#!/usr/bin/env bash
#
# Deploy static files using release directories and an atomic symlink switch.
#
# This pattern reduces partial deployments because files are copied to a new
# release directory first. The live path changes only when the copy succeeds.
#
# Usage:
#   bash deploy_static_site.sh --source ./dist --releases /var/www/releases --current /var/www/current
#   bash deploy_static_site.sh --source ./dist --releases /var/www/releases --current /var/www/current --keep 10
#
# Options:
#   --source DIR     Directory containing built static files.
#   --releases DIR   Directory that stores timestamped releases.
#   --current PATH   Symlink path used by the web server.
#   --keep N         Number of releases to keep. Default: 5.
#   --help           Show this help message.

set -Eeuo pipefail

source_dir=""
releases_dir=""
current_link=""
keep_releases="5"

usage() {
  sed -n '2,22p' "$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
      ;;
    --releases)
      releases_dir="${2:-}"
      shift 2
      ;;
    --current)
      current_link="${2:-}"
      shift 2
      ;;
    --keep)
      keep_releases="${2:-}"
      [[ "$keep_releases" =~ ^[0-9]+$ ]] || { printf 'ERROR: --keep must be an integer.\n' >&2; exit 1; }
      shift 2
      ;;
    --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 "$releases_dir" ]] || { printf 'ERROR: --releases is required.\n' >&2; exit 1; }
[[ -n "$current_link" ]] || { printf 'ERROR: --current is required.\n' >&2; exit 1; }

mkdir -p "$releases_dir"

release_id="$(date +%Y%m%d-%H%M%S)"
release_path="${releases_dir}/${release_id}"

log "Creating release directory: ${release_path}"
mkdir -p "$release_path"

log "Copying files from ${source_dir}"
if command -v rsync >/dev/null 2>&1; then
  rsync -a --delete "${source_dir}/" "${release_path}/"
else
  cp -a "${source_dir}/." "$release_path/"
fi

log "Switching current symlink to ${release_path}"
ln -sfn "$release_path" "$current_link"

log "Removing old releases, keeping the newest ${keep_releases}."
find "$releases_dir" -mindepth 1 -maxdepth 1 -type d -printf '%T@ %p\n' \
  | sort -nr \
  | awk -v keep="$keep_releases" 'NR > keep {print $2}' \
  | xargs -r rm -rf

log "Deployment completed successfully."