Aniworld/QualityTODO.md

# Aniworld Web Application Development Instructions

This document provides detailed tasks for AI agents to implement a modern web application for the Aniworld anime download manager. All tasks should follow the coding guidelines specified in the project's copilot instructions.

## Project Overview

The goal is to create a FastAPI-based web application that provides a modern interface for the existing Aniworld anime download functionality. The core anime logic should remain in `SeriesApp.py` while the web layer provides REST API endpoints and a responsive UI.

## Architecture Principles

-   **Single Responsibility**: Each file/class has one clear purpose
-   **Dependency Injection**: Use FastAPI's dependency system
-   **Clean Separation**: Web layer calls core logic, never the reverse
-   **File Size Limit**: Maximum 500 lines per file
-   **Type Hints**: Use comprehensive type annotations
-   **Error Handling**: Proper exception handling and logging

## Additional Implementation Guidelines

### Code Style and Standards

-   **Type Hints**: Use comprehensive type annotations throughout all modules
-   **Docstrings**: Follow PEP 257 for function and class documentation
-   **Error Handling**: Implement custom exception classes with meaningful messages
-   **Logging**: Use structured logging with appropriate log levels
-   **Security**: Validate all inputs and sanitize outputs
-   **Performance**: Use async/await patterns for I/O operations

## 📞 Escalation

If you encounter:

-   Architecture issues requiring design decisions
-   Tests that conflict with documented requirements
-   Breaking changes needed
-   Unclear requirements or expectations

**Document the issue and escalate rather than guessing.**

---

## 📚 Helpful Commands

```bash
# Run all tests
conda run -n AniWorld python -m pytest tests/ -v --tb=short

# Run specific test file
conda run -n AniWorld python -m pytest tests/unit/test_websocket_service.py -v

# Run specific test class
conda run -n AniWorld python -m pytest tests/unit/test_websocket_service.py::TestWebSocketService -v

# Run specific test
conda run -n AniWorld python -m pytest tests/unit/test_websocket_service.py::TestWebSocketService::test_broadcast_download_progress -v

# Run with extra verbosity
conda run -n AniWorld python -m pytest tests/ -vv

# Run with full traceback
conda run -n AniWorld python -m pytest tests/ -v --tb=long

# Run and stop at first failure
conda run -n AniWorld python -m pytest tests/ -v -x

# Run tests matching pattern
conda run -n AniWorld python -m pytest tests/ -v -k "auth"

# Show all print statements
conda run -n AniWorld python -m pytest tests/ -v -s
```

---

## 📊 Detailed Analysis: The 7 Quality Criteria

### 5️⃣ No Shortcuts or Hacks Used

**Logging Configuration Workarounds**

-   No outstanding issues (reviewed - no manual handler removal found)

**Hardcoded Values**

-   No outstanding issues (all previously identified issues have been addressed)

**Exception Handling Shortcuts**

-   No outstanding issues (reviewed - OSError handling implemented where appropriate)

**Type Casting Workarounds**

-   No outstanding issues (reviewed - model serialization appropriate for backward compatibility)

**Conditional Hacks**

-   No outstanding issues (completed - proper test mode flag now used)

---

### 6️⃣ Security Considerations Addressed

#### Authentication & Authorization

**Weak CORS Configuration**

-   No outstanding issues (completed - environment-based CORS configuration implemented with origin-based rate limiting)

**Missing Authorization Checks**

-   No outstanding issues (completed - proper 401 responses and public path definitions implemented)

**In-Memory Session Storage**

-   No outstanding issues (completed - documented limitation with production recommendation)

#### Input Validation

**Unvalidated User Input**

-   No outstanding issues (completed - comprehensive validation implemented)

**Missing Parameter Validation**

-   No outstanding issues (completed - comprehensive validation with range checks implemented)

#### Secrets and Credentials

**Hardcoded Secrets**

-   No outstanding issues (completed - secure defaults and .gitignore updated)

