#!/usr/bin/env bash
# Pull the latest LLeMbas into the deployment and restart the service.
#
# Run this after pushing. It fetches, hard-resets the deployment checkout to the
# remote branch, reinstalls dependencies if they changed, and restarts. Nothing
# is ever edited in place under the deployment prefix, so a hard reset is safe
# and avoids merge conflicts from a dirty tree.
set -euo pipefail

SERVICE_USER="${SERVICE_USER:-lembas}"
PREFIX="${PREFIX:-/srv/lembas}"
BRANCH="${LEMBAS_BRANCH:-main}"

APP="$PREFIX/app"
VENV="$PREFIX/venv"

if [[ ! -d "$APP/.git" ]]; then
  echo "No deployment at $APP. Run deploy/install.sh first." >&2
  exit 1
fi

git_as() { sudo -u "$SERVICE_USER" git -C "$APP" "$@"; }

before=$(git_as rev-parse HEAD)

echo "== fetching =="
git_as fetch --quiet origin "$BRANCH"
git_as reset --hard --quiet "origin/$BRANCH"

after=$(git_as rev-parse HEAD)

if [[ "$before" == "$after" ]]; then
  echo "   already at ${after:0:7}, nothing to pull"
else
  echo "   ${before:0:7} -> ${after:0:7}"
  git_as --no-pager log --oneline "$before..$after" | sed 's/^/     /'
fi

# Cheap and idempotent; catches a dependency added since the last deploy.
# The extras a deployment gets. `search` because DuckDuckGo is the default web
# search provider and is meant to need no setup; `ssh` because agent chats reach
# their machine over it and a deployment without it offers the feature with an
# install hint instead. Listed here AND in install.sh -- an extra added to only
# one of them means existing deployments silently miss it.
LEMBAS_EXTRAS="${LEMBAS_EXTRAS:-search,ssh}"
echo "== dependencies =="
sudo -u "$SERVICE_USER" "$VENV/bin/pip" install --quiet -e "$APP[$LEMBAS_EXTRAS]"

# The unit is NOT reinstalled automatically. An installed unit usually carries
# host-specific lines the template cannot know about -- an ordering dependency
# on whatever serves the models, a note about how the prefix is mounted -- and
# overwriting those on every update would be a worse surprise than drifting.
#
# So this compares the *template* against the one last applied here, not the
# template against the installed file. Comparing the files would warn forever
# about the local lines, and a warning that always fires is one nobody reads.
#
# The drift is worth catching: a change in the unit can be what makes a release
# work at all, and a host that pulled the code without it would run the new
# version under the old settings and fail confusingly.
STAMP="$PREFIX/.unit-applied"
current=$(sha256sum "$APP/deploy/lembas.service" | cut -d' ' -f1)
if [[ -f "$STAMP" && "$(cat "$STAMP")" != "$current" ]]; then
  echo "== systemd unit ==" >&2
  echo "   deploy/lembas.service has changed since it was last applied here." >&2
  echo "   Review it and merge by hand, keeping this host's own lines:" >&2
  echo "     diff /etc/systemd/system/lembas.service <(sed \\" >&2
  echo "       -e 's|__PREFIX__|$PREFIX|g' -e 's|__SERVICE_USER__|$SERVICE_USER|g' \\" >&2
  echo "       $APP/deploy/lembas.service)" >&2
  echo "   Then: sudo systemctl daemon-reload && sudo systemctl restart lembas" >&2
  echo "   And record it as applied: echo $current | sudo tee $STAMP" >&2
elif [[ ! -f "$STAMP" ]]; then
  # First run after this check was added. Assume what is installed is current;
  # there is nothing to compare against and crying wolf on every host once is
  # not worth it.
  echo "$current" | sudo tee "$STAMP" >/dev/null
fi

# The same argument for the vhost, and the failure is worse. A stale unit at
# least says something in the journal; a stale vhost breaks a feature two layers
# away, and the only symptom is a panel that says it could not connect. The
# terminal is a WebSocket, and a `location` that does not pass an upgrade
# through fails every handshake while every test in the suite still passes.
VHOST_STAMP="$PREFIX/.vhost-applied"
vhost_now=$(sha256sum "$APP/deploy/nginx-vhost.conf" | cut -d' ' -f1)

site_host=""; app_port=""
# Written by install.sh, and absent on every deployment that predates it --
# which is the case that most needs the one-time check below, so the port is
# recovered from the environment file and the vhost found by what it proxies to.
# Guessing "your-host" instead would have skipped the check on exactly the hosts
# it was added for.
if [[ -f "$PREFIX/.deploy-env" ]]; then
  . "$PREFIX/.deploy-env"
  site_host="$SITE_HOST"; app_port="$APP_PORT"
fi
if [[ -z "$app_port" && -f "$PREFIX/lembas.env" ]]; then
  app_port=$(sed -n 's/^LEMBAS_PORT=//p' "$PREFIX/lembas.env" | tail -1)
fi
app_port="${app_port:-8080}"

installed_vhost=""
if [[ -n "$site_host" && -f "/etc/nginx/conf.d/$site_host.conf" ]]; then
  installed_vhost="/etc/nginx/conf.d/$site_host.conf"
else
  installed_vhost=$(grep -ls "proxy_pass http://127.0.0.1:$app_port" \
                      /etc/nginx/conf.d/*.conf 2>/dev/null | head -1)
fi

vhost_stale=""
if [[ -f "$VHOST_STAMP" ]]; then
  [[ "$(cat "$VHOST_STAMP")" != "$vhost_now" ]] && vhost_stale="the template has changed"
elif [[ -n "$installed_vhost" ]]; then
  # First run with this check, so there is no stamp to compare against. Rather
  # than assume what is installed is current -- which is what the unit check
  # does, and would hide exactly the change this was added for -- look for the
  # one thing that must be there. Everything else is left to the stamp.
  grep -q 'lembas_connection_upgrade' "$installed_vhost" \
    || vhost_stale="the installed vhost does not pass WebSocket upgrades through, so the terminal cannot connect"
fi

if [[ -n "$vhost_stale" ]]; then
  echo "== nginx vhost ==" >&2
  echo "   $vhost_stale." >&2
  echo "   Review and reinstall it:" >&2
  echo "     diff ${installed_vhost:-/etc/nginx/conf.d/your-host.conf} <(sed \\" >&2
  echo "       -e 's|__SITE_HOST__|${site_host:-your-host}|g' -e 's|__APP_PORT__|$app_port|g' \\" >&2
  echo "       $APP/deploy/nginx-vhost.conf)" >&2
  echo "   Then: sudo nginx -t && sudo systemctl reload nginx" >&2
  echo "   And record it as applied: echo $vhost_now | sudo tee $VHOST_STAMP" >&2
elif [[ ! -f "$VHOST_STAMP" ]]; then
  echo "$vhost_now" | sudo tee "$VHOST_STAMP" >/dev/null
fi

echo "== restart =="
sudo systemctl restart lembas
sleep 2

if systemctl is-active --quiet lembas; then
  echo "   lembas is running"
else
  echo "   lembas FAILED to start:" >&2
  sudo journalctl -u lembas -n 30 --no-pager >&2
  exit 1
fi
