# FSM Package Implementation Plan

## Overview
This document provides a detailed implementation plan and checklist for developing the DataKnobs FSM package. The implementation follows a phased approach, building from core components to advanced features.

## Development Phases

### Phase 1: Core Foundation (Week 1-2)
Establish the basic FSM structure and core components.

#### Checklist:
- [ ] **Project Setup**
  - [ ] Create package directory structure
  - [ ] Configure pyproject.toml with dependencies
  - [ ] Set up testing framework (pytest)
  - [ ] Configure linting and formatting (ruff, black)
  - [ ] Create initial __init__.py files

- [ ] **Base Interfaces** (`functions/base.py`)
  - [ ] Define IValidationFunction interface
  - [ ] Define ITransformFunction interface
  - [ ] Define IStateTestFunction interface
  - [ ] Define IEndStateTestFunction interface
  - [ ] Create base exception classes
  - [ ] Add type hints and documentation

- [ ] **Core Data Models** (`core/state.py`)
  - [ ] Implement StateDefinition class
    - [ ] Name and metadata properties
    - [ ] Schema definition using dataknobs_data.Field
    - [ ] Start/end state flags
    - [ ] Function references (validity, state test, end test)
  - [ ] Implement StateInstance class
    - [ ] Unique ID generation
    - [ ] Data storage (record or reference)
    - [ ] Status tracking (successful/failed/processing)
    - [ ] Arc execution history
  - [ ] Add validation methods
  - [ ] Create unit tests

- [ ] **Arc Implementation** (`core/arc.py`)
  - [ ] Implement ArcDefinition class
    - [ ] Target state reference
    - [ ] Pre-test function reference
    - [ ] Transform function reference
  - [ ] Implement PushArc subclass
    - [ ] Target network reference
    - [ ] Return state reference
  - [ ] Implement ArcExecution class
    - [ ] Execute pre-test
    - [ ] Execute transform
    - [ ] Handle failures gracefully
  - [ ] Create unit tests

### Phase 2: Network and FSM Structure (Week 2-3)
Build the state network management and main FSM class.

#### Checklist:
- [ ] **State Network** (`core/network.py`)
  - [ ] Implement StateNetwork class
    - [ ] Network name/label
    - [ ] State collection management
    - [ ] Arc collection management
    - [ ] Start/end state validation
  - [ ] Add methods for:
    - [ ] Adding/removing states
    - [ ] Adding/removing arcs
    - [ ] Validating network consistency
    - [ ] Finding paths between states
  - [ ] Integrate with networkx for graph operations
  - [ ] Create unit tests

- [ ] **Main FSM Class** (`core/fsm.py`)
  - [ ] Implement FSM class
    - [ ] FSM name and metadata
    - [ ] Network collection management
    - [ ] Global configuration
  - [ ] Add methods for:
    - [ ] Adding/removing networks
    - [ ] Validating FSM consistency
    - [ ] Creating execution contexts
  - [ ] Create factory method for instantiation
  - [ ] Create unit tests

- [ ] **Execution Context** (`execution/context.py`)
  - [ ] Implement ExecutionContext class
    - [ ] Current state tracking
    - [ ] Data management
    - [ ] Network stack (for push operations)
  - [ ] Add context isolation
  - [ ] Support for parallel execution paths
  - [ ] Create unit tests

### Phase 3: Execution Engine (Week 3-4)
Implement the core execution logic and history tracking.

#### Checklist:
- [ ] **Execution Engine** (`execution/engine.py`)
  - [ ] Implement ExecutionEngine class
    - [ ] Execute single transition
    - [ ] Handle branching paths
    - [ ] Manage push/pop for network calls
  - [ ] Add execution strategies:
    - [ ] Depth-first traversal
    - [ ] Breadth-first traversal
    - [ ] Priority-based traversal
  - [ ] Implement error handling
  - [ ] Add execution hooks/callbacks
  - [ ] Create unit tests

- [ ] **History Tracking** (`execution/history.py`)
  - [ ] Implement ExecutionHistory class
    - [ ] Use dataknobs_structures.Tree
    - [ ] Track state instances
    - [ ] Track arc executions
    - [ ] Record timestamps
  - [ ] Add methods for:
    - [ ] Adding execution steps
    - [ ] Querying paths
    - [ ] Pruning old history
    - [ ] Serializing history
  - [ ] Create visualization methods
  - [ ] Create unit tests

- [ ] **Storage Interface** (`storage/base.py`)
  - [ ] Define IHistoryStorage interface
  - [ ] Define storage configuration
  - [ ] Create storage factory
  - [ ] Add unit tests