**Plaintext Password Storage**

-   No outstanding issues (completed - warning comments added for development-only usage)

**Master Password Implementation**

-   No outstanding issues (completed - comprehensive password requirements implemented)

#### Data Protection

**No Encryption of Sensitive Data**

-   [x] Downloaded files not verified with checksums -> **COMPLETED**
    -   Implemented FileIntegrityManager with SHA256 checksums
    -   Integrated into download process (enhanced_provider.py)
    -   Checksums stored and verified automatically
    -   Tests added and passing (test_file_integrity.py)
-   [x] No integrity checking of stored data -> **COMPLETED**
    -   Implemented DatabaseIntegrityChecker with comprehensive checks
    -   Checks for orphaned records, invalid references, duplicates
    -   Data consistency validation (season/episode numbers, progress, status)
    -   Repair functionality to remove orphaned records
    -   API endpoints added: /api/maintenance/integrity/check and /repair
-   [x] No encryption of sensitive config values -> **COMPLETED**
    -   Implemented ConfigEncryption with Fernet (AES-128)
    -   Auto-detection of sensitive fields (password, secret, key, token, etc.)
    -   Encryption key stored securely with restrictive permissions (0o600)
    -   Support for encrypting/decrypting entire config dictionaries
    -   Key rotation functionality for enhanced security

**File Permission Issues**

-   No outstanding issues (completed - absolute paths and proper permissions implemented)

**Logging of Sensitive Data**

-   No outstanding issues (completed - sensitive data excluded from logs)

#### Network Security

**Unvalidated External Connections**

-   No outstanding issues (completed - SSL verification enabled and server error logging added)

**Missing SSL/TLS Configuration**

-   No outstanding issues (completed - all verify=False instances fixed)
    -   doodstream.py (2 instances)
    -   loadx.py (2 instances)
    -   Added timeout parameters where missing
-   [x] Check for `verify=False` in requests calls -> completed
    -   All requests now use SSL verification

#### Database Security

**No SQL Injection Protection**

-   [x] Check `src/server/database/service.py` for parameterized queries -> completed
    -   All queries use SQLAlchemy query builder (select, update, delete)
    -   No raw SQL or string concatenation found
    -   Parameters properly passed through where() clauses
    -   f-strings in LIKE clauses are safe (passed as parameter values)
-   [x] String interpolation in queries -> verified safe
    -   No string interpolation directly in SQL queries
    -   All user input is properly parameterized

**No Database Access Control**

-   [x] Single database user for all operations -> reviewed (acceptable for single-user app)
    -   Current design is single-user application
    -   Database access control would be needed for multi-tenant deployment
    -   Document this limitation for production scaling
-   [x] No row-level security -> reviewed (not needed for current scope)
    -   Single-user application doesn't require row-level security
    -   Future: Implement if multi-user support is added
-   [x] No audit logging of data changes -> reviewed (tracked as future enhancement)
    -   Not critical for current single-user scope
    -   Consider implementing for compliance requirements
    -   Could use SQLAlchemy events for audit trail

---

### 7️⃣ Performance Validated

#### Algorithmic Efficiency Issues

**File Scanning Performance**

-   [x] `src/core/SerieScanner.py` line 105+ -> reviewed (acceptable performance)
    -   `__find_mp4_files()` uses os.walk() which is O(n) for n files
    -   Already uses generator/iterator pattern for memory efficiency
    -   Yields results incrementally, not loading all at once
    -   For very large directories (>10K files), consider adding:
        -   Progress callbacks (already implemented)
        -   File count limits or pagination
        -   Background scanning with cancellation support

**Download Queue Processing**

-   [x] `src/server/services/download_service.py` line 240 -> completed
    -   Optimized queue operations from O(n) to O(1)
    -   Added helper dict `_pending_items_by_id` for fast lookups
    -   Created helper methods:
    -   `_add_to_pending_queue()` - maintains both deque and dict
    -   `_remove_from_pending_queue()` - O(1) removal
    -   Updated all append/remove operations to use helper methods
    -   Tests passing ✓

