"use server";

import { auth } from "@/auth";
import { db } from "@/lib/db";
import { buildPoPdfKey, uploadBuffer, generateDownloadUrl, statObject } from "@/lib/storage";
import { renderPoPdf, isPdfServiceConfigured, PdfServiceError } from "@/lib/pdf-service";

type Result = { ok: true; mailto: string; to: string } | { error: string };

// PO must be approved (a valid document) before it can be emailed to a vendor;
// available through every later state, incl. once payment is recorded (issue #14).
const EMAILABLE = ["MGR_APPROVED", "SENT_FOR_PAYMENT", "PARTIALLY_PAID", "PAID_DELIVERED", "PARTIALLY_CLOSED", "CLOSED"];
const VIEW_ALL_ROLES = ["ACCOUNTS", "MANAGER", "SUPERUSER", "AUDITOR", "ADMIN"];
const LINK_TTL_SECONDS = 7 * 24 * 60 * 60; // 7 days

/**
 * Build an "email this PO to the vendor" Outlook draft: render the PO to a PDF,
 * store it (R2), and return a mailto: addressed to the vendor's primary contact
 * with a time-limited download link in the body. The user reviews & sends it.
 */
export async function prepareVendorEmail(poId: string): Promise<Result> {
  const session = await auth();
  if (!session?.user) return { error: "Unauthorized" };

  const po = await db.purchaseOrder.findUnique({
    where: { id: poId },
    include: {
      company: { select: { name: true } },
      vendor: { include: { contacts: { where: { isPrimary: true }, take: 1 } } },
    },
  });
  if (!po) return { error: "PO not found" };

  const canView = VIEW_ALL_ROLES.includes(session.user.role) || po.submitterId === session.user.id;
  if (!canView) return { error: "You cannot access this purchase order." };

  if (!EMAILABLE.includes(po.status)) {
    return { error: "The PO must be approved before it can be emailed to the vendor." };
  }

  const to = po.vendor?.contacts?.[0]?.email?.trim();
  if (!to) {
    return { error: "The vendor has no primary contact email. Add one on the vendor before emailing." };
  }

  if (!isPdfServiceConfigured()) {
    return { error: "PDF emailing is not configured on this environment." };
  }

  // Render → store → presigned link. The PDF is cached at a deterministic
  // per-PO key: if a copy already exists and is at least as new as the PO's last
  // change, reuse it and only mint a fresh presigned URL (refreshing the 7-day
  // timer). Re-render only when there's no copy yet or the PO changed since.
  let link: string;
  try {
    const slug = po.poNumber.replace(/\//g, "-");
    const key = buildPoPdfKey(poId, `${slug}.pdf`);
    const cached = await statObject(key);
    const isFresh = cached !== null && cached.lastModified >= po.updatedAt;
    if (!isFresh) {
      const pdf = await renderPoPdf(poId);
      await uploadBuffer(key, pdf, "application/pdf");
    }
    link = await generateDownloadUrl(key, LINK_TTL_SECONDS);
  } catch (e) {
    if (e instanceof PdfServiceError) return { error: `Could not generate the PO PDF: ${e.message}` };
    return { error: "