### Phase 4: Configuration and Building (Week 4-5)
Implement configuration loading and FSM building from configs.

#### Checklist:
- [ ] **Configuration Schema** (`config/schema.py`)
  - [ ] Define configuration schema using pydantic
  - [ ] Support for YAML and JSON
  - [ ] Schema for:
    - [ ] FSM definition
    - [ ] Network definition
    - [ ] State definition
    - [ ] Arc definition
    - [ ] Function references
  - [ ] Add validation rules
  - [ ] Create example schemas
  - [ ] Create unit tests

- [ ] **Configuration Loader** (`config/loader.py`)
  - [ ] Implement ConfigLoader class
    - [ ] Load from file
    - [ ] Load from dictionary
    - [ ] Variable substitution (via dataknobs_config)
  - [ ] Add validation
  - [ ] Support for includes/imports
  - [ ] Create unit tests

- [ ] **FSM Builder** (`config/builder.py`)
  - [ ] Implement FSMBuilder class
    - [ ] Build FSM from configuration
    - [ ] Resolve function references
    - [ ] Validate completeness
  - [ ] Integration with dataknobs_config.ConfigurableBase
  - [ ] Support for custom function registration
  - [ ] Create unit tests

- [ ] **Built-in Functions** (`functions/validators.py`, `functions/transformers.py`)
  - [ ] Implement common validators:
    - [ ] RequiredFieldsValidator
    - [ ] SchemaValidator
    - [ ] RangeValidator
    - [ ] PatternValidator
  - [ ] Implement common transformers:
    - [ ] FieldMapper
    - [ ] ValueNormalizer
    - [ ] TypeConverter
    - [ ] DataEnricher
  - [ ] Create unit tests

### Phase 5: Storage Implementations (Week 5-6)
Implement different storage backends for history.

#### Checklist:
- [ ] **Memory Storage** (`storage/memory.py`)
  - [ ] Implement InMemoryStorage class
  - [ ] Add size limits
  - [ ] Implement LRU eviction
  - [ ] Create unit tests

- [ ] **Database Storage** (`storage/database.py`)
  - [ ] Implement DatabaseStorage class
  - [ ] Use dataknobs_data abstractions
  - [ ] Support for:
    - [ ] PostgreSQL
    - [ ] SQLite
    - [ ] MongoDB
  - [ ] Add indexing for queries
  - [ ] Create unit tests

- [ ] **File Storage** (`storage/file.py`)
  - [ ] Implement FileStorage class
  - [ ] Support for JSON/YAML serialization
  - [ ] Implement rotation policies
  - [ ] Add compression support
  - [ ] Create unit tests

### Phase 6: Streaming and Performance (Week 6-7)
Add streaming capabilities and performance optimizations.

#### Checklist:
- [ ] **Stream Processor** (`streaming/processor.py`)
  - [ ] Implement StreamProcessor class
  - [ ] Integration with dataknobs_data.StreamProcessor
  - [ ] Support for:
    - [ ] Single record processing
    - [ ] Batch processing
    - [ ] Async processing
  - [ ] Add backpressure handling
  - [ ] Create unit tests

- [ ] **Batch Optimizations** (`streaming/batch.py`)
  - [ ] Implement BatchExecutor class
  - [ ] Parallel execution for independent paths
  - [ ] Batch validation
  - [ ] Batch transformations
  - [ ] Create performance benchmarks

- [ ] **Performance Optimizations**
  - [ ] Add caching for:
    - [ ] Validation results
    - [ ] Transform results
    - [ ] Path computations
  - [ ] Implement lazy evaluation
  - [ ] Add profiling instrumentation
  - [ ] Create performance tests

### Phase 7: Testing and Documentation (Week 7-8)
Comprehensive testing and documentation.

#### Checklist:
- [ ] **Unit Tests**
  - [ ] Achieve >90% code coverage
  - [ ] Test all error conditions
  - [ ] Test edge cases
  - [ ] Mock external dependencies

- [ ] **Integration Tests**
  - [ ] Test with dataknobs_config
  - [ ] Test with dataknobs_data
  - [ ] Test with dataknobs_structures
  - [ ] Test storage backends
  - [ ] Test streaming scenarios

- [ ] **Example FSMs** (`examples/`)
  - [ ] Data validation pipeline
  - [ ] ETL processing workflow
  - [ ] Document processing system
  - [ ] Multi-network orchestration
  - [ ] Error handling patterns

- [ ] **Documentation**
  - [ ] API documentation (docstrings)
  - [ ] README with quick start
  - [ ] User guide
  - [ ] Configuration reference
  - [ ] Architecture documentation
  - [ ] Performance tuning guide