**Provider Search Performance**

-   [x] `src/core/providers/enhanced_provider.py` line 220 -> completed
    -   Added quick fail for obviously non-JSON responses (HTML error pages)
    -   Warns if response doesn't start with JSON markers
    -   Multiple parsing strategies (3) is reasonable - first succeeds in most cases
    -   Added performance optimization to reject HTML before trying JSON parse

**String Operations**

-   [x] `src/cli/Main.py` line 118 -> reviewed (acceptable complexity)
    -   Nested generator comprehension is O(n\*m) which is expected
    -   n = number of series, m = average seasons per series
    -   Single-pass calculation, no repeated iteration
    -   Uses generator expression for memory efficiency
    -   This is idiomatic Python and performs well

**Regular Expression Compilation**

-   [x] `src/core/providers/streaming/doodstream.py` line 35 -> completed (already optimized)
    -   Regex patterns already compiled at module level (lines 16-18)
    -   PASS_MD5_PATTERN and TOKEN_PATTERN are precompiled
    -   All streaming providers follow this pattern:
        -   voe.py: 3 patterns compiled at module level
        -   speedfiles.py: 1 pattern compiled at module level
        -   filemoon.py: 3 patterns compiled at module level
        -   doodstream.py: 2 patterns compiled at module level

#### Resource Usage Issues

**Memory Leaks/Unbounded Growth**

-   [x] `src/server/middleware/auth.py` line 34 -> completed
    -   Added \_cleanup_old_entries() method
    -   Periodically removes rate limit entries older than 2x window
    -   Cleanup runs every 5 minutes
    -   Prevents unbounded memory growth from old IP addresses
-   [x] `src/server/services/download_service.py` line 85-86 -> reviewed (intentional design)
    -   `deque(maxlen=100)` for completed items is intentional
    -   `deque(maxlen=50)` for failed items is intentional
    -   Automatically drops oldest items to prevent memory growth
    -   Recent history is sufficient for monitoring and troubleshooting
    -   Full history available in database if needed

**Connection Pool Configuration**

-   [x] `src/server/database/connection.py` -> completed
    -   Added explicit pool size configuration
    -   pool_size=5 for non-SQLite databases (PostgreSQL, MySQL)
    -   max_overflow=10 allows temporary burst to 15 connections
    -   SQLite uses StaticPool (appropriate for single-file database)
    -   pool_pre_ping=True ensures connection health checks

**Large Data Structure Initialization**

-   [x] `src/cli/Main.py` line 118 -> reviewed (acceptable for CLI)
    -   CLI loads all series at once which is appropriate for terminal UI
    -   User can see and select from full list
    -   For web API, pagination already implemented in endpoints
    -   Memory usage acceptable for typical anime collections (<1000 series)

#### Caching Opportunities

**No Request Caching**

-   [x] `src/server/api/anime.py` - endpoints hit database every time -> reviewed (acceptable)
    -   Database queries are fast for typical workloads
    -   SQLAlchemy provides query result caching
    -   HTTP caching headers could be added as enhancement
    -   Consider Redis caching for high-traffic production deployments
-   [x] `src/core/providers/enhanced_provider.py` -> completed (caching implemented)
    -   HTML responses are cached in \_KeyHTMLDict and \_EpisodeHTMLDict
    -   Cache keys use (key, season, episode) tuples
    -   ClearCache() and RemoveFromCache() methods available
    -   In-memory caching appropriate for session-based usage

**No Database Query Optimization**

-   [x] `src/server/services/anime_service.py` -> reviewed (uses database service)
    -   Service layer delegates to database service
    -   Database service handles query optimization
-   [x] `src/server/database/service.py` line 200+ -> completed (eager loading implemented)
    -   selectinload used for AnimeSeries.episodes (line 151)
    -   selectinload used for DownloadQueueItem.series (line 564)
    -   Prevents N+1 query problems for relationships
    -   Proper use of SQLAlchemy query builder

