# Architecture

**Analysis Date:** 2026-02-28

## Pattern Overview

**Overall:** Single-Binary CLI/TUI Application (Rust)

**Key Characteristics:**
- Monolithic Rust binary using Ratatui for terminal UI
- Minimal dependency footprint (only Ratatui as external dependency)
- Single entry point with main function
- Early-stage project with foundational structure only

## Layers

**Presentation Layer:**
- Purpose: Terminal user interface rendering and interaction
- Location: `src/main.rs` (currently)
- Contains: TUI initialization, event handling, widget rendering
- Depends on: Ratatui framework
- Used by: End users through terminal

**Business Logic Layer:**
- Purpose: Core application functionality
- Location: TBD - not yet implemented
- Contains: Data processing, command handling, state management
- Depends on: None currently defined
- Used by: Presentation layer

**Data Layer:**
- Purpose: Data persistence and retrieval
- Location: TBD - not yet implemented
- Contains: File I/O, caching, serialization
- Depends on: Standard library (File, IO)
- Used by: Business logic layer

## Data Flow

**Typical User Interaction Flow:**

1. Terminal input captured by Ratatui event handling
2. User action (keyboard/mouse) parsed into application command
3. Command dispatched to business logic handler
4. Handler processes request, potentially reads/writes data
5. State updated based on result
6. UI re-rendered with new state in next frame

**State Management:**
- Single application state entity (not yet defined)
- Immutable state passed to rendering function
- Ratatui handles incremental screen updates

## Key Abstractions

**Terminal User Interface (TUI):**
- Purpose: Encapsulate all terminal rendering and input handling
- Examples: `src/main.rs` (current single module)
- Pattern: React-like paradigm via Ratatui (state -> render)

**Application Command/Action:**
- Purpose: Abstract user intentions from input events
- Examples: Not yet implemented
- Pattern: Enum-based command pattern expected

## Entry Points

**Binary Entry:**
- Location: `src/main.rs`
- Triggers: `cargo run` or binary execution
- Responsibilities:
  - Initialize Ratatui terminal
  - Set up event loop
  - Handle application lifecycle
  - Render UI each frame
  - Currently: Placeholder with "Hello, world!" output

## Error Handling

**Strategy:** Not yet defined

**Patterns:**
- Ratatui provides Result types for I/O operations
- Expected approach: Result-based error propagation using ? operator
- Terminal restoration should be ensured on panic (Ratatui provides Drop impl)

## Cross-Cutting Concerns

**Logging:** Not yet implemented. Standard approach would use `log` crate or println! macros during development.

**Validation:** Not yet implemented. Expected in business logic layer once commands are defined.

**Terminal State:** Ratatui manages terminal state (raw mode, cursor visibility, etc.). Must ensure proper cleanup on application exit.

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*Architecture analysis: 2026-02-28*