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

CONFIG_FILE="${RECEIVER_CONFIG_FILE:-/etc/hyb-oa-offhost-backup.conf}"
if [[ -f "$CONFIG_FILE" ]]; then
  # Root-owned installer output with path-only assignments.
  # shellcheck disable=SC1090
  source "$CONFIG_FILE"
fi

BACKUP_INBOX_DIR="${BACKUP_INBOX_DIR:-}"
BACKUP_ARCHIVE_DIR="${BACKUP_ARCHIVE_DIR:-}"
BACKUP_WEEKLY_DIR="${BACKUP_WEEKLY_DIR:-}"
RRSYNC_BIN="${RRSYNC_BIN:-/usr/bin/rrsync}"
PYTHON_BIN="${PYTHON_BIN:-python3}"
DAILY_KEEP="${DAILY_KEEP:-7}"
WEEKLY_KEEP="${WEEKLY_KEEP:-4}"

fail() {
  echo "[offhost-receiver][ERROR] $1" >&2
  exit 1
}

validate_absolute_path() {
  local name="$1"
  local value="$2"
  if [[ -z "$value" || "$value" != /* || ! "$value" =~ ^/[A-Za-z0-9._/-]+$ ]]; then
    fail "$name must be an explicit safe absolute path"
  fi
  if [[ "$value" == "/" || "$value" == */ || "$value" == *"//"* \
    || "/$value/" == *"/../"* || "/$value/" == *"/./"* ]]; then
    fail "$name contains an unsafe path segment"
  fi
}

validate_layout() {
  local name value
  for name in BACKUP_INBOX_DIR BACKUP_ARCHIVE_DIR BACKUP_WEEKLY_DIR; do
    value="${!name:-}"
    validate_absolute_path "$name" "$value"
    [[ -d "$value" && ! -L "$value" ]] || fail "$name is not an existing regular directory"
  done
  if [[ "$BACKUP_INBOX_DIR" == "$BACKUP_ARCHIVE_DIR" \
    || "$BACKUP_INBOX_DIR" == "$BACKUP_WEEKLY_DIR" \
    || "$BACKUP_ARCHIVE_DIR" == "$BACKUP_WEEKLY_DIR" ]]; then
    fail "backup receiver directories must be distinct"
  fi
  local first second
  for first in "$BACKUP_INBOX_DIR" "$BACKUP_ARCHIVE_DIR" "$BACKUP_WEEKLY_DIR"; do
    for second in "$BACKUP_INBOX_DIR" "$BACKUP_ARCHIVE_DIR" "$BACKUP_WEEKLY_DIR"; do
      if [[ "$first" != "$second" && ( "$first" == "$second"/* || "$second" == "$first"/* ) ]]; then
        fail "backup receiver directories must not be nested"
      fi
    done
  done
  if [[ "$(stat -c %d "$BACKUP_INBOX_DIR")" != "$(stat -c %d "$BACKUP_ARCHIVE_DIR")" \
    || "$(stat -c %d "$BACKUP_ARCHIVE_DIR")" != "$(stat -c %d "$BACKUP_WEEKLY_DIR")" ]]; then
    fail "receiver directories must share a filesystem for atomic finalize and weekly hardlinks"
  fi
  [[ "$DAILY_KEEP" =~ ^[1-9][0-9]*$ ]] || fail "DAILY_KEEP must be positive"
  [[ "$WEEKLY_KEEP" =~ ^[1-9][0-9]*$ ]] || fail "WEEKLY_KEEP must be positive"
  command -v "$PYTHON_BIN" >/dev/null 2>&1 || fail "python3 is required"
  command -v flock >/dev/null 2>&1 || fail "flock is required"
}

validate_run_id() {
  local run_id="$1"
  [[ "$run_id" =~ ^auto-[0-9]{8}T[0-9]{6}Z$ ]] \
    || fail "run id must use auto-YYYYMMDDTHHMMSSZ"
  local run_day="${run_id#auto-}"
  run_day="${run_day%%T*}"
  [[ "$run_day" == "$(date -u +%Y%m%d)" || "$run_day" == "$(date -u -d yesterday +%Y%m%d)" ]] \
    || fail "run id UTC day is outside the accepted receiver window"
}

validate_batch() {
  local batch_dir="$1"
  local run_id="$2"
  local expected_manifest_sha="$3"

