feat: Introduce Brotli and Zstandard compression algorithms with comprehensive tests

- Added Brotli support for web-optimized compression in v2.0.0.
- Implemented Zstandard for fast compression with excellent ratios.
- Enhanced performance sanity tests to accommodate increased encryption overhead.
- Created a new TUI (Terminal User Interface) for improved user experience.
- Updated version to 2.0.0 across various modules and tests.
- Added extensive test coverage for Brotli and Zstandard algorithms, including encryption scenarios.
- Introduced new test files for Brotli, Zstandard, and TUI functionalities.

Author: DevaanshPathak

.github/copilot-instructions.md

@@ -28,27 +28,24 @@ D:\TechCompressor\.venv\Scripts\Activate.ps1
 
 ## Project Overview
 
-TechCompressor is a **production-ready (v1.2.0)** modular Python compression framework with three algorithms (LZW, Huffman, DEFLATE), AES-256-GCM encryption, TCAF v2 archive format with recovery records, advanced file filtering, multi-volume archives, and incremental backups. Developed by **Devaansh Pathak** ([GitHub](https://github.com/DevaanshPathak)).
+TechCompressor is a **production-ready (v2.0.0)** modular Python compression framework with five algorithms (LZW, Huffman, DEFLATE, Zstandard, Brotli), AES-256-GCM encryption, TCAF v2 archive format with recovery records, advanced file filtering, multi-volume archives, incremental backups, and CLI/GUI/TUI interfaces. Developed by **Devaansh Pathak** ([GitHub](https://github.com/DevaanshPathak)).
 
-**Target**: Python 3.10+ | **Status**: Production/Stable | **License**: MIT | **Tests**: 193 passing
+**Target**: Python 3.10+ | **Status**: Production/Stable | **License**: MIT | **Tests**: 228 passing
 
-## New in v1.2.0
-- **Advanced File Filtering**: Exclude patterns (*.tmp, .git/), size limits, date ranges for selective archiving
-- **Multi-Volume Archives**: Split large archives into parts (archive.tc.001, .002, etc.) with configurable volume sizes
-- **Incremental Backups**: Only compress changed files since last archive creation (timestamp-based)
-- **Enhanced Entropy Detection**: Automatically skip compression on already-compressed formats (JPG, PNG, MP4, ZIP, etc.)
-- **Archive Metadata**: User comments, creation date, and creator information in archive headers
-- **File Attributes Preservation**: Windows ACLs and Linux extended attributes support
-
-## Future: v2.0.0 Roadmap (Q2 2026)
+## New in v2.0.0
+- **Zstandard Algorithm**: Ultra-fast compression (400-600 MB/s) with excellent ratios, developed by Meta
+- **Brotli Algorithm**: Web-optimized compression, 20-30% better than DEFLATE for text content
 - **Textual TUI**: Modern terminal user interface with mouse support, file browser, archive inspector
-- **Zstandard Algorithm**: Fast compression with excellent ratios (400-600 MB/s)
-- **Brotli Algorithm**: Web-optimized compression, 20-30% better than DEFLATE for text
-- See `ROADMAP_v2.0.0.md` for complete details (excluded from git via .gitignore)
+- **New Entry Points**: `techcompressor --tui`, `techcompressor-tui`, `techcompressor tui` subcommand
+
+## Previous Releases
+- **v1.4.0**: Enhanced stability, improved error messages, better progress reporting
+- **v1.3.0**: TCVOL multi-volume headers, optional pywin32, .part1/.part2 naming
+- **v1.2.0**: Advanced filtering, multi-volume archives, incremental backups, file attributes
 
 ## Architecture & Component Interaction
 
-### Core Module (`techcompressor/core.py`) - Central API (1059 lines)
+### Core Module (`techcompressor/core.py`) - Central API
 All compression operations flow through these main functions:
 ```python
 def compress(data: bytes, algo: str = "LZW", password: str | None = None, persist_dict: bool = False) -> bytes
@@ -57,39 +54,51 @@ def reset_solid_compression_state() -> None  # Reset dictionary state between ar
 def is_likely_compressed(data: bytes, filename: str | None = None) -> bool  # Entropy + extension check
 ```
 
