#!/bin/sh
set -eu

BASE_DIR="/usr/local/hitme_plugins/global-autoresponders"
STATE_FILE="$BASE_DIR/config/backend-state.json"
PLUGIN_DIR="/usr/local/directadmin/plugins/global-autoresponder"
CUSTOM_DIR="/usr/local/directadmin/custombuild/custom/exim"
CUSTOM_CONF="$CUSTOM_DIR/exim.conf"
SOURCE_CONF="/usr/local/directadmin/custombuild/configure/exim/exim.conf"
ROUTER_SNIPPET="$PLUGIN_DIR/scripts/exim/global_autoresponder_router.conf"
TRANSPORT_SNIPPET="$PLUGIN_DIR/scripts/exim/global_autoresponder_transport.conf"
ROLLBACK_ACTIVE=0
ROLLBACK_CREATED=0
ROLLBACK_REBUILD=0
ROLLBACK_FILE=

usage() {
  echo "Usage: scripts/backend.sh da|exim" >&2
}

if [ "${1:-}" != "da" ] && [ "${1:-}" != "exim" ]; then
  usage
  exit 2
fi

mkdir -p "$BASE_DIR/config" "$BASE_DIR/data" "$BASE_DIR/state" "$BASE_DIR/logs"
chmod 700 "$BASE_DIR/config" "$BASE_DIR/logs"

write_state() {
  backend="$1"
  printf '{"active_backend":"%s","migration_status":"complete"}\n' "$backend" > "$STATE_FILE"
  chmod 600 "$STATE_FILE"
}

remove_marked_block() {
  marker="$1"
  file="$2"
  tmp="${file}.global-autoresponder.$$"
  awk -v marker="$marker" '
    $0 == "# BEGIN global-autoresponder " marker { skip=1; next }
    $0 == "# END global-autoresponder " marker { skip=0; next }
    skip != 1 { print }
  ' "$file" > "$tmp"
  mv "$tmp" "$file"
}

insert_after_section() {
  section="$1"
  snippet="$2"
  file="$3"
  tmp="${file}.global-autoresponder.$$"
  if ! awk -v section="$section" -v snippet="$snippet" '
    BEGIN {
      while ((getline line < snippet) > 0) {
        block = block line "\n"
      }
      close(snippet)
    }
    { print }
    $0 == section && inserted != 1 {
      printf "\n%s\n", block
      inserted = 1
    }
    END {
      if (inserted != 1) {
        exit 3
      }
    }
  ' "$file" > "$tmp"; then
    rm -f "$tmp"
    echo "Cannot install exim backend: section $section not found in custom exim.conf." >&2
    exit 1
  fi
  mv "$tmp" "$file"
}

backup_custom_conf() {
  mkdir -p "$CUSTOM_DIR"
  ROLLBACK_FILE="${CUSTOM_CONF}.global-autoresponder.backup.$$"
  if [ -f "$CUSTOM_CONF" ]; then
    cp "$CUSTOM_CONF" "$ROLLBACK_FILE"
    ROLLBACK_CREATED=0
  else
    : > "$ROLLBACK_FILE"
    ROLLBACK_CREATED=1
  fi
  ROLLBACK_ACTIVE=1
}

restore_custom_conf() {
  if [ "$ROLLBACK_ACTIVE" != "1" ]; then
    return
  fi
  set +e
  if [ "$ROLLBACK_CREATED" = "1" ]; then
    rm -f "$CUSTOM_CONF"
  else
    cp "$ROLLBACK_FILE" "$CUSTOM_CONF"
  fi
  rm -f "$ROLLBACK_FILE"
  if [ "$ROLLBACK_REBUILD" = "1" ]; then
    rebuild_and_reload_exim >/dev/null 2>&1
  fi
  ROLLBACK_ACTIVE=0
}

commit_custom_conf() {
  rm -f "$ROLLBACK_FILE"
  ROLLBACK_ACTIVE=0
  ROLLBACK_CREATED=0
  ROLLBACK_REBUILD=0
}

trap 'restore_custom_conf' EXIT
trap 'restore_custom_conf; exit 1' HUP INT TERM

validate_exim_conf() {
  if command -v exim >/dev/null 2>&1; then
    exim -C "$CUSTOM_CONF" -bV >/dev/null
  elif command -v exim4 >/dev/null 2>&1; then
    exim4 -C "$CUSTOM_CONF" -bV >/dev/null
  else
    echo "Cannot validate exim backend: exim binary not found." >&2
    exit 1
  fi
}

rebuild_and_reload_exim() {
  if command -v da >/dev/null 2>&1; then
    da build exim_conf
  elif [ -x /usr/local/directadmin/custombuild/build ]; then
    /usr/local/directadmin/custombuild/build exim_conf
  else
    echo "Cannot rebuild exim configuration: da/build command not found." >&2
    exit 1
  fi
  if command -v systemctl >/dev/null 2>&1; then
    systemctl reload exim 2>/dev/null || systemctl restart exim
  else
    service exim reload 2>/dev/null || service exim restart
  fi
}

if [ "$1" = "da" ]; then
  if [ -f "$CUSTOM_CONF" ]; then
    backup_custom_conf
    remove_marked_block "router" "$CUSTOM_CONF"
    remove_marked_block "transport" "$CUSTOM_CONF"
    if grep -Fq "global_autoresponder_" "$CUSTOM_CONF"; then
      echo "Cannot switch to da: plugin Exim markers were not removed cleanly." >&2
      exit 1
    fi
    validate_exim_conf
    ROLLBACK_REBUILD=1
    rebuild_and_reload_exim
    commit_custom_conf
  fi
  write_state "da"
  echo "Backend set to da"
  exit 0
fi

if [ ! -d "$(dirname "$SOURCE_CONF")" ]; then
  echo "Cannot enable exim backend: DirectAdmin CustomBuild exim source config not found." >&2
  exit 1
fi
if [ ! -f "$ROUTER_SNIPPET" ] || [ ! -f "$TRANSPORT_SNIPPET" ]; then
  echo "Cannot enable exim backend: plugin Exim snippets are missing." >&2
  exit 1
fi

backup_custom_conf
if [ ! -f "$CUSTOM_CONF" ]; then
  cp "$SOURCE_CONF" "$CUSTOM_CONF"
fi

remove_marked_block "router" "$CUSTOM_CONF"
remove_marked_block "transport" "$CUSTOM_CONF"
insert_after_section "begin routers" "$ROUTER_SNIPPET" "$CUSTOM_CONF"
insert_after_section "begin transports" "$TRANSPORT_SNIPPET" "$CUSTOM_CONF"
validate_exim_conf
ROLLBACK_REBUILD=1
rebuild_and_reload_exim
commit_custom_conf
write_state "exim"
echo "Backend set to exim"