DAS-1926: Adds common Harmony Message functionality (#38)

Makefile

@@ -22,6 +22,7 @@ clean:
 # HARMONY-1188 - revert this command to:
 # pip install -e .[dev]
 install:
+	pip install pip --upgrade
 	pip install -r dev-requirements.txt
 	pip install -r requirements.txt
 

harmony/message_utility.py

@@ -0,0 +1,163 @@
+"""Utilities for acting on Harmony Messages.
+
+These are a collection of useful routines for validation and interrogation of
+harmony Messages.
+"""
+
+from typing import Any, List
+
+from harmony.message import Message
+
+
+def has_self_consistent_grid(message: Message) -> bool:
+    """ Check the input Harmony message provides enough information to fully
+        define the target grid. At minimum the message should contain the scale
+        extents (minimum and maximum values) in the horizontal spatial
+        dimensions and one of the following two pieces of information:
+
+        * Message.format.scaleSize - defining the x and y pixel size.
+        * Message.format.height and Message.format.width - the number of pixels
+          in the x and y dimension.
+
+        If all three pieces of information are supplied, they will be checked
+        to ensure they are consistent with one another.
+
+        If scaleExtent and scaleSize are defined, along with only one of
+        height or width, the grid will be considered consistent if the three
+        values for scaleExtent, scaleSize and specified dimension length,
+        height or width, are consistent.
+
+    """
+    if (
+        has_scale_extents(message) and has_scale_sizes(message)
+        and has_dimensions(message)
+    ):
+        consistent_grid = (_has_consistent_dimension(message, 'x')
+                           and _has_consistent_dimension(message, 'y'))
+    elif (
+        has_scale_extents(message) and has_scale_sizes(message)
+        and rgetattr(message, 'format.height') is not None
+    ):
+        consistent_grid = _has_consistent_dimension(message, 'y')
+    elif (
+        has_scale_extents(message) and has_scale_sizes(message)
+        and rgetattr(message, 'format.width') is not None
+    ):
+        consistent_grid = _has_consistent_dimension(message, 'x')
+    elif (
+        has_scale_extents(message)
+        and (has_scale_sizes(message) or has_dimensions(message))
+    ):
+        consistent_grid = True
+    else:
+        consistent_grid = False
+
+    return consistent_grid
+
+
+def has_dimensions(message: Message) -> bool:
+    """ Ensure the supplied Harmony message contains values for height and
+        width of the target grid, which define the sizes of the x and y
+        horizontal spatial dimensions.
+
+    """
+    return _has_all_attributes(message, ['format.height', 'format.width'])
+
+
+def has_crs(message: Message) -> bool:
+    """Returns true if Harmony message contains a crs."""
+    target_crs = rgetattr(message, 'format.crs')
+    return target_crs is not None
+
+
+def has_scale_extents(message: Message) -> bool:
+    """ Ensure the supplied Harmony message contains values for the minimum and
+        maximum extents of the target grid in both the x and y dimensions.
+
+    """
+    scale_extent_attributes = ['format.scaleExtent.x.min',
+                               'format.scaleExtent.x.max',
+                               'format.scaleExtent.y.min',
+                               'format.scaleExtent.y.max']
+
+    return _has_all_attributes(message, scale_extent_attributes)
+
+
+def has_scale_sizes(message: Message) -> bool:
+    """ Ensure the supplied Harmony message contains values for the x and y
+        horizontal scale sizes for the target grid.
+
+    """
+    scale_size_attributes = ['format.scaleSize.x', 'format.scaleSize.y']
+    return _has_all_attributes(message, scale_size_attributes)
+
+
+def has_valid_scale_extents(message: Message) -> bool:
+    """Ensure any input scale_extents are valid."""
+    if has_scale_extents(message):
+        return (
+            float(rgetattr(message, 'format.scaleExtent.x.min'))
+            < float(rgetattr(message, 'format.scaleExtent.x.max'))
+        ) and (
+            float(rgetattr(message, 'format.scaleExtent.y.min'))
+            < float(rgetattr(message, 'format.scaleExtent.y.max'))
+        )
+    return True
+
+
+def _has_all_attributes(message: Message, attributes: List[str]) -> bool:
+    """ Ensure that the supplied Harmony message has non-None attribute values
+        for all the listed attributes.
+
+    """
+    return all(rgetattr(message, attribute_name) is not None
+               for attribute_name in attributes)
+
+
+def _has_consistent_dimension(message: Message, dimension_name: str) -> bool:
+    """ Ensure a grid dimension has consistent values for the scale extent
+        (e.g., minimum and maximum values), scale size (resolution) and
+        dimension length (e.g., width or height). For the grid x dimension, the
+        calculation is as follows:
+
+        scaleSize.x = (scaleExtent.x.max - scaleExtent.x.min) / (width)
+
+        The message scale sizes is compared to that calculated as above, to
+        ensure it is within a relative tolerance (1 x 10^-3).
+
+    """
+    message_scale_size = getattr(message.format.scaleSize, dimension_name)
+    scale_extent = getattr(message.format.scaleExtent, dimension_name)
+
+    if dimension_name == 'x':
+        dimension_elements = message.format.width
+    else:
+        dimension_elements = message.format.height
+
+    derived_scale_size = (scale_extent.max - scale_extent.min) / dimension_elements
+
+    return abs(message_scale_size - derived_scale_size) <= 1e-3
+
+
+def rgetattr(input_object: Any, requested_attribute: str, *args) -> Any:
+    """ This is a recursive version of the inbuilt `getattr` method, such that
+        it can be called to retrieve nested attributes. For example:
+        the Message.subset.shape within the input Harmony message.
+
+        Note, if a default value is specified, this will be returned if any
+        attribute in the specified chain is absent from the supplied object.
+        Alternatively, if an absent attribute is specified and no default value
+        if given in the function call, this function will return `None`.
+
+    """
+    if len(args) == 0:
+        args = (None, )
+
+    if '.' not in requested_attribute:
+        result = getattr(input_object, requested_attribute, *args)
+    else:
+        attribute_pieces = requested_attribute.split('.')
+        result = rgetattr(getattr(input_object, attribute_pieces[0], *args),
+                          '.'.join(attribute_pieces[1:]), *args)
+
+    return result