#!/usr/bin/env bash
#
# bootstrap.sh - standardize a fresh Debian/Ubuntu host.
#
# Usage:
#   ./bootstrap.sh                 # run default modules
#   ./bootstrap.sh --only nvim     # run a single module
#   ./bootstrap.sh --skip hardening
#   ./bootstrap.sh --list          # show modules
#   ./bootstrap.sh --hostname web01
#
set -Eeuo pipefail

# resolve repo dir even when invoked via symlink / different cwd
SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)"
# shellcheck source=lib/common.sh
. "${SCRIPT_DIR}/lib/common.sh"

trap 'err "failed at line $LINENO (exit $?)"' ERR

# ---- module registry --------------------------------------------------------
# order matters; "default" controls whether it runs without an explicit --only
MODULES=(base cli neovim motd shell hardening)
declare -A MOD_DEFAULT=(
  [base]=1 [cli]=1 [neovim]=1 [motd]=1 [shell]=1 [hardening]=0
)
declare -A MOD_DESC=(
  [base]="apt update/upgrade + essential packages (git, curl, tmux, ...)"
  [cli]="modern CLI quality-of-life tools (ripgrep, fd, bat, fzf, btop, ...)"
  [neovim]="neovim + standardized lua config"
  [motd]="dynamic welcome message / login banner"
  [shell]="shared aliases, sane bash defaults, tool symlinks"
  [hardening]="OPT-IN: unattended-upgrades, fail2ban, sshd defaults"
)

# ---- args -------------------------------------------------------------------
ONLY=""; SKIP=""; SET_HOSTNAME=""
usage() {
  cat <<EOF
${C_BOLD}linux-bootstrap${C_RESET}

  --only <m>        run only module <m> (repeatable, comma-ok)
  --skip <m>        skip module <m> (repeatable, comma-ok)
  --hostname <h>    set the system hostname
  --list            list modules and exit
  -h | --help       this help

Modules (default = runs unless --only given):
EOF
  for m in "${MODULES[@]}"; do
    local mark="  "; [[ ${MOD_DEFAULT[$m]} -eq 1 ]] && mark="${C_GRN}*${C_RESET} "
    printf '  %s%-10s %s\n' "$mark" "$m" "${MOD_DESC[$m]}"
  done
  echo
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --only)     ONLY="${ONLY}${ONLY:+,}$2"; shift 2 ;;
    --skip)     SKIP="${SKIP}${SKIP:+,}$2"; shift 2 ;;
    --hostname) SET_HOSTNAME="$2"; shift 2 ;;
    --list)     usage; exit 0 ;;
    -h|--help)  usage; exit 0 ;;
    *) die "unknown arg: $1 (try --help)" ;;
  esac
done

in_csv() { [[ ",$1," == *",$2,"* ]]; }

should_run() {
  local m="$1"
  in_csv "$SKIP" "$m" && return 1
  if [[ -n "$ONLY" ]]; then in_csv "$ONLY" "$m"; return; fi
  [[ ${MOD_DEFAULT[$m]} -eq 1 ]]
}

# =============================================================================
# MODULES
# =============================================================================

mod_base() {
  step "base packages"
  pkg_refresh
  if [[ -z "$ONLY" || "$ONLY" == *base* ]]; then
    log "apt-get upgrade (security + bugfixes)"
    $SUDO apt-get -y -qq upgrade || \
      warn "upgrade had non-fatal issues"
  fi
  # one shot install of the essentials
  pkg_install \
    ca-certificates curl wget git gnupg \
    tmux htop tree unzip zip rsync \
    build-essential \
    dnsutils mtr-tiny net-tools iproute2 \
    jq ncdu lsof
  ok "base packages installed"

  if [[ -n "$SET_HOSTNAME" ]]; then
    log "setting hostname -> ${SET_HOSTNAME}"
    $SUDO hostnamectl set-hostname "$SET_HOSTNAME" 2>/dev/null || \
      echo "$SET_HOSTNAME" | $SUDO tee /etc/hostname >/dev/null
    ok "hostname set"
  fi
}

mod_cli() {
  step "modern CLI tools"
  # these package names are stable on Debian bookworm+ / Ubuntu 22.04+
  pkg_install ripgrep fd-find bat fzf || warn "some CLI pkgs unavailable on this release"
  # btop fell back to htop if missing in old repos
  ensure_cmd btop btop || warn "btop not in repo (htop already installed)"
  ok "CLI tools installed (symlinks handled by 'shell' module)"
}

mod_neovim() {
  step "neovim + config"
  ensure_cmd nvim neovim
  ensure_cmd rsync rsync   # module is self-contained even with --only neovim

