From bada848ca16ae70fbc66cfe67c5c1e072dee03ff Mon Sep 17 00:00:00 2001
From: technofab <admin@technofab.de>
Date: Fri, 11 Jul 2025 20:54:35 +0200
Subject: [PATCH] chore: initial commit

---
 README.md |  15 ++
 direnvrc  | 411 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 426 insertions(+)
 create mode 100644 README.md
 create mode 100644 direnvrc

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c7ebdda
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+# Rensa Direnv Integration
+
+## Usage
+
+```console
+direnv fetchurl https://gitlab.com/rensa-nix/direnv/-/raw/main/direnvrc
+```
+
+`.envrc`:
+```bash
+source $(fetchurl https://gitlab.com/rensa-nix/direnv/-/raw/main/direnvrc <hash>)
+
+use envreload //repo/shells/default
+```
+
diff --git a/direnvrc b/direnvrc
new file mode 100644
index 0000000..c1052b5
--- /dev/null
+++ b/direnvrc
@@ -0,0 +1,411 @@
+#!/usr/bin/env bash
+#
+# A direnv hook for loading Nix flake-based development environments
+# with built-in caching and garbage-collection root management.
+#
+# Based on
+# https://github.com/nix-community/nix-direnv
+# and
+# https://github.com/paisano-nix/direnv
+#
+set -euo pipefail
+
+readonly RENSA_DIRENV_VERSION="0.1.0"
+readonly DIRENV_MIN_VERSION="2.21.3"
+readonly BASH_MIN_VERSION="4.4"
+
+#
+# LOGGING
+#
+
+# Usage: __ren_log <LEVEL> "message"
+# LEVEL can be: TRACE, INFO, WARN, ERROR
+__ren_log() {
+  local level="$1" msg="$2"
+  local format=$'\E[mren: \E[38;5;8m%s\E[m'
+  case "$level" in
+  TRACE)
+    if [[ -n "${REN_TRACE:-}" ]]; then
+      # shellcheck disable=SC2059
+      log_status "$(printf "$format" "[TRACE] ${msg}")"
+    fi
+    ;;
+  INFO)
+    # shellcheck disable=SC2059
+    log_status "$(printf "$format" "${msg}")"
+    ;;
+  WARN)
+    # shellcheck disable=SC2059
+    log_error "$(printf "$format" "[WARN] ${msg}")"
+    ;;
+  ERROR)
+    # shellcheck disable=SC2059
+    log_error "$(printf "$format" "[ERROR] ${msg}")"
+    ;;
+  esac
+}
+
+#
+# UTILS
+#
+
+__ren_require_version() {
+  local name="$1" version="$2" required="$3"
+  if ! printf "%s\n%s\n" "$required" "$version" | LC_ALL=C sort --check --version-sort &>/dev/null; then
+    __ren_log ERROR "Minimum required ${name} version is ${required} (found: ${version})."
+    return 1
+  fi
+}
+
+__ren_require_cmd_version() {
+  local cmd="$1" required="$2" version
+  if ! has "$cmd"; then
+    __ren_log ERROR "Command not found: $cmd"
+    return 1
+  fi
+  version=$($cmd --version)
+  if [[ $version =~ ([0-9]+\.[0-9]+\.[0-9]+) ]]; then
+    __ren_require_version "$cmd" "${BASH_REMATCH[1]}" "$required"
+  else
+    __ren_log WARN "Could not parse version for '$cmd'. Skipping version check."
+  fi
+}
+
+__cell_path_cache=""
+__ren_get_cell_path() {
+  if [[ -z "$__cell_path_cache" ]]; then
+    local cell="$1"
+    local cellsFrom
+    cellsFrom=$(__ren_nix eval --raw ".#__std.cellsFrom" 2>/dev/null || true)
+    if [[ -z "$cellsFrom" ]]; then
+      __ren_log TRACE "Could not determine 'cellsFrom' path from flake."
+      return 1
+    fi
+    __cell_path_cache=$cellsFrom
+  fi
+  echo "${REN_ROOT}/${__cell_path_cache}/${cell}"
+}
+
+# set in the entrypoint
+__nix_cmd=""
+__ren_nix() {
+  "$__nix_cmd" --no-warn-dirty --extra-experimental-features "nix-command flakes" "$@"
+}
+
+#
+# INIT
+#
+
+# discovers the project root (git repo) and sets up state directories and variables
+__ren_init_project() {
+  [[ -n "${REN_ROOT:-}" ]] && return 0
+  local git_repo
+  git_repo=$(git rev-parse --show-toplevel 2>/dev/null || true)
+  if [[ -z "$git_repo" ]]; then
+    __ren_log ERROR "Not inside a git repository. Cannot determine project root."
