#!/usr/bin/env bash
# /usr/local/bin/musehub-set-slot
#
# The only sanctioned way to switch MuseHub's nginx upstream between blue and green.
# Accepts a slot name, constructs the correct nginx directive, validates, and reloads.
#
# Usage:
#   sudo musehub-set-slot blue
#   sudo musehub-set-slot green
#
# Called by deploy.sh automatically. For manual recovery:
#   sudo musehub-set-slot blue    ← blue  is port 1337
#   sudo musehub-set-slot green   ← green is port 1338

set -euo pipefail

NGINX_PORT_FILE="/etc/nginx/musehub-active-port"
SLOT_FILE="/opt/musehub/.active-slot"

slot="${1:-}"

case "$slot" in
    blue)  port=1337 ;;
    green) port=1338 ;;
    *)
        echo "ERROR: slot must be 'blue' or 'green', got: '$slot'" >&2
        echo "Usage: sudo musehub-set-slot blue|green" >&2
        exit 1
        ;;
esac

echo "server 127.0.0.1:${port};" > "$NGINX_PORT_FILE"
echo "$slot" > "$SLOT_FILE"

nginx -t 2>&1 || { echo "ERROR: nginx config test failed — aborting" >&2; exit 1; }
nginx -s reload
echo "nginx → $slot (127.0.0.1:${port})"