#!/bin/sh

# check if a command is available
has_command() { # $command
    command -v "${1}" 1>/dev/null 2>/dev/null
}

needs_commands() { # $status $cmd1 $cmd2 ...
    _nc_status="${1}"
    shift 1

    for _nc_cmd in "${@}"; do
        if ! has_command "${_nc_cmd}"; then
            echo "Command '${_nc_cmd}' not available!" >&2
            exit "${_nc_status}"
        fi
    done
}

download_gui() { # $uri $file $sha256
    needs_commands "curl" "zenity" "sha256sum" || return 1
    echo "Downloading '${1}' to '${2}'"

    curl --show-error --fail --location \
      --output "${2}" \
      "${1}" &
    _dg_curlpid=$!

    yes | zenity \
      --progress --pulsate --auto-close \
      --title="Downloading" \
      --text="Downloading '${2}' ..." &
    _dg_zenpid=$!

    while kill -0 "${_dg_curlpid}" 2>/dev/null; do
        if ! kill -0 "${_dg_zenpid}" 2>/dev/null; then
            # progress bar died; ask for abort
            if zenity \
              --question \
              --text="Abort Download?"; then
                kill "${_dg_curlpid}" 2>/dev/null || true
                echo "Download cancelled!" >&2
                break
            fi

            # restart progress bar
            yes | zenity \
              --progress --pulsate --auto-close \
              --title="Downloading" \
              --text="Downloading '${2}' ..." &
            _dg_zenpid=$!
        fi

        sleep 0.2
    done

    kill "${_dg_zenpid}" 2>/dev/null || true
    wait "${_dg_curlpid}"

    if [ -z "${3}" ]; then
        echo "No SHA256 (OK)!" >&2
        return 0
    elif [ "$( sha256sum "${2}" | cut -d' ' -f1 )" = "${3}" ]; then
        echo "SHA256 ${3} OK!" >&2
        return 0
    else
        echo "SHA256 ${3} mismatch!" >&2
        return 1
    fi
}