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

APP_DIR="${APP_DIR:-/opt/proxpanel}"
BACKUP_ROOT="${BACKUP_ROOT:-/opt/proxpanel-backups}"
GREEN_DIR="${GREEN_DIR:-/opt/proxpanel-green}"
GREEN_PROJECT="${GREEN_PROJECT:-proxpanel_green}"
GREEN_FRONTEND_PORT="${GREEN_FRONTEND_PORT:-18081}"
GREEN_BACKEND_PORT="${GREEN_BACKEND_PORT:-18080}"
NGINX_SITE="${NGINX_SITE:-/etc/nginx/sites-available/proxpanel.conf}"

usage() {
  cat <<'EOF'
Usage:
  sudo bash infra/deploy/rollback-blue-green.sh --backup-dir /opt/proxpanel-backups/<timestamp> [--cutover]

Behavior:
  1) Stages backup app/env into /opt/proxpanel-green
  2) Boots green stack on ports 18081/18080
  3) Restores DB dump from selected backup into green postgres
  4) Verifies green API health
  5) If --cutover is provided, switches Nginx upstream to green frontend port

Notes:
  - This script requires backup directory format created by deployment steps:
      <backup-dir>/app/
      <backup-dir>/env.production.bak (or .env.production.bak)
      <backup-dir>/db_pre_*.sql
EOF
}

log() {
  printf '\n[%s] %s\n' "$(date -u +'%Y-%m-%d %H:%M:%S UTC')" "$*"
}

die() {
  printf '\n[ERROR] %s\n' "$*" >&2
  exit 1
}

require_root() {
  [[ "${EUID:-$(id -u)}" -eq 0 ]] || die "Run as root (or with sudo)."
}

parse_args() {
  BACKUP_DIR=""
  CUTOVER="false"
  while [[ $# -gt 0 ]]; do
    case "$1" in
      --backup-dir)
        BACKUP_DIR="${2:-}"
        shift 2
        ;;
      --cutover)
        CUTOVER="true"
        shift
        ;;
      -h|--help)
        usage
        exit 0
        ;;
      *)
        die "Unknown argument: $1"
        ;;
    esac
  done

  [[ -n "$BACKUP_DIR" ]] || die "--backup-dir is required"
}

pick_db_dump() {
  find "$BACKUP_DIR" -maxdepth 1 -type f -name 'db_pre*.sql' | sort | tail -n 1
}

pick_env_backup() {
  if [[ -f "$BACKUP_DIR/env.production.bak" ]]; then
    printf '%s' "$BACKUP_DIR/env.production.bak"
    return
  fi
  if [[ -f "$BACKUP_DIR/.env.production.bak" ]]; then
    printf '%s' "$BACKUP_DIR/.env.production.bak"
    return
  fi
  printf ''
}

wait_for_green_health() {
  local i
  for i in $(seq 1 90); do
    if curl -fsS "http://127.0.0.1:${GREEN_BACKEND_PORT}/api/health" >/dev/null 2>&1; then
      return
    fi
    sleep 2
  done
  die "Green backend health check failed."
}

main() {
  require_root
  parse_args "$@"

  [[ -d "$BACKUP_DIR/app" ]] || die "Missing backup app directory: $BACKUP_DIR/app"
  local env_backup
  env_backup="$(pick_env_backup)"
  [[ -n "$env_backup" ]] || die "Missing env backup in $BACKUP_DIR (.env.production.bak or env.production.bak)"
  local db_dump
  db_dump="$(pick_db_dump)"
  [[ -n "$db_dump" ]] || die "Missing DB dump in backup dir: $BACKUP_DIR"

  log "Preparing green staging directory at $GREEN_DIR"
  rm -rf "$GREEN_DIR"
  mkdir -p "$GREEN_DIR"
  rsync -a "$BACKUP_DIR/app/" "$GREEN_DIR/"
  cp "$env_backup" "$GREEN_DIR/.env.production"

