#!/bin/sh
# shellcheck shell=dash
# shellcheck disable=SC2039  # local is non-POSIX
#
#    Copyright (C)  2016 The Rust Project Developers
#    Copyright (C)  2024 A.J. Ianozi <aj@ianozi.com>
#
#    This file is part of Getada-Download: A script to install GetAda
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
#

# This is just a little script that can be downloaded from the internet to
# install GetAda. It just does platform detection, downloads the installer
# and runs it.
# Adapted from rustup's script at https://github.com/rust-lang/rustup which is
# why references to Rust may be in some variables.

# It runs on Unix shells like {a,ba,da,k,z}sh. It uses the common `local`
# extension. Note: Most shells limit `local` to 1 var per line, contra bash.

# Some versions of ksh have no `local` keyword. Alias it to `typeset`, but
# beware this makes variables global with f()-style function syntax in ksh93.
# mksh has this alias by default.
has_local() {
    # shellcheck disable=SC2034  # deliberately unused
    local _has_local
}

has_local 2>/dev/null || alias local=typeset

# zsh does not split words by default, Required for curl retry arguments below.
if [ -n "$ZSH_VERSION" ]; then
    setopt shwordsplit
fi

set -u

# If GETADA_UPDATE_ROOT is unset or empty, default it.
GETADA_UPDATE_ROOT="${GETADA_UPDATE_ROOT:-https://getada.dev}"

# NOTICE: If you change anything here, please make the same changes in defaults.ads and options.adb
usage() {
    cat <<EOF
Welcome to the unofficial Alire Installer (""GetAda"") v0.2.0
Alire is the official Ada Package Manager. For more information
please visit https://ada-lang.io or https://alire.ada.dev
Copyright (C) 2022-2023 A.J. Ianozi licensed GPL3.

Options:
-h --help: Print this message and exit.
-s --show-version: Print the version of this binary and exit.
-p --no-path: Don't update path.
-n --non-interactive: Suppress prompts; answer with defaults.
-q --quiet: Be quiet (does not suppress propmts)
-t /directory --tmp=/directory: Set tmp/metadata
-c /directory --cfg=/directory: Set config directory
-b /directory --bin=/directory: Set binary directory
-v x.y.z --version=x.y.z: Download a specific version of alire.
-u --uninstall: Uninstall Alire. This only works if Alire was
                installed with GetAda.  Works out of the box if
                default directory was used, otherwise you must
                pass --cfg= so the uninstaller can find the log.
You can also set the version and tmp/cfg/binary directories by
setting the following environment variables:
* GETADA_ALIRE_VERSION for Alire's version
* GETADA_TMP for metadata directory
* GETADA_CFG for config directory
* GETADA_BIN for binary directory
That's it for right now!
EOF
}

main() {
    downloader --check
    need_cmd uname
    need_cmd mktemp
    need_cmd chmod
    need_cmd mkdir
    need_cmd rm
    need_cmd rmdir

    get_architecture || return 1
    local _arch="$RETVAL"
    assert_nz "$_arch" "arch"

    local _ext=""
    case "$_arch" in
        *windows*)
            _ext=".exe"
            ;;
    esac

    local _url="${GETADA_UPDATE_ROOT}/dist/${_arch}/getada${_ext}"

    local _dir
    if ! _dir="$(ensure mktemp -d)"; then
        # Because the previous command ran in a subshell, we must manually
        # propagate exit status.
        exit 1
    fi
    local _file="${_dir}/getada${_ext}"

    local _ansi_escapes_are_valid=false
    if [ -t 2 ]; then
        if [ "${TERM+set}" = 'set' ]; then
            case "$TERM" in
                xterm*|rxvt*|urxvt*|linux*|vt*)
                    _ansi_escapes_are_valid=true
                ;;
            esac
        fi
    fi