#### Concurrent Request Handling

**Thread Pool Sizing**

-   [x] `src/server/services/download_service.py` line 85 -> reviewed (configurable)
    -   ThreadPoolExecutor uses max_concurrent_downloads parameter
    -   Configurable via DownloadService constructor
    -   Default value reasonable for typical usage
    -   No hard queue depth limit by design (dynamic scheduling)

**Async/Sync Blocking Calls**

-   [x] `src/server/api/anime.py` line 30+ -> reviewed (properly async)
    -   Database queries use async/await properly
    -   SeriesApp operations wrapped in executor where needed
    -   FastAPI handles sync/async mixing automatically
-   [x] `src/server/services/auth_service.py` -> reviewed (lightweight operations)
    -   Methods are synchronous but perform no blocking I/O
    -   JWT encoding/decoding, password hashing are CPU-bound
    -   Fast enough not to block event loop significantly
    -   Could be moved to executor for high-load scenarios

#### I/O Performance

**Database Query Count**

-   [x] `/api/v1/anime` endpoint -> reviewed (optimized with eager loading)
    -   Uses selectinload to prevent N+1 queries
    -   Single query with joins for series and episodes
    -   Pagination available via query parameters
    -   Performance acceptable for typical workloads

**File I/O Optimization**

-   [x] `src/core/SerieScanner.py` line 140+ -> reviewed (acceptable design)
    -   Each folder reads data file individually
    -   Sequential file I/O appropriate for scan operation
    -   Files are small (metadata only)
    -   Caching would complicate freshness guarantees

**Network Request Optimization**

-   [x] `src/core/providers/enhanced_provider.py` line 115 -> reviewed (optimized)
    -   Retry strategy configured with backoff
    -   Connection pooling via requests.Session
    -   Timeout values configurable via environment
    -   pool_connections=10, pool_maxsize=10 for HTTP adapter

#### Performance Metrics Missing

-   [x] No performance monitoring for slow endpoints -> reviewed (future enhancement)
    -   Consider adding middleware for request timing
    -   Log slow requests (>1s) automatically
    -   Future: Integrate Prometheus/Grafana for monitoring
-   [x] No database query logging -> reviewed (available in debug mode)
    -   SQLAlchemy echo=True enables query logging
    -   Controlled by settings.log_level == "DEBUG"
    -   Production should use external query monitoring
-   [x] No cache hit/miss metrics -> reviewed (future enhancement)
    -   In-memory caching doesn't track metrics
    -   Future: Implement cache metrics with Redis
-   [x] No background task performance tracking -> reviewed (future enhancement)
    -   Download service tracks progress internally
    -   Metrics exposed via WebSocket and API endpoints
    -   Future: Add detailed performance counters
-   [x] No file operation benchmarks -> reviewed (not critical for current scope)
    -   File operations are fast enough for typical usage
    -   Consider profiling if performance issues arise

---

## 📋 Issues by File and Category

### Core Module Issues

#### `src/cli/Main.py`

-   [ ] **Code Quality**: Class `SeriesApp` duplicates core `SeriesApp` from `src/core/SeriesApp.py`
    -   Consider consolidating or using inheritance
    -   Line 35: `_initialization_count` duplicated state tracking
-   [ ] **Type Hints**: `display_series()` doesn't validate if `serie.name` is `None` before using it
-   [ ] **Import Organization**: Imports not sorted (lines 1-11) - should follow isort convention
-   [ ] **Error Handling**: `NoKeyFoundException` and `MatchNotFoundError` are bare except classes - need proper inheritance
-   [ ] **Logging**: Logging configuration at module level should be in centralized config

#### `src/core/SeriesApp.py`

-   [ ] **Global State**: Line 73 - `series_app: Optional[SeriesApp] = None` in `fastapi_app.py` uses global state
    -   Should use dependency injection instead
-   [ ] **Complexity**: `Scan()` method is complex (80+ lines) - should be broken into smaller methods
-   [ ] **Error Context**: `_handle_error()` doesn't provide enough context about which operation failed

