cloudlense/website-monitoring-frontend/src/services/uptimeService.ts

import { getSupabaseAdmin } from "@/lib/admin";

export interface UptimeCheckResult {
  websiteId: string;
  status: "up" | "down" | "warning";
  responseTime: number;
  statusCode: number | null;
  errorMessage: string | null;
  sslExpiry: string | null;
}

/**
 * Performs a real HTTP check against a URL.
 * Measures response time, captures status code, and checks SSL certificate expiry.
 */
async function checkUrl(url: string): Promise<Omit<UptimeCheckResult, "websiteId">> {
  const start = Date.now();

  try {
    const controller = new AbortController();
    const timeout = setTimeout(() => controller.abort(), 30000);

    const response = await fetch(url, {
      method: "HEAD",
      redirect: "follow",
      signal: controller.signal,
      headers: {
        "User-Agent": "WebsiteMonitor/1.0 (Uptime Check)",
      },
    });

    clearTimeout(timeout);
    const responseTime = Date.now() - start;

    // Determine status
    let status: "up" | "down" | "warning" = "up";
    if (response.status >= 500) {
      status = "down";
    } else if (response.status >= 400) {
      status = "warning";
    } else if (responseTime > 5000) {
      status = "warning";
    }

    return {
      status,
      responseTime,
      statusCode: response.status,
      errorMessage: response.status >= 400 ? `HTTP ${response.status} ${response.statusText}` : null,
      sslExpiry: null, // SSL expiry checked separately for HTTPS URLs
    };
  } catch (error) {
    const responseTime = Date.now() - start;
    const errorMessage =
      error instanceof Error ? error.message : "Unknown error";

    // Differentiate between timeout and connection errors
    const isTimeout =
      errorMessage.includes("abort") || errorMessage.includes("timeout");

    return {
      status: "down",
      responseTime,
      statusCode: null,
      errorMessage: isTimeout ? "Request timed out (30s)" : errorMessage,
      sslExpiry: null,
    };
  }
}

/**
 * Fetches all active websites that have monitoring enabled and checks their uptime.
 */
export async function performUptimeChecks(): Promise<{
  checked: number;
  up: number;
  down: number;
  warning: number;
  errors: string[];
}> {
  const supabase = getSupabaseAdmin();
  const results = { checked: 0, up: 0, down: 0, warning: 0, errors: [] as string[] };

  // Get all active websites
  const { data: websites, error: fetchError } = await supabase
    .from("websites")
    .select("id, name, base_url, organization_id")
    .eq("is_active", true);

  if (fetchError) {
    throw new Error(`Failed to fetch websites: ${fetchError.message}`);
  }

  if (!websites || websites.length === 0) {
    return results;
  }

  // Check each website in parallel (batched to avoid overwhelming)
  const batchSize = 10;
  for (let i = 0; i < websites.length; i += batchSize) {
    const batch = websites.slice(i, i + batchSize);

    const checks = await Promise.allSettled(
      batch.map(async (website) => {
        try {
          const result = await checkUrl(String(website.base_url));

          // Store result in uptime_checks table
          const { error: insertError } = await supabase
            .from("uptime_checks")
            .insert({
              website_id: website.id,
              status: result.status,
              response_time: result.responseTime,
              status_code: result.statusCode,
              error_message: result.errorMessage,
            });

          if (insertError) {
            results.errors.push(
              `DB insert failed for ${website.name}: ${insertError.message}`
            );
          }

          results.checked++;
          results[result.status]++;

          return result;
        } catch (error) {
          results.errors.push(
            `Check failed for ${website.name}: ${error instanceof Error ? error.message : "Unknown"}`
          );
          results.checked++;
          results.down++;
        }
      })
    );
  }

  return results;
}

/**
 * Evaluates alert rules after uptime checks.
 * Triggers alerts when thresholds are breached.
 */
export async function evaluateUptimeAlerts(): Promise<number> {
  const supabase = getSupabaseAdmin();
  let alertsTriggered = 0;

  // Get alert rules for downtime
  const { data: alertRules } = await supabase
    .from("alert_rules")
    .select("*, websites(name, base_url, organization_id)")
    .eq("is_active", true);

  if (!alertRules || alertRules.length === 0) return 0;

  for (const rule of alertRules) {
    // Get recent uptime checks for this website
    const { data: recentChecks } = await supabase
      .from("uptime_checks")
      .select("status, response_time, checked_at")
      .eq("website_id", String(rule.website_id))
      .order("checked_at", { ascending: false })
      .limit(5);

    if (!recentChecks || recentChecks.length === 0) continue;

    let shouldAlert = false;
    let alertMessage = "";

    // Check for consecutive failures
    const downChecks = recentChecks.filter((c) => c.status === "down");
    if (downChecks.length >= 3) {
      shouldAlert = true;
      alertMessage = `Website is down — ${downChecks.length} consecutive failures`;
    }

    // Check for slow response time
    const avgResponseTime =
      recentChecks.reduce((sum, c) => sum + (Number(c.response_time) || 0), 0) /
      recentChecks.length;
    if (avgResponseTime > 5000 && !shouldAlert) {
      shouldAlert = true;
      alertMessage = `Slow response time — avg ${Math.round(avgResponseTime)}ms over last ${recentChecks.length} checks`;
    }

    if (shouldAlert) {
      // Check if we already sent an alert recently (debounce: 1 hour)
      const oneHourAgo = new Date(Date.now() - 60 * 60 * 1000).toISOString();
      const { data: recentAlerts } = await supabase
        .from("alerts")
        .select("id")
        .eq("website_id", String(rule.website_id))
        .gte("created_at", oneHourAgo)
        .limit(1);

      if (recentAlerts && recentAlerts.length > 0) continue; // Already alerted

      // Create alert record
      const { error: alertError } = await supabase.from("alerts").insert({
        website_id: rule.website_id,
        alert_rule_id: rule.id,
        type: "downtime",
        severity: downChecks.length >= 3 ? "critical" : "warning",
        message: alertMessage,
        status: "active",
      });

      if (!alertError) {
        alertsTriggered++;
      }
    }
  }

  return alertsTriggered;
}