  [[ -d "$batch_dir" && ! -L "$batch_dir" ]] || fail "partial batch is missing"
  [[ "$expected_manifest_sha" =~ ^[0-9a-f]{64}$ ]] || fail "manifest SHA-256 is invalid"

  local entry_count regular_count
  entry_count="$(find "$batch_dir" -mindepth 1 -maxdepth 1 -printf '.' | wc -c | tr -d ' ')"
  regular_count="$(find "$batch_dir" -mindepth 1 -maxdepth 1 -type f -printf '.' | wc -c | tr -d ' ')"
  [[ "$entry_count" == "3" && "$regular_count" == "3" ]] \
    || fail "batch must contain exactly three regular files"
  for file_name in database.dump storage.tar.gz manifest.json; do
    [[ -f "$batch_dir/$file_name" && ! -L "$batch_dir/$file_name" ]] \
      || fail "batch required file is missing"
  done

  local actual_manifest_sha
  actual_manifest_sha="$(sha256sum "$batch_dir/manifest.json" | awk '{print $1}')"
  [[ "$actual_manifest_sha" == "$expected_manifest_sha" ]] \
    || fail "manifest checksum mismatch"

  "$PYTHON_BIN" - "$batch_dir" "$run_id" <<'PYTHON'
import hashlib
import json
import os
import sys

batch_dir, expected_run_id = sys.argv[1:]
manifest_path = os.path.join(batch_dir, "manifest.json")
with open(manifest_path, "r", encoding="utf-8") as handle:
    manifest = json.load(handle)

if manifest.get("schemaVersion") != 1:
    raise SystemExit("unsupported manifest schema")
if manifest.get("status") != "complete" or manifest.get("runId") != expected_run_id:
    raise SystemExit("manifest identity mismatch")
if not manifest.get("buildSha") and not manifest.get("sourceImageDigest"):
    raise SystemExit("manifest source identity missing")

artifacts = manifest.get("artifacts") or {}
expected = {
    "database": "database.dump",
    "storage": "storage.tar.gz",
}
for key, expected_name in expected.items():
    artifact = artifacts.get(key) or {}
    if artifact.get("file") != expected_name:
        raise SystemExit("manifest artifact name mismatch")
    file_path = os.path.join(batch_dir, expected_name)
    if os.path.getsize(file_path) != artifact.get("bytes"):
        raise SystemExit("manifest artifact size mismatch")
    digest = hashlib.sha256()
    with open(file_path, "rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    if digest.hexdigest() != artifact.get("sha256"):
        raise SystemExit("manifest artifact checksum mismatch")
PYTHON
}

prune_named_directories() {
  local root="$1"
  local prefix="$2"
  local keep="$3"
  local -a entries=()
  mapfile -t entries < <(find "$root" -mindepth 1 -maxdepth 1 -type d \
    -name "${prefix}*" -printf '%f\n' | LC_ALL=C sort)
  local remove_count=$((${#entries[@]} - keep))
  if (( remove_count <= 0 )); then
    return 0
  fi
  local index entry target
  for ((index = 0; index < remove_count; index += 1)); do
    entry="${entries[$index]}"
    target="$root/$entry"
    [[ "$entry" == "$prefix"* && -d "$target" && ! -L "$target" ]] \
      || fail "retention target failed safety validation"
    rm -rf -- "$target"
  done
}

publish_weekly_checkpoint() {
  local archive_dir="$1"
  local weekly_dir="$2"
  local replace_existing="$3"
  if [[ -e "$weekly_dir" && "$replace_existing" != "1" ]]; then
    return 0
  fi
  local weekly_temp="${weekly_dir}.new.$$"
  local weekly_rollback="${weekly_dir}.rollback.$$"
  [[ ! -e "$weekly_temp" && ! -e "$weekly_rollback" ]] || return 1
  if ! cp -al -- "$archive_dir" "$weekly_temp"; then
    rm -rf -- "$weekly_temp"
    return 1
  fi
  if [[ -e "$weekly_dir" ]]; then
    [[ -d "$weekly_dir" && ! -L "$weekly_dir" ]] || return 1
    mv -- "$weekly_dir" "$weekly_rollback" || return 1
  fi
  if ! mv -- "$weekly_temp" "$weekly_dir"; then
    rm -rf -- "$weekly_temp"
    if [[ -e "$weekly_rollback" ]]; then
      mv -- "$weekly_rollback" "$weekly_dir"
    fi
    return 1
  fi
  if [[ -e "$weekly_rollback" ]]; then
    rm -rf -- "$weekly_rollback"
  fi
}

finalize_batch() {
  local run_id="$1"
  local expected_manifest_sha="$2"
  validate_run_id "$run_id"
  validate_layout
  exec 9>"$BACKUP_ARCHIVE_DIR/.finalize.lock"
  chmod 0600 "$BACKUP_ARCHIVE_DIR/.finalize.lock"
  flock -n 9 || fail "another finalize operation is already running"

  local batch_name="hyb-oa-backup-$run_id"
  local partial_dir="$BACKUP_INBOX_DIR/${batch_name}.partial"
  local archive_dir="$BACKUP_ARCHIVE_DIR/$batch_name"
  local already_archived=0
  if [[ -e "$archive_dir" ]]; then
    [[ -d "$archive_dir" && ! -L "$archive_dir" ]] || fail "archive target is invalid"
    validate_batch "$archive_dir" "$run_id" "$expected_manifest_sha"
    already_archived=1
  fi