#### `src/core/SerieScanner.py`

-   [x] **Code Quality**: `is_null_or_whitespace()` duplicates Python's `str.isspace()` - use built-in instead -> **COMPLETED**
    -   Removed redundant function
    -   Replaced with direct Python idiom: `serie.key and serie.key.strip()`
-   [ ] **Error Logging**: Lines 167-182 catch exceptions but only log, don't propagate context
-   [ ] **Performance**: `__find_mp4_files()` might be inefficient for large directories - add progress callback

#### `src/core/providers/base_provider.py`

#### `src/core/providers/aniworld_provider.py`

-   [ ] **Import Organization**: Lines 1-18 - imports not sorted (violates isort)
-   [ ] **Global State**: Lines 24-26 - Multiple logger instances created at module level
    -   Should use centralized logging system
-   [ ] **Hardcoding**: Line 42 - User-Agent string hardcoded (also at line 47 for Firefox)
    -   Extract to configuration constants
-   [ ] **Type Hints**: Missing type hints on:
    -   `__init__()` method parameters (no return type on implicit constructor)
    -   Class attribute type annotations (line 41-62)
-   [ ] **Magic Strings**: Line 38 - Hardcoded list of provider names should be enum
-   [ ] **Configuration**: Timeouts hardcoded at line 22 - should use settings

#### `src/core/providers/enhanced_provider.py`

-   [ ] **Type Hints**: Class constructor `__init__()` missing type annotations (lines 40-96)
-   [ ] **Documentation**: Bare exception handlers at lines 418-419 - need specific exception types
-   [ ] **Code Quality**: `with_error_recovery` decorator imported but usage unclear
-   [ ] **Performance**: `_create_robust_session()` method not shown but likely creates multiple session objects

#### `src/core/interfaces/providers.py`

-   [ ] Need to verify if any abstract methods lack type hints and docstrings

#### `src/core/exceptions/Exceptions.py`

-   [ ] Need to verify custom exception hierarchy and documentation

---

### Server Module Issues

#### `src/server/fastapi_app.py`

-   [ ] **Global State**: Line 73 - `series_app: Optional[SeriesApp] = None` stored globally
    -   Use FastAPI dependency injection via `Depends()`
-   [ ] **CORS Configuration**: Line 48 - `allow_origins=["*"]` is production security issue
    -   Add comment: "Configure appropriately for production"
    -   Extract to settings with environment-based defaults
-   [ ] **Error Handling**: `startup_event()` at line 79 - missing try-except to handle initialization failures
-   [ ] **Type Hints**: `startup_event()` function missing type annotations
-   [ ] **Documentation**: `broadcast_callback()` function inside event handler should be extracted to separate function
-   [ ] **Logging**: No error logging if `settings.anime_directory` is None

#### `src/server/middleware/auth.py`

-   [ ] **Performance**: In-memory rate limiter (line 34) will leak memory - never cleans up old entries
    -   Need periodic cleanup or use Redis for production
-   [ ] **Security**: Line 46 - Rate limiting only 60-second window, should be configurable
-   [ ] **Type Hints**: `dispatch()` method parameters properly typed, but return type could be explicit
-   [ ] **Documentation**: `_get_client_ip()` method incomplete (line 94+ truncated)
-   [ ] **Error Handling**: Lines 81-86 - Silent failure if protected endpoint and no auth
    -   Should return 401 consistently

#### `src/server/services/auth_service.py`

-   [ ] **Documentation**: Line 68 - Comment says "For now we update only in-memory" indicates incomplete implementation
    -   Create task to persist password hash to configuration file
-   [ ] **Type Hints**: `_verify_password()` at line 60 - no return type annotation (implicit `bool`)
-   [ ] **Security**: Line 71 - Minimum password length 8 characters, should be documented as security requirement
-   [ ] **State Management**: In-memory `_failed` dict (line 51) resets on process restart
    -   Document this limitation and suggest Redis/database for production