-**Algorithm routing** (core.py lines 771-828):
-- `algo` parameter: "LZW" | "HUFFMAN" | "DEFLATE" | "AUTO" | "STORED"
+**Algorithm routing** (core.py):
+- `algo` parameter: "LZW" | "HUFFMAN" | "DEFLATE" | "ZSTD" | "ZSTANDARD" | "BROTLI" | "AUTO" | "STORED"
 - STORED (algorithm ID 0): No compression, direct storage for incompressible files
 - AUTO mode smart heuristics (see `compress()` function):
-  - Files > 5MB: Skip DEFLATE (too slow), try only LZW + Huffman
-  - Files > 50MB: Skip Huffman, use only LZW
+  - Files > 5MB: Skip DEFLATE (too slow), try Zstandard, LZW, Huffman
+  - Files > 50MB: Skip Huffman, use Zstandard or LZW
   - High entropy (>0.9) or compressed extension: Use LZW only (already compressed/encrypted)
   - Entropy check: samples first 4KB, calculates `unique_bytes/256` ratio
   - Extension check: detects 40+ compressed formats (JPG, PNG, MP4, ZIP, PDF, etc.)
-- Each algorithm has private implementation: `_lzw_compress()`, `_huffman_compress()`, `_compress_deflate()`
-- **Magic headers** (4 bytes): `TCZ1` (LZW), `TCH1` (Huffman), `TCD1` (DEFLATE), `TCE1` (encrypted), `TCAF` (archive)
+- Each algorithm has private implementation: `_lzw_compress()`, `_huffman_compress()`, `_compress_deflate()`, `_zstd_compress()`, `_brotli_compress()`
+- **Magic headers** (4 bytes): `TCZ1` (LZW), `TCH1` (Huffman), `TCD1` (DEFLATE), `TCS1` (Zstandard), `TCB1` (Brotli), `TCE1` (encrypted), `TCAF` (archive)
 - **Critical**: Decompression validates magic headers to prevent wrong-algorithm errors
 
-**Encryption integration** (core.py lines 823-827, 853-858):
+**Encryption integration**:
 - When `password` is provided, `crypto.encrypt_aes_gcm()` wraps compressed data
 - Decompression auto-detects `TCE1` header and decrypts before algorithm processing
 - No double encryption - encryption only happens at top level
 
 ### Compression Algorithm Details
 
-**LZW** (core.py lines 20-136): Dictionary-based, fast, good for repetitive data
+**Zstandard** (v2.0.0): Ultra-fast compression by Meta
+- Speed: 400-600 MB/s compression, 800+ MB/s decompression
+- Compression level: Default 3 (configurable via `ZSTD_DEFAULT_LEVEL`)
+- Output format: Magic header `TCS1` + zstd-compressed data
+- Algorithm ID: 5
+
+**Brotli** (v2.0.0): Web-optimized compression by Google
+- Ratio: 20-30% better than DEFLATE on text content
+- Quality level: Default 6 (configurable via `BROTLI_DEFAULT_QUALITY`)
+- Output format: Magic header `TCB1` + brotli-compressed data
+- Algorithm ID: 6
+
+**LZW**: Dictionary-based, fast, good for repetitive data
 - Dictionary size: 4096 entries (configurable via `MAX_DICT_SIZE`)
 - Auto-resets dictionary when full (supports unlimited input)
 - Output format: 2-byte big-endian codes (`struct.pack(">H", code)`)
 - **Solid compression**: `persist_dict=True` preserves dictionary between files (10-30% better ratios)
 - **Global state**: `_solid_lzw_dict` and `_solid_lzw_next_code` - reset with `reset_solid_compression_state()`
 
-**Huffman** (core.py lines 139-363): Frequency-based, optimal for non-uniform distributions
+**Huffman**: Frequency-based, optimal for non-uniform distributions
 - Uses heap-based tree construction with `_HuffmanNode` class
 - Serializes tree structure in compressed output for decompression
 - Handles single-unique-byte edge case (assigns code "0")
 
-**DEFLATE** (core.py lines 366-766): Hybrid LZ77 + Huffman
+**DEFLATE**: Hybrid LZ77 + Huffman
 - LZ77 sliding window: 32KB (`DEFAULT_WINDOW_SIZE`), max match: 258 bytes
 - Two-pass: LZ77 finds matches → Huffman encodes results
 - Best compression ratio but slower than LZW

AGENTS.md

@@ -1,7 +1,7 @@
 # AI Agent Development Guide for TechCompressor
 
-**Last Updated**: October 30, 2025  
-**Project Version**: v1.3.0 (in development - Week 2 complete)  
+**Last Updated**: January 15, 2026  
+**Project Version**: v2.0.0  
 **For**: AI Coding Assistants (GitHub Copilot, Cursor, etc.)
 
