import { CheckContext, RuleViolation } from '../engine';

interface FileChange {
  filename: string;
  status: string;
  patch?: string;
}

/**
 * Detect invariant violations in code changes
 * 
 * This is a stubbed implementation that demonstrates the concept.
 * In a full implementation, this would check for:
 * - Breaking changes to contracts
 * - Violations of documented invariants
 * - Changes that break assumptions
 */
export async function detectInvariantViolation(
  files: FileChange[],
  _context: CheckContext
): Promise<RuleViolation[]> {
  const violations: RuleViolation[] = [];

  // Stub: Check for obvious breaking changes
  for (const file of files) {
    if (!file.patch) continue;

    const lines = file.patch.split('\n');
    
    // Example: Detect removal of public API methods
    for (let i = 0; i < lines.length; i++) {
      const line = lines[i];
      
      // Detect removal of exported functions
      if (line.startsWith('-') && /export\s+(async\s+)?function\s+\w+/.test(line)) {
        violations.push({
          rule: 'invariant-violation',
          severity: 'warning',
          message: 'Public API function removed. This may be a breaking change.',
          path: file.filename,
          line: i + 1,
        });
      }

      // Detect removal of type definitions
      if (line.startsWith('-') && /export\s+(interface|type)\s+\w+/.test(line)) {
        violations.push({
          rule: 'invariant-violation',
          severity: 'warning',
          message: 'Public type definition removed. This may be a breaking change.',
          path: file.filename,
          line: i + 1,
        });
      }
    }
  }

  return violations;
}