activate_version_manager.sh

#!/usr/bin/env bash

# The purpose of these functions is to detect and activate the correct
# installed version manager in the current shell session. Currently, we
# try to detect asdf, rtx, and mise (new name for rtx).
#
# The general approach involves the following steps:
#
#   1. Try to detect an already activated version manager that provides
#      Elixir. If one is present, there's nothing more to do.
#   2. Try to find and activate an asdf installation. If it provides
#      Elixir, we're all set.
#   3. Try to find and activate an rtx installation. If it provides
#      Elixir, we're all set.
#   4. Try to find and activate a mise installation. If it provides
#      Elixir, we're all set.
#

activate_version_manager() {
    if (_detect_asdf || _detect_rtx || _detect_mise); then
        return 0
    fi

    echo >&2 "No activated version manager detected. Searching for version manager..."

    { _try_activating_asdf && _detect_asdf; } ||
        { _try_activating_rtx && _detect_rtx; } ||
            { _try_activating_mise && _detect_mise; }
    return $?
}

_detect_asdf() {
    if command -v asdf >/dev/null && asdf which elixir >/dev/null 2>&1 && _ensure_which_elixir asdf; then
        echo >&2 "Detected Elixir through asdf: $(asdf which elixir)"
        return 0
    else
        return 1
    fi
}

_detect_rtx() {
    if command -v rtx >/dev/null && rtx which elixir >/dev/null 2>&1 && _ensure_which_elixir rtx; then
        echo >&2 "Detected Elixir through rtx: $(rtx which elixir)"
        return 0
    else
        return 1
    fi
}

_detect_mise() {
    if command -v mise >/dev/null && mise which elixir >/dev/null 2>&1 && _ensure_which_elixir mise; then
        echo >&2 "Detected Elixir through mise: $(mise which elixir)"
        return 0
    else
        return 1
    fi
}

_ensure_which_elixir() {
    [[ $(which elixir) == *"$1"* ]]
    return $?
}

_try_activating_asdf() {
    local asdf_dir="${ASDF_DIR:-"$HOME/.asdf"}"
    local asdf_vm="$asdf_dir/asdf.sh"

    if test -f "$asdf_vm"; then
        echo >&2 "Found asdf. Activating..."
        # shellcheck disable=SC1090
        . "$asdf_vm"
        return $?
    else
        return 1
    fi
}

_try_activating_rtx() {
    if which rtx >/dev/null; then
        echo >&2 "Found rtx. Activating..."
        eval "$(rtx activate bash)"
        eval "$(rtx env)"
        return $?
    else
        return 1
    fi
}

_try_activating_mise() {
    if which mise >/dev/null; then
        echo >&2 "Found mise. Activating..."
        eval "$(mise activate bash)"
        eval "$(mise env)"
        return $?
    else
        return 1
    fi
}

activate_version_manager