#!/usr/bin/env bash
# Apply a Pi-hole configuration directory to a destination Pi-hole instance.
#
# Usage: apply-config.sh <source-dir> <dest-host>
#   source-dir   Local directory containing config files (as written by pull-config.sh)
#   dest-host    SSH-reachable hostname or IP of the destination Pi-hole
#
# Example:
#   ./apply-config.sh ./config root@pihole-new
#   ./apply-config.sh /backup/pihole-20260723 root@192.168.2.101
#
# The destination Pi-hole must already have Pi-hole v6 installed.
# pihole-FTL is restarted at the end to apply the new config.

set -euo pipefail

usage() {
  echo "Usage: $(basename "$0") <source-dir> <dest-host>" >&2
  echo "  source-dir   Local directory with config files (from pull-config.sh)" >&2
  echo "  dest-host    SSH target for the destination Pi-hole (e.g. root@pihole)" >&2
  exit 1
}

[[ $# -eq 2 ]] || usage

SOURCE="$1"
DEST="$2"

[[ -d "${SOURCE}" ]] || { echo "Error: source directory '${SOURCE}' not found" >&2; exit 1; }
[[ -f "${SOURCE}/pihole.toml" ]] || { echo "Error: '${SOURCE}/pihole.toml' not found — is this a valid config dir?" >&2; exit 1; }

echo "Applying Pi-hole config from ${SOURCE} → ${DEST}"

# ── Verify destination is running Pi-hole ──────────────────────────────────────
ssh "${DEST}" "command -v pihole-FTL >/dev/null 2>&1 || { echo 'pihole-FTL not found on destination'; exit 1; }"

# ── pihole.toml ────────────────────────────────────────────────────────────────
echo "  pihole.toml"
ssh "${DEST}" "cp /etc/pihole/pihole.toml /etc/pihole/pihole.toml.pre-apply 2>/dev/null || true"
scp "${SOURCE}/pihole.toml" "${DEST}:/etc/pihole/pihole.toml"
ssh "${DEST}" "chown pihole:pihole /etc/pihole/pihole.toml; chmod 640 /etc/pihole/pihole.toml"

# ── custom dnsmasq drop-ins ────────────────────────────────────────────────────
if [[ -d "${SOURCE}/dnsmasq.d" ]] && [[ -n "$(ls "${SOURCE}/dnsmasq.d/"*.conf 2>/dev/null)" ]]; then
  echo "  dnsmasq.d/ (custom drop-ins)"
  for f in "${SOURCE}/dnsmasq.d/"*.conf; do
    name="$(basename "$f")"
    echo "    ${name}"
    scp "${f}" "${DEST}:/etc/dnsmasq.d/${name}"
  done
fi

# ── Restart pihole-FTL ─────────────────────────────────────────────────────────
echo "  Restarting pihole-FTL"
ssh "${DEST}" "systemctl restart pihole-FTL"
sleep 2
ssh "${DEST}" "systemctl is-active pihole-FTL"

echo "Done. Config applied to ${DEST}."
echo "Note: gravity (blocklists) is not transferred — run 'pihole updateGravity' on ${DEST} to rebuild."