+    return 1
+  fi
+
+  export REN_ROOT="$git_repo"
+  export REN_STATE="${REN_ROOT}/.ren"
+  mkdir -p "${REN_STATE}/direnv"
+  # shellcheck disable=SC2034
+  direnv_layout_dir="${REN_STATE}/direnv"
+}
+
+#
+# NIX GCROOTS & ENV STUFF
+#
+
+__ren_import_env() {
+  local profile_rc="$1"
+  [[ -f "$profile_rc" ]] || return 0
+  local -A to_restore
+  to_restore=(
+    ["NIX_BUILD_TOP"]="${NIX_BUILD_TOP:-__UNSET__}"
+    ["TMP"]="${TMP:-__UNSET__}"
+    ["TMPDIR"]="${TMPDIR:-__UNSET__}"
+    ["TEMP"]="${TEMP:-__UNSET__}"
+    ["TEMPDIR"]="${TEMPDIR:-__UNSET__}"
+    ["terminfo"]="${terminfo:-__UNSET__}"
+  )
+  local old_xdg_data_dirs="${XDG_DATA_DIRS:-}"
+
+  # shellcheck source=/dev/null
+  eval "$(<"$profile_rc")"
+
+  if [[ -n "${NIX_BUILD_TOP+x}" && $NIX_BUILD_TOP == */nix-shell.* && -d $NIX_BUILD_TOP ]]; then rm -rf "$NIX_BUILD_TOP"; fi
+  for key in "${!to_restore[@]}"; do
+    if [[ "${to_restore[$key]}" == "__UNSET__" ]]; then unset "$key"; else export "$key=${to_restore[$key]}"; fi
+  done
+  local new_xdg_data_dirs="${XDG_DATA_DIRS:-}"
+  export XDG_DATA_DIRS=""
+  local IFS=:
+  for dir in $new_xdg_data_dirs${old_xdg_data_dirs:+:}$old_xdg_data_dirs; do
+    dir="${dir%/}"
+    [[ -z "$dir" || ":$XDG_DATA_DIRS:" == *:"$dir":* ]] && continue
+    XDG_DATA_DIRS="${XDG_DATA_DIRS}${XDG_DATA_DIRS:+:}$dir"
+  done
+}
+
+__ren_add_gcroot() {
+  local storepath="$1" symlink="$2"
+  __ren_log TRACE "Adding GC root: $symlink -> $storepath"
+  __ren_nix build --out-link "$symlink" "$storepath" >/dev/null
+}
+
+__ren_clean_old_gcroots() {
+  __ren_log TRACE "Cleaning old GC roots in $1"
+  rm -rf "${1}/flake-inputs/" "${1}/profile-"*
+}
+
+__ren_argsum_suffix() {
+  local out checksum
+  if [[ -n "$1" ]]; then
+    if has sha1sum; then
+      out=$(sha1sum <<<"$1")
+    elif has shasum; then
+      out=$(shasum <<<"$1")
+    else
+      __ren_log WARN "sha1sum/shasum not found; cannot create stable profile name."
+      return
+    fi
+    read -r checksum _ <<<"$out"
+    echo "-$checksum"
+  fi
+}
+
+# archive flake inputs and gcroot them
+__ren_add_flake_input_gcroots() {
+  local flake_dir="$1" __layout_dir="$2"
+  __ren_log TRACE "Archiving flake inputs from '$flake_dir'"
+
+  local flake_inputs_dir="${__layout_dir}/flake-inputs/"
+  mkdir -p "$flake_inputs_dir"
+
+  local flake_inputs_json
+  # run in subshell to not affect the current directory and handle errors gracefully
+  flake_inputs_json=$( (cd "$flake_dir" && __ren_nix flake archive --json --no-write-lock-file -- ".") 2>/dev/null || true)
+
+  if [[ -z "$flake_inputs_json" ]]; then
+    __ren_log TRACE "No inputs found or error archiving flake at '$flake_dir'. Skipping."
