Playlist CLI

A simple Command Line Interface (CLI) playlist manager built in Java. This project simulates a music or video playlist using a custom doubly linked list with sentinel nodes.

It was created as a mini-project to practice and solidify understanding of linked list data structures in an interactive and hands-on way.

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Diagram: Doubly Linked List with Sentinels

This project uses a doubly linked list with two sentinel nodes, head and tail, which simplifies the logic for adding and removing nodes. The sentinels do not store actual video data but act as fixed start and end markers.

                    Doubly Linked List with Sentinel Nodes
                              
    null                                                            null
     ↑                                                               ↑
┌─────────┐      ┌─────────────┐      ┌─────────────┐      ┌─────────┐
│  HEAD   │◄────►│ VideoNode 1 │◄────►│ VideoNode 2 │◄────►│  TAIL   │
│(sentinel)│     │             │      │             │      │(sentinel)│
│  prev   │      │    prev     │      │    prev     │      │  prev   │
│  next   │      │    data     │      │    data     │      │  next   │
│  data=∅ │      │    next     │      │    next     │      │  data=∅ │
└─────────┘      └─────────────┘      └─────────────┘      └─────────┘

Empty Playlist:
┌─────────┐      ┌─────────┐
│  HEAD   │◄────►│  TAIL   │
│(sentinel)│     │(sentinel)│
│  next   │      │  prev   │
│  data=∅ │      │  data=∅ │
└─────────┘      └─────────┘

• Head Sentinel: head.next points to the first real video in the playlist.
• Tail Sentinel: tail.prev points to the last real video.
• An empty playlist looks like this: head <--> tail.

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Demo

demoPlayListManager.mp4

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Features

• Add Videos: Add new videos to the beginning or end of the playlist.
• Remove Videos: Remove videos from the beginning or end.
• Display Playlist: Show all videos currently in the list.
• Playback Simulation:
  • play: Start playback from the first video.
  • next: Move to the next video.
  • prev: Move to the previous video.
  • stop: Stop the current playback.
• Quick Inspection: Instantly view the first and last videos in the list.
• Interactive CLI: A user-friendly command-line interface built with Scanner.

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How to Run

1. Clone or Download: Clone the repository or download the source files (Video.java, VideoNode.java, PlayList.java, MainCLI.java).

2. Compile the Java files: Open a terminal in the project directory and run the compiler.

   javac *.java

3. Run the CLI application:

   java MainCLI

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Example Usage

Here is a sample session interacting with the Playlist CLI:

 Welcome to the Playlist CLI 
Type 'help' to see available commands.

> addlast
Enter video ID: 1
Enter title: Intro to Java
Enter channel: CodeAcademy
Enter duration (minutes): 10.5
✅ Video added.

> addfirst
Enter video ID: 2
Enter title: Data Structures Explained
Enter channel: CS Dojo
Enter duration (minutes): 15.0
✅ Video added.

> list
--- Playlist ---
1. Data Structures Explained (CS Dojo) - 15.0 min
2. Intro to Java (CodeAcademy) - 10.5 min
----------------

> play
▶️ Now playing: Data Structures Explained

> next
▶️ Now playing: Intro to Java

> next
✅ Done! You reached the end of the playlist.

> prev
▶️ Now playing: Data Structures Explained

> stop
⏹️ Stopped.

> exit
👋 Goodbye!

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Available Commands

Command	Description
help	Show all available commands.
addfirst	Add a new video at the beginning.
addlast	Add a new video at the end.
removefirst	Remove the first video from the playlist.
removelast	Remove the last video from the playlist.
list	Show all videos in the playlist.
first	Show the first video.
last	Show the last video.
play	Start playing from the first video.
next	Move to the next video during playback.
prev	Move to the previous video during playback.
stop	Stop playback.
exit	Quit the program.

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To-Do / Future Features

Here are some ideas for future improvements:

Core Features

• Circular Playback: After the last video, loop back to the first (and vice versa).
• Shuffle Mode: Play videos in a random order.
• Search: Find a video by its title or channel.
• Remove by ID/Title: Delete a specific video from anywhere in the list.
• Insert at Position: Add videos at specific positions in the playlist.
• Move Videos: Reorder videos by moving them to different positions.

Data & Persistence

• Persistence: Save the current playlist to a file and load it back later.
• Import/Export: Support for M3U, JSON, or CSV playlist formats.
• Multiple Playlists: Create and manage multiple named playlists.

Advanced Features

• Queue System: Allow temporary queueing of "up next" videos.
• History Tracking: Keep track of recently played videos.
• Repeat Modes: Single repeat, playlist repeat, no repeat.
• Bookmarks: Save playback positions for videos.
• Rating System: Rate videos and sort by rating.

Technical Improvements

• Unit Tests: Add JUnit tests to validate the PlayList class functionality.
• Error Handling: Improve input validation and error messages.
• Performance: Optimize for large playlists (1000+ videos).
• Logging: Add proper logging for debugging and monitoring.

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Purpose

This is a practice project and is not intended for production use. Its main goals are to:

• Deepen understanding of doubly linked lists in Java.
• Practice fundamental object-oriented design principles.
• Get comfortable with building interactive CLI applications.
• Serve as a foundation for more complex projects, such as a REST API using Spring Boot.

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Contributions

Contributions are welcome! If you have ideas for improvements or new features, feel free to fork this repository, make your changes, and open a pull request.

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License

This project is created for learning purposes and is not bound by any specific license. You are free to use, modify, and share the code as you see fit.