Initialise

ziffers/parser.py

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+from parsimonious.grammar import Grammar
+from parsimonious.nodes import NodeVisitor
+from .ebnf import ebnf
+
+__all__ = ('ZiffersVisitor', 'parse_expression',)
+
+GRAMMAR = Grammar(ebnf)
+
+class ZiffersVisitor(NodeVisitor):
+    def visit_expr(self, node, visited_children):
+        """ Returns the overall output. """
+        output = {}
+        for child in visited_children:
+            output.update(child[0])
+        return output
+
+    def visit_entry(self, node, visited_children):
+        """ Makes a dict of the section (as key) and the key/value pairs. """
+        key, values = visited_children
+        return {key: dict(values)}
+
+    def visit_section(self, node, visited_children):
+        """ Gets the section name. """
+        _, section, *_ = visited_children
+        return section.text
+
+    def visit_pair(self, node, visited_children):
+        """ Gets each key/value pair, returns a tuple. """
+        key, _, value, *_ = node.children
+        return key.text, value.text
+
+    def generic_visit(self, node, visited_children):
+        """ The generic visit method. """
+        return visited_children or node
+
+def parse_expression(expression: str) -> dict:
+    tree = GRAMMAR.parse(expression)
+    visitor = ZiffersVisitor()
+    return visitor.visit(tree)
+