+    return
+  fi
+
+  while [[ $flake_inputs_json =~ /nix/store/[^\"]+ ]]; do
+    local store_path="${BASH_REMATCH[0]}"
+    [[ -z "$store_path" ]] && continue
+    __ren_add_gcroot "$store_path" "${flake_inputs_dir}/${store_path##*/}"
+    flake_inputs_json="${flake_inputs_json/${store_path}/}"
+  done
+}
+
+# updates gcroots
+__ren_update_gcroots() {
+  local __layout_dir="$1" tmp_profile="$2" profile="$3" cell="$4"
+  __ren_add_gcroot "$tmp_profile" "$profile"
+  rm -f "$tmp_profile"*
+  # add gcroots for the main flake
+  __ren_add_flake_input_gcroots "$REN_ROOT" "$__layout_dir"
+
+  # if a cell is specified, also gcroot it's flake inputs, if it has a flake
+  if [[ -n "$cell" ]]; then
+    local cell_path
+    if cell_path=$(__ren_get_cell_path "$cell"); then
+      if [[ -f "${cell_path}/flake.nix" ]]; then
+        __ren_log TRACE "Found cell flake. Adding GC roots for inputs from '${cell_path}'."
+        __ren_add_flake_input_gcroots "$cell_path" "$__layout_dir"
+      fi
+    fi
+  fi
+}
+
+#
+# WATCHERS
+#
+
+__ren_get_direnv_watches() {
+  local -n _watches_ref=$1
+  [[ -z "${DIRENV_WATCHES-}" ]] && return 0
+  # shellcheck disable=SC2154
+  while IFS= read -r line; do
+    local regex='"[Pp]ath": "(.+)"$'
+    if [[ $line =~ $regex ]]; then
+      local path
+      # shellcheck disable=SC2059
+      path=$(printf "${BASH_REMATCH[1]}")
+      if [[ $path != "${XDG_DATA_HOME:-${HOME:-/var/empty}/.local/share}/direnv/allow/"* ]]; then
+        _watches_ref+=("$path")
+      fi
+    fi
+  done < <("$direnv" show_dump "${DIRENV_WATCHES}")
+}
+
+__ren_watch_cell() {
+  local target_spec="$1"
+  read -r cell block _ <<<"${target_spec//\// }"
+  local cell_path
+  if ! cell_path=$(__ren_get_cell_path "$cell"); then
+    __ren_log WARN "Could not determine 'cellsFrom' path from flake. File watching for target files will be incomplete."
+    return
+  fi
+
+  if [[ -f "${cell_path}/${block}.nix" ]]; then
+    __ren_log TRACE "Watching: ${cell_path}/${block}.nix"
+    watch_file "${cell_path}/${block}.nix"
+  fi
+  if [[ -f "${cell_path}/default.nix" ]]; then
+    __ren_log TRACE "Watching: ${cell_path}/default.nix"
+    watch_file "${cell_path}/default.nix"
+  fi
+  if [[ -d "${cell_path}/${block}" ]]; then
+    __ren_log TRACE "Watching dir: ${cell_path}/${block}"
+    watch_dir "${cell_path}/${block}"
+  fi
+
+  # watch for cell-level flake.nix and flake.lock
+  if [[ -f "${cell_path}/flake.nix" ]]; then
+    __ren_log TRACE "Watching cell flake: ${cell_path}/flake.nix"
+    watch_file "${cell_path}/flake.nix"
+  fi
+  if [[ -f "${cell_path}/flake.lock" ]]; then
+    __ren_log TRACE "Watching cell flake lock: ${cell_path}/flake.lock"
+    watch_file "${cell_path}/flake.lock"
+  fi
+}
+
+__ren_setup_watches() {
+  watch_file "$REN_ROOT/flake.nix" "$REN_ROOT/flake.lock"
+  for target in "$@"; do
+    if [[ "$target" != *"#"* ]]; then
+      __ren_watch_cell "$target"
+    fi
+  done
+}
+
+#
+# BUILD & CACHE
+#
+
+# returns 1 if rebuild is needed
+__ren_is_rebuild_needed() {
+  local profile_rc="$1"
+  if [[ ! -f "$profile_rc" ]]; then
+    __ren_log TRACE "No cached profile found at '$profile_rc'. Rebuilding."
