# shellcheck shell=bash
# adapted from https://github.com/nix-community/nix-direnv/blob/master/direnvrc

REQUIRED_DIRENV_VERSION="2.21.3"

_nix_direnv_preflight () {
  if [[ -z "$direnv" ]]; then
    printf '%s\n' "\$direnv environment variable was not defined. Was this script run inside direnv?"
    exit 1
  fi

  if [[ -z ${DEVENV_BIN:-} ]]; then
    DEVENV_BIN=$(command -v devenv)
    if [[ -z "${DEVENV_BIN}" ]]; then
      log_status "command not found: devenv, see https://devenv.sh/getting-started/"
      exit 1
    fi
  fi

  if ! has direnv_version || ! direnv_version "$REQUIRED_DIRENV_VERSION" 2>/dev/null; then
    log_status "base direnv version is older than the required v$REQUIRED_DIRENV_VERSION."
    exit 1
  fi

  local layout_dir
  layout_dir=$(direnv_layout_dir)

  if [[ ! -d "$layout_dir" ]]; then
    mkdir -p "$layout_dir"
  fi
}

_nix_export_or_unset() {
  local key=$1 value=$2
  if [[ "$value" == __UNSET__ ]]; then
    unset "$key"
  else
    export "$key=$value"
  fi
}

_nix_import_env() {
  local profile_rc=$1

  local old_nix_build_top=${NIX_BUILD_TOP:-__UNSET__}
  local old_tmp=${TMP:-__UNSET__}
  local old_tmpdir=${TMPDIR:-__UNSET__}
  local old_temp=${TEMP:-__UNSET__}
  local old_tempdir=${TEMPDIR:-__UNSET__}
  local old_xdg_data_dirs=${XDG_DATA_DIRS:-}
  eval "$(< "$profile_rc")"
  # `nix print-dev-env` will create a temporary directory and use it as TMPDIR
  # We cannot rely on this directory being availble at all times,
  # as it may be garbage collected.
  # Instead - just remove it immediately.
  # Use recursive & force as it may not be empty.
  if [[ -n "${NIX_BUILD_TOP+x}" && "$NIX_BUILD_TOP" == */nix-shell.* && -d "$NIX_BUILD_TOP" ]]; then
    rm -rf "$NIX_BUILD_TOP"
  fi

  _nix_export_or_unset NIX_BUILD_TOP "$old_nix_build_top"
  _nix_export_or_unset TMP "$old_tmp"
  _nix_export_or_unset TMPDIR "$old_tmpdir"
  _nix_export_or_unset TEMP "$old_temp"
  _nix_export_or_unset TEMPDIR "$old_tempdir"
  local new_xdg_data_dirs=${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%/}" # remove trailing slashes
    if [[ :$XDG_DATA_DIRS: = *:$dir:* ]]; then
      continue # already present, skip
    fi
    XDG_DATA_DIRS="$XDG_DATA_DIRS${XDG_DATA_DIRS:+:}$dir"
  done
}

_nix_argsum_suffix() {
  local out checksum content

  content=$(cat "$@" 2>/dev/null)

  if has sha1sum; then
    out=$(sha1sum <<< "$content")
  elif has shasum; then
    out=$(shasum <<< "$content")
  else
    log_status "not hashing your cache, please install sha1sum"
    # degrate gracefully both tools are not present
    return
  fi
  read -r checksum _ <<< "$out"
  echo "-$checksum"
}

nix_direnv_watch_file() {
  watch_file "$@"
  nix_watches+=("$@")
}

use_devenv() {
  _nix_direnv_preflight

  flake_expr="${1:-.}"
  flake_dir="${flake_expr%#*}"

  local files_to_watch
  files_to_watch=(".envrc" "$HOME/.direnvrc" "$HOME/.config/direnv/direnvrc")

  if [[ -d "$flake_dir" ]]; then
    files_to_watch+=("$flake_dir/devenv.nix" "$flake_dir/devenv.lock" "$flake_dir/devenv.yaml" "$flake_dir/devenv.local.nix")
    if [[ -f "$flake_dir/devenv.yaml" ]]; then
      if ! devenv assemble; then
        log_status "$(devenv version) failed to parse devenv.yaml, make sure to use version 0.6 or newer and fix the errors above."
        exit 1
      fi

      if [[ -f "$flake_dir/.devenv/imports.txt" ]]; then
        for file in $(cat "$flake_dir/.devenv/imports.txt"); do
            files_to_watch+=("$file")
        done
      fi
    fi
  fi

  nix_direnv_watch_file "${files_to_watch[@]}"

  local layout_dir profile_rc
  layout_dir=$(direnv_layout_dir)
  profile_rc="${layout_dir}/devenv-profile$(_nix_argsum_suffix "${files_to_watch[@]}").rc"

  local need_update=0
  local file=
  for file in "${nix_watches[@]}"; do
    if [[ "$file" -nt "$profile_rc" ]]; then
      need_update=1
      log_status "$file changed, reloading"
      break
    fi
  done

  if [[ ! -e "$profile_rc" || "$need_update" == "1" ]];
  then
    # We need to update our cache
    local env
    env=$("${DEVENV_BIN}" print-dev-env)
    if [[ "$env" == *"DEVENV_ROOT"* ]]; then
      echo "$env" > "$profile_rc"
      log_status "updated devenv shell cache"
      _nix_import_env "$profile_rc"
    else
      log_status "loading the environment failed"
      exit 1
    fi
  else
    log_status "using cached devenv shell"
    _nix_import_env "$profile_rc"
  fi
}