A CLI Bash multimedia downloader/player!

#!/usr/bin/env bash

help() {
  cat << EOF
Usage: ./ytd.sh [URL] [Format] [Folder] [Purge]

This script downloads a video from the provided URL using yt-dlp, plays it using mpv, and optionally deletes the downloaded files.

Arguments:
  URL      The URL of the video to download. If not provided as an argument, you will be prompted to enter it.
  Format   The format number to download. If not provided as an argument, you will be prompted to select from available formats.
  Folder   The directory where the video will be downloaded. If not provided as an argument, you will be prompted to specify it.
  Purge    A yes/no (default yes) on whether to purge the downloaded media's directory, delete the 'ytdv' subdirectory.

Behavior:
1. Prompt the user for the URL if it is not provided as an argument.
2. Use yt-dlp to fetch and display the list of available formats for the provided URL.
3. Prompt the user to select a format number if it is not provided as an argument.
4. Prompt the user for the download directory if it is not provided as an argument.
5. Create a subdirectory named 'ytdv' within the specified download directory and change into it.
6. Download the selected format using yt-dlp.
7. Play the downloaded files using mpv.
8. Prompt the user to remove the downloaded files after playback. If the user confirms, delete the 'ytdv' subdirectory.

Exit Codes:
  0  Script executed successfully.
  1  Failed to fetch formats for the provided URL.
  2  The selected format is unavailable for the provided URL.
  3  Invalid input for removing downloaded files (expected Y or N).
EOF
}

# Check if the first argument is a help flag and display help message if so
if [[ "$1" == "--help" || "$1" == "-h" || "$1" == "-?" ]]; then
  help
  exit 0
fi

# Function to prompt the user and read input if not provided as an argument
prompt_user() {
  local prompt_message=$1
  local input_variable_name=$2
  local default_value=$3
  local input_value

  if [[ -n "${!input_variable_name}" ]]; then
    input_value="${!input_variable_name}"
  else
    read -p "$prompt_message" input_value
    input_value=${input_value:-$default_value}
  fi

  eval "$input_variable_name='$input_value'"
}

# Get the URL from the argument or prompt the user
prompt_user "URL?: " lnk "$1"

# Get the list of available formats
/usr/bin/yt-dlp -F "$lnk"
if [[ "$?" -ne 0 ]]; then
  echo "Failed to fetch formats for the URL: $lnk"
  exit 1
fi

# Prompt the user for the format
prompt_user "Format #: " fmt "$2"

# Prompt the user for the download directory
prompt_user "Folder: " dr "$3"

# Create the directory and change into it
mkdir -p "$dr/ytdv" && cd "$dr/ytdv"

# Download the selected format
/usr/bin/yt-dlp -f "$fmt" "$lnk"
if [[ "$?" -ne 0 ]]; then
  echo "Format $fmt unavailable for \"$lnk\"."
  exit 2
fi

# Play the downloaded files with mpv
/usr/bin/mpv ./*

# Prompt the user to remove the downloaded files
prompt_user "Remove downloaded files [Y/n]? " rfm "$4"
rfm=${rfm:-Y}

case "$rfm" in
  [Yy]*)
    cd "$dr"
    rm -rf ./ytdv
    ;;
  [Nn]*)
    ;;
  *)
    echo "ERROR: Invalid input, expected Y or N, but got $rfm!"
    exit 3
    ;;
esac