# Plan 08-03 Summary: Performance Sampling + Cache Integration

## Status: COMPLETE

## What Was Done

### Task 1: Created RDEPUBTextPerformanceSampler.swift
- **File**: `Sources/RDReaderView/EPUBTextRendering/RDEPUBTextPerformanceSampler.swift` (new)
- `RDEPUBTextPerformanceSample` struct with `chapterHref`, `renderDuration`, `paginateDuration`, `pageCount`, `attributedStringLength`, `cacheHit`
- `RDEPUBTextPerformanceSampler` class with `record(_:)`, `summary()`, `reset()`, `totalBuildDuration`, `samples`
- Per-chapter `[PERF]` console logging with millisecond formatting

### Task 2: Instrumented RDEPUBTextBookBuilder with cache + performance
- **File**: `Sources/RDReaderView/EPUBTextRendering/RDEPUBTextBookBuilder.swift` (modified)
- Added `cache: RDEPUBTextBookCache?` (optional, defaults to nil for backward compat)
- Added `sampler: RDEPUBTextPerformanceSampler` (always created)
- Added `lastBuildPerformanceSamples: [RDEPUBTextPerformanceSample]`
- Added `lastBuildCacheStats: (hits: Int, misses: Int)`
- `build()` method now:
  - Checks cache before building (cache HIT returns immediately)
  - Wraps `renderer.renderChapter()` with `CFAbsoluteTimeGetCurrent()` timing
  - Wraps `content.rd_paginatedFrames()` with timing
  - Records per-chapter `RDEPUBTextPerformanceSample`
  - Saves to cache on miss after successful build
  - Prints `[PERF]` summary at end
- Added `makeCacheKey()` helper using `publication.metadata.identifier ?? publication.metadata.title`

### Pre-existing fixes (not in plan scope but required for clean build)
- **RDEPUBTextBookCache.swift**: Changed 4 `private final class` to `final class` to fix NSCoding "unstable name" errors (Swift compiler change in newer SDK)
- **RDEPUBSelectionOverlayView.swift**: Fixed empty array literal type annotation and commented-out code

## Files Modified
| File | Action |
|------|--------|
| `Sources/RDReaderView/EPUBTextRendering/RDEPUBTextPerformanceSampler.swift` | CREATED |
| `Sources/RDReaderView/EPUBTextRendering/RDEPUBTextBookBuilder.swift` | MODIFIED |
| `Sources/RDReaderView/EPUBTextRendering/RDEPUBTextBookCache.swift` | MODIFIED (pre-existing NSCoding fix) |
| `Sources/RDReaderView/EPUBUI/RDEPUBSelectionOverlayView.swift` | MODIFIED (pre-existing error fix) |

## Build Verification
- `xcodebuild build -scheme ReadViewDemo -destination 'platform=iOS Simulator,name=iPhone 17 Pro'` -- **BUILD SUCCEEDED**

## Key Links Established
- `RDEPUBTextBookBuilder` -> `RDEPUBTextBookCache` via `cache.load(key:)` / `cache.save(_:key:)`
- `RDEPUBTextBookBuilder` -> `RDEPUBTextPerformanceSampler` via `sampler.record(sample)`