Implement file hash-based library matching and remove fuzzy ASIN matching

Adds file hash-based matching for Audiobookshelf library items to ensure 100% accurate ASIN assignment for RMAB-organized content. Removes fuzzy matching from library availability checks, making all matching ASIN-only to eliminate false positives and race conditions. Updates database schema, processors, and matcher utilities; adds new tests and documentation for the new matching strategy. Removes obsolete scripts, Dockerfile, and related tests; updates docker-compose for test environments.
2026-06-02 20:30:10 +00:00 · 2026-01-28 10:32:14 -05:00
parent 497849f427
commit a97979358f
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+# File Hash-Based Library Matching
+
+**Status:** ✅ Implemented | Accurate ASIN matching for RMAB-organized audiobooks
+
+## Overview
+Solves false positive matches in Audiobookshelf fuzzy search by using file hash matching for RMAB-downloaded content.
+
+## Problem
+- New ABS items without ASIN → fuzzy Audible search by title/author
+- Risk: Wrong book matches (e.g., "Foundation" → "Foundation and Empire")
+- Result: Incorrect metadata, false positives
+
+## Solution
+**File Hash Matching Strategy:**
+1. Generate SHA256 hash of audio filenames during organization
+2. Store hash in `Audiobook.filesHash` field
+3. During library scan: compare ABS item files against database hashes
+4. Match found → Use request's ASIN for 100% accurate metadata
+5. No match → Fallback to fuzzy search (external content)
+
+## How It Works
+
+### Organization Phase
+**File:** `src/lib/processors/organize-files.processor.ts`
+
+```typescript
+const filesHash = generateFilesHash(result.audioFiles);
+await prisma.audiobook.update({
+  data: {
+    filesHash: filesHash,  // SHA256 of sorted audio filenames
+    // ... other fields
+  }
+});
+```
+
+### Library Scan Phase
+**Files:** `scan-plex.processor.ts`, `plex-recently-added.processor.ts`
+
+**Phase 1: File Hash Matching (Items WITHOUT ASIN)**
+```typescript
+const itemsWithoutAsin = libraryItems.filter(item => !item.asin && item.externalId);
+
+for (const item of itemsWithoutAsin) {
+  // 1. Fetch ABS item details
+  const absItem = await getABSItem(item.externalId);
+
+  // 2. Generate hash from ABS audio filenames
+  const audioFilenames = absItem.media.audioFiles.map(f => f.metadata.filename);
+  const itemHash = generateFilesHash(audioFilenames);
+
+  // 3. Query for matching RMAB download
+  const matched = await prisma.audiobook.findFirst({
+    where: { filesHash: itemHash, status: 'completed' }
+  });
+
+  // 4. Trigger metadata match (with ASIN if matched, undefined if not)
+  await triggerABSItemMatch(item.externalId, matched?.audibleAsin);
+}
+```
+
+**Phase 2: Request Matching**
+```typescript
+// Match requests to library items and mark as available
+const match = await findPlexMatch({
+  asin: audiobook.audibleAsin,
+  title: audiobook.title,
+  author: audiobook.author
+});
+
+if (match) {
+  // Update audiobook and request status
+  await prisma.audiobook.update({ data: { absItemId: match.plexGuid } });
+  await prisma.request.update({ data: { status: 'available' } });
+
+  // No metadata match triggering needed:
+  // - Items without ASIN: Already handled in Phase 1
+  // - Items with ASIN: Already have correct metadata
+}
+```
+
+## Hash Generation Algorithm
+**File:** `src/lib/utils/files-hash.ts`
+
+**Process:**
+1. Extract basenames from file paths
+2. Filter to audio extensions: `.m4b`, `.m4a`, `.mp3`, `.mp4`, `.aa`, `.aax`
+3. Normalize to lowercase (case-insensitive)
+4. Sort alphabetically (deterministic order)
+5. Generate SHA256: `crypto.createHash('sha256').update(JSON.stringify(sorted)).digest('hex')`
+
+**Properties:**
+- Deterministic: Same files → same hash (regardless of order/path)
+- Path-agnostic: Only basenames matter
+- Case-insensitive: "CHAPTER 01.mp3" === "chapter 01.mp3"
+- Fast: O(1) database lookup with indexed field
