#!/bin/bash
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
cd "$SCRIPT_DIR"
# shellcheck source=/dev/null
[ -f "${SCRIPT_DIR}/env-postgresql" ]  && source "${SCRIPT_DIR}/env-postgresql"
[ -f "${SCRIPT_DIR}/_credentials.env" ] && source "${SCRIPT_DIR}/_credentials.env"

POSTGRESQL_NAMESPACE="${POSTGRESQL_NAMESPACE:-data}"
POSTGRESQL_IMAGE="${POSTGRESQL_IMAGE:-postgres:18-bookworm}"
POSTGRESQL_PORT="${POSTGRESQL_PORT:-5432}"
POSTGRESQL_DATA_DIR="${POSTGRESQL_DATA_DIR:-/var/lib/data/postgresql}"
POSTGRESQL_STORAGE_CLASS="${POSTGRESQL_STORAGE_CLASS:-nfs-shared}"
POSTGRESQL_STORAGE_SIZE="${POSTGRESQL_STORAGE_SIZE:-10Gi}"

CMD_TSK="${CMD_TSK:-${1:-install}}"

_resolve_kubeconfig() {
  if [ -n "${KUBECONFIG:-}" ] && [ -f "$KUBECONFIG" ]; then
    return
  fi
  for candidate in \
    /var/lib/k0s/pki/admin.conf \
    /etc/kubernetes/admin.conf \
    /root/.kube/config; do
    if [ -f "$candidate" ]; then
      export KUBECONFIG="$candidate"
      return
    fi
  done
  if command -v k0s >/dev/null 2>&1; then
    local tmp
    tmp="$(mktemp)"
    k0s kubeconfig admin > "$tmp" 2>/dev/null && export KUBECONFIG="$tmp" && return
    rm -f "$tmp"
  fi
  echo "ERROR: kubeconfig not found — set KUBECONFIG explicitly" >&2; exit 1
}

_kubectl() {
  if command -v kubectl >/dev/null 2>&1; then
    command kubectl "$@"
  elif command -v k0s >/dev/null 2>&1; then
    k0s kubectl "$@"
  else
    echo "ERROR: no kubectl or k0s binary found" >&2; exit 127
  fi
}

_require_env() {
  local var="$1"
  if [ -z "${!var:-}" ]; then
    echo "ERROR: required variable $var is not set" >&2
    exit 1
  fi
}

_namespace_exists() {
  _kubectl get namespace "$POSTGRESQL_NAMESPACE" >/dev/null 2>&1
}

_pod_name() {
  _kubectl get pod \
    --namespace "$POSTGRESQL_NAMESPACE" \
    --selector "app.kubernetes.io/name=postgresql" \
    -o jsonpath='{.items[0].metadata.name}' 2>/dev/null
}

_wait_for_pod() {
  local timeout="${1:-180}"
  _kubectl wait pod \
    --namespace "$POSTGRESQL_NAMESPACE" \
    --selector "app.kubernetes.io/name=postgresql" \
    --for=condition=Ready \
    --timeout="${timeout}s"
}

_do_install() {
  _require_env POSTGRES_PASSWORD

  if ! _namespace_exists; then
    _kubectl create namespace "$POSTGRESQL_NAMESPACE"
  fi

  _kubectl create secret generic postgresql-credentials \
    --namespace "$POSTGRESQL_NAMESPACE" \
    --from-literal=POSTGRES_PASSWORD="$POSTGRES_PASSWORD" \
    --dry-run=client -o yaml | _kubectl apply -f -

  for manifest in storageclass.yaml namespace.yaml pvc.yaml statefulset.yaml service.yaml; do
    local path="$SCRIPT_DIR/manifests/${manifest}"
    [ -f "$path" ] && _kubectl apply -f "$path"
  done

  echo "Waiting for PostgreSQL pod to be ready..."
  _wait_for_pod 180

  local post_install="$SCRIPT_DIR/manifests/post-install.sh"
  if [ -f "$post_install" ]; then
    bash "$post_install"
  fi

  echo "PostgreSQL installed in namespace $POSTGRESQL_NAMESPACE"
}

_do_update() {
  _kubectl rollout restart statefulset/postgresql --namespace "$POSTGRESQL_NAMESPACE"
  echo "Waiting for PostgreSQL to restart..."
  _wait_for_pod 120
  echo "PostgreSQL updated"
}

_do_delete() {
  if _namespace_exists; then
    _kubectl delete namespace "$POSTGRESQL_NAMESPACE" --timeout=60s
    echo "Namespace $POSTGRESQL_NAMESPACE deleted"
  else
    echo "Namespace $POSTGRESQL_NAMESPACE does not exist, nothing to delete"
  fi
}

_do_backup() {
  _require_env BACKUP_DIR
  local pod timestamp backup_file
  pod=$(_pod_name)
  timestamp=$(date +%Y%m%d_%H%M%S)
  backup_file="${BACKUP_DIR}/postgresql_${timestamp}.sql.gz"
  mkdir -p "$BACKUP_DIR"
  _kubectl exec --namespace "$POSTGRESQL_NAMESPACE" "$pod" -- \
    pg_dumpall -U postgres | gzip > "$backup_file"
  echo "Backup written to $backup_file"
}

_do_restore() {
  _require_env BACKUP_FILE
  local pod
  pod=$(_pod_name)
  if [[ "$BACKUP_FILE" == *.gz ]]; then
    gunzip -c "$BACKUP_FILE" | _kubectl exec --stdin --namespace "$POSTGRESQL_NAMESPACE" "$pod" -- \
      psql -U postgres
  else
    _kubectl exec --stdin --namespace "$POSTGRESQL_NAMESPACE" "$pod" -- \
      psql -U postgres < "$BACKUP_FILE"
  fi
  echo "Restore completed from $BACKUP_FILE"
}

_do_health() {
  local pod
  pod=$(_pod_name 2>/dev/null || true)
  if [ -z "$pod" ]; then
    echo "UNHEALTHY: no postgresql pod found in namespace $POSTGRESQL_NAMESPACE" >&2
    exit 1
  fi
  if _kubectl exec --namespace "$POSTGRESQL_NAMESPACE" "$pod" -- psql -U postgres -c "SELECT 1" >/dev/null 2>&1; then
    echo "HEALTHY: postgresql is accepting queries"
  else
    echo "UNHEALTHY: postgresql did not respond to SELECT 1" >&2
    exit 1
  fi
}

_do_config() {
  local pod
  pod=$(_pod_name)
  _kubectl exec --namespace "$POSTGRESQL_NAMESPACE" "$pod" -- \
    psql -U postgres -c "SELECT name, setting, unit FROM pg_settings WHERE name IN ('max_connections','shared_buffers','work_mem','effective_cache_size') ORDER BY name;"
}

_resolve_kubeconfig

case "$CMD_TSK" in
  install|reinstall) _do_install ;;
  update)  _do_update  ;;
  delete)  _do_delete  ;;
  backup)  _do_backup  ;;
  restore) _do_restore ;;
  health)  _do_health  ;;
  config)  _do_config  ;;
  *)
    echo "ERROR: unknown CMD_TSK='$CMD_TSK'. Valid: install|reinstall|update|delete|backup|restore|health|config" >&2
    exit 1
    ;;
esac