    # check if we have to use /dev/tty to prompt the user
    local need_tty=yes
    for arg in "$@"; do
        case "$arg" in
            --help)
                usage
                exit 0
                ;;
            *)
                OPTIND=1
                if [ "${arg%%--*}" = "" ]; then
                    # Long option (other than --help);
                    # don't attempt to interpret it.
                    continue
                fi
                while getopts :hn sub_arg "$arg"; do
                    case "$sub_arg" in
                        h)
                            usage
                            exit 0
                            ;;
                        n)
                            # user wants to skip the prompt --
                            # we don't need /dev/tty
                            need_tty=no
                            ;;
                        *)
                            ;;
                        esac
                done
                ;;
        esac
    done

    if $_ansi_escapes_are_valid; then
        printf "\33[1minfo:\33[0m downloading installer\n" 1>&2
    else
        printf '%s\n' 'info: downloading installer' 1>&2
    fi

    ensure mkdir -p "$_dir"
    ensure downloader "$_url" "$_file" "$_arch"
    ensure chmod u+x "$_file"
    if [ ! -x "$_file" ]; then
        printf '%s\n' "Cannot execute $_file (likely because of mounting /tmp as noexec)." 1>&2
        printf '%s\n' "Please copy the file to a location where you can execute binaries and run ./getada${_ext}." 1>&2
        exit 1
    fi

    if [ "$need_tty" = "yes" ] && [ ! -t 0 ]; then
        # The installer is going to want to ask for confirmation by
        # reading stdin.  This script was piped into `sh` though and
        # doesn't have stdin to pass to its children. Instead we're going
        # to explicitly connect /dev/tty to the installer's stdin.
        if [ ! -t 1 ]; then
            err "Unable to run interactively. Run with -n to accept defaults, --help for additional options"
        fi

        ignore "$_file" "$@" < /dev/tty
    else
        ignore "$_file" "$@"
    fi

    local _retval=$?

    ignore rm "$_file"
    ignore rmdir "$_dir"

    return "$_retval"
}

check_proc() {
    # Check for /proc by looking for the /proc/self/exe link
    # This is only run on Linux
    if ! test -L /proc/self/exe ; then
        err "fatal: Unable to find /proc/self/exe.  Is /proc mounted?  Installation cannot proceed without /proc."
    fi
}

get_bitness() {
    need_cmd head
    # Architecture detection without dependencies beyond coreutils.
    # ELF files start out "\x7fELF", and the following byte is
    #   0x01 for 32-bit and
    #   0x02 for 64-bit.
    # The printf builtin on some shells like dash only supports octal
    # escape sequences, so we use those.
    local _current_exe_head
    _current_exe_head=$(head -c 5 /proc/self/exe )
    if [ "$_current_exe_head" = "$(printf '\177ELF\001')" ]; then
        echo 32
    elif [ "$_current_exe_head" = "$(printf '\177ELF\002')" ]; then
        echo 64
    else
        err "unknown platform bitness"
    fi
}

is_host_amd64_elf() {
    need_cmd head
    need_cmd tail
    # ELF e_machine detection without dependencies beyond coreutils.
    # Two-byte field at offset 0x12 indicates the CPU,
    # but we're interested in it being 0x3E to indicate amd64, or not that.
    local _current_exe_machine
    _current_exe_machine=$(head -c 19 /proc/self/exe | tail -c 1)
    [ "$_current_exe_machine" = "$(printf '\076')" ]
}

get_endianness() {
    local cputype=$1
    local suffix_eb=$2
    local suffix_el=$3

    # detect endianness without od/hexdump, like get_bitness() does.
    need_cmd head
    need_cmd tail

    local _current_exe_endianness
    _current_exe_endianness="$(head -c 6 /proc/self/exe | tail -c 1)"
    if [ "$_current_exe_endianness" = "$(printf '\001')" ]; then
        echo "${cputype}${suffix_el}"
    elif [ "$_current_exe_endianness" = "$(printf '\002')" ]; then
        echo "${cputype}${suffix_eb}"
    else
        err "unknown platform endianness"
    fi
}