+
+## Database Schema
+
+**Model:** `Audiobook`
+
+```prisma
+model Audiobook {
+  // ... existing fields
+  filesHash String? @map("files_hash") @db.Text  // SHA256 (64 chars)
+
+  @@index([filesHash])  // Fast O(1) lookups
+}
+```
+
+**Migration:** `20260126100000_add_audiobook_files_hash`
+
+## Implementation Details
+
+### Metadata Match Strategy
+
+**Phase 1 (File Hash):** Handle NEW items WITHOUT ASIN
+- Filter: `libraryItems.filter(item => !item.asin)`
+- Trigger metadata match with file-hash-matched ASIN or undefined
+- **This is the ONLY phase that triggers ABS metadata matching**
+
+**Phase 2 (Request Match):** Match requests, no metadata triggering
+- Match requests to library items by ASIN/title/author
+- Update request status to 'available'
+- **No metadata match triggering** - items either:
+  - Were handled in Phase 1 (new items without ASIN)
+  - Already have correct metadata (items with ASIN from ABS)
+
+**Why This Works:**
+- **Single source of truth**: Only file hash phase triggers metadata matching
+- **No redundant API calls**: Items with ASIN already have correct metadata
+- **Clean separation**: Phase 1 = metadata, Phase 2 = request matching
+- **Simple and efficient**: No duplicate checks, no wasted API calls
+
+## Edge Cases
+
+### Externally-Added Content
+- User manually imports audiobook to ABS (not via RMAB)
+- No matching `filesHash` in database
+- **Fallback:** Fuzzy metadata match (current behavior preserved)
+
+### Modified Files
+- User adds/removes chapters after organization
+- ABS hash won't match RMAB hash
+- **Fallback:** Fuzzy metadata match
+
+### Existing Content (Before Feature)
+- Audiobooks organized before hash feature
+- `filesHash` field is NULL
+- **Behavior:** Continues using fuzzy matching
+- **Future:** Admin job could backfill hashes (out of scope)
+
+### Chapter-Merged Files
+- 20 MP3s → 1 M4B via chapter merging
+- Hash generated AFTER merging
+- **Works correctly:** Hash reflects final organized state
+
+### Multiple Downloads (Same Book)
+- User re-downloads same audiobook (different edition/request)
+- Multiple records with same `filesHash`
+- **Solution:** `findFirst()` returns first match (acceptable - same ASIN)
+
+## Performance
+
+**Storage:**
+- New index: ~8 bytes per row (minimal)
+- SHA256 hash: 64 characters per record
+
+**API Calls:**
+- One additional `getABSItem()` call per item without ASIN
+- Typical response: ~1-5KB JSON
+- Latency: ~50-100ms per call
+
+**Database:**
+- Index lookup: O(1) with hash index (extremely fast)
+
+**Impact:**
+- 10 items without ASIN → +500-1000ms per scan (acceptable)
+
+## Logging
+
+**Organization:**
+```
+[INFO] Generated files hash: abc123def456... (5 audio files)
+```
+
+**Library Scan (Match Found):**
+```
+[INFO] File hash match found for "Foundation" → ASIN: B08G9PRS1K (from "Foundation (Unabridged)")
+[INFO] Triggered metadata match with ASIN B08G9PRS1K for: "Foundation"
+```
+
+**Library Scan (No Match):**
+```
+[INFO] No file match found, triggering fuzzy metadata match for: "The Expanse"
+```
+
+## Benefits
+
+✅ **100% Accurate Matching** - RMAB-organized content always gets correct ASIN
+✅ **Path-Agnostic** - Works regardless of folder structure differences
+✅ **Fast Lookups** - O(1) database query with indexed field
+✅ **Graceful Fallback** - External content still works via fuzzy matching
+✅ **No Breaking Changes** - Existing content continues working
+
+## Testing
+
+**Unit Tests:** `tests/utils/files-hash.test.ts`
+- Hash generation correctness
+- Deterministic behavior
+- Edge case handling
+
+**Integration Tests:** `tests/processors/*.test.ts`
+- Hash storage during organization
+- Hash matching during library scan
+- Fallback to fuzzy matching
+
+## Related
+- [Audiobookshelf Integration](../integrations/audiobookshelf.md) - Backend mode
+- [File Organization](../phase3/file-organization.md) - Organization flow
+- [Database Schema](../backend/database.md) - Audiobook model