  # config goes to the *invoking* user's home, not root's, when run via sudo
  local target_user target_home
  target_user="${SUDO_USER:-$(id -un)}"
  target_home="$(getent passwd "$target_user" | cut -d: -f6)"
  [[ -d "$target_home" ]] || die "cannot resolve home for ${target_user}"

  local nvim_dst="${target_home}/.config/nvim"
  log "deploying nvim config -> ${nvim_dst}"
  install -d -m 0755 "${target_home}/.config"
  # mirror repo config; remove stale lua we own, keep user additions elsewhere
  rsync -a --delete "${SCRIPT_DIR}/config/nvim/" "${nvim_dst}/"
  # fix ownership if we wrote as root
  if [[ -n "${SUDO_USER:-}" ]]; then
    chown -R "${target_user}:$(id -gn "$target_user")" "${target_home}/.config/nvim"
  fi

  # make nvim the default editor system-wide where possible
  if have update-alternatives; then
    $SUDO update-alternatives --install /usr/bin/editor editor "$(command -v nvim)" 100 \
      >/dev/null 2>&1 || true
  fi
  ok "neovim configured for user ${target_user}"
}

mod_motd() {
  step "welcome message / motd"
  # disable distro default motd noise where safe
  if [[ -d /etc/update-motd.d ]]; then
    for f in /etc/update-motd.d/10-help-text /etc/update-motd.d/50-motd-news \
             /etc/update-motd.d/00-header; do
      if [[ -e "$f" ]]; then
        $SUDO chmod -x "$f" 2>/dev/null || true
      fi
    done
    if write_if_changed /etc/update-motd.d/01-bootstrap-banner 0755 \
        < "${SCRIPT_DIR}/config/motd/01-banner.sh"; then
      ok "dynamic motd installed"
    else
      log "motd already up to date"
    fi
  else
    # fallback: static /etc/motd
    "${SCRIPT_DIR}/config/motd/01-banner.sh" 2>/dev/null | $SUDO tee /etc/motd >/dev/null
    ok "static /etc/motd written"
  fi
}

mod_shell() {
  step "shell defaults + aliases"
  # Debian ships fd as 'fdfind' and bat as 'batcat'. add friendly symlinks.
  local bindir="/usr/local/bin"
  have fdfind && [[ ! -e "$bindir/fd" ]]  && $SUDO ln -s "$(command -v fdfind)" "$bindir/fd"   && ok "symlink fd"
  have batcat && [[ ! -e "$bindir/bat" ]] && $SUDO ln -s "$(command -v batcat)" "$bindir/bat" && ok "symlink bat"

  # drop a managed aliases file sourced from /etc/profile.d (system-wide)
  if write_if_changed /etc/profile.d/zz-bootstrap-aliases.sh 0644 <<'EOF'
# managed by linux-bootstrap - do not edit by hand
alias ll='ls -alh --color=auto'
alias la='ls -A --color=auto'
alias l='ls -CF --color=auto'
alias ..='cd ..'
alias ...='cd ../..'
alias grep='grep --color=auto'
alias df='df -h'
alias du='du -h'
alias ip='ip -color=auto'
command -v bat  >/dev/null 2>&1 && alias cat='bat --paging=never --style=plain'
command -v btop >/dev/null 2>&1 && alias top='btop'
export EDITOR=nvim
export VISUAL=nvim
alias vi='nvim'
alias vim='nvim'
EOF
  then ok "system-wide aliases installed"; else log "aliases already up to date"; fi
}

mod_hardening() {
  step "hardening (opt-in)"
  warn "hardening enabled - review before using on hosts you SSH into"

  # automatic security updates
  pkg_install unattended-upgrades apt-listchanges
  $SUDO dpkg-reconfigure -f noninteractive unattended-upgrades >/dev/null 2>&1 || true
  ok "unattended-upgrades enabled"

  # fail2ban with sane sshd defaults
  pkg_install fail2ban
  if write_if_changed /etc/fail2ban/jail.d/sshd-bootstrap.conf 0644 <<'EOF'
[sshd]
enabled  = true
backend  = systemd
maxretry = 4
bantime  = 1h
findtime = 10m
EOF
  then $SUDO systemctl restart fail2ban 2>/dev/null || true; fi
  ok "fail2ban configured for sshd"

  # NOTE: deliberately NOT touching PasswordAuthentication / PermitRootLogin /
  # firewall here. Locking yourself out of a remote box is too easy. Add those
  # as a separate, explicit step once key-based access is verified.
  log "sshd/firewall changes left to a deliberate manual step (see README)"
}

# =============================================================================
# RUN
# =============================================================================
main() {
  detect_sudo
  detect_distro
  case "$DISTRO_ID:$DISTRO_LIKE" in
    *debian*|*ubuntu*) : ;;  # supported
    *) [[ "$PKG_MGR" == "apt" ]] || warn "non-apt distro: best-effort only" ;;
  esac

  local ran=0
  for m in "${MODULES[@]}"; do
    if should_run "$m"; then
      "mod_${m}"
      ran=$((ran+1))
    fi
  done
  [[ $ran -gt 0 ]] || { warn "no modules ran (check --only/--skip)"; exit 0; }

  printf '\n%s== done: %d module(s) ==%s\n' "$C_BOLD" "$ran" "$C_RESET"
  ok "re-login or 'source /etc/profile' to pick up aliases"
}
main "$@"