Class: Metaschema::MetapathEvaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/metaschema/metapath_evaluator.rb

Overview

Evaluates Metapath (XPath subset) expressions against Ruby object instances.

Supported patterns (covering OSCAL constraint targets):

"."                                  — current instance
"@flag-name"                         — flag value
"child-name"                         — child field value
"child-name/@attr"                   — child's flag value
"//descendant"                       — descendant values
"child[@attr='val']"                 — filtered children
"child[@attr='val']/@attr2"          — filtered child's attribute
"child[func(...)]/@attr"             — function-based filter
".[condition]/path"                  — conditional navigation
".[condition]"                       — filter current instance
"(.)[condition]/path"                — parenthesized self with filter

Supported predicate functions:

has-oscal-namespace('uri')           — checks prop/element ns attribute
starts-with(@attr, 'prefix')         — string prefix check

Supported predicate operators:

@attr='value'                        — attribute equals
@attr=('v1','v2',...)                — attribute in set
and / or                             — logical operators

Constant Summary collapse

OSCAL_NS = 
"http://csrc.nist.gov/ns/oscal"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(context) ⇒ MetapathEvaluator

Returns a new instance of MetapathEvaluator.



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# File 'lib/metaschema/metapath_evaluator.rb', line 33

def initialize(context)
  @context = context
end

Instance Attribute Details

#context ⇒ Object (readonly)

Returns the value of attribute context.



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# File 'lib/metaschema/metapath_evaluator.rb', line 31

def context
  @context
end

Instance Method Details

#resolve(path) ⇒ Object

Resolve a Metapath expression to values from the context instance. Returns an array of values.



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# File 'lib/metaschema/metapath_evaluator.rb', line 39

def resolve(path)
  return [extract_value(@context)] if path == "."

  path = normalize_path(path)
  steps = parse_steps(path)
  evaluate_steps(@context, steps)
end

#resolve_collection(path) ⇒ Object

Resolve a path to a collection of items (for uniqueness/cardinality checks).



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# File 'lib/metaschema/metapath_evaluator.rb', line 48

def resolve_collection(path)
  path = normalize_path(path)
  steps = parse_steps(path)
  evaluate_steps_collection(@context, steps)
end