if status is-interactive
  # Commands to run in interactive sessions can go here


  #
  # shell prompt 
  #

  # match prompt symbol to OS logo
  if test -e /etc/os-release
    posix-source /etc/os-release
  end

  if test -e /System
    set os_icon ""
    eval "$(/opt/homebrew/bin/brew shellenv)"
  else if [ "$ID" = "nixos" ]
    set os_icon ""
  else if [ "$ID" = "debian" ]
    set os_icon ""
  else if [ "$ID" = "fedora" ]
    set os_icon ""
  else if [ "$ID" = "arch" ]
    set os_icon "󰣇"
  else
    set os_icon "\$"
  end

  # set prompt colours
  if test -e ~/.cache/zsh_colours.sh
    posix-source-universal (string replace -fra "{|}|#|\"" "" (cat ~/.cache/zsh_colours.sh) | psub)
  else
    set -Ux PRIMARY_COLOUR blue
    set -Ux SECONDARY_COLOUR purple
  end


  # construct final prompt
  function fish_prompt
    # turn os_icon red if an error occurs
    set -l prompt_icon
    if test $status -ne 0
      set prompt_icon (set_color red)"$os_icon"(set_color normal)
    else
      set prompt_icon "$os_icon"
    end

    # set ssh status
    set -l ssh_status
    if set -q SSH_CONNECTION
      set ssh_status (prompt_login)
    end

    # concatenate $HOME to a ~ eg. /home/user to ~
    set shorten_path (string replace -r "^$HOME" "~" "$PWD")

    echo (set_color $PRIMARY_COLOUR)$shorten_path $ssh_status (set_color $SECONDARY_COLOUR)$prompt_icon (set_color normal) 
  end

  #
  # shell intergration
  #

  zoxide init fish | source

  #
  # environment variables
  #

  set -gx EDITOR nvim
  set fish_greeting ""
  set HOMEBREW_AUTO_UPDATE_SECS 86400

  # xdg variables
  set -gx XDG_CONFIG_HOME "$HOME/.config"      # config
  set -gx XDG_CACHE_HOME "$HOME/.cache"        # cache
  set -gx XDG_DATA_HOME "$HOME/.local/share"  # data files eg. /usr/share
  set -gx XDG_STATE_HOME "$HOME/.local/state"  # state files eg. /var/lib

  # make apps use XDG folders
  set -gx PYTHON_HISTORY "$XDG_STATE_HOME"/python_history
  set -gx PYTHONPYCACHEPREFIX "$XDG_CACHE_HOME"/python
  set -gx PYTHONUSERBASE "$XDG_DATA_HOME"/python
  set -gx GOPATH "$XDG_STATE_HOME"/go
  set -gx GOMODCACHE "$XDG_CACHE_HOME"/go/mod
  set -gx NPM_CONFIG_USERCONFIG "$XDG_CONFIG_HOME"/npm/npmrc

  function wget --wraps=wget
    wget --hsts-file="$XDG_STATE_HOME/wget-hsts" $argv
  end

end