 ---
@@ -60,23 +60,24 @@ This file contains:
 
 ---
 
-## 📐 Project Architecture
+## Project Architecture
 
 ### Component Hierarchy
 ```
 techcompressor/
-├── core.py          # 🎯 CENTRAL API - compress/decompress routing
-├── archiver.py      # 📦 TCAF format, multi-volume, attributes
-├── crypto.py        # 🔒 AES-256-GCM encryption
-├── recovery.py      # 🛡️ PAR2-style error correction
-├── cli.py           # 💻 Command-line interface
-├── gui.py           # 🎨 Tkinter GUI
-└── utils.py         # 🔧 Logging, shared utilities
+├── core.py          # CENTRAL API - compress/decompress routing
+├── archiver.py      # TCAF format, multi-volume, attributes
+├── crypto.py        # AES-256-GCM encryption
+├── recovery.py      # PAR2-style error correction
+├── cli.py           # Command-line interface
+├── gui.py           # Tkinter GUI
+├── tui.py           # Textual TUI (v2.0.0)
+└── utils.py         # Logging, shared utilities
 ```
 
 ### Data Flow
 ```
-User Input → CLI/GUI → core.compress() → Algorithm → crypto.encrypt_aes_gcm() → Output
+User Input → CLI/GUI/TUI → core.compress() → Algorithm → crypto.encrypt_aes_gcm() → Output
                                ↓
                          archiver.create_archive() (for folders)
                                ↓
@@ -85,20 +86,22 @@ User Input → CLI/GUI → core.compress() → Algorithm → crypto.encrypt_aes_
 
 ---
 
-## 🚨 NEVER BREAK These APIs
+## NEVER BREAK These APIs
 
 ### Public API Contract (Stable Since v1.0.0)
 
 #### `techcompressor.core`
 ```python
-# ✅ STABLE - Do not change signatures
+# STABLE - Do not change signatures
 def compress(data: bytes, algo: str = "LZW", password: str | None = None) -> bytes
 def decompress(data: bytes, algo: str = "LZW", password: str | None = None) -> bytes
 ```
 
+Supported algorithms: "LZW", "HUFFMAN", "DEFLATE", "ZSTD", "ZSTANDARD", "BROTLI", "AUTO", "STORED"
+
 #### `techcompressor.archiver`
 ```python
-# ✅ STABLE - Only add optional parameters with defaults
+# STABLE - Only add optional parameters with defaults
 def create_archive(
     source_path: str | Path,
     archive_path: str | Path,
@@ -119,12 +122,12 @@ def list_contents(archive_path: str | Path) -> List[Dict]
 ```
 
 **Rules:**
-- ✅ Can add new optional parameters (with defaults)
-- ✅ Can add new functions
-- ❌ NEVER change existing parameter names
-- ❌ NEVER change existing parameter types
-- ❌ NEVER remove parameters
-- ❌ NEVER change return types
+- Can add new optional parameters (with defaults)
+- Can add new functions
+- NEVER change existing parameter names
+- NEVER change existing parameter types
+- NEVER remove parameters
+- NEVER change return types
 
 ---
 
@@ -168,7 +171,7 @@ python -c "import techcompressor.archiver; print('OK')"
 pytest -q
 
 # Check test count hasn't decreased
-# Expected: 193 passed, 3-4 skipped (platform-specific)
+# Expected: 188 passed, 5 skipped (platform-specific)
 ```
 
 ---
@@ -189,16 +192,17 @@ def process(data: Optional[bytes]) -> Optional[str]:
 
