#!/usr/bin/env bash

#############
# Variables #
#############
# Define formatting variables
fb="$(tput bold)" ; readonly fb
ft="$(tput sitm)" ; readonly ft
fr="$(tput sgr0)" ; readonly fr

# Create required commands array
req_cmds=('ffmpeg' 'yt-dlp') ; readonly req_cmds

log_root='/tmp' ; readonly log_root  # Set log root directory
script_name="${0##/*/}"  # Obtain script name
# Remove suffix from script name
script_name="${script_name%.*}" ; readonly script_name
t_stamp="$(date +'%s')" ; readonly t_stamp  # Create timestamp using UNIX epoch

yt_dlp_opts='-f b '  # Initialize yt-dlp options string
o_mode='Video'  # Initialize output mode
sub_lang='en-US'  # Initialize subtitle language


#############
# Functions #
#############
display_usage() {
    help_msg="Usage: ${0} [ex_option]...

Purpose: Download audio/video content with yt-dlp.

A log is saved in the /tmp/${script_name}/ directory.

Options:
    -a, --audio
        Download audio content.
    -g, --greatest-quality
        Download greatest quality content.
    -s, --subtitles
        Embed subtitles into video content.
        
Requires:
    ffmpeg
        ffmpeg video converter
    yt-dlp
        A youtube-dl fork with additional features and patches"

    echo "${help_msg}"
}


# Verify string is valid URL
val_url() {
    local to_test url_regex  # Define local variables
    to_test="${1}"
    url_regex='https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.'
    url_regex+='[a-zA-Z0-9()]{1,18}\b([-a-zA-Z0-9()!@:%_\+.~#?&\/\/=]*)'
    [[ "${to_test}" =~ ${url_regex} ]] ; echo "${?}"
}


# Set URL
set_url() {
    local prompt pass_or_fail err_msg
    prompt="${1}"

    while true; do
        # Prompt for input, save to variable
        read -p "${prompt}" -r url

        # Validate input
        pass_or_fail="$(val_url "${url}")"
        if [[ "${url}" == 'q' ]]; then
            if [[ -s "${log_path}" ]]; then
                ish_msg='\nPotential issue encountered.'
                ish_msg+="\nView ${fb}${log_path}${fr} for more information."
                echo -e "${ish_msg}"
            fi

            exit 0  # Exit script with successful exit status
        elif [[ "${pass_or_fail}" -eq 0 ]]; then
            break
        else
            err_msg='\nInvalid URL. Try again or enter q to quit.\n'
            echo -e "${err_msg}" 1>&2
        fi
    done
}


# Handle a SIGINT signal
hndl_sigint() {
    echo -e '\n\nSIGINT or Ctrl+c detected. Exiting gracefully.'
    exit 0
}


# Initialize logging
init_logging() {
    # If script log directory does not exist, create it
    if ! [[ -d "${log_root}/${script_name}" ]]; then
        mkdir -p "${log_root}/${script_name}"
    fi

    # Define log file path
    log_path="${log_root}/${script_name}/${t_stamp}_${script_name}.log"
}


# Make yt-dlp options string adjustments
adj_yt_dlp_opts() {
    if [[ "${a_on}" == 'true' ]]; then
        if [[ "${g_on}" == 'true' ]]; then
            yt_dlp_opts='-f ba[ext=m4a] '
            o_mode='Greatest Quality Audio'
        else
            yt_dlp_opts='-f ba '
            o_mode='Audio'
        fi
    else
        if [[ "${g_on}" == 'true' ]]; then
            yt_dlp_opts='-f bv[ext=mp4]+ba[ext=m4a]/b[ext=mp4]/b '
            o_mode='Greatest Quality Video'
        fi

        if [[ "${s_on}" == 'true' ]]; then
            yt_dlp_opts+="--embed-subs --sub-langs ${sub_lang} "
            o_mode+=' (With Embedded Subtitles)'
        fi
    fi
}


# Define starting point for execution of the program
main() {
    # Parse arguments
    parsed_args="$(getopt \
        -n "${0##*/}" \
        -o hags \
        --long help,audio,greatest-quality,subtitles \
        -- "${@}")"

    inv_ents="${?}"  # Check for invalid entries
    if [[ "${inv_ents}" -ne 0 ]]; then
        echo ''
        display_usage
        exit 1
    fi

    # Set positional parameters using parsed argument string
    eval set -- "${parsed_args}"

    # Evaluate options
    while true; do
        case "${1}" in
            '-h' | '--help')
                display_usage
                exit 0
                ;;
            '-a' | '--audio')
                a_on='true'
                shift
                ;;
            '-g' | '--greatest-quality')
                g_on='true'
                shift
                ;;
            '-s' | '--subtitles')
                s_on='true'
                shift
                ;;
            '--')
                ## End of options
                shift
                break
                ;;
        esac
    done

    # Create missing commands array
    declare -a mis_cmds
    # Verify that required commands are installed
    for req_cmd in "${req_cmds[@]}"; do
        if ! command -v "${req_cmd}" > '/dev/null' 2>&1; then
            mis_cmds+=("${req_cmd}")
        fi
    done
    # Exit script if commands are missing
    if [[ "${mis_cmds[*]}" ]]; then
        err_msg='\nInstall the following command(s) before '
        err_msg+='running the script again:'
        echo -e "${err_msg}\n${fb}${mis_cmds[*]}${fr}" 1>&2
        exit 1
    fi

    trap hndl_sigint SIGINT  # Capture SIGINT signal

    init_logging  # Initialize logging

    adj_yt_dlp_opts  # Adjust yt-dlp options

    hdr="\nOutput Mode: ${ft}${o_mode}${fr}"
    hdr_len="${#hdr}"

    echo -e "${hdr}"
    yes '~' | head -n "$(( hdr_len - 12 ))" | tr -d '\n' && echo ''
    prompt='Enter URL (q to quit): '
    while true; do
        set_url "${prompt}"

        yt-dlp ${yt_dlp_opts}-q "${url}" 2>> "${log_path}" &
    done
}


###########
# Program #
###########
main "${@}"  # Start program