# Complexity Review Report

**Branch**: feat/186-query-engine -> main
**Date**: 2026-05-18
**Scope**: Incremental (4 commits since last review: c4c3cef, 21b07d2, 5312a63, 2a563b4)

## Issues in Your Changes (BLOCKING)

### CRITICAL

(none)

### HIGH

(none)

## Issues in Code You Touched (Should Fix)

(none)

## Pre-existing Issues (Not Blocking)

(none)

## Suggestions (Lower Confidence)

- **Repetitive BM25F config test setup** - `query_tests.rs:128-180` (Confidence: 65%) -- Four tests (`test_invalid_bm25f_config_rejected_before_search`, `test_nan_bm25f_config_rejected`, `test_infinity_bm25f_config_rejected`, `test_neg_infinity_bm25f_config_rejected`) share identical setup: create engine, build `BM25FConfig`, set one bad field, assert error. A parameterized helper like `assert_bm25f_rejected(k1_value: f32, expected_field: &str)` could eliminate ~40 lines. However, explicit test cases are acceptable and improve readability for distinct edge cases (negative, NaN, infinity, neg-infinity), so this is a style preference rather than a real complexity problem.

## Summary

| Category | CRITICAL | HIGH | MEDIUM | LOW |
|----------|----------|------|--------|-----|
| Blocking | 0 | 0 | 0 | 0 |
| Should Fix | 0 | 0 | 0 | 0 |
| Pre-existing | 0 | 0 | 0 | 0 |

**Complexity Score**: 9/10
**Recommendation**: APPROVED

## Detailed Metrics

### Production Code: `query.rs` (81 lines)

| Function | Lines | Cyclomatic Complexity | Nesting Depth | Parameters |
|----------|-------|-----------------------|---------------|------------|
| `QueryEngine::new()` | 1 | 1 | 0 | 1 |
| `QueryEngine::search()` | 17 | 4 | 2 | 1 |
| `QueryEngine::name()` | 1 | 1 | 0 | 0 |

All metrics are comfortably in the "Good" range. The `search()` method has 4 decision paths (empty check, size check, config check, delegate) with max nesting depth 2 -- well below the warning threshold of 5.

### Test Code: `query_tests.rs` (358 lines)

| Metric | Value | Threshold | Status |
|--------|-------|-----------|--------|
| File length | 358 | 500 (warning) | Good |
| Longest test function | ~18 lines (`test_deterministic_results`) | 30 (warning) | Good |
| Max nesting depth | 2 (`for` + `for` in deterministic test) | 3 (warning) | Good |
| Test count | 16 | - | Healthy |
| Bounded loops | All bounded (explicit `0..10`) | - | Good |

### Incremental Change Impact

These 4 commits **reduced** complexity:
- Replaced verbose `match result.unwrap_err() { SearchError::InvalidQuery(msg) => { ... }, other => panic!(...) }` patterns (8 lines each) with concise `format!("{}", result.unwrap_err())` + assert (3 lines each). This eliminated nested match arms in 3 tests.
- Replaced duplicated `NgramIndexBuilder` setup in `test_search_delegates_to_inner_layer` with `SpyLayer` test double, removing 12 lines of builder boilerplate and eliminating the need for two temp directories.
- Converted silent `if all_results.len() < 2 { return; }` skip in pagination test to an explicit `assert!` -- removing a hidden control flow path that could silently pass without exercising the test.