+    echo 1
+    return
+  fi
+  local watches=()
+  __ren_get_direnv_watches watches
+  for file in "${watches[@]}"; do
+    if [[ "$file" -nt "$profile_rc" ]]; then
+      __ren_log INFO "Cache invalidated by: $file"
+      echo 1
+      return
+    fi
+  done
+  echo 0
+}
+
+# returns 0 on success, 1 on failure
+__ren_build_and_cache() {
+  local target_spec="$1" __layout_dir="$2" profile="$3" profile_rc="$4"
+  __ren_log INFO "Building shell from '$target_spec'..."
+  local flake_attr cell=""
+  # allows specifying either flake attr like `./path#devShells.default` or through
+  # ren style `//repo/devShells/default`
+  if [[ "$target_spec" == *"#"* ]]; then
+    flake_attr="$target_spec"
+    __ren_log TRACE "Using direct flake attribute: $flake_attr"
+  else
+    read -r cell block target <<<"${target_spec//\// }"
+    local system
+    system=$(__ren_nix eval --raw --impure --expr builtins.currentSystem)
+    flake_attr=".#${system}.${cell}.${block}.${target}"
+  fi
+  local tmp_profile="${__layout_dir}/tmp-profile.$$"
+  if build_output=$(__ren_nix print-dev-env --profile "$tmp_profile" "$flake_attr"); then
+    __ren_clean_old_gcroots "$__layout_dir"
+    echo "$build_output" >"$profile_rc"
+    __ren_update_gcroots "$__layout_dir" "$tmp_profile" "$profile" "$cell"
+
+    __ren_log TRACE "Cache for '$target_spec' renewed successfully."
+    return 0
+  else
+    rm -f "$tmp_profile"*
+    return 1
+  fi
+}
+
+#
+# ENTRYPOINTS
+#
+
+# usage in .envrc: use_envreload <target>
+# <target> can be `//cell/block/target` or a direct flake attr like `.#myShell`
+use_envreload() {
+  if [[ -z ${REN_SKIP_VERSION_CHECK:-} ]]; then
+    __ren_require_version "bash" "$BASH_VERSION" "$BASH_MIN_VERSION"
+    __ren_require_cmd_version "direnv" "$DIRENV_MIN_VERSION"
+  fi
+
+  if command -v nix &>/dev/null; then
+    __nix_cmd=$(command -v nix)
+  elif [[ -n "${REN_FALLBACK_NIX:-}" ]]; then
+    __nix_cmd="${REN_FALLBACK_NIX}"
+  else
+    __ren_log ERROR "Could not find Nix. Add 'nix' to PATH or set REN_FALLBACK_NIX."
+    return 1
+  fi
+
+  local target_spec="${1-}"
+  if [[ -z "$target_spec" ]]; then
+    __ren_log ERROR "use_envreload requires a target argument, e.g., //repo/devShells/default or .#myShell"
+    return 1
+  fi
+
+  __ren_setup_watches "$@"
+
+  local __layout_dir profile profile_rc
+  __layout_dir=$(direnv_layout_dir)
+  profile="${__layout_dir}/profile$(__ren_argsum_suffix "$target_spec")"
+  profile_rc="${profile}.rc"
+
+  if [[ $(__ren_is_rebuild_needed "$profile_rc") -eq 1 ]]; then
+    if ! __ren_build_and_cache "$target_spec" "$__layout_dir" "$profile" "$profile_rc"; then
+      if [[ -f "$profile_rc" ]]; then
+        __ren_log WARN "Nix evaluation failed. Falling back to the last known-good environment."
+        export REN_DID_FALLBACK=1
+      else
+        __ren_log ERROR "Nix evaluation failed, and no cached environment is available."
+        return 1
+      fi
+    fi
+  else
+    __ren_log INFO "Using cached environment for '$target_spec'."
+  fi
+
+  __ren_import_env "$profile_rc"
+}
+
+# initialize project environment variables immediately upon sourcing the script,
+# allows the user to use $REN_STATE etc. in .envrc
+__ren_init_project
+__ren_log TRACE "Rensa v${RENSA_DIRENV_VERSION}"
+
+#
+# HELPERS
+# to use in .envrc, eg. to switch between shells etc.
+#
+
+# read state from the project
+read_state() {
+  if [[ -f "$REN_STATE/$1" ]]; then
+    cat "$REN_STATE/$1"
+  fi
+}
+
+# set/write state for the project
+write_state() {
+  echo "$2" >"$REN_STATE/$1"
+}