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

MODE="${1:-}"
ARCHIVE_PATH="${2:-}"
COUCH_HOME="${COUCH_HOME:-/home/couch}"
STAMP="$(date +%Y%m%d-%H%M%S)"

usage() {
  cat <<'EOF'
Usage:
  ./scripts/backup_restore.sh backup [archive.tar.gz]
  ./scripts/backup_restore.sh restore <archive.tar.gz>
EOF
}

if [[ -z "${MODE}" ]]; then
  usage >&2
  exit 1
fi

build_backup_manifest() {
  python3 - <<'PY' "${COUCH_HOME}"
import os
import sys
from pathlib import Path

couch_home = Path(sys.argv[1])
roots = [
    Path(".config/couchd/runtime.json"),
    Path(".config/dolphin-emu"),
    Path(".config/Slippi"),
    Path(".local/share/dolphin-emu"),
    Path("Slippi"),
]
excluded_dirs = tuple(
    item.lower()
    for item in (
        ".config/Slippi Launcher",
        ".local/share/accounts",
        ".local/share/sessions",
        "Slippi/Replay",
        "Slippi/Replays",
    )
)
excluded_suffixes = (".slp", ".iso", ".gcm", ".wbfs", ".nkit.iso")

for root in roots:
    source = couch_home / root
    if not source.exists():
        continue
    if source.is_file():
        print(str(root), end="\0")
        continue
    for current_root, dir_names, file_names in os.walk(source):
        rel_root = Path(current_root).relative_to(couch_home)
        dir_names[:] = [
            name
            for name in dir_names
            if str(rel_root / name).lower() not in excluded_dirs
        ]
        for file_name in file_names:
            rel_path = rel_root / file_name
            rel_lower = str(rel_path).lower()
            if any(rel_lower == item or rel_lower.startswith(f"{item}/") for item in excluded_dirs):
                continue
            if rel_lower.endswith(excluded_suffixes):
                continue
            print(str(rel_path), end="\0")
PY
}

validate_restore_archive() {
  python3 - <<'PY' "${ARCHIVE_PATH}" "${COUCH_HOME}"
import sys
import tarfile
from pathlib import Path

archive_path = Path(sys.argv[1])
couch_home = Path(sys.argv[2]).resolve(strict=False)

with tarfile.open(archive_path, "r:*") as archive:
    for member in archive.getmembers():
        member_path = Path(member.name)
        if member_path.is_absolute():
            raise SystemExit(f"unsafe archive entry: {member.name}")
        if any(part == ".." for part in member_path.parts):
            raise SystemExit(f"unsafe archive entry: {member.name}")
        if member.isdev():
            raise SystemExit(f"unsafe archive entry: {member.name}")
        target_path = (couch_home / member_path).resolve(strict=False)
        if couch_home != target_path and couch_home not in target_path.parents:
            raise SystemExit(f"unsafe archive entry: {member.name}")
        if member.issym() or member.islnk():
            link_target = Path(member.linkname)
            if link_target.is_absolute():
                raise SystemExit(f"unsafe archive entry: {member.name}")
            resolved_link = (target_path.parent / link_target).resolve(strict=False)
            if couch_home != resolved_link and couch_home not in resolved_link.parents:
                raise SystemExit(f"unsafe archive entry: {member.name}")
PY
}

case "${MODE}" in
  backup)
    ARCHIVE_PATH="${ARCHIVE_PATH:-${COUCH_HOME}/Slippi/couchos-backup-${STAMP}.tar.gz}"
    umask 077
    mapfile -d '' manifest < <(build_backup_manifest)
    if [[ "${#manifest[@]}" -eq 0 ]]; then
      printf 'no backup sources found under %s\n' "${COUCH_HOME}" >&2
      exit 1
    fi
    tar -C "${COUCH_HOME}" -czf "${ARCHIVE_PATH}" \
      --exclude='.config/couchd/token' \
      "${manifest[@]}"
    chmod 0600 "${ARCHIVE_PATH}"
    printf 'backup written to %s\n' "${ARCHIVE_PATH}"
    ;;
  restore)
    if [[ -z "${ARCHIVE_PATH}" || ! -f "${ARCHIVE_PATH}" ]]; then
      printf 'restore archive is required\n' >&2
      exit 1
    fi
    if ! validation_error="$(validate_restore_archive 2>&1)"; then
      printf '%s\n' "${validation_error}" >&2
      exit 1
    fi
    tar -C "${COUCH_HOME}" -xzf "${ARCHIVE_PATH}"
    printf 'restored from %s\n' "${ARCHIVE_PATH}"
    ;;
  *)
    usage >&2
    exit 1
    ;;
esac