#!/usr/bin/env bash
#
# Archive old log files into compressed tarballs.
#
# This script is useful when logrotate is unavailable or when application logs
# need custom archival handling. It does not delete active logs by default.
#
# Usage:
#   bash log_rotate_archive.sh --source /var/log/myapp --archive /backup/logs
#   bash log_rotate_archive.sh --source ./logs --archive ./archives --older-than-days 3 --delete-originals
#
# Options:
#   --source DIR           Directory containing log files.
#   --archive DIR          Directory where archives will be stored.
#   --older-than-days N    Archive files older than N days. Default: 7.
#   --delete-originals     Delete original files after a successful archive.
#   --help                 Show this help message.

set -Eeuo pipefail

source_dir=""
archive_dir=""
older_than_days="7"
delete_originals=false

usage() {
  sed -n '2,21p' "$0" | sed 's/^# \{0,1\}//'
}

log() {
  printf '[%s] %s\n' "$(date -Is)" "$*"
}

while [[ "$#" -gt 0 ]]; do
  case "$1" in
    --source)
      source_dir="${2:-}"
      shift 2
      ;;
    --archive)
      archive_dir="${2:-}"
      shift 2
      ;;
    --older-than-days)
      older_than_days="${2:-}"
      [[ "$older_than_days" =~ ^[0-9]+$ ]] || { printf 'ERROR: --older-than-days must be an integer.\n' >&2; exit 1; }
      shift 2
      ;;
    --delete-originals)
      delete_originals=true
      shift
      ;;
    --help|-h)
      usage
      exit 0
      ;;
    *)
      printf 'ERROR: unknown option: %s\n' "$1" >&2
      usage >&2
      exit 1
      ;;
  esac
done

[[ -d "$source_dir" ]] || { printf 'ERROR: source directory does not exist: %s\n' "$source_dir" >&2; exit 1; }
[[ -n "$archive_dir" ]] || { printf 'ERROR: --archive is required.\n' >&2; exit 1; }
mkdir -p "$archive_dir"

timestamp="$(date +%Y%m%d-%H%M%S)"
manifest="$(mktemp)"
archive_file="${archive_dir}/logs-${timestamp}.tar.gz"

find "$source_dir" -type f -name '*.log' -mtime "+${older_than_days}" -print > "$manifest"

if [[ ! -s "$manifest" ]]; then
  log "No log files older than ${older_than_days} days were found."
  rm -f "$manifest"
  exit 0
fi

log "Creating archive: ${archive_file}"
tar -czf "$archive_file" --files-from "$manifest"

if [[ ! -s "$archive_file" ]]; then
  printf 'ERROR: archive was not created or is empty: %s\n' "$archive_file" >&2
  rm -f "$manifest"
  exit 1
fi

if [[ "$delete_originals" == true ]]; then
  log "Deleting archived original files."
  xargs -r rm -f < "$manifest"
fi

rm -f "$manifest"
log "Log archive completed successfully."