#!/usr/bin/env bash

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


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

Purpose: Select a random object from a provided directory and place its path
         on the system clipboard.

Options:
    -o
        Open last selected random object before quitting
        with default application.
        
Requires:
    xclip
        command line interface to X selections (clipboard)"

    echo "${help_msg}"
}


# Verify object exists and is a directory
val_extant_dir() {
    local to_test
    to_test="${1}"
    [[ -d "${to_test}" ]] ; echo "${?}"
}


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

    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
                ;;
            '-o' | '--open')
                o_on='true'
                shift
                ;;
            '--')
                ## End of options
                shift
                break
                ;;
        esac
    done

    # Evaluate argument
    pass_or_fail="$(val_extant_dir "${1}")"
    if [[ "${pass_or_fail}" -eq 0 ]]; then
        entd_dir="${1%/}"  # Remove trailing slash if present
    else
        err_msg='\nInvalid directory path provided. Try again.'
        echo -e "${err_msg}" 1>&2
        exit 1
    fi

    # Verify script being run from desktop environment
    if ! [[ "${XDG_CURRENT_DESKTOP}" ]]; then
        err_msg='\nA desktop environment must be available to '
        err_msg+='use this script.'
        echo -e "${err_msg}" 1>&2
        exit 1
    fi

    # Verify that command is installed
    if ! command -v 'xclip' > '/dev/null' 2>&1; then
        # Prompt user to install command and exit
        err_msg="\nInstall ${fb}xclip${fr} before running "
        err_msg+='the script again.'
        echo -e "${err_msg}" 1>&2
        exit 1
    fi

    # Determine number of objects for provided directory
    num_of_objs="$(find "${entd_dir}" -mindepth 1 -maxdepth 1 ! -name '.*' | 
        wc -l)"

    # Create object paths associated array
    declare -a obj_paths
    mapfile -t obj_paths < \
        <(find "${entd_dir}" -mindepth 1 -maxdepth 1 ! -name '.*')

    # Initiate random object path generation loop
    prompt='Enter any key to continue or q to quit: '
    while echo '' && read -p "${prompt}" -r choice; do
        if [[ "${choice}" == 'q' ]]; then
            if [[ "${o_on}" ]]; then
                xdg-open "${obj_paths[${ran_num}]}" > '/dev/null' 2>&1
            fi
            break
        else
            ran_num="$(shuf -i 0-"$(( num_of_objs - 1 ))" -n 1)"

            output="\nChosen random index: ${ran_num}"
            output+="\n${obj_paths[${ran_num}]}"
            echo -e "${output}"
        fi
    done

    # Save last object path to clipboard
    echo "${obj_paths[${ran_num}]}" | xclip -selection c
}


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

exit 0  # Exit script with successful exit status