⭕ OrbitTask: C Circular Linked List To-Do Manager

A lightweight, zero-dependency CLI Task Manager engineered to demonstrate low-level pointer arithmetic, safe heap management, and O(1) tail-insertion mechanics.

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📂 Repository Architecture

.
├── main.c          # App entry point, master execution loop, and CLI menu router
├── tasks.c         # Core business logic, linked-list operations, and File I/O
├── tasks.h         # Struct definitions, enums, and public function prototypes
├── Makefile        # Automation script for clean building, running, and leak testing
└── tasklist.txt    # (Auto-generated) Persistent pipe-delimited session database

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🧠 Under the Hood: The Circular Tail Model

Standard singly-linked lists require O(n) traversal to append an item to the end. By maintaining a single pointer to the tail, and mapping tail->next back to the head, this application achieves O(1) insertions at both ends of the list:

         ┌────────────────────────────────────────┐
         ▼                                        │
   ┌───────────┐      ┌───────────┐         ┌─────┴─────┐
   │   Head    │ ───► │  Node 2   │ ───►... │   Tail    │
   │ (Task #1) │      │ (Task #2) │         │ (Task #N) │
   └───────────┘      └───────────┘         └───────────┘
                                                  ▲
TaskManager->tail ────────────────────────────────┘

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✨ Key Features

• O(1) Appending: Instantly attach new items whether the list has 5 tasks or 50,000.
• Triage Priority: Categorize tasks as [ ! ] HIGH, [ - ] MEDIUM, or [ v ] LOW.
• Date Tracking: Built-in integer parsing for custom DD/MM/YYYY deadlines.
• Safe Memory Lifecycle: Strict malloc/strdup heap allocation paired with a recursive freeList() sweep to guarantee zero memory leaks upon exit.
• Session Persistence: Automatically dumps your live linked list into a serialized text file on quit, and reconstructs the pointer map on boot.

💾 Storage Schema (tasklist.txt)

The application serializes memory into a flat text file using standard pipe (|) delimiters.

• Row 1 (Metadata): [Total_List_Size]|[Next_Assigned_ID]
• Row 2+ (Nodes): [ID]|[Task_Name]|[Priority_Enum]|[Is_Completed]|[DD]/[MM]/[YYYY]

Example data payload:

4|5
1|Gaming|2|0|23/6/2026
2|Going on a Run|1|0|30/7/2025
3|Job Searching|3|0|11/3/2025
4|Work|2|1|14/5/2025

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🛠️ Compilation & Execution

This project includes a Makefile to simplify compilation, execution, and memory testing.

1. Build the Project

Compile the source files and generate the executable:

make

2. Run the Application

Compile (if changes were made) and launch the task manager immediately:

make run

3. Check for Memory Leaks

Run the suite through Valgrind to monitor dynamic heap allocation and ensure freeList() executes safely:

make valgrind

4. Clean Build Files

Remove compiled object (.o) files and binary executables to reset your directory:

make clean

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🛠️ How to Install Valgrind

On Ubuntu/Debian Linux:

sudo apt update
sudo apt install valgrind

On macOS (using Homebrew):

brew install valgrind

(Note for macOS: Valgrind can sometimes be finicky on newer Apple Silicon M1/M2/M3 chips. If it gives you trouble, developers often use leaks --atExit -- ./todomanager instead).