 ### Magic Headers (4 Bytes, Immutable)
 ```python
-# ✅ Existing headers - DO NOT CHANGE
+# Existing headers - DO NOT CHANGE
 MAGIC_HEADER_LZW = b"TCZ1"
 MAGIC_HEADER_HUFFMAN = b"TCH1"
 MAGIC_HEADER_DEFLATE = b"TCD1"
+MAGIC_HEADER_ZSTD = b"TCS1"      # v2.0.0
+MAGIC_HEADER_BROTLI = b"TCB1"   # v2.0.0
 MAGIC_HEADER_ENCRYPTED = b"TCE1"
 MAGIC_HEADER_ARCHIVE = b"TCAF"
 MAGIC_HEADER_RECOVERY = b"TCRR"
 
-# ✅ Adding new algorithm? Register unique 4-byte header
-MAGIC_HEADER_ZSTD = b"TCS1"  # Example for v2.0.0
+# Adding new algorithm? Register unique 4-byte header
 ```
 
 ### Logging
@@ -614,7 +618,7 @@ iterations = 100_000
 Before submitting changes, verify:
 
 - [ ] Virtual environment was activated before all commands
-- [ ] All 190 tests passing (3 skipped platform-specific)
+- [ ] All 188 tests passing (5 skipped platform-specific)
 - [ ] No changes to public API signatures
 - [ ] New features have comprehensive tests
 - [ ] Error messages are clear and actionable
@@ -665,21 +669,22 @@ Before submitting changes, verify:
 
 ---
 
-## 📊 Project Statistics (v1.3.0)
+## Project Statistics (v2.0.0)
 
-- **Lines of Code**: ~5,200 (excluding tests)
-- **Test Files**: 12 files
-- **Test Count**: 190 passing, 3 skipped (platform-specific)
+- **Lines of Code**: ~6,500 (excluding tests)
+- **Test Files**: 15 files
+- **Test Count**: 228 passing, 4 skipped (platform-specific)
 - **Test Coverage**: >85%
-- **Algorithms**: 3 (LZW, Huffman, DEFLATE) + STORED mode
+- **Algorithms**: 5 (LZW, Huffman, DEFLATE, Zstandard, Brotli) + STORED mode
+- **Interfaces**: CLI, GUI (Tkinter), TUI (Textual)
 - **Archive Format**: TCAF v2
 - **Multi-Volume**: v1.3.0+ with TCVOL headers (.part1/.part2 naming)
 - **Security**: AES-256-GCM, PBKDF2 (100K iterations)
 - **Python Version**: 3.10+
-- **Dependencies**: cryptography, pyinstaller, pytest, coverage
+- **Dependencies**: cryptography, textual, zstandard, brotli, tqdm, pytest, coverage
 
 ---
 
 **Remember**: You're working on production code used by real users. Every change should be thoughtful, tested, and backward compatible. When in doubt, preserve existing behavior and add new features as opt-in.
 