### Phase 8: Advanced Features (Week 8+)
Optional advanced features for future releases.

#### Checklist:
- [ ] **Visualization**
  - [ ] Graph visualization of FSM
  - [ ] Execution path visualization
  - [ ] Real-time monitoring dashboard

- [ ] **Distributed Execution**
  - [ ] Support for distributed state storage
  - [ ] Network execution on different nodes
  - [ ] Coordination protocols

- [ ] **Machine Learning Integration**
  - [ ] Adaptive transition probabilities
  - [ ] Learning optimal paths
  - [ ] Anomaly detection in executions

## Development Guidelines

### Code Style
- Follow PEP 8 guidelines
- Use type hints throughout
- Maintain comprehensive docstrings
- Keep functions focused and testable

### Testing Strategy
- Write tests before implementation (TDD)
- Use pytest fixtures for common setups
- Mock external dependencies
- Test both success and failure paths

### Documentation
- Update documentation as you code
- Include examples in docstrings
- Maintain a CHANGELOG
- Document breaking changes

### Version Control
- Use feature branches
- Commit frequently with clear messages
- Create PRs for review
- Tag releases appropriately

## Resource Requirements

### Team Composition
- **Lead Developer**: Architecture and core implementation
- **Backend Developer**: Storage and execution engine
- **Integration Developer**: DataKnobs package integration
- **Test Engineer**: Testing framework and test cases
- **Documentation Writer**: User guides and API docs

### Tools and Infrastructure
- Python 3.10+
- Development environment with DataKnobs packages
- CI/CD pipeline (GitHub Actions)
- Test databases for storage testing
- Performance testing environment

## Risk Mitigation

### Technical Risks
1. **Performance Issues**
   - Mitigation: Early performance testing, profiling
   
2. **Complex State Networks**
   - Mitigation: Graph analysis tools, validation

3. **Memory Management**
   - Mitigation: Configurable limits, storage backends

4. **Integration Complexity**
   - Mitigation: Clear interfaces, comprehensive testing

### Schedule Risks
1. **Dependency Updates**
   - Mitigation: Pin versions, regular updates

2. **Scope Creep**
   - Mitigation: Phased approach, clear priorities

3. **Testing Delays**
   - Mitigation: Continuous testing, automation

## Success Criteria

### Functional
- [ ] All core features implemented
- [ ] Integration with DataKnobs packages working
- [ ] Examples running successfully
- [ ] Documentation complete

### Non-Functional
- [ ] Performance benchmarks met
- [ ] Code coverage >90%
- [ ] No critical bugs
- [ ] Clean code analysis

### Deliverables
- [ ] Source code in packages/fsm
- [ ] Comprehensive test suite
- [ ] Documentation and examples
- [ ] Performance benchmarks
- [ ] Migration guide (if applicable)

## Notes for Contributors

### Getting Started
1. Review the FSM_DESIGN.md document
2. Set up development environment
3. Run existing tests to ensure setup
4. Pick tasks from current phase
5. Follow TDD approach

### Communication
- Daily standups for active developers
- Weekly architecture reviews
- PR reviews within 24 hours
- Documentation updates with each PR

### Quality Standards
- No PR without tests
- No PR without documentation
- Code review required
- Performance impact assessment

## Appendix: Configuration Example

```yaml
# Example FSM configuration for reference
fsm:
  name: "SampleFSM"
  version: "1.0.0"
  
  # Global settings
  settings:
    history_storage: "memory"
    max_history_depth: 1000
    execution_timeout: 300
    
  # Function registry
  functions:
    validators:
      - module: "dataknobs_fsm.functions.validators"
        register_all: true
      - module: "custom.validators"
        classes:
          - "CustomValidator"
    
    transformers:
      - module: "dataknobs_fsm.functions.transformers"
        register_all: true
  
  # Networks definition
  networks:
    - name: "main"
      description: "Main processing network"
      states:
        - name: "start"
          is_start: true
          schema:
            $ref: "schemas/input_schema.yaml"
          validity_test:
            function: "RequiredFieldsValidator"
            params:
              fields: ["id", "data"]
          arcs:
            - target: "process"
              pre_test:
                function: "NonEmptyValidator"
                params:
                  field: "data"
                  
        - name: "process"
          state_test:
            function: "CustomValidator"
          arcs:
            - target: "complete"
              transform:
                function: "DataEnricher"
                params:
                  enrichment_source: "database"
                  
        - name: "complete"
          is_end: true
          end_state_test:
            function: "CompletionValidator"
```

This implementation plan provides a structured approach to building the FSM package with clear milestones and deliverables.