#!/bin/bash

SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" >/dev/null 2>&1 &&
  pwd)"
PROFILES_DIR="${SCRIPT_DIR}/profiles"
STOW_ARGS=(
  "--no-folding"
  "--adopt"
  "--dir" "${PROFILES_DIR}"
  "--target" "${HOME}"
)
SCRIPT_NAME="${0##*/}"

readonly SCRIPT_DIR
readonly PROFILES_DIR
readonly -a STOW_ARGS
readonly SCRIPT_NAME

print_opt() {
  local -r option="$1"
  local -r description="$2"
  printf "  %-22s %s\n" "${option}" "${description}"
}

shell_quote() {
  local -r string="$1"
  printf "'%s'" "${string//'/'\\''/}"
}

array_contains() {
  local -r target_item="$1"
  shift
  local -a -r array=("$@")
  local item
  for item in "${array[@]}"; do
    if [[ ${item} == "${target_item}" ]]; then
      return 0
    fi
  done
  return 1
}

die() {
  local -r message="$1"
  printf "%s: %b\n" "${SCRIPT_NAME}" "${message}" >&2
  exit 1
}

invalid_option() {
  local -r option="$1"
  die "invalid option $(shell_quote "${option}")
Try '${SCRIPT_NAME} --help' for usage."
}

check_deps() {
  if ! command -v stow >/dev/null 2>&1; then
    cat >&2 <<EOF
Error: 'stow' not found in PATH.

GNU Stow is a symlink farm manager used to deploy dotfiles/packages
by creating symbolic links into \${HOME}.

Install it first:
  Arch Linux:     pacman -S stow
  Debian/Ubuntu:  apt install stow
  Fedora:         dnf install stow
Typically, on other Linux distributions you can use their own package
managers. For other systems, you can find in the Internet installation
instructions appropriate to them or build manually GNU Stow from the
source if GNU Stow is not packaged or your system requires it.

Project: https://www.gnu.org/software/stow/
EOF
    exit 1
  fi
}

require_profiles_dir() {
  if [[ ! -d "${PROFILES_DIR}" ]]; then
    cat >&2 <<EOF
Error: profiles directory not found: ${PROFILES_DIR}

This directory must contain profile subdirectories with dotfiles.

Make sure you:
  - run the script from the repository root, or
  - create the directory, or
  - clone the dotfiles repository correctly.

More information about what is profile can be found using '${SCRIPT_NAME} --help profile'.
EOF
    exit 1
  fi
  mapfile -t PROFILES < <(find "${PROFILES_DIR}" -mindepth 1 -maxdepth 1 \
    -type d -printf '%f\n')
  readonly PROFILES
}

parse_args() {
  while (($# > 0)); do
    case $1 in
    -h)
      show_general_help
      exit 0
      ;;
    --help)
      if (($# >= 2)) && [[ $2 ]] && [[ $2 != -* ]]; then
        show_help_topic "$2"
      else
        show_general_help
      fi
      exit 0
      ;;
    --help=*)
      local -r topic="${1#*=}"
      [[ -z ${topic} ]] && show_general_help && exit 0
      show_help_topic "${topic}"
      exit 0
      ;;
    -l | --list-profiles)
      list_profiles="true"
      shift
      ;;
    -P | --prune-symlinks)
      prune_symlinks="true"
      shift
      ;;
    -v | --verbose)
      verbose="true"
      shift
      ;;
    -p | --profile)
      ( (($# < 2)) || [[ -z "$2" ]]) && die "--profile requires an argument"
      profile="$2"
      shift 2
      ;;
    *) invalid_option "$1" ;;
    esac
  done
}

validate_args() {
  if [[ -n "${list_profiles}" ]] &&
    [[ -n "${prune_symlinks}" || -n "${verbose}" || -n "${profile}" ]]; then
    die "options '--list-profiles' and others cannot be used together"
  fi

  if [[ -n "${profile}" ]] &&
    ! array_contains "${profile}" "${PROFILES[@]}"; then
    die "profile $(shell_quote "${profile}") cannot be found"
  fi
}