# Detect the Linux/LoongArch UAPI flavor, with all errors being non-fatal.
# Returns 0 or 234 in case of successful detection, 1 otherwise (/tmp being
# noexec, or other causes).
check_loongarch_uapi() {
    need_cmd base64

    local _tmp
    if ! _tmp="$(ensure mktemp)"; then
        return 1
    fi

    # Minimal Linux/LoongArch UAPI detection, exiting with 0 in case of
    # upstream ("new world") UAPI, and 234 (-EINVAL truncated) in case of
    # old-world (as deployed on several early commercial Linux distributions
    # for LoongArch).
    #
    # See https://gist.github.com/xen0n/5ee04aaa6cecc5c7794b9a0c3b65fc7f for
    # source to this helper binary.
    ignore base64 -d > "$_tmp" <<EOF
f0VMRgIBAQAAAAAAAAAAAAIAAgEBAAAAeAAgAAAAAABAAAAAAAAAAAAAAAAAAAAAQQAAAEAAOAAB
AAAAAAAAAAEAAAAFAAAAAAAAAAAAAAAAACAAAAAAAAAAIAAAAAAAJAAAAAAAAAAkAAAAAAAAAAAA
AQAAAAAABCiAAwUAFQAGABUAByCAAwsYggMAACsAC3iBAwAAKwAxen0n
EOF

    ignore chmod u+x "$_tmp"
    if [ ! -x "$_tmp" ]; then
        ignore rm "$_tmp"
        return 1
    fi

    "$_tmp"
    local _retval=$?

    ignore rm "$_tmp"
    return "$_retval"
}

ensure_loongarch_uapi() {
    check_loongarch_uapi
    case $? in
        0)
            return 0
            ;;
        234)
            echo >&2
            echo 'Your Linux kernel does not provide the ABI required by this Alire' >&2
            echo 'distribution.  Please check with your OS provider for how to obtain a' >&2
            echo 'compatible Alire package for your system.' >&2
            echo >&2
            exit 1
            ;;
        *)
            echo "Warning: Cannot determine current system's ABI flavor, continuing anyway." >&2
            echo >&2
            echo 'Note that the official Alire distribution only works with the upstream' >&2
            echo 'kernel ABI.  Installation will fail if your running kernel happens to be' >&2
            echo 'incompatible.' >&2
            ;;
    esac
}

get_architecture() {
    local _ostype _cputype _bitness _arch _clibtype
    _ostype="$(uname -s)"
    _cputype="$(uname -m)"
    _clibtype="gnu"

    if [ "$_ostype" = Linux ]; then
        if [ "$(uname -o)" = Android ]; then
            _ostype=Android
        fi
        if ldd --version 2>&1 | grep -q 'musl'; then
            _clibtype="musl"
        fi
    fi

    if [ "$_ostype" = Darwin ]; then
        # Darwin `uname -m` can lie due to Rosetta shenanigans. If you manage to
        # invoke a native shell binary and then a native uname binary, you can
        # get the real answer, but that's hard to ensure, so instead we use
        # `sysctl` (which doesn't lie) to check for the actual architecture.
        if [ "$_cputype" = i386 ]; then
            # Handling i386 compatibility mode in older macOS versions (<10.15)
            # running on x86_64-based Macs.
            # Starting from 10.15, macOS explicitly bans all i386 binaries from running.
            # See: <https://support.apple.com/en-us/HT208436>

            # Avoid `sysctl: unknown oid` stderr output and/or non-zero exit code.
            if sysctl hw.optional.x86_64 2> /dev/null || true | grep -q ': 1'; then
                _cputype=x86_64
            fi
        elif [ "$_cputype" = x86_64 ]; then
            # Handling x86-64 compatibility mode (a.k.a. Rosetta 2)
            # in newer macOS versions (>=11) running on arm64-based Macs.
            # Rosetta 2 is built exclusively for x86-64 and cannot run i386 binaries.

