# Requirements Document: The Polyglot Bridge

## Introduction

The Polyglot Bridge is a Rust library that provides high-performance computational functions accessible from Python through FFI (Foreign Function Interface). The library demonstrates cross-language interoperability while delivering measurable performance improvements over pure Python implementations for computationally intensive operations.

## Glossary

- **Rust_Library**: The core computational library written in Rust
- **Python_Bindings**: The PyO3-generated interface layer that exposes Rust functions to Python
- **FFI_Layer**: The Foreign Function Interface that handles cross-language communication
- **Performance_Benchmark**: Automated tests that measure and compare execution time between Rust and Python implementations
- **Type_Converter**: The component that translates data types between Rust and Python
- **Error_Handler**: The component that translates Rust errors into Python exceptions

## Requirements

### Requirement 1: Python Function Exposure

**User Story:** As a Python developer, I want to import and call Rust functions as if they were native Python functions, so that I can leverage Rust's performance without learning Rust.

#### Acceptance Criteria

1. WHEN a Python developer imports the library THEN the Python_Bindings SHALL expose all public Rust functions as callable Python functions
2. WHEN a Python function is called with valid arguments THEN the FFI_Layer SHALL convert Python types to Rust types, execute the Rust function, and return the result as a Python type
3. WHEN a Python function is called THEN the Python_Bindings SHALL maintain Python's calling conventions (keyword arguments, default values where applicable)
4. THE Python_Bindings SHALL provide type hints for all exposed functions
5. WHEN the library is imported THEN the Python_Bindings SHALL load without requiring manual memory management from the Python developer

### Requirement 2: Performance-Critical Operations

**User Story:** As a performance engineer, I want to execute computationally intensive operations in Rust, so that I can achieve significant speedups over pure Python implementations.

#### Acceptance Criteria

1. THE Rust_Library SHALL implement mathematical computation functions that are CPU-intensive
2. THE Rust_Library SHALL implement data processing functions that operate on large datasets
3. WHEN processing large arrays or matrices THEN the Rust_Library SHALL utilize efficient memory layouts and algorithms
4. WHERE parallel processing is beneficial, THE Rust_Library SHALL leverage Rust's concurrency features
5. THE Rust_Library SHALL avoid unnecessary memory allocations and copies during computation

### Requirement 3: Cross-Language Error Handling

**User Story:** As a Python developer, I want Rust errors to be translated into Python exceptions, so that I can handle errors using familiar Python patterns.

#### Acceptance Criteria

1. WHEN a Rust function encounters an error THEN the Error_Handler SHALL convert it into an appropriate Python exception
2. WHEN a Python exception is raised THEN the Error_Handler SHALL include descriptive error messages from the Rust layer
3. IF invalid input types are provided THEN the Python_Bindings SHALL raise a TypeError with a clear message
4. IF a computation fails THEN the Error_Handler SHALL raise a RuntimeError or domain-specific exception
5. THE Error_Handler SHALL prevent Rust panics from crashing the Python interpreter

### Requirement 4: Type Safety and Conversion

**User Story:** As a library maintainer, I want automatic type conversion between Python and Rust, so that data integrity is maintained across language boundaries.

#### Acceptance Criteria

1. WHEN Python integers are passed THEN the Type_Converter SHALL convert them to appropriate Rust integer types
2. WHEN Python floats are passed THEN the Type_Converter SHALL convert them to Rust f64 or f32 types
3. WHEN Python lists are passed THEN the Type_Converter SHALL convert them to Rust Vec types
4. WHEN Python strings are passed THEN the Type_Converter SHALL convert them to Rust String or &str types
5. WHEN Rust results are returned THEN the Type_Converter SHALL convert them to appropriate Python types
6. IF type conversion fails THEN the Type_Converter SHALL raise a TypeError with details about the expected type

### Requirement 5: Performance Benchmarking

**User Story:** As a performance engineer, I want automated benchmarks comparing Rust and Python implementations, so that I can quantify the performance improvements.

#### Acceptance Criteria

1. THE Performance_Benchmark SHALL implement equivalent algorithms in both Rust and pure Python
2. WHEN benchmarks are executed THEN the Performance_Benchmark SHALL measure execution time for both implementations
3. WHEN benchmarks complete THEN the Performance_Benchmark SHALL report speedup ratios (Rust vs Python)
4. THE Performance_Benchmark SHALL test performance across different input sizes
5. THE Performance_Benchmark SHALL measure memory usage for both implementations
6. WHEN benchmarks are run THEN the Performance_Benchmark SHALL produce reproducible results with statistical significance

### Requirement 6: Build and Distribution

**User Story:** As a Python developer, I want to install the library using pip, so that I can integrate it into my Python projects easily.

#### Acceptance Criteria

1. THE Rust_Library SHALL compile to a Python wheel package
2. WHEN building the package THEN the build system SHALL use maturin or setuptools-rust
3. THE Python_Bindings SHALL be compatible with Python 3.8 or later
4. WHEN the package is installed THEN the Python_Bindings SHALL work on Linux, macOS, and Windows
5. THE build configuration SHALL specify Rust edition 2024 and minimum Rust version 1.93

### Requirement 7: API Documentation

**User Story:** As a Python developer, I want comprehensive documentation with examples, so that I can understand how to use the library effectively.

#### Acceptance Criteria

1. THE Python_Bindings SHALL include docstrings for all exposed functions
2. WHEN help() is called on a function THEN the Python_Bindings SHALL display parameter types, return types, and descriptions
3. THE documentation SHALL include code examples demonstrating common use cases
4. THE documentation SHALL include a quickstart guide for installation and basic usage
5. THE documentation SHALL explain the performance characteristics of each function

### Requirement 8: Rust Code Quality

**User Story:** As a library maintainer, I want the Rust code to follow best practices, so that the library is maintainable and reliable.

#### Acceptance Criteria

1. THE Rust_Library SHALL compile without warnings when using clippy
2. THE Rust_Library SHALL use Result types for error handling instead of panics
3. THE Rust_Library SHALL include unit tests for all core functions
4. THE Rust_Library SHALL use Rust edition 2024
5. THE Rust_Library SHALL specify rust-version = "1.93" in Cargo.toml
6. WHERE appropriate, THE Rust_Library SHALL use iterators and functional patterns over imperative loops