  local run_day="${run_id#auto-}"
  run_day="${run_day%%T*}"
  local existing_for_day="" replacement_rollback=""
  local -a existing_for_day_entries=()
  mapfile -t existing_for_day_entries < <(find "$BACKUP_ARCHIVE_DIR" -mindepth 1 -maxdepth 1 -type d \
    -name "hyb-oa-backup-auto-${run_day}T*Z" ! -name "$batch_name" -print)
  [[ "${#existing_for_day_entries[@]}" -le 1 ]] || fail "daily archive invariant is already violated"
  if [[ "${#existing_for_day_entries[@]}" -eq 1 ]]; then
    existing_for_day="${existing_for_day_entries[0]}"
  fi

  if [[ "$already_archived" == "0" ]]; then
    validate_batch "$partial_dir" "$run_id" "$expected_manifest_sha"
    chmod 0400 "$partial_dir/database.dump" "$partial_dir/storage.tar.gz" "$partial_dir/manifest.json"
    if [[ -n "$existing_for_day" ]]; then
      [[ "$existing_for_day" =~ /hyb-oa-backup-auto-${run_day}T[0-9]{6}Z$ \
        && -d "$existing_for_day" && ! -L "$existing_for_day" ]] \
        || fail "existing daily archive is invalid"
      replacement_rollback="$BACKUP_ARCHIVE_DIR/.daily-replacement-${run_day}.$$"
      [[ ! -e "$replacement_rollback" ]] || fail "daily replacement rollback target already exists"
      mv -- "$existing_for_day" "$replacement_rollback"
    fi
    if ! mv -- "$partial_dir" "$archive_dir"; then
      if [[ -n "$replacement_rollback" && -e "$replacement_rollback" ]]; then
        mv -- "$replacement_rollback" "$existing_for_day"
      fi
      fail "daily archive publication failed"
    fi
  fi

  local iso_week
  iso_week="$($PYTHON_BIN - "$run_day" <<'PYTHON'
from datetime import datetime
import sys
day = datetime.strptime(sys.argv[1], "%Y%m%d").date()
iso = day.isocalendar()
print(f"week-{iso.year:04d}-W{iso.week:02d}")
PYTHON
  )"
  local weekly_dir="$BACKUP_WEEKLY_DIR/$iso_week"
  if ! publish_weekly_checkpoint "$archive_dir" "$weekly_dir" "$([[ -n "$replacement_rollback" ]] && echo 1 || echo 0)"; then
    if [[ -n "$replacement_rollback" && -e "$replacement_rollback" ]]; then
      rm -rf -- "$archive_dir"
      mv -- "$replacement_rollback" "$existing_for_day"
    fi
    fail "weekly checkpoint update failed"
  fi
  if [[ -n "$replacement_rollback" && -e "$replacement_rollback" ]]; then
    rm -rf -- "$replacement_rollback"
  fi

  prune_named_directories "$BACKUP_ARCHIVE_DIR" "hyb-oa-backup-auto-" "$DAILY_KEEP"
  prune_named_directories "$BACKUP_WEEKLY_DIR" "week-" "$WEEKLY_KEEP"
  echo "[offhost-receiver][PASS] finalized batch with verified manifest"
}

run_forced_command() {
  validate_layout
  local original_command="${SSH_ORIGINAL_COMMAND:-}"
  if [[ "$original_command" == rsync\ --server\ * ]]; then
    if [[ "$original_command" =~ (^|[[:space:]])--sender([[:space:]]|$) ]]; then
      fail "read access is forbidden"
    fi
    if [[ "$original_command" =~ (^|[[:space:]])--(delete|delete-before|delete-after|delete-during|delete-delay|delete-excluded|remove-source-files|remove-sent-files|inplace)(=|[[:space:]]|$) ]]; then
      fail "destructive rsync option is forbidden"
    fi
    [[ -x "$RRSYNC_BIN" ]] || fail "rrsync is required"
    exec "$RRSYNC_BIN" -wo "$BACKUP_INBOX_DIR"
  fi

  if [[ "$original_command" =~ ^hyb-backup-finalize[[:space:]](auto-[0-9]{8}T[0-9]{6}Z)[[:space:]]([0-9a-f]{64})$ ]]; then
    finalize_batch "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}"
    return 0
  fi
  fail "unsupported forced command"
}

case "${1:-forced}" in
  forced)
    run_forced_command
    ;;
  finalize-test)
    [[ "${RECEIVER_TEST_MODE:-0}" == "1" ]] || fail "test mode is disabled"
    finalize_batch "${2:-}" "${3:-}"
    ;;
  validate-config)
    validate_layout
    echo "[offhost-receiver][PASS] configuration valid"
    ;;
  *)
    fail "unsupported mode"
    ;;
esac