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

SERVICE_NAME="${SERVICE_NAME:-hg_web_server.service}"
RELEASE_ROOT="${RELEASE_ROOT:-/opt/hg_web_server_releases}"
ACTIVE_PATH="${ACTIVE_PATH:-/opt/hg_web_server_bundle_active}"
HEALTH_URL="${HEALTH_URL:-http://127.0.0.1:6970/}"
SERVICE_USER="${SERVICE_USER:-hg_web_server}"
SERVICE_GROUP="${SERVICE_GROUP:-zenbu_team}"

workspace="$(hg root)"
cd "$workspace"

revision="$(hg log -r . -T '{node|short}')"
release_name="${revision}-$(date -u +%Y%m%dT%H%M%SZ)"
release_dir="${RELEASE_ROOT}/${release_name}"
staging_dir="${RELEASE_ROOT}/.${release_name}.tmp"
next_link="${ACTIVE_PATH}.next"
bundle_dir="bazel-bin/hg-web/hg_web_server_bundle"
previous_release=""
promoted=0

health_check() {
  for _ in $(seq 1 20); do
    if curl --fail --silent --max-time 3 "$HEALTH_URL" >/dev/null; then
      return 0
    fi
    sleep 1
  done
  echo "Health check failed: $HEALTH_URL" >&2
  return 1
}

point_active_at() {
  local target="$1"
  sudo rm -f "$next_link"
  sudo ln -s "$target" "$next_link"
  sudo mv -Tf "$next_link" "$ACTIVE_PATH"
}

rollback() {
  trap - ERR
  if [[ "$promoted" -eq 1 && -n "$previous_release" && -d "$previous_release" ]]; then
    echo "Deployment failed; rolling back to $previous_release" >&2
    point_active_at "$previous_release"
    sudo systemctl restart "$SERVICE_NAME"
    health_check || echo "Rollback completed, but the health check still fails." >&2
  else
    echo "Deployment failed and no previous release is available for rollback." >&2
  fi
  sudo rm -rf "$staging_dir"
  exit 1
}
trap rollback ERR

bazel build -c opt //hg-web:hg_web_server_bundle

sudo install -d -o root -g "$SERVICE_GROUP" -m 0755 "$RELEASE_ROOT"
sudo rm -rf "$staging_dir"
sudo install -d -o "$SERVICE_USER" -g "$SERVICE_GROUP" -m 0755 "$staging_dir"
sudo cp -a "${bundle_dir}/." "$staging_dir/"
sudo chown -R "$SERVICE_USER:$SERVICE_GROUP" "$staging_dir"

sudo test -x "$staging_dir/hg_web_server"
sudo test -f "$staging_dir/hg-web/src/index.html"
sudo test -f "$staging_dir/hg-web/src/page.js"
sudo mv "$staging_dir" "$release_dir"

if [[ -L "$ACTIVE_PATH" ]]; then
  previous_release="$(readlink -f "$ACTIVE_PATH")"
elif [[ -d "$ACTIVE_PATH" ]]; then
  previous_release="${RELEASE_ROOT}/legacy-$(date -u +%Y%m%dT%H%M%SZ)"
  sudo mv "$ACTIVE_PATH" "$previous_release"
fi

point_active_at "$release_dir"
promoted=1
sudo systemctl restart "$SERVICE_NAME"
health_check

trap - ERR
echo "Deployment complete: $release_dir"