show_general_help() {
  echo "Usage: ${SCRIPT_NAME} [options]"
  echo "       ${SCRIPT_NAME} -l | --list-profiles"
  echo "       ${SCRIPT_NAME} --help[=TOPIC]"
  echo
  echo "Options:"
  print_opt "-h, --help[=TOPIC]" \
    "show general help or help for a specific topic"
  print_opt "-p, --profile PROFILE" "select profile"
  print_opt "-v, --verbose" "increase verbosity"
  print_opt "-P, --prune-symlinks" \
    "remove dangling symlinks in home directory"
  print_opt "-l, --list-profiles" \
    "list available profiles (cannot be combined with other options)"
  echo
  echo "Topics:"
  print_opt "profile" "explanation of profile structure and usage"
  echo
  echo "Profile:"
  echo "  Directory containing dotfiles plus optional parent and hooks/."
  echo "  Used by the installer to group and deploy related configurations."
}

show_help_topic() {
  local topic="$1"
  case "${topic}" in
  profile)
    cat <<EOF
A profile is a directory under 'profiles/' that groups dotfiles to be
installed together using GNU Stow.

Contents:
  dotfiles/        files or directories to deploy (e.g. .config)
  parent           optional text file with parent profile name
  hooks/pre/       scripts run before installation
  hooks/post/      scripts run after installation

Only executable files inside hooks are executed.

Profiles may inherit from a parent. The installer builds the dependency
tree automatically and installs profiles in the correct order.

Use .stow-local-ignore to prevent linking internal files such as hooks/
and parent.
EOF
    ;;
  *) die "unknown help topic: ${topic}" ;;
  esac
}

run_pre_hooks() {
  local -r target_profile="$1"
  for hook in "${PROFILES_DIR}/${target_profile}"/hooks/pre/*; do
    if [[ -f "${hook}" && -x "${hook}" ]]; then
      echo "Running pre-install hook ${hook##*/}"
      "${hook}"
    fi
  done
}

run_post_hooks() {
  local -r target_profile="$1"
  for hook in "${PROFILES_DIR}/${target_profile}"/hooks/post/*; do
    if [[ -f "${hook}" && -x "${hook}" ]]; then
      echo "Running post-install hook ${hook##*/}"
      "${hook}"
    fi
  done
}

prune_symlinks() {
  echo -n "Removing dangling symlinks in home directory... "

  pushd "${HOME}" >/dev/null || exit 1
  local common_files
  local -r target_profile="$1"
  mapfile -t common_files < <(comm -12 <(find "${HOME}" -type l \
    -printf '%P\n' 2>/dev/null | sort) \
    <(find "${PROFILES_DIR}/${target_profile}" -type f -printf '%P\n' | sort))
  local target_file
  for target_file in "${common_files[@]}"; do
    local -a rm_args=("--force")
    [[ ${verbose} ]] && rm_args+=("--verbose")
    rm "${rm_args[@]}" -- "${target_file}"
  done
  popd >/dev/null || exit 1

  echo "OK"
}

stow_profile() {
  local -r target_profile="$1"
  if stow "${STOW_ARGS[@]}" "${target_profile}" 2>&1; then
    echo "Profile ${target_profile} has been stowed"
  else
    echo "Failed to create symlinks pointing to dotfiles" \
      "in profile ${target_profile}"
  fi
}

fetch_parents() {
  local -r target_profile="$1"
  if [[ -s "${PROFILES_DIR}/${target_profile}/parent" ]]; then
    local parent
    parent="$(cat "${PROFILES_DIR}/${target_profile}/parent")"
    if [[ -s "${PROFILES_DIR}/${parent}/parent" ]]; then
      fetch_parents "${parent}"
    fi
    echo "${parent}"
  fi
}

build_deptree() {
  local -r target_profile="$1"
  fetch_parents "${target_profile}"
  echo "${target_profile}"
}

install_dotfiles() {
  local target_profile
  for target_profile in $(build_deptree "${profile}"); do
    run_pre_hooks "${target_profile}"
    [[ -n "${prune_symlinks}" ]] && prune_symlinks "${target_profile}"
    stow_profile "${target_profile}"
    run_post_hooks "${target_profile}"
  done
}

main() {
  check_deps
  parse_args "$@"
  require_profiles_dir
  (($# == 0)) && show_general_help && exit 1
  validate_args
  [[ -n "${list_profiles}" ]] && echo "${PROFILES[@]}" && exit 0
  install_dotfiles
}

main "$@"