# LightTAM: Detailed Overview

LightTAM (Lightweight Time And Attendance Manager) is a terminal-based application for managing employee or student attendance using RFID cards. The system is modular, with each component responsible for a specific aspect of the program's functionality. Below is a detailed overview of how the program works, referencing the component UML diagram (`component_uml.png`).

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## Component Overview

![Component UML Diagram](component_uml.png)

### 1. **Main Application (`main.c`)**
- **Role:** Entry point of the program. Initializes all subsystems, parses command-line arguments, loads the user database, and starts the main event loop.
- **Key Functions:**
  - `main` – program entry, initialization, TUI start, graceful shutdown.
  - `handle_sigint` – signal handler for program termination.
  - Calls to initialize logger (`initLogger`), load users (`loadListFromCSV`), start RFID thread (`uartListener`).

### 2. **Terminal User Interface (TUI) (`tui.c`, `tui.h`)**
- **Role:** Provides all user interaction via a terminal-based UI using ncurses.
- **Key Functions:**
  - `mainMenu` – main menu display and navigation.
  - `personListing` – list all users.
  - `personSearch` – search users by name or UUID.
  - `personInfo` – show detailed user info.
  - `editDatabaseMenu` – add, remove, or edit users.
  - `dialogWindow` – show dialogs (errors, warnings, confirmations).
  - `exportDialog` – export user or database data.
  - Keyboard input handling, navigation, and forms.

### 3. **User Management (`users.c`, `users.h`)**
- **Role:** Manages the in-memory linked list of users.
- **Key Functions and Structures:**
  - `person_t`, `node_t`, `list_t` – data structures for users and the list.
  - `addPersonToList` – add a user.
  - `removePersonFromList` – remove a user.
  - `findPersonByUUID`, `findPersonByName` – search for users.
  - `updatePerson` – update user data.
  - `calculatePresenceTime` – compute attendance.
  - Synchronization using mutex (`pthread_mutex_t`).

### 4. **File Handler (`file_handler.c`, `file_handler.h`)**
- **Role:** Handles reading and writing user data to CSV files.
- **Key Functions:**
  - `loadListFromCSV` – load user list from file.
  - `saveListToCSV` – save user list to file.
  - `exportPersonInfo` – export a user's data to an external file.

### 5. **RFID Handler (`rfid_handler.c`, `rfid_handler.h`)**
- **Role:** Interfaces with the RFID reader hardware via a serial port.
- **Key Functions:**
  - `uartListener` – thread for reading data from the serial port.
  - `processRFIDEvent` – process a detected RFID card.
  - `sendPacketToDevice` – send data to the device.
  - CRC check, card-to-user matching, attendance event logging.

### 6. **Logger (`logger.c`, `logger.h`)**
- **Role:** Logs all actions, errors, and system events to a journal file.
- **Key Functions:**
  - `initLogger` – initialize the logger.
  - `logErrorEvent` – log errors.
  - `logWarningEvent` – log warnings.
  - `logHardwareEvent` – log hardware events (e.g., RFID).
  - `logInfoEvent` – log general information.
  - `endLogger` – close the log file.

### 7. **Utilities (`utils.c`,`utils.h`)**
- **Role:** Provides helper functions used throughout the program.
- **Key Functions:**
  - `printDateAndTimeInString` – time formatting.
  - String manipulation, input validation, type conversions.

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## Component Interactions

- **TUI ↔ User Management:** TUI calls user management functions to modify or query the user list.
- **TUI ↔ File Handler:** TUI triggers file operations for loading, saving, and exporting data.
- **TUI ↔ RFID Handler:** TUI may display status or prompt for RFID actions.
- **RFID Handler ↔ User Management:** When a card is read, the handler updates the user list.
- **All Components ↔ Logger:** All modules log actions and errors via the logger.

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## Error Handling & Logging

- All errors (file I/O, serial port, invalid input) are reported to the user via TUI dialogs and logged in the journal file.
- The logger ensures traceability for all critical operations.

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## Extensibility

- The modular design allows for easy extension, such as supporting new file formats, additional authentication methods, or a graphical UI.

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For further details, see the [README.md](../README.md) and the code documentation in each header file.