Improve input variables (closes #152)

climix/etc/b4est_indices.yml

@@ -17,10 +17,7 @@ indices:
         - time: minimum within days
         - time: minimum over days
     input:
-      var_name: tasmin
-      standard_name: air_temperature
-      cell_methods:
-        - time: minimum
+      data: tasmin
     index_function:
       name: first_occurrence
       parameters:
@@ -57,10 +54,7 @@ indices:
         - time: minimum within days
         - time: maximum over days
     input:
-      var_name: tasmin
-      standard_name: air_temperature
-      cell_methods:
-        - time: minimum
+      data: tasmin
     index_function:
       name: last_occurrence
       parameters:

climix/etc/variables.yml

+variables:
+  pr:
+    standard_name: precipitation_flux
+    cell_methods:
+      - time: mean
+  tas:
+    standard_name: air_temperature
+    cell_methods:
+      - time: mean
+  tasmax:
+    standard_name: air_temperature
+    cell_methods:
+      - time: maximum
+  tasmin:
+    standard_name: air_temperature
+    cell_methods:
+      - time: minimum

climix/metadata.py

@@ -74,6 +74,12 @@ class InputVariable:
             self.cell_methods)
 
 
+def build_variable(name, variable, path):
+    cell_methods = [CellMethod(*cm.popitem())
+                    for cm in variable.pop('cell_methods')]
+    return InputVariable(name, variable['standard_name'], cell_methods)
+
+
 class ParameterKind(Enum):
     QUANTITY = 'quantity'
     OPERATOR = 'operator'
@@ -178,7 +184,7 @@ class IndexDefinition:
     reference: str
     period: Mapping[str, Union[str, Mapping[str, Optional[str]]]]
     output: OutputVariable
-    input: InputVariable
+    input: Mapping[str, InputVariable]
     index_function: IndexFunction
     source: str
 
@@ -187,7 +193,8 @@ class IndexDefinition:
             self.reference,
             self.period,
             self.output.instantiate(parameters),
-            self.input.instantiate(parameters),
+            {key: iv.instantiate(parameters)
+             for key, iv in self.input.items()},
             self.index_function.instantiate(parameters),
             self.source)
         return idx
@@ -197,7 +204,7 @@ def build_parameter(name, metadata):
     return PARAMETER_KINDS[metadata['kind']](name, **metadata)
 
 
-def build_index(metadata, source=None):
+def build_index(metadata, variables, source=None):
     output = OutputVariable(
         metadata['output']['var_name'],
         metadata['output']['standard_name'],
@@ -206,11 +213,11 @@ def build_index(metadata, source=None):
         metadata['output']['units'],
         [CellMethod(*cm.popitem())
          for cm in metadata['output']['cell_methods']])
-    input = InputVariable(
-        metadata['input']['var_name'],
-        metadata['input']['standard_name'],
-        [CellMethod(*cm.popitem())
-         for cm in metadata['input']['cell_methods']])
+    if isinstance(metadata['input'], str):
+        input_metadata = {'data': metadata['input']}
+    else:
+        input_metadata = metadata['input']
+    input = {key: variables[name] for key, name in input_metadata.items()}
     params = metadata['index_function']['parameters']
     if params is None:
         parameters = {}
@@ -350,11 +357,24 @@ def find_metadata_files():
 
 
 def load_metadata():
+    variables = {}
     indices = {}
-    for metadata_path in find_metadata_files():
-        with open(metadata_path) as md_file:
+    variable_metadata = []
+    index_metadata = []
+    for path in find_metadata_files():
+        with open(path) as md_file:
             metadata = yaml.safe_load(md_file)
-        index_metadata = metadata.get('indices', {})
-        for name, idx_meta in index_metadata.items():
-            indices[name] = build_index(idx_meta, metadata_path)
+        index_metadata.append((metadata.get('indices', {}), path))
+        variable_metadata.append((metadata.get('variables', {}), path))
+    for var_metadata, path in variable_metadata:
+        for name, var in var_metadata.items():
+            variables[name] = build_variable(name, var, path)
+    for idx_metadata, path in index_metadata:
+        for name, idx_meta in idx_metadata.items():
+            try:
+                indices[name] = build_index(idx_meta, variables, path)
+            except KeyError:
+                logging.error(
+                    'Metadata error for index {} from {}.'.format(name, path))
+                raise
     return IndexCatalog(indices)