '/metakernel.tm', kernels=KERNELS, load_kernels=True)
+
+    assert len(SpicePool) == 3
+    assert mk in SpicePool
+    assert KERNELS + '/naif0012.tls' in SpicePool
+    assert KERNELS + '/dummy.tf' in SpicePool
+
+    # Check metakernel hash
+    assert hash(mk) in SpicePool.MK_HASH.values()
+
+    # Check debugger message
+    reload_msg = [
+        'The content of the pool changed -> the metakernel will be reloaded.',
+        'Purge the pool',
+        'Add `metakernel.tm` in the SPICE pool',
+        'Cache metakernel original hash.',
+    ]
+
+    assert caplog.messages == reload_msg
+
+    # Re-load the pool with the same metakernel (no reload)
+    caplog.clear()
+
+    mk.load_kernels()
+    assert not caplog.messages
+
+    # Remove metakernel
+    SpicePool.remove(mk)
+
+    assert len(SpicePool) == 0