#!/bin/bash
# GoChat Prometheus Metrics Exporter Helper Script
# Reference: Chatwoot monitoring setup pattern
# Assists in configuring Prometheus scraping for GoChat metrics
#
# Usage:
#   ./scripts/prometheus_exporter.sh [--generate-config] [--scrape] [--check]
#
# Metrics exposed on port 9090 at /metrics (via Gin + prometheus client)
# Key metrics:
#   - gochat_http_requests_total (counter, by method/path/status)
#   - gochat_http_request_duration_seconds (histogram)
#   - gochat_conversations_active (gauge)
#   - gochat_messages_sent_total (counter, by channel)
#   - gochat_websocket_connections (gauge)
#   - gochat_worker_jobs_processed_total (counter, by queue)
#   - gochat_worker_jobs_failed_total (counter, by queue)
#   - gochat_db_query_duration_seconds (histogram)
#   - gochat_redis_commands_total (counter)
#   - go_* (standard Go runtime metrics)

set -euo pipefail

GOCHAT_HOST="${GOCHAT_HOST:-localhost}"
GOCHAT_METRICS_PORT="${GOCHAT_METRICS_PORT:-9090}"
METRICS_URL="http://${GOCHAT_HOST}:${GOCHAT_METRICS_PORT}/metrics"
PROMETHEUS_CONFIG_DIR="${PROMETHEUS_CONFIG_DIR:-/etc/prometheus}"
TIMEOUT="${TIMEOUT:-5}"

# Parse arguments
ACTION="check"
while [[ $# -gt 0 ]]; do
    case "$1" in
        --generate-config) ACTION="generate-config"; shift ;;
        --scrape)          ACTION="scrape"; shift ;;
        --check)           ACTION="check"; shift ;;
        --help)            echo "Usage: $0 [--generate-config] [--scrape] [--check]"; exit 0 ;;
        *)                 echo "Unknown option: $1"; exit 1 ;;
    esac
done

case "${ACTION}" in
    generate-config)
        echo "# GoChat Prometheus scrape configuration"
        echo "# Add this to your prometheus.yml scrape_configs section"
        echo ""
        echo "scrape_configs:"
        echo "  - job_name: 'gochat'"
        echo "    scrape_interval: 15s"
        echo "    scrape_timeout: 10s"
        echo "    metrics_path: '/metrics'"
        echo "    static_configs:"
        echo "      - targets:"
        echo "          - '${GOCHAT_HOST}:${GOCHAT_METRICS_PORT}'"
        echo "        labels:"
        echo "          app: 'gochat'"
        echo "          env: '${GOCHAT_ENV:-production}'"
        echo ""
        echo "# For Kubernetes with ServiceMonitor (preferred):"
        echo "# The Helm chart creates a ServiceMonitor automatically when"
        echo "# metrics.enabled=true and metrics.serviceMonitor.enabled=true"
        echo "# No manual Prometheus config needed — operator handles discovery."
        ;;

    scrape)
        echo "=== Scraping GoChat metrics from ${METRICS_URL} ==="
        curl -sf --max-time "${TIMEOUT}" "${METRICS_URL}" | head -50 || {
            echo "ERROR: Failed to scrape metrics endpoint at ${METRICS_URL}"
            exit 1
        }
        echo ""
        echo "--- Full metrics available at: ${METRICS_URL} ---"
        ;;

    check)
        echo "=== Checking GoChat metrics endpoint ==="
        # Verify endpoint is reachable
        curl -sf --max-time "${TIMEOUT}" "${METRICS_URL}" > /dev/null 2>&1 && {
            echo "✅ Metrics endpoint is reachable at ${METRICS_URL}"
            # Count available metric families
            metric_count=$(curl -sf --max-time "${TIMEOUT}" "${METRICS_URL}" 2>/dev/null | grep -c "^# TYPE" || echo "0")
            echo "   Available metric families: ${metric_count}"
            # Check for key GoChat metrics
            for metric in gochat_http_requests_total gochat_conversations_active gochat_messages_sent_total gochat_websocket_connections gochat_worker_jobs_processed_total; do
                curl -sf --max-time "${TIMEOUT}" "${METRICS_URL}" 2>/dev/null | grep -q "^${metric}" && {
                    echo "   ✅ ${metric} present"
                } || {
                    echo "   ⚠️  ${metric} not found"
                }
            done
        } || {
            echo "❌ Metrics endpoint unreachable at ${METRICS_URL}"
            exit 1
        }
        ;;

    *)
        echo "Unknown action: ${ACTION}"
        exit 1
        ;;
esac