# Complexity Audit Report

**Branch**: fix/issue-28-graph-corruption-shallow-copy
**Base**: main
**Date**: 2025-11-28 08:37

---

## Executive Summary

This branch addresses Issue #28, a critical graph corruption bug caused by shallow copying in the `wouldCreateCycle()` method. The fix is minimal and correct: replacing `new Map(this.graph)` with a proper deep copy that also clones the Set values.

Additionally, this branch introduces a "settling workers" tracking mechanism to prevent worker over-spawning due to load average lag, and increases the default spawn delay from 50ms to 1000ms.

**Overall Assessment**: The changes are well-implemented with low complexity. The code is clear, well-documented, and follows the project's patterns. No blocking issues found.

---

## Analysis of Changed Files

### Files Modified:
1. `src/core/dependency-graph.ts` - Deep copy fix for cycle detection
2. `src/core/configuration.ts` - Spawn delay configuration change
3. `src/core/interfaces.ts` - New optional `recordSpawn()` method
4. `src/implementations/resource-monitor.ts` - Settling workers tracking
5. `src/services/handlers/worker-handler.ts` - Call recordSpawn after spawn
6. `tests/unit/core/dependency-graph.test.ts` - Regression tests for Issue #28

---

## Issues in Your Changes (BLOCKING)

**None identified.**

The changes are minimal, focused, and well-implemented.

---

## Issues in Code You Touched (Should Fix)

### Issue 1: Consider extracting deep copy to a reusable utility

**Severity**: LOW
**File**: `/workspace/delegate/src/core/dependency-graph.ts`
**Lines**: 253-255

```typescript
const tempGraph = new Map(
  Array.from(this.graph.entries()).map(([k, v]) => [k, new Set(v)])
);
```

**Analysis**: The deep copy pattern is correct but slightly complex. If this pattern is needed elsewhere in the codebase, consider extracting it to a utility function like `deepCopyMapOfSets<K, V>()`.

**Recommendation**: Not blocking, but could improve maintainability if the pattern appears elsewhere.

---

### Issue 2: Magic number for SETTLING_WINDOW_MS

**Severity**: LOW
**File**: `/workspace/delegate/src/implementations/resource-monitor.ts`
**Line**: 30

```typescript
private readonly SETTLING_WINDOW_MS = 15000; // 15 seconds for worker to "settle"
```

**Analysis**: The 15-second settling window is a reasonable heuristic but is hardcoded. This could potentially be made configurable via the `Configuration` object for environments with different characteristics.

**Recommendation**: Consider adding to configuration schema in a future iteration. Not blocking.

---

### Issue 3: Optional method in interface

**Severity**: LOW
**File**: `/workspace/delegate/src/core/interfaces.ts`
**Lines**: 47-53

```typescript
/**
 * Record a spawn event for settling worker tracking
 * Call immediately after spawning to track workers during their settling period
 * (before they appear in system metrics like load average)
 */
recordSpawn?(): void;
```

**Analysis**: The optional method (`recordSpawn?`) is a valid TypeScript pattern, but it means callers must use optional chaining (`this.resourceMonitor.recordSpawn?.()`). This is correctly handled in `worker-handler.ts:296`. However, consider whether this should be a required method with a no-op default implementation in `TestResourceMonitor` for interface consistency.

**Recommendation**: Acceptable as-is. The optional chaining is appropriate since not all implementations need this functionality.

---

## Pre-existing Issues (Not Blocking)

### Issue 1: canSpawnWorker() method complexity

**Severity**: MEDIUM
**File**: `/workspace/delegate/src/implementations/resource-monitor.ts`
**Method**: `canSpawnWorker()` (lines 79-169)

**Analysis**: This method is 90 lines long with 6 different check conditions. The settling worker additions make the method even longer. Cyclomatic complexity is approximately 7-8.

**Metrics**:
- Lines: 90
- Conditions: 6 (effectiveWorkerCount check, getResources error check, cores check, memory check, load average check, success path)
- Return points: 6

**Recommendation**: Consider refactoring into smaller helper methods in a future PR:
- `checkMaxWorkersLimit()`
- `checkCpuAvailability()`
- `checkMemoryAvailability()`
- `checkLoadAverage()`

---

### Issue 2: Repeated resource calculation patterns

**Severity**: LOW
**File**: `/workspace/delegate/src/implementations/resource-monitor.ts`
**Lines**: 110-115, 132-133, 147

**Analysis**: The pattern of calculating projected resource usage appears multiple times:
```typescript
const projectedCoresUsed = settlingWorkers * this.CORES_PER_WORKER;
const projectedMemoryUsed = settlingWorkers * this.MEMORY_PER_WORKER_MB * 1024 * 1024;
```

These calculations are done once and reused, which is correct. No action needed.

