Refactor Method Complexity Reduce

Refactor Method to Reduce Cognitive Complexity

Objective

Refactor the method ${input:methodName}, to reduce its cognitive complexity to ${input:complexityThreshold} or below, by extracting logic into focused helper methods.

Instructions

1. Analyze the current method to identify sources of cognitive complexity:

   • Nested conditional statements
   • Multiple if-else or switch chains
   • Repeated code blocks
   • Multiple loops with conditions
   • Complex boolean expressions

2. Identify extraction opportunities:

   • Validation logic that can be extracted into a separate method
   • Type-specific or case-specific processing that repeats
   • Complex transformations or calculations
   • Common patterns that appear multiple times

3. Extract focused helper methods:

   • Each helper should have a single, clear responsibility
   • Extract validation into separate Validate* methods
   • Extract type-specific logic into handler methods
   • Create utility methods for common operations
   • Use appropriate access levels (static, private, async)

4. Simplify the main method:

   • Reduce nesting depth
   • Replace massive if-else chains with smaller orchestrated calls
   • Use switch statements where appropriate for cleaner dispatch
   • Ensure the main method reads as a high-level flow

5. Preserve functionality:

   • Maintain the same input/output behavior
   • Keep all validation and error handling
   • Preserve exception types and error messages
   • Ensure all parameters are properly passed to helpers

6. Best practices:

   • Make helper methods static when they don't need instance state
   • Use null checks and guard clauses early
   • Avoid creating unnecessary local variables
   • Consider using tuples for multiple return values
   • Group related helper methods together

Implementation Approach

• Extract helper methods before refactoring the main flow
• Test incrementally to ensure no regressions
• Use meaningful names that describe the extracted responsibility
• Keep extracted methods close to where they're used
• Consider making repeated code patterns into generic methods

Result

The refactored method should:

• Have cognitive complexity reduced to the target threshold of ${input:complexityThreshold} or below
• Be more readable and maintainable
• Have clear separation of concerns
• Be easier to test and debug
• Retain all original functionality

Testing and Validation

CRITICAL: After completing the refactoring, you MUST:

1. Run all existing tests related to the refactored method and its surrounding functionality
2. MANDATORY: Explicitly verify test results show "failed=0"
   • NEVER assume tests passed - always examine the actual test output
   • Search for the summary line containing pass/fail counts (e.g., "passed=X failed=Y")
   • If the summary shows any number other than "failed=0", tests have FAILED
   • If test output is in a file, read the entire file to locate and verify the failure count
   • Running tests is NOT the same as verifying tests passed
   • Do not proceed until you have explicitly confirmed zero failures
3. If any tests fail (failed > 0):
   • State clearly how many tests failed
   • Analyze each failure to understand what functionality was broken
   • Common causes: null handling, empty collection checks, condition logic errors
   • Identify the root cause in the refactored code
   • Correct the refactored code to restore the original behavior
   • Re-run tests and verify "failed=0" in the output
   • Repeat until all tests pass (failed=0)
4. Verify compilation - Ensure there are no compilation errors
5. Check cognitive complexity - Confirm the metric is at or below the target threshold of ${input:complexityThreshold}

Confirmation Checklist

• Code compiles without errors
• Test results explicitly state "failed=0" (verified by reading the output)
• All test failures analyzed and corrected (if any occurred)
• Cognitive complexity is at or below the target threshold of ${input:complexityThreshold}
• All original functionality is preserved
• Code follows project conventions and standards

Source: github/awesome-copilot → skills/refactor-method-complexity-reduce/SKILL.md