#!/bin/bash
# Install the eco status server as a *user* systemd service on this host.
#
# User-level (`systemctl --user`) rather than system-level on purpose: it
# needs no root, and the service then runs as the invoking account - which
# matters twice for this server. It writes status.json into the pgroup's
# res/ tree, so it needs that account's pgroup membership; and several
# bernina components authenticate to auxiliary machines over SSH during
# __init__, so it needs that account's SSH credentials.
#
# The unit just calls `eco-status-server start` in the foreground, so the
# interactive command and the service run exactly the same thing.
set -euo pipefail

SELF_DIR="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")" && pwd)"
LAUNCHER="${ECO_STATUS_SERVER_LAUNCHER:-$SELF_DIR/eco-status-server}"
UNIT_DIR="$HOME/.config/systemd/user"
UNIT="$UNIT_DIR/eco-status-server.service"
ENV_FILE="${ECO_STATUS_SERVER_ENV:-$HOME/.config/eco-status-server.env}"

usage() {
    cat <<EOF
usage: $(basename "$0") [--launcher PATH] [--env-file PATH] [--force]

Writes:
  $UNIT
and, if it does not exist yet, a template environment file at
  $ENV_FILE

Then prints the systemctl commands to enable and start it.
EOF
}

FORCE=0
while [ $# -gt 0 ]; do
    case "$1" in
        --launcher)  LAUNCHER="$2"; shift 2 ;;
        --env-file)  ENV_FILE="$2"; shift 2 ;;
        --force)     FORCE=1; shift ;;
        -h|--help)   usage; exit 0 ;;
        *) echo "unknown option: $1" >&2; usage; exit 2 ;;
    esac
done

[ -x "$LAUNCHER" ] || { echo "launcher not executable: $LAUNCHER" >&2; exit 1; }

mkdir -p "$UNIT_DIR" "$(dirname "$ENV_FILE")"

if [ ! -e "$ENV_FILE" ]; then
    {
        echo "# Environment for the eco status server (systemd EnvironmentFile"
        echo "# syntax: KEY=value, no export, no shell expansion). Edit to taste."
        echo "ECO_STATUS_SERVER_CHECKOUT=${ECO_STATUS_SERVER_CHECKOUT:-/sf/bernina/code/gac-bernina/eco}"
        echo "ECO_STATUS_SERVER_CONFIG=${ECO_STATUS_SERVER_CONFIG:-/sf/bernina/config/eco_status_server/bernina_namespace.json}"
        echo "ECO_STATUS_SERVER_PYTHON=${ECO_STATUS_SERVER_PYTHON:-/sf/bernina/applications/python/.pixi/envs/bpy312/bin/python}"
        echo
        echo "# Channel Access settings, captured from the shell that ran the"
        echo "# installer. A systemd user service inherits almost nothing, and"
        echo "# without EPICS_CA_ADDR_LIST the server talks to the local"
        echo "# broadcast domain instead of the beamline gateway: measured on"
        echo "# saresb-cons-04, that is the difference between 77 of 87"
        echo "# components initializing and 49 of 87."
        env | grep '^EPICS_' | sort || true
    } > "$ENV_FILE"
    echo "wrote template $ENV_FILE - check it before starting the service"
    if ! grep -q '^EPICS_CA_ADDR_LIST=' "$ENV_FILE"; then
        echo
        echo "WARNING: EPICS_CA_ADDR_LIST was not set in this shell, so it is" >&2
        echo "         not in $ENV_FILE either. Re-run this from a shell where" >&2
        echo "         Channel Access works, or add it by hand - otherwise the" >&2
        echo "         service will start but most components will not connect." >&2
    fi
else
    echo "keeping existing $ENV_FILE"
fi

if [ -e "$UNIT" ] && [ "$FORCE" -eq 0 ]; then
    echo "$UNIT already exists; re-run with --force to overwrite" >&2
    exit 1
fi

cat > "$UNIT" <<EOF
[Unit]
Description=eco status/monitor server (namespace mode)
After=network-online.target
Wants=network-online.target
# Rate limiting lives in [Unit], not [Service] - systemd logs
# "Unknown key name 'StartLimitIntervalSec' in section 'Service', ignoring"
# and silently applies no limit at all if these are put with the other
# Restart= settings, which is where they look like they belong.
StartLimitIntervalSec=600
StartLimitBurst=5

[Service]
Type=simple
EnvironmentFile=$ENV_FILE
ExecStart=$LAUNCHER start
# The port is bound immediately and /health answers from the first second;
# namespace.init_all() then runs on a background thread for several minutes.
# So "started" here means "answering /health with state=initializing", and
# clients wait for state=ready themselves - no long TimeoutStartSec needed.
Restart=on-failure
RestartSec=10

[Install]
WantedBy=default.target
EOF

echo "wrote $UNIT"
cat <<EOF

Next steps:

  # let the service keep running when you are not logged in
  loginctl enable-linger $USER

  systemctl --user daemon-reload
  systemctl --user enable --now eco-status-server
  systemctl --user status eco-status-server
  journalctl --user -u eco-status-server -f

  # kill -USR1 <mainpid> dumps every thread's stack into the journal -
  # the way to see which component a stuck initialization is sitting in.
EOF