Cyclomatic complexity calculation (McCabe metric).

Cyclomatic complexity measures the number of linearly independent paths through a program's source code. It is calculated as the number of decision points plus one.

3-Tuple Format

All MetaAST nodes use the uniform 3-tuple structure: {type_atom, keyword_meta, children_or_value}

Decision Points

• conditional - if/else statements (+1)
• loop - while/for loops (+1)
• binary_op with :boolean and :or/:and operators (+1 each)
• exception_handling - try/catch blocks (+1 per catch clause)
• pattern_match - case statements (+1 per branch)

Thresholds

• 1-10: Simple, low risk
• 11-20: More complex, moderate risk
• 21-50: Complex, high risk
• 51+: Untestable, very high risk

Examples

# Simple sequence: complexity = 1
iex> ast = {:literal, [subtype: :integer], 42}
iex> Metastatic.Analysis.Complexity.Cyclomatic.calculate(ast)
1

# Single conditional: complexity = 2
iex> ast = {:conditional, [], [{:variable, [], "x"}, {:literal, [subtype: :integer], 1}, {:literal, [subtype: :integer], 2}]}
iex> Metastatic.Analysis.Complexity.Cyclomatic.calculate(ast)
2

# Conditional with loop: complexity = 3
iex> ast = {:conditional, [], [
...>   {:variable, [], "x"},
...>   {:loop, [loop_type: :while], [{:variable, [], "y"}, {:literal, [subtype: :integer], 1}]},
...>   {:literal, [subtype: :integer], 2}]}
iex> Metastatic.Analysis.Complexity.Cyclomatic.calculate(ast)
3