            # Avoid `sysctl: unknown oid` stderr output and/or non-zero exit code.
            if sysctl hw.optional.arm64 2> /dev/null || true | grep -q ': 1'; then
                _cputype=arm64
            fi
        fi
    fi

    if [ "$_ostype" = SunOS ]; then
        # Both Solaris and illumos presently announce as "SunOS" in "uname -s"
        # so use "uname -o" to disambiguate.  We use the full path to the
        # system uname in case the user has coreutils uname first in PATH,
        # which has historically sometimes printed the wrong value here.
        if [ "$(/usr/bin/uname -o)" = illumos ]; then
            _ostype=illumos
        fi

        # illumos systems have multi-arch userlands, and "uname -m" reports the
        # machine hardware name; e.g., "i86pc" on both 32- and 64-bit x86
        # systems.  Check for the native (widest) instruction set on the
        # running kernel:
        if [ "$_cputype" = i86pc ]; then
            _cputype="$(isainfo -n)"
        fi
    fi

    case "$_ostype" in

        Android)
            err "Android not yet supported"
            #  _ostype=linux-android
            ;;

        Linux)
            check_proc
            _ostype=unknown-linux-$_clibtype
            _bitness=$(get_bitness)
            ;;

        FreeBSD)
            _ostype=unknown-freebsd
            ;;

        NetBSD)
            err "Netbesd not yet supported"
            _ostype=unknown-netbsd
            ;;

        DragonFly)
            err "Dragonfly not yet supported"
            _ostype=unknown-dragonfly
            ;;

        Darwin)
            _ostype=apple-darwin
            ;;

        illumos)
            err "Illumos not yet supported"
            _ostype=unknown-illumos
            ;;

        MINGW* | MSYS* | CYGWIN* | Windows_NT)
            err "Please download the Windows installer on alire.ada.dev"
            _ostype=pc-windows-gnu
            ;;

        *)
            err "unrecognized OS type: $_ostype"
            ;;

    esac

    case "$_cputype" in

        i386 | i486 | i686 | i786 | x86)
            _cputype=i686
            ;;

        xscale | arm)
            _cputype=arm
            if [ "$_ostype" = "linux-android" ]; then
                _ostype=linux-androideabi
            fi
            ;;

        armv6l)
            _cputype=arm
            if [ "$_ostype" = "linux-android" ]; then
                _ostype=linux-androideabi
            else
                _ostype="${_ostype}eabihf"
            fi
            ;;

        armv7l | armv8l)
            _cputype=armv7
            if [ "$_ostype" = "linux-android" ]; then
                _ostype=linux-androideabi
            else
                _ostype="${_ostype}eabihf"
            fi
            ;;

        aarch64 | arm64)
            _cputype=aarch64
            ;;

        x86_64 | x86-64 | x64 | amd64)
            _cputype=x86_64
            ;;

        mips)
            _cputype=$(get_endianness mips '' el)
            ;;

        mips64)
            if [ "$_bitness" -eq 64 ]; then
                # only n64 ABI is supported for now
                _ostype="${_ostype}abi64"
                _cputype=$(get_endianness mips64 '' el)
            fi
            ;;

        ppc)
            _cputype=powerpc
            ;;

        ppc64)
            _cputype=powerpc64
            ;;

        ppc64le)
            _cputype=powerpc64le
            ;;

        s390x)
            _cputype=s390x
            ;;
        riscv64)
            _cputype=riscv64gc
            ;;
        loongarch64)
            _cputype=loongarch64
            ensure_loongarch_uapi
            ;;
        *)
            err "unknown CPU type: $_cputype"