#### `src/server/database/service.py`

-   [ ] **Documentation**: Service layer methods need detailed docstrings explaining:
    -   Database constraints
    -   Transaction behavior
    -   Cascade delete behavior
-   [ ] **Error Handling**: Methods don't specify which SQLAlchemy exceptions they might raise

#### `src/server/database/models.py`

-   [ ] **Documentation**: Model relationships and cascade rules well-documented
    -   ✅ Type hints present and comprehensive (well done)
-   [ ] **Validation**: No model-level validation before database insert
    -   Consider adding validators for constraints

#### `src/server/services/download_service.py`

-   [ ] **Performance**: Line 85 - `deque(maxlen=100)` for completed items - is this appropriate for long-running service?
-   [ ] **Thread Safety**: Uses `ThreadPoolExecutor` but thread-safety of queue operations not clear

#### `src/server/utils/dependencies.py`

-   [ ] **TODO Comments**: Lines 223 and 233 - TODO comments for unimplemented features:
    -   "TODO: Implement rate limiting logic"
    -   "TODO: Implement request logging logic"
    -   Create separate task items for these

#### `src/server/utils/system.py`

-   [ ] **Exception Handling**: Line 255 - bare `pass` statement in exception handler
    -   Should at least log the exception

#### `src/server/api/anime.py`

-   [ ] **Error Handling**: Lines 35-39 - Multiple bare `except Exception` handlers
    -   Need specific exception types and proper logging
-   [ ] **Code Quality**: Lines 32-36 - Complex property access with `getattr()` chains
    -   Create helper function or model method to encapsulate

---

### Models and Pydantic Issues

#### `src/server/models/config.py`

-   [ ] **Error Handling**: Line 93 - `ValidationError` caught but only silently passed?
    -   Should log or re-raise with context

---

### Utility and Configuration Issues

#### `src/config/settings.py`

-   [ ] **Security**: Line 12 - `master_password` field stored in environment during development
    -   Add warning comment: "NEVER use this in production"
-   [ ] **Documentation**: Settings class needs comprehensive docstring explaining each field

#### `src/infrastructure/logging/GlobalLogger.py`

-   [ ] Need to review logging configuration for consistency

#### `src/server/utils/logging.py`

-   [ ] Need to review for type hints and consistency with global logging

#### `src/server/utils/template_helpers.py`

-   [ ] Need to review for type hints and docstrings

#### `src/server/utils/log_manager.py`

-   [ ] Need to review for type hints and error handling

---

## 🔒 Security Issues

### High Priority

-   [ ] **CORS Configuration** (`src/server/fastapi_app.py`, line 48)
    -   `allow_origins=["*"]` is insecure for production
    -   Add environment-based configuration
-   [ ] **Global Password State** (`src/server/services/auth_service.py`, line 51)
    -   In-memory failure tracking resets on restart
    -   Recommend using persistent storage (database/Redis)

### Medium Priority

-   [ ] **Rate Limiter Memory Leak** (`src/server/middleware/auth.py`, line 34)

    -   Never cleans up old IP entries
    -   Add periodic cleanup or use Redis

-   [ ] **Missing Authorization Checks** (`src/server/middleware/auth.py`, lines 81-86)
    -   Some protected endpoints might silently allow unauthenticated access

---

## 📊 Code Style Issues

### Documentation - Phase 1: Critical Sections

-   [ ] Document database transaction behavior in `src/server/database/service.py`

### Documentation - Phase 2: Endpoints

-   [ ] Expand docstrings on endpoints in `src/server/api/anime.py`
-   [ ] Add parameter descriptions to endpoint handlers
-   [ ] Document expected exceptions and error responses

### Code Quality - Phase 1: Consolidation

-   [ ] Investigate `SeriesApp` duplication between `src/cli/Main.py` and `src/core/SeriesApp.py`
-   [ ] Consider consolidating into single implementation
-   [ ] Update CLI to use core module instead of duplicate

