#! /usr/bin/env sh

_pre_cache_log() {
    printf "pre-cache: %s\n" "$1"
}
_pre_cache_preflight() {
    set -eu
    _nix_direnv_preflight

    repo="%DEVSHELLS_REPO%"
    system="x86_64-linux"
    cache_dir="$XDG_CACHE_HOME/pre_cache"
    [ -d "$cache_dir" ] || mkdir --parents "$cache_dir"

    repo_ref=$(git -C "$repo" rev-parse HEAD)
    final_cache="$cache_dir/$repo_ref"

    if ! [ -d "$final_cache" ]; then
        _pre_cache_log "Cache dir invalidated"

        # There is not yet a final cache directory, so the ref must have changed.
        # Therefore we delete the whole cache directory, so we invalidate old cached shells.
        set -u
        rm --recursive "$cache_dir"

        mkdir --parents "$final_cache"
    fi
}

_pre_cache_load_shell() {
    lang="$1"
    lang_cache="$final_cache/$lang"

    if ! [ -f "$lang_cache" ]; then
        tmp_profile="$final_cache/__tmp_profile"
        profile="$final_cache/__profile"

        # It does not already exists, we need to evaluate it.
        _nix print-dev-env --profile "$tmp_profile" "$repo#$lang" >"$lang_cache"

        _nix_add_gcroot "$tmp_profile" "$profile"
        rm "$tmp_profile" "$tmp_profile"*
    fi

    _pre_cache_log "Loaded dev-shell for $lang."
    _nix_import_env "$lang_cache"
}

_pre_cache_build_shells() {
    installables=""

    for lang in "$@"; do
        new_part="$repo#devShells.$system.$lang"

        if [ -z "$installables" ]; then
            installables="$new_part"
        else
            installables="$installables $new_part"
        fi
    done

    # We want shell-spliting
    # shellcheck disable=SC2086
    _nix build --no-link $installables

}

pre_cache_load() {
    _pre_cache_preflight

    _pre_cache_build_shells "$@"

    for lan in "$@"; do
        _pre_cache_load_shell "$lan"
    done
}

# vim: ft=sh