    esac

    # Detect 64-bit linux with 32-bit userland
    if [ "${_ostype}" = unknown-linux-gnu ] && [ "${_bitness}" -eq 32 ]; then
        case $_cputype in
            x86_64)
                if [ -n "${GETADA_CPUTYPE:-}" ]; then
                    _cputype="$GETADA_CPUTYPE"
                else {
                    # 32-bit executable for amd64 = x32
                    if is_host_amd64_elf; then {
                         echo "This host is running an x32 userland; as it stands, x32 support is poor," 1>&2
                         echo "and there isn't a native toolchain -- you will have to install" 1>&2
                         echo "multiarch compatibility with i686 and/or amd64, then select one" 1>&2
                         echo "by re-running this script with the GETADA_CPUTYPE environment variable" 1>&2
                         echo "set to i686 or x86_64, respectively." 1>&2
                         exit 1
                    }; else
                        _cputype=i686
                    fi
                }; fi
                ;;
            mips64)
                err "mips unsupported"
                #  _cputype=$(get_endianness mips '' el)
                ;;
            powerpc64)
                err "powerpc unsupported"
                #  _cputype=powerpc
                ;;
            aarch64)
                _cputype=armv7
                if [ "$_ostype" = "linux-android" ]; then
                    err "Android not yet supported"
                    #  _ostype=linux-androideabi
                else
                    _ostype="${_ostype}eabihf"
                fi
                ;;
            riscv64gc)
                err "riscv64 with 32-bit userland unsupported"
                ;;
        esac
    fi

    # Detect armv7 but without the CPU features Ada needs in that build,
    # and fall back to arm.
    # See https://github.com/rust-lang/rustup.rs/issues/587.
    if [ "$_ostype" = "unknown-linux-gnueabihf" ] && [ "$_cputype" = armv7 ]; then
        if ensure grep '^Features' /proc/cpuinfo | grep -E -q -v 'neon|simd'; then
            # At least one processor does not have NEON (which is asimd on armv8+).
            _cputype=arm
        fi
    fi

    _arch="${_cputype}-${_ostype}"

    RETVAL="$_arch"
}

say() {
    printf 'getada: %s\n' "$1"
}

err() {
    say "$1" >&2
    exit 1
}

need_cmd() {
    if ! check_cmd "$1"; then
        err "need '$1' (command not found)"
    fi
}

check_cmd() {
    command -v "$1" > /dev/null 2>&1
}

assert_nz() {
    if [ -z "$1" ]; then err "assert_nz $2"; fi
}

# Run a command that should never fail. If the command fails execution
# will immediately terminate with an error showing the failing
# command.
ensure() {
    if ! "$@"; then err "command failed: $*"; fi
}

# This is just for indicating that commands' results are being
# intentionally ignored. Usually, because it's being executed
# as part of error handling.
ignore() {
    "$@"
}

# This wraps curl or wget. Try curl first, if not installed,
# use wget instead.
downloader() {
    local _dld
    local _ciphersuites
    local _err
    local _status
    local _retry
    if check_cmd curl; then
        _dld=curl
    elif check_cmd wget; then
        _dld=wget
    else
        _dld='curl or wget' # to be used in error message of need_cmd
    fi

