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

# Migrate S3 buckets from Hetzner Object Storage to Backblaze B2 via rclone.
#
# Prerequisites:
#   1. Install rclone: https://rclone.org/install/
#   2. Configure two rclone remotes:
#        rclone config create hetzner s3 \
#          provider=Other \
#          env_auth=false \
#          access_key_id=YOUR_HETZNER_KEY \
#          secret_access_key=YOUR_HETZNER_SECRET \
#          endpoint=fsn1.your-objectstorage.com   # adjust region
#
#        rclone config create backblaze s3 \
#          provider=Other \
#          env_auth=false \
#          access_key_id=YOUR_B2_KEY \
#          secret_access_key=YOUR_B2_APP_KEY \
#          endpoint=s3.us-west-004.backblazeb2.com  # adjust region
#
# Usage:
#   ./migrate-s3-hetzner-to-backblaze.sh <src:dst> [src:dst] ...
#   ./migrate-s3-hetzner-to-backblaze.sh hetzner-bucket:backblaze-bucket

HETZNER_REMOTE="${HETZNER_REMOTE:-hetzner}"
BACKBLAZE_REMOTE="${BACKBLAZE_REMOTE:-backblaze}"
RCLONE_FLAGS="${RCLONE_FLAGS:---transfers=64 --checkers=64 --fast-list}"

if [[ $# -eq 0 ]]; then
  echo "Usage: $0 <src-bucket:dst-bucket> [src-bucket:dst-bucket...]"
  echo ""
  echo "  Each argument is a source:destination bucket pair separated by a colon."
  echo ""
  echo "Environment variables:"
  echo "  HETZNER_REMOTE   rclone remote name for Hetzner (default: hetzner)"
  echo "  BACKBLAZE_REMOTE rclone remote name for Backblaze (default: backblaze)"
  echo "  RCLONE_FLAGS     extra rclone flags (default: --transfers=16 --checkers=16 --fast-list)"
  echo "  DRY_RUN=1        show what would be copied without copying"
  exit 1
fi

for cmd in rclone; do
  if ! command -v "$cmd" &>/dev/null; then
    echo "Error: $cmd is not installed." >&2
    exit 1
  fi
done

# Verify remotes exist
for remote in "$HETZNER_REMOTE" "$BACKBLAZE_REMOTE"; do
  if ! rclone listremotes | grep -q "^${remote}:$"; then
    echo "Error: rclone remote '${remote}' not found. Run 'rclone config' to set it up." >&2
    exit 1
  fi
done

DRY_RUN_FLAG=""
if [[ "${DRY_RUN:-0}" == "1" ]]; then
  DRY_RUN_FLAG="--dry-run"
  echo "=== DRY RUN MODE ==="
fi

for pair in "$@"; do
  if [[ "$pair" != *:* ]]; then
    echo "Error: '$pair' is not a valid src:dst pair. Use format 'hetzner-bucket:backblaze-bucket'." >&2
    exit 1
  fi

  src_bucket="${pair%%:*}"
  dst_bucket="${pair#*:}"
  src="${HETZNER_REMOTE}:${src_bucket}"
  dst="${BACKBLAZE_REMOTE}:${dst_bucket}"

  echo ""
  echo "--- Migrating: ${src} -> ${dst} ---"

  # shellcheck disable=SC2086
  rclone sync \
    ${RCLONE_FLAGS} \
    ${DRY_RUN_FLAG} \
    --progress \
    "$src" "$dst"

  echo "--- Done: ${src_bucket} -> ${dst_bucket} ---"
done

echo ""
echo "Migration complete."