#!/usr/bin/env bash
set -euo pipefail

DOTFILES_REPO="https://github.com/tylerkeyes/dotfiles.git"
DOTFILES_NVIM_PATH="shared/.config/nvim"

INSTALL_ROOT="${HOME}/.local/opt/nvim"
BIN_DIR="${HOME}/.local/bin"
CONFIG_DIR="${HOME}/.config"
NVIM_CONFIG_DIR="${CONFIG_DIR}/nvim"

log() {
  printf '[nvim-installer] %s\n' "$*"
}

fail() {
  printf '[nvim-installer] ERROR: %s\n' "$*" >&2
  exit 1
}

require_cmd() {
  local cmd="$1"
  command -v "${cmd}" >/dev/null 2>&1 || fail "Missing required command: ${cmd}"
}

detect_os() {
  case "$(uname -s)" in
    Darwin) echo "macos" ;;
    Linux) echo "linux" ;;
    *) fail "Unsupported OS. Only macOS and Linux are supported." ;;
  esac
}

detect_arch() {
  case "$(uname -m)" in
    x86_64|amd64) echo "x86_64" ;;
    arm64|aarch64) echo "arm64" ;;
    *) fail "Unsupported architecture: $(uname -m)" ;;
  esac
}

latest_nvim_tag() {
  local latest_url
  latest_url="$(curl -fsSL -o /dev/null -w '%{url_effective}' "https://github.com/neovim/neovim/releases/latest")"
  [[ -n "${latest_url}" ]] || fail "Failed to resolve latest Neovim release."
  echo "${latest_url##*/}"
}

asset_candidates() {
  local os="$1"
  local arch="$2"

  if [[ "${os}" == "macos" && "${arch}" == "x86_64" ]]; then
    echo "nvim-macos-x86_64.tar.gz nvim-macos.tar.gz"
    return
  fi

  if [[ "${os}" == "macos" && "${arch}" == "arm64" ]]; then
    echo "nvim-macos-arm64.tar.gz nvim-macos.tar.gz"
    return
  fi

  if [[ "${os}" == "linux" && "${arch}" == "x86_64" ]]; then
    echo "nvim-linux-x86_64.tar.gz nvim-linux64.tar.gz"
    return
  fi

  if [[ "${os}" == "linux" && "${arch}" == "arm64" ]]; then
    echo "nvim-linux-arm64.tar.gz"
    return
  fi

  fail "No download asset mapping found for ${os}/${arch}"
}

download_nvim_archive() {
  local tag="$1"
  local os="$2"
  local arch="$3"
  local out_file="$4"
  local candidates candidate url

  candidates="$(asset_candidates "${os}" "${arch}")"
  for candidate in ${candidates}; do
    url="https://github.com/neovim/neovim/releases/download/${tag}/${candidate}"
    log "Trying ${candidate}"
    if curl -fL "${url}" -o "${out_file}"; then
      log "Downloaded ${candidate}"
      return 0
    fi
  done

  fail "Could not download a Neovim release asset for ${os}/${arch} from tag ${tag}."
}

install_nvim() {
  local tag="$1"
  local archive="$2"
  local unpack_dir install_dir extracted_dir

  unpack_dir="$(mktemp -d)"

  tar -xzf "${archive}" -C "${unpack_dir}"
  extracted_dir="$(find "${unpack_dir}" -mindepth 1 -maxdepth 1 -type d | head -n1)"
  [[ -d "${extracted_dir}" ]] || fail "Unable to find extracted Neovim directory."

  install_dir="${INSTALL_ROOT}/${tag}"
  mkdir -p "${INSTALL_ROOT}" "${BIN_DIR}"
  rm -rf "${install_dir}"
  mv "${extracted_dir}" "${install_dir}"

  ln -sfn "${install_dir}" "${INSTALL_ROOT}/current"
  ln -sfn "${INSTALL_ROOT}/current/bin/nvim" "${BIN_DIR}/nvim"
  ln -sfn "${INSTALL_ROOT}/current/bin/nvim" "${BIN_DIR}/vim"
  ln -sfn "${INSTALL_ROOT}/current/bin/nvim" "${BIN_DIR}/vi"

  log "Installed Neovim ${tag} at ${install_dir}"
  rm -rf "${unpack_dir}"
}

install_config() {
  local tmp_root tmp_repo src timestamp backup_dir
  tmp_root="$(mktemp -d)"

  tmp_repo="${tmp_root}/dotfiles"
  git clone --depth=1 --filter=blob:none --sparse "${DOTFILES_REPO}" "${tmp_repo}" >/dev/null
  (
    cd "${tmp_repo}"
    git sparse-checkout set "${DOTFILES_NVIM_PATH}"
  )

  src="${tmp_repo}/${DOTFILES_NVIM_PATH}"
  [[ -d "${src}" ]] || fail "Expected Neovim config path not found in repo: ${DOTFILES_NVIM_PATH}"

  mkdir -p "${CONFIG_DIR}"
  if [[ -e "${NVIM_CONFIG_DIR}" ]]; then
    timestamp="$(date +%Y%m%d%H%M%S)"
    backup_dir="${NVIM_CONFIG_DIR}.backup.${timestamp}"
    mv "${NVIM_CONFIG_DIR}" "${backup_dir}"
    log "Backed up existing config to ${backup_dir}"
  fi

  cp -R "${src}" "${NVIM_CONFIG_DIR}"
  log "Installed Neovim config to ${NVIM_CONFIG_DIR}"
  rm -rf "${tmp_root}"
}

print_path_hint() {
  case ":${PATH}:" in
    *":${BIN_DIR}:"*) return 0 ;;
  esac

  log "${BIN_DIR} is not on your PATH."
  log "Add this line to your shell profile (~/.zshrc, ~/.bashrc, etc.):"
  printf 'export PATH="%s:$PATH"\n' "${BIN_DIR}"
}

main() {
  require_cmd curl
  require_cmd tar
  require_cmd git
  require_cmd uname
  require_cmd find

  local os arch tag tmp_archive
  os="$(detect_os)"
  arch="$(detect_arch)"
  tag="$(latest_nvim_tag)"
  tmp_archive="$(mktemp)"
  trap 'rm -f "${tmp_archive}"' EXIT

  log "Detected ${os}/${arch}"
  log "Latest Neovim release tag: ${tag}"

  download_nvim_archive "${tag}" "${os}" "${arch}" "${tmp_archive}"
  install_nvim "${tag}" "${tmp_archive}"
  install_config
  print_path_hint

  log "Done. Run 'nvim --version' to verify."
}

main "$@"