    if [ "$1" = --check ]; then
        need_cmd "$_dld"
    elif [ "$_dld" = curl ]; then
        check_curl_for_retry_support
        _retry="$RETVAL"
        get_ciphersuites_for_curl
        _ciphersuites="$RETVAL"
        if [ -n "$_ciphersuites" ]; then
            _err=$(curl $_retry --proto '=https' --tlsv1.2 --ciphers "$_ciphersuites" --silent --show-error --fail --location "$1" --output "$2" 2>&1)
            _status=$?
        else
            echo "Warning: Not enforcing strong cipher suites for TLS, this is potentially less secure"
            if ! check_help_for "$3" curl --proto --tlsv1.2; then
                echo "Warning: Not enforcing TLS v1.2, this is potentially less secure"
                _err=$(curl $_retry --silent --show-error --fail --location "$1" --output "$2" 2>&1)
                _status=$?
            else
                _err=$(curl $_retry --proto '=https' --tlsv1.2 --silent --show-error --fail --location "$1" --output "$2" 2>&1)
                _status=$?
            fi
        fi
        if [ -n "$_err" ]; then
            echo "$_err" >&2
            if echo "$_err" | grep -q 404$; then
                err "installer for platform '$3' not found, this may be unsupported"
            fi
        fi
        return $_status
    elif [ "$_dld" = wget ]; then
        if [ "$(wget -V 2>&1|head -2|tail -1|cut -f1 -d" ")" = "BusyBox" ]; then
            echo "Warning: using the BusyBox version of wget.  Not enforcing strong cipher suites for TLS or TLS v1.2, this is potentially less secure"
            _err=$(wget "$1" -O "$2" 2>&1)
            _status=$?
        else
            get_ciphersuites_for_wget
            _ciphersuites="$RETVAL"
            if [ -n "$_ciphersuites" ]; then
                _err=$(wget --https-only --secure-protocol=TLSv1_2 --ciphers "$_ciphersuites" "$1" -O "$2" 2>&1)
                _status=$?
            else
                echo "Warning: Not enforcing strong cipher suites for TLS, this is potentially less secure"
                if ! check_help_for "$3" wget --https-only --secure-protocol; then
                    echo "Warning: Not enforcing TLS v1.2, this is potentially less secure"
                    _err=$(wget "$1" -O "$2" 2>&1)
                    _status=$?
                else
                    _err=$(wget --https-only --secure-protocol=TLSv1_2 "$1" -O "$2" 2>&1)
                    _status=$?
                fi
            fi
        fi
        if [ -n "$_err" ]; then
            echo "$_err" >&2
            if echo "$_err" | grep -q ' 404 Not Found$'; then
                err "installer for platform '$3' not found, this may be unsupported"
            fi
        fi
        return $_status
    else
        err "Unknown downloader"   # should not reach here
    fi
}

check_help_for() {
    local _arch
    local _cmd
    local _arg
    _arch="$1"
    shift
    _cmd="$1"
    shift

    local _category
    if "$_cmd" --help | grep -q 'For all options use the manual or "--help all".'; then
      _category="all"
    else
      _category=""
    fi

    case "$_arch" in

        *darwin*)
        if check_cmd sw_vers; then
            case $(sw_vers -productVersion) in
                10.*)
                    # If we're running on macOS, older than 10.13, then we always
                    # fail to find these options to force fallback
                    if [ "$(sw_vers -productVersion | cut -d. -f2)" -lt 13 ]; then
                        # Older than 10.13
                        echo "Warning: Detected macOS platform older than 10.13"
                        return 1
                    fi
                    ;;
                11.*)
                    # We assume Big Sur will be OK for now
                    ;;
                *)
                    # Unknown product version, warn and continue
                    echo "Warning: Detected unknown macOS major version: $(sw_vers -productVersion)"
                    echo "Warning TLS capabilities detection may fail"
                    ;;
            esac
        fi
        ;;

    esac

    for _arg in "$@"; do
        if ! "$_cmd" --help "$_category" | grep -q -- "$_arg"; then
            return 1
        fi
    done

    true # not strictly needed
}

# Check if curl supports the --retry flag, then pass it to the curl invocation.
check_curl_for_retry_support() {
    local _retry_supported=""
    # "unspecified" is for arch, allows for possibility old OS using macports, homebrew, etc.
    if check_help_for "notspecified" "curl" "--retry"; then
        _retry_supported="--retry 3"
        if check_help_for "notspecified" "curl" "--continue-at"; then
            # "-C -" tells curl to automatically find where to resume the download when retrying.
            _retry_supported="--retry 3 -C -"
        fi
    fi