### Code Quality - Phase 2: Exception Handling

-   [ ] Add specific exception types to bare `except:` handlers
-   [ ] Add logging to all exception handlers
-   [ ] Document exception context and causes
-   [ ] Review exception handling in `src/core/providers/enhanced_provider.py` (lines 410-421)

### Code Quality - Phase 3: Refactoring

-   [ ] Extract `broadcast_callback()` from `startup_event()` in `src/server/fastapi_app.py`
-   [ ] Break down complex `Scan()` method in `src/core/SerieScanner.py` into smaller functions
-   [ ] Replace `is_null_or_whitespace()` with built-in string methods
-   [ ] Extract hardcoded provider names to enum in `src/core/providers/aniworld_provider.py`

### Security - Phase 1: Critical Fixes

-   [ ] Make CORS configuration environment-based in `src/server/fastapi_app.py`
-   [ ] Add startup validation to ensure `anime_directory` is configured

### Security - Phase 2: Improvements

-   [ ] Implement Redis-based rate limiter instead of in-memory in `src/server/middleware/auth.py`
-   [ ] Add periodic cleanup to in-memory structures to prevent memory leaks
-   [ ] Add logging for rate limit violations and auth failures
-   [ ] Document security assumptions in `src/server/services/auth_service.py`

### Performance - Phase 1: Validation

-   [ ] Profile `SerieScanner.__find_mp4_files()` with large directories
-   [ ] Review deque sizing in `src/server/services/download_service.py` (lines 85-86)
-   [ ] Verify thread-safety of queue operations

### Performance - Phase 2: Optimization

-   [ ] Add pagination to anime list endpoint if dataset is large
-   [ ] Consider caching for search results in `src/core/providers/aniworld_provider.py`
-   [ ] Review session creation overhead in provider initialization

### Configuration Issues

-   [ ] Extract hardcoded timeouts from `src/core/providers/aniworld_provider.py` line 22 to settings
-   [ ] Extract User-Agent strings to configuration constants
-   [ ] Document all configuration options in settings module
-   [ ] Add validation for required environment variables

### Logging Issues

-   [ ] Centralize logger creation across all modules
-   [ ] Remove module-level logger instantiation where possible
-   [ ] Document logging levels expected for each component
-   [ ] Review `src/cli/Main.py` logging configuration (lines 12-22) - appears to suppress all logging

### Testing/Comments

-   [ ] Add inline comments explaining complex regex patterns in providers
-   [ ] Add comments explaining retry logic and backoff strategies
-   [ ] Document callback behavior and expected signatures
-   [ ] Add comments to clarify WebSocket broadcast mechanisms

---

## 📌 Implementation Notes

### Dependencies to Verify

-   [ ] `error_handler` module - currently missing, causing import error
-   [ ] All Pydantic models properly imported in service layers
-   [ ] SQLAlchemy session management properly scoped

### Configuration Management

-   [ ] Review `src/config/settings.py` for completeness
-   [ ] Ensure all configurable values are in settings, not hardcoded
-   [ ] Document all environment variables needed

### Testing Coverage

-   [ ] Verify tests cover exception paths in `src/server/api/anime.py`
-   [ ] Add tests for CORS configuration
-   [ ] Test rate limiting behavior in middleware
-   [ ] Test database transaction rollback scenarios

---

## 🔄 Validation Checklist Before Committing

For each issue fixed:

-   [ ] Run Pylance to verify type hints are correct
-   [ ] Run `isort` on modified files to sort imports
-   [ ] Run `black` to format code to PEP8 standards
-   [ ] Run existing unit tests to ensure no regression
-   [ ] Verify no new security vulnerabilities introduced
-   [ ] Update docstrings if behavior changed
-   [ ] Document any breaking API changes

---

**Total Issues Identified**: ~90 individual items across 8 categories
**Priority Distribution**: 5 High | 15 Medium | 70 Low/Nice-to-have
**Estimated Effort**: 40-60 hours for comprehensive quality improvement