---

### Issue 3: Worker handler processNextTask() complexity

**Severity**: MEDIUM
**File**: `/workspace/delegate/src/services/handlers/worker-handler.ts`
**Method**: `processNextTask()` (lines 201-319)

**Analysis**: This method is 118 lines with multiple responsibilities:
1. Spawn delay enforcement
2. Resource availability check
3. Task retrieval
4. Event emission
5. Worker spawning
6. Error handling

This is pre-existing complexity not introduced by this PR.

**Recommendation**: Consider decomposing in a future refactoring PR.

---

## Test Quality Assessment

The new regression tests are well-structured and comprehensive:

**File**: `/workspace/delegate/tests/unit/core/dependency-graph.test.ts`
**New Tests Added**: Lines 248-338 (3 new test cases)

### Test 1: Graph immutability after cycle detection with existing task
- Properly captures state before and after
- Verifies the critical assertion that would catch the bug
- Excellent documentation explaining the bug

### Test 2: Graph immutability when no cycle detected
- Covers the non-cycle path for completeness

### Test 3: Multiple cycle checks don't accumulate corruption
- Tests temporal aspect of the bug (repeated operations)

**Assessment**: HIGH QUALITY - Tests are well-designed to prevent regression.

---

## Summary

**Your Changes (Lines Added/Modified):**
- No CRITICAL or HIGH issues
- 3 LOW complexity observations

**Code You Touched:**
- No HIGH issues  
- 3 LOW observations about potential improvements

**Pre-existing:**
- 2 MEDIUM complexity issues (method length)
- 1 LOW issue

---

## Complexity Metrics

| File | Lines Changed | Cyclomatic Complexity | Assessment |
|------|---------------|----------------------|------------|
| dependency-graph.ts | 6 | 1 (constant) | GOOD |
| configuration.ts | 4 | 0 | GOOD |
| interfaces.ts | 7 | 0 | GOOD |
| resource-monitor.ts | 69 | +2 (now ~8 total) | ACCEPTABLE |
| worker-handler.ts | 3 | 0 | GOOD |
| dependency-graph.test.ts | 92 | N/A (tests) | GOOD |

---

## Complexity Score: 2/10

The changes are minimal, focused, and well-documented. The fix for the shallow copy bug is correct and the settling workers mechanism is a reasonable solution to the load average lag problem.

---

## Merge Recommendation

**APPROVED**

Rationale:
1. The core fix (deep copy in `wouldCreateCycle`) is correct and minimal
2. The settling workers feature is well-implemented and addresses a real problem
3. Tests are comprehensive and would catch regressions
4. Code follows project patterns (Result types, logging, documentation)
5. No security or performance concerns

**Pre-merge Checklist**:
- [ ] Run `npm run test:core` to verify dependency-graph tests pass
- [ ] Consider staging the changes (`git add`) and committing

---

## Appendix: Key Code Snippets

### The Fix (dependency-graph.ts:250-255)

```typescript
// SECURITY FIX (Issue #28): Deep copy required to prevent graph corruption
// Shallow copy (new Map(this.graph)) only copies Map structure - Set values are REFERENCES
// When we modify temp graph's Sets, we would mutate the original graph's Sets
const tempGraph = new Map(
  Array.from(this.graph.entries()).map(([k, v]) => [k, new Set(v)])
);
```

### Settling Workers Tracking (resource-monitor.ts:79-85)

```typescript
// Clean up old spawn timestamps (outside settling window)
const now = Date.now();
this.recentSpawnTimestamps = this.recentSpawnTimestamps.filter(
  t => now - t < this.SETTLING_WINDOW_MS
);
const settlingWorkers = this.recentSpawnTimestamps.length;
```

### Critical Regression Test (dependency-graph.test.ts:286-290)

```typescript
const depsBAfter = graph.getDirectDependencies(TaskId('task-B'));
expect(depsBAfter.ok).toBe(true);
expect(depsBAfter.value).toHaveLength(0); // B should STILL have no dependencies

// CRITICAL: This assertion catches the bug
// With shallow copy bug, B -> A edge is added to original graph
expect(depsBAfter.value).not.toContain(TaskId('task-A'));
```