    RETVAL="$_retry_supported"
}

# Return cipher suite string specified by user, otherwise return strong TLS 1.2-1.3 cipher suites
# if support by local tools is detected. Detection currently supports these curl backends:
# GnuTLS and OpenSSL (possibly also LibreSSL and BoringSSL). Return value can be empty.
get_ciphersuites_for_curl() {
    if [ -n "${GETADA_TLS_CIPHERSUITES-}" ]; then
        # user specified custom cipher suites, assume they know what they're doing
        RETVAL="$GETADA_TLS_CIPHERSUITES"
        return
    fi

    local _openssl_syntax="no"
    local _gnutls_syntax="no"
    local _backend_supported="yes"
    if curl -V | grep -q ' OpenSSL/'; then
        _openssl_syntax="yes"
    elif curl -V | grep -iq ' LibreSSL/'; then
        _openssl_syntax="yes"
    elif curl -V | grep -iq ' BoringSSL/'; then
        _openssl_syntax="yes"
    elif curl -V | grep -iq ' GnuTLS/'; then
        _gnutls_syntax="yes"
    else
        _backend_supported="no"
    fi

    local _args_supported="no"
    if [ "$_backend_supported" = "yes" ]; then
        # "unspecified" is for arch, allows for possibility old OS using macports, homebrew, etc.
        if check_help_for "notspecified" "curl" "--tlsv1.2" "--ciphers" "--proto"; then
            _args_supported="yes"
        fi
    fi

    local _cs=""
    if [ "$_args_supported" = "yes" ]; then
        if [ "$_openssl_syntax" = "yes" ]; then
            _cs=$(get_strong_ciphersuites_for "openssl")
        elif [ "$_gnutls_syntax" = "yes" ]; then
            _cs=$(get_strong_ciphersuites_for "gnutls")
        fi
    fi

    RETVAL="$_cs"
}

# Return cipher suite string specified by user, otherwise return strong TLS 1.2-1.3 cipher suites
# if support by local tools is detected. Detection currently supports these wget backends:
# GnuTLS and OpenSSL (possibly also LibreSSL and BoringSSL). Return value can be empty.
get_ciphersuites_for_wget() {
    if [ -n "${GETADA_TLS_CIPHERSUITES-}" ]; then
        # user specified custom cipher suites, assume they know what they're doing
        RETVAL="$GETADA_TLS_CIPHERSUITES"
        return
    fi

    local _cs=""
    if wget -V | grep -q '\-DHAVE_LIBSSL'; then
        # "unspecified" is for arch, allows for possibility old OS using macports, homebrew, etc.
        if check_help_for "notspecified" "wget" "TLSv1_2" "--ciphers" "--https-only" "--secure-protocol"; then
            _cs=$(get_strong_ciphersuites_for "openssl")
        fi
    elif wget -V | grep -q '\-DHAVE_LIBGNUTLS'; then
        # "unspecified" is for arch, allows for possibility old OS using macports, homebrew, etc.
        if check_help_for "notspecified" "wget" "TLSv1_2" "--ciphers" "--https-only" "--secure-protocol"; then
            _cs=$(get_strong_ciphersuites_for "gnutls")
        fi
    fi

    RETVAL="$_cs"
}

# Return strong TLS 1.2-1.3 cipher suites in OpenSSL or GnuTLS syntax. TLS 1.2
# excludes non-ECDHE and non-AEAD cipher suites. DHE is excluded due to bad
# DH params often found on servers (see RFC 7919). Sequence matches or is
# similar to Firefox 68 ESR with weak cipher suites disabled via about:config.
# $1 must be openssl or gnutls.
get_strong_ciphersuites_for() {
    if [ "$1" = "openssl" ]; then
        # OpenSSL is forgiving of unknown values, no problems with TLS 1.3 values on versions that don't support it yet.
        echo "TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_256_GCM_SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384"
    elif [ "$1" = "gnutls" ]; then
        # GnuTLS isn't forgiving of unknown values, so this may require a GnuTLS version that supports TLS 1.3 even if wget doesn't.
        # Begin with SECURE128 (and higher) then remove/add to build cipher suites. Produces same 9 cipher suites as OpenSSL but in slightly different order.
        echo "SECURE128:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS-ALL:-CIPHER-ALL:-MAC-ALL:-KX-ALL:+AEAD:+ECDHE-ECDSA:+ECDHE-RSA:+AES-128-GCM:+CHACHA20-POLY1305:+AES-256-GCM"
    fi
}

main "$@" || exit 1
