#!/bin/bash

# Space-separated list of containers to stop before backup.
# Prefix with context to target a specific Docker context (e.g. "rootless:app-db default:app-web").
# Uses the $GLOBAL_CONTEXT specified below if no context is provided.
CONTAINER_NAMES="${CONTAINER_NAMES}"

# Space-separated list of volumes to backup.
# Prefix with context to target a specific Docker context (e.g. "rootless:app-db_data default:app-uploads").
# Uses the $GLOBAL_CONTEXT specified below if no context is provided.
VOLUME_NAMES="${VOLUME_NAMES}"

# Default Docker context to use when entries don't specify one.
GLOBAL_CONTEXT="${DOCKER_CONTEXT}"

# Directory on the host where backup archives are stored.
BACKUP_DIR="${BACKUP_DIR:-/data/backups}"

# Set to "true" to preview actions without executing them.
DRY_RUN="${DRY_RUN:-false}"

IFS=' ' read -r -a container_entries <<< "$CONTAINER_NAMES"
IFS=' ' read -r -a volume_entries <<< "$VOLUME_NAMES"

stopped=()

if [ "$DRY_RUN" = "true" ]; then
  echo "=== DRY RUN MODE - No changes will be made ==="
  echo ""
fi

parse_entry() {
  local entry="$1"
  if [[ "$entry" == *":"* ]]; then
    local context="${entry%%:*}"
    local name="${entry#*:}"
    echo "$context $name"
  else
    local context="${GLOBAL_CONTEXT:-default}"
    local name="$entry"
    echo "$context $name"
  fi
}

ensure_context() {
  local ctx="$1"
  if [ "$DRY_RUN" = "true" ]; then
    echo "  [dry-run] Would switch to context '$ctx'"
    return
  fi
  if [ "$ctx" = "default" ]; then
    docker context use default >/dev/null 2>&1
    return
  fi
  if docker context ls --format '{{.Name}}' | grep -q "^${ctx}$"; then
    docker context use "$ctx" >/dev/null 2>&1
  else
    echo "! Creating Docker Context '$ctx' !"
    docker context create "$ctx" \
      --docker host="unix:///var/run/docker_${ctx}.sock"
    docker context use "$ctx" >/dev/null 2>&1
  fi
}

restart_containers() {
  local -n restarts_ref=$1
  if [ ${#restarts_ref[@]} -eq 0 ]; then
    return
  fi
  echo ""
  echo "Re-starting containers..."
  for entry in "${restarts_ref[@]}"; do
    read -r ctx name <<< "$(parse_entry "$entry")"
    ensure_context "$ctx"
    if [ "$DRY_RUN" = "true" ]; then
      echo "  [dry-run] Would start $name (context: $ctx)"
    else
      echo "  Starting $name (context: $ctx)"
      docker start "$name"
    fi
  done
}

current_context=""
echo "Stopping containers:"
for entry in "${container_entries[@]}"; do
  [ -z "$entry" ] && continue
  read -r ctx name <<< "$(parse_entry "$entry")"
  if [ "$ctx" != "$current_context" ]; then
    ensure_context "$ctx"
    current_context="$ctx"
  fi
  if [ "$DRY_RUN" = "true" ]; then
    echo "  [dry-run] Would stop $name"
    stopped+=("$entry")
  elif docker ps --format '{{.Names}}' | grep -q "^${name}$"; then
    echo "  Stopping $name..."
    docker stop -t 30 "$name"
    exit_code=$?
    if [[ ${exit_code} -ne 0 ]]; then
      echo "  ⚠ Failed to stop $name"
      restart_containers stopped
      exit 1
    else
      stopped+=("$entry")
      echo "  ✓ $name stopped"
    fi
  else
    echo "  ⚠ $name not running, skipping"
  fi
done

echo ""
echo "Preparing volumes for export..."
for entry in "${volume_entries[@]}"; do
  [ -z "$entry" ] && continue
  read -r ctx name <<< "$(parse_entry "$entry")"
  if [ "$ctx" != "$current_context" ]; then
    ensure_context "$ctx"
    current_context="$ctx"
  fi

  archive_name="${name}.tar.gz"
  if [ "$DRY_RUN" = "true" ]; then
    echo "  [dry-run] Would backup $name to ${BACKUP_DIR}/${archive_name}"
  elif docker volume ls --format "{{.Name}}" | grep -q "^${name}$"; then
    echo "  Backing up $name to ${BACKUP_DIR}/${archive_name}..."
    docker run --rm \
      -v "${name}":/source:ro \
      -v "${BACKUP_DIR}":/backup \
      alpine:3 tar czf "/backup/${archive_name}" -C /source .
    echo "  ✓ $name exported"
  else
    echo "  ⚠ Volume $name not found, skipping"
  fi
done

restart_containers stopped
echo ""
echo "Backup complete."