  # Override ports for green stack and keep CORS aligned to production hostname.
  if grep -q '^FRONTEND_PORT=' "$GREEN_DIR/.env.production"; then
    sed -i "s/^FRONTEND_PORT=.*/FRONTEND_PORT=${GREEN_FRONTEND_PORT}/" "$GREEN_DIR/.env.production"
  else
    echo "FRONTEND_PORT=${GREEN_FRONTEND_PORT}" >> "$GREEN_DIR/.env.production"
  fi
  if grep -q '^BACKEND_PORT=' "$GREEN_DIR/.env.production"; then
    sed -i "s/^BACKEND_PORT=.*/BACKEND_PORT=${GREEN_BACKEND_PORT}/" "$GREEN_DIR/.env.production"
  else
    echo "BACKEND_PORT=${GREEN_BACKEND_PORT}" >> "$GREEN_DIR/.env.production"
  fi

  # Remove fixed container_name lines for project-isolated blue/green operation.
  local compose_green
  compose_green="$GREEN_DIR/infra/deploy/docker-compose.green.yml"
  awk '!/^[[:space:]]*container_name:/' "$GREEN_DIR/infra/deploy/docker-compose.production.yml" > "$compose_green"

  log "Stopping previous green project (if any)"
  (
    cd "$GREEN_DIR"
    docker compose -p "$GREEN_PROJECT" --env-file .env.production -f "$compose_green" down -v || true
  )

  log "Starting green stack on ${GREEN_FRONTEND_PORT}/${GREEN_BACKEND_PORT}"
  (
    cd "$GREEN_DIR"
    docker compose -p "$GREEN_PROJECT" --env-file .env.production -f "$compose_green" up -d --build
  )

  log "Restoring backup DB into green postgres"
  local green_postgres_id green_pg_user green_pg_db
  green_postgres_id="$(
    cd "$GREEN_DIR" && docker compose -p "$GREEN_PROJECT" --env-file .env.production -f "$compose_green" ps -q postgres
  )"
  [[ -n "$green_postgres_id" ]] || die "Could not locate green postgres container."

  # shellcheck disable=SC1090
  source "$GREEN_DIR/.env.production"
  green_pg_user="${POSTGRES_USER:-proxpanel}"
  green_pg_db="${POSTGRES_DB:-proxpanel}"

  docker exec "$green_postgres_id" psql -U "$green_pg_user" -d "$green_pg_db" -v ON_ERROR_STOP=1 \
    -c 'DROP SCHEMA public CASCADE; CREATE SCHEMA public;'

  cat "$db_dump" | docker exec -i "$green_postgres_id" psql -U "$green_pg_user" -d "$green_pg_db" -v ON_ERROR_STOP=1 >/dev/null

  log "Validating green health"
  wait_for_green_health
  curl -fsS "http://127.0.0.1:${GREEN_BACKEND_PORT}/api/health" >/dev/null

  if [[ "$CUTOVER" == "true" ]]; then
    log "Cutting over Nginx upstream to green frontend port ${GREEN_FRONTEND_PORT}"
    [[ -f "$NGINX_SITE" ]] || die "Missing nginx site config: $NGINX_SITE"
    cp "$NGINX_SITE" "${NGINX_SITE}.pre-green.$(date -u +%Y%m%d-%H%M%S).bak"
    sed -i -E "s#proxy_pass http://127\\.0\\.0\\.1:[0-9]+;#proxy_pass http://127.0.0.1:${GREEN_FRONTEND_PORT};#g" "$NGINX_SITE"
    nginx -t
    systemctl reload nginx
    log "Nginx cutover complete."
  fi

  log "Blue/green rollback prep complete."
  printf '\nGreen frontend: http://127.0.0.1:%s\n' "$GREEN_FRONTEND_PORT"
  printf 'Green backend : http://127.0.0.1:%s/api/health\n' "$GREEN_BACKEND_PORT"
  if [[ "$CUTOVER" == "true" ]]; then
    printf 'Traffic switched to green.\n'
  else
    printf 'Traffic still on blue. Re-run with --cutover when ready.\n'
  fi
}

main "$@"