import { createClient } from "https://esm.sh/@supabase/supabase-js@2.45.0";

const corsHeaders = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Headers": "authorization, x-client-info, apikey, content-type",
};

function addInterval(dateStr: string, freq: string): string {
  const d = new Date(dateStr + "T12:00:00");
  switch (freq) {
    case "weekly": d.setDate(d.getDate() + 7); break;
    case "biweekly": d.setDate(d.getDate() + 14); break;
    case "monthly": d.setMonth(d.getMonth() + 1); break;
    case "quarterly": d.setMonth(d.getMonth() + 3); break;
    case "semiannual": d.setMonth(d.getMonth() + 6); break;
    case "annual": d.setFullYear(d.getFullYear() + 1); break;
    default: d.setMonth(d.getMonth() + 1);
  }
  return d.toISOString().slice(0, 10);
}

Deno.serve(async (req) => {
  if (req.method === "OPTIONS") return new Response("ok", { headers: corsHeaders });

  const supabase = createClient(
    Deno.env.get("SUPABASE_URL")!,
    Deno.env.get("SUPABASE_SERVICE_ROLE_KEY")!
  );

  const today = new Date().toISOString().slice(0, 10);
  const { data: due, error } = await supabase
    .from("invoices")
    .select("*")
    .not("recurrence_frequency", "is", null)
    .lte("next_generation_date", today);

  if (error) {
    return new Response(JSON.stringify({ error: error.message }), {
      status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" },
    });
  }

  let created = 0;
  const errors: string[] = [];

  for (const tmpl of due || []) {
    try {
      if (tmpl.recurrence_end_date && tmpl.next_generation_date > tmpl.recurrence_end_date) continue;

      const issueDate = tmpl.next_generation_date || today;
      const dueOffset = tmpl.due_date && tmpl.issue_date
        ? Math.round((new Date(tmpl.due_date).getTime() - new Date(tmpl.issue_date).getTime()) / 86400000)
        : 30;
      const newDue = new Date(issueDate + "T12:00:00");
      newDue.setDate(newDue.getDate() + dueOffset);

      const { error: insErr } = await supabase.from("invoices").insert({
        association_id: tmpl.association_id,
        vendor_name: tmpl.vendor_name,
        invoice_number: tmpl.invoice_number ? `${tmpl.invoice_number}-${issueDate}` : null,
        amount: tmpl.amount,
        status: "pending",
        issue_date: issueDate,
        due_date: newDue.toISOString().slice(0, 10),
        description: tmpl.description,
        category: tmpl.category,
        line_items: tmpl.line_items,
        rate: tmpl.rate,
        parent_invoice_id: tmpl.id,
      });
      if (insErr) { errors.push(insErr.message); continue; }

      const next = addInterval(issueDate, tmpl.recurrence_frequency);
      const stop = tmpl.recurrence_end_date && next > tmpl.recurrence_end_date;
      await supabase.from("invoices").update({
        next_generation_date: stop ? null : next,
        recurrence_frequency: stop ? null : tmpl.recurrence_frequency,
      }).eq("id", tmpl.id);

      created++;
    } catch (e) {
      errors.push(String(e));
    }
  }

  return new Response(JSON.stringify({ created, errors }), {
    headers: { ...corsHeaders, "Content-Type": "application/json" },
  });
});