have() {
  command -v "$1" >/dev/null 2>&1
}

# Prepend $2 to variable $1 using $3 as separator, but only if $2 is not already
# contained in $1. This is useful for prepending to PATH while avoiding
# duplicates.
prepend_unique() {
  local var="$1" new="$2" sep="${3-:}"  # Default separator is colon.
  local old="${(P)var}"

  case "${sep}${old}${sep}" in
    *"${sep}${new}${sep}"*)  # Skip duplicate.
      ;;
    "${sep}${sep}")  # Variable was empty, set without separator.
      typeset -g $var="${new}"
      ;;
    *) # Prepend with separator.
      typeset -g $var="${new}${sep}${old}"
      ;;
  esac
}

setup_environment() {
  export XDG_CACHE_HOME="${XDG_CACHE_HOME:-$HOME/.cache}"
  export XDG_CONFIG_HOME="${XDG_CONFIG_HOME:-$HOME/.config}"
  export XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"

  export LANG="en_US.UTF-8"
  export LANGUAGE="en_US"
  export LC_ALL="en_US.UTF-8"
  export LC_CTYPE="en_US.UTF-8"
  export LC_COLLATE="C"

  export INPUTRC="$XDG_CONFIG_HOME/readline/inputrc"
  export LESS="-i -j.49 -M -R -z-2"
  export LESSHISTFILE="$XDG_DATA_HOME/less/history"
  export LESSHISTSIZE=1000
  export PAGER=less
  export PYTHONSTARTUP="$XDG_CONFIG_HOME/python/startup.py"
}

setup_path_and_manpath() {
  # Prevent path_helper from messing with the PATH when starting tmux.
  #
  # Clearing PATH before path_helper executes (from /etc/profile) will prevent it
  # from prepending the default PATH to our (previously) chosen PATH, and will
  # allow the rest of this file to set up PATH and MANPATH correctly.
  #
  #   For details see: https://superuser.com/a/583502
  #
  [ "$(uname -s)" = "Darwin" ] && { PATH=""; source /etc/profile; }

  local prefix="/usr/local"
  have brew && prefix="$(brew --prefix)"

  local custom_paths=(
    "$prefix/opt/curl/bin"
    "$prefix/bin"
    "$HOME/.local/bin"
    "$HOME/.bin"
  )

  local bindir=""
  for bindir in $custom_paths; do
    [ -d "$bindir" ] && prepend_unique PATH "$bindir"
  done
  export PATH

  # Now that PATH is set, we should pick up all relevant man page locations, as
  # for all directories ending in `<pathname>/bin` found in PATH, `manpath` will
  # print the first existing directory of:
  #   - `<pathname>/man`
  #   - `<pathname>/../share/man`
  #   - `<pathname>/../man`
  have manpath && { MANPATH="$(unset MANPATH; manpath)"; export MANPATH; }
}

# Some packages are installed by Homebrew in non-standard locations, in order to
# prevent conflicts with their system versions.
setup_brew_keg_only_packages() {
  have brew || return

  local packages=(
    make
    grep
    gnu-tar
    gnu-sed
    findutils
    coreutils
  )

  local prefix="$(brew --prefix)"
  local pkg="" bindir="" mandir=""

  for pkg in $packages; do
    bindir="$prefix/opt/$pkg/libexec/gnubin"
    [ -d "$bindir" ] && prepend_unique PATH "$bindir"

    mandir="$prefix/opt/$pkg/libexec/gnuman"
    [ -d "$mandir" ] && prepend_unique MANPATH "$mandir"
  done
}

setup_tools() {
  have nvim && EDITOR="nvim"
  [ -z $EDITOR ] && have vim && EDITOR="vim"
  [ -z $EDITOR ] && have vi && EDITOR="vi"
  [ -n $EDITOR ] && export EDITOR

  have brew && {
    export HOMEBREW_NO_ANALYTICS=1
    export HOMEBREW_NO_AUTO_UPDATE=1
  }

  have dotnet && {
    export DOTNET_CLI_TELEMETRY_OPTOUT=1
    export DOTNET_NOLOGO=1
  }
}

# Set $DISPLAY if running in WSL and an Xserver is reachable
#
# How to configure Windows Firewall for Xserver: https://skeptric.com/wsl2-xserver/
# How to check if running in WSL: https://stackoverflow.com/a/61014411
setup_wsl_display() {
  if [ -n "$(uname -r | sed -n 's/.*\( *Microsoft *\).*/\1/ip')" ] && have xset; then
    local xdisplay="$(awk '/nameserver/ {print $2; exit}' /etc/resolv.conf 2>/dev/null):0.0"
    if DISPLAY="$xdisplay" timeout '0.2s' xset q >/dev/null 2>&1; then
      export DISPLAY="$xdisplay"
      export LIBGL_ALWAYS_INDIRECT=1
    fi
  fi
}

# Load additional local configuration if present.
setup_local_profile() {
  local profile="$HOME/.local/etc/zsh/zprofile"
  [ -r "$profile" ] && source "$profile"
}

# zmodload zsh/zprof
setup_environment
setup_path_and_manpath
setup_brew_keg_only_packages
setup_tools  # NOTE: this must be done _after_ `setup_environment`.
setup_wsl_display
setup_local_profile
# zprof