TaskTrackerCLI 📝

A minimalist command-line task tracker built with Java, using no external libraries and following MVC architecture.

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🎯 Learning Objectives

This project was designed to deepen my understanding of core Java concepts while overcoming the challenges of working without external libraries. Key learnings include:

• Manual JSON Handling:

  • Parsing and writing JSON files without libraries like Gson or Jackson.
  • Implementing robust string manipulation to avoid ArrayIndexOutOfBoundsException and malformed JSON.
  • Handling edge cases (e.g., empty files, missing fields) with custom logic.

• MVC Architecture:

  • Model: TaskModel and TaskListModel manage data and business logic.
  • View: TaskCli handles user input/output.
  • Controller: TaskController bridges Model and View.
  • Reinforced separation of concerns and modular design.

• File I/O Operations:

  • Reading/writing to tasks.json in the user’s home directory.
  • Ensuring atomicity and error handling for file operations.

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🛠 Challenges & Solutions

1. JSON Without Libraries

Challenge: Parsing and generating JSON manually is error-prone.
Solutions:

• Used String.split() and regex to extract key-value pairs.
• Added validation for missing/empty fields (e.g., finishedAt).
• Wrote a custom toJson()/fromJson() in TaskModel.

2. Data Consistency

Challenge: Avoiding corruption when saving/loading tasks.
Solutions:

• Atomic writes with FileWriter and backups (e.g., tasks.json.bak).
• Checks for file existence and empty content in TaskListModel.

3. MVC Pitfalls

Challenge: Tight coupling between components.
Solutions:

• Strict separation:
  • View (TaskCli) only interacts with Controller.
  • Model has no dependency on View.

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🚀 How to Use

Commands

# Add a task
java View.TaskCli add "Buy groceries"

# Remove a task (by ID)
java View.TaskCli remove 1

# List all tasks
java View.TaskCli list all

File Structure

src/
├── Model/           # Business logic and data
│   ├── TaskModel.java
│   └── TaskListModel.java
├── View/            # CLI interface
│   └── TaskCli.java
└── Controller/      # Mediates Model-View
    └── TaskController.java

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🔍 Key Code Snippets

Manual JSON Parsing

// From TaskModel.java
public static TaskModel fromJson(String json) {
    json = json.replace("{", "").replace("}", "").replace("\"", "").trim();
    String[] pairs = json.split(",");
    // Iterate over key-value pairs...
}

MVC Workflow

// In TaskCli.java (View)
addTaskFromCli(args[1]);  // Calls Controller

// In TaskController.java
list.addTask(description); // Delegates to Model
list.saveTasks();          // Saves to JSON

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📌 Why This Matters

• Fundamentals Over Convenience:
  By avoiding libraries, I gained hands-on experience with file I/O, data serialization, and error handling—skills transferable to low-level systems programming.

• MVC in Practice:
  Learned how to decouple logic, making the codebase scalable and testable.

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🔗 Links

• GitHub Repository
• Java Docs
• Project idea

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Built with ♥ and javac. Feedback welcome! 🚀