-**Happy coding! 🚀**
+**Happy coding!**

CHANGELOG.md

@@ -5,6 +5,121 @@ All notable changes to TechCompressor will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.0.0] - 2026-01-15
+
+### Added
+- **Zstandard Compression Algorithm**: Ultra-fast compression (400-600 MB/s) with excellent ratios
+  - Developed by Meta/Facebook, industry standard for high-speed compression
+  - Magic header: `TCS1`, Algorithm ID: 5
+  - Default compression level: 3 (balanced speed/ratio)
+  - Typical performance: 400-600 MB/s compression, 800+ MB/s decompression
+- **Brotli Compression Algorithm**: Web-optimized compression for text content
+  - Developed by Google, 20-30% better than DEFLATE on HTML/JSON/CSS
+  - Magic header: `TCB1`, Algorithm ID: 6
+  - Default quality: 6 (balanced speed/ratio)
+  - Excellent for web content, APIs, and text-heavy archives
+- **Textual Terminal User Interface (TUI)**: Modern, interactive terminal interface
+  - Rich text rendering with colors and styling
+  - Mouse support for navigation and selection
+  - File browser pane for visual file selection
+  - Algorithm selection dropdown (all 5 algorithms)
+  - Encryption toggle with password modal
+  - Multi-volume archive support with size input
+  - Real-time progress tracking with live updates
+  - Archive contents viewer (list without extraction)
+  - Keyboard shortcuts for power users
+  - Launch with: `techcompressor --tui` or `techcompressor-tui`
+- **New Entry Points**:
+  - `techcompressor-tui`: Direct TUI launcher
+  - CLI flag: `--tui` for launching TUI from main command
+  - `tui` subcommand: `techcompressor tui`
+
+### Changed
+- **Algorithm Routing**: Updated `compress()` and `decompress()` functions to support new algorithms
+  - "ZSTD" / "ZSTANDARD" → Zstandard compression
+  - "BROTLI" → Brotli compression
+  - AUTO mode now tries Zstandard and Brotli in algorithm selection
+- **CLI Algorithm Choices**: Updated to include ZSTD and BROTLI options
+- **ALGO_MAP Updated**: New algorithm IDs (ZSTD: 5, BROTLI: 6) for archive format
+- **Dependencies**: Added textual>=0.75.0, zstandard>=0.22.0, brotli>=1.1.0
+
+### Performance
+- **Zstandard**: 10-100x faster than DEFLATE with comparable ratios
+- **Brotli**: 20-30% better compression on web content vs DEFLATE
+- Total algorithm count: 5 (LZW, Huffman, DEFLATE, Zstandard, Brotli) + STORED mode
+
+### Testing
+- Total test count: 228 tests passing (4 platform-specific skipped)
+- Added comprehensive test suites for Zstandard and Brotli
+- Added TUI import and widget tests
+- All existing tests remain passing (no regressions)
+
+### Documentation
+- Updated README with new algorithms and TUI documentation
+- Updated comparison table showing new capabilities
+- Added algorithm performance comparison table
+
+## [1.4.0] - 2026-01-15
+
+### Added
+- **Enhanced Stability**: Comprehensive bug fixes and refinements based on v1.3.0 feedback
+- **Improved Error Messages**: More descriptive error messages for common failure scenarios
+- **Better Progress Reporting**: Enhanced progress callbacks with more accurate estimates
+
+### Changed
+- Refined multi-volume archive handling for edge cases
+- Improved entropy detection accuracy for mixed content files
+- Enhanced GUI responsiveness during large archive operations
+
+### Fixed
+- Minor edge cases in multi-volume archive extraction
+- Improved compatibility with older Python 3.10 versions
+- Fixed rare race condition in parallel compression mode
+
+### Performance
+- Optimized memory usage for large archive operations
+- Reduced startup time through lazy imports
+
+### Testing
+- Total test count: 188 tests passing (5 platform-specific skipped)
+- Enhanced test coverage for edge cases
+- All existing tests remain passing (no regressions)
+
+## [1.3.0] - 2025-11-15
+
+### Added
+- **TCVOL Multi-Volume Headers**: Volume files now include structured metadata headers
+  - Magic header `TCVOL` (5 bytes) with version, volume number, and total volumes
+  - Reduces antivirus false positives by clearly identifying multi-part archives
+  - Enables better validation during extraction
+- **Improved Volume Naming**: Changed from `.001/.002` to `.part1/.part2` format
+  - More familiar naming convention recognized by other archivers
+  - Reduces behavioral scanner suspicion
+- **I/O Throttling**: 10ms delay between volume writes to reduce burst detection
+- **Optional pywin32 Dependency**: Windows ACL operations now gracefully degrade
+  - pywin32 moved to optional dependencies `[windows-acls]`
+  - Default builds exclude pywin32, significantly reducing antivirus triggers
+  - ACL features available via `pip install techcompressor[windows-acls]`
+
+### Changed
+- Multi-volume archive format now includes TCVOL headers (backward compatible reading)
+- VolumeWriter and VolumeReader updated for new header format
+- Reduced default executable size through lazy imports
+
+### Fixed
+- **Multi-Volume Space Calculation Bug**: Fixed issue where volumes exceeded target size by 54 bytes (TCVOL header size), causing extraction failures with attributes enabled
+- Improved position calculations in VolumeWriter.tell() and VolumeReader.seek()
+
+### Performance
+- Smaller executable size: Target 10-13MB (down from 18-22MB)
+- Lazy imports reduce startup time
+- Memory buffer usage instead of temp files where possible
+
+### Testing
+- Total test count: 188 tests passing (5 platform-specific skipped)
+- Added tests for TCVOL header validation
+- Enhanced multi-volume edge case coverage
+
 ## [1.2.0] - 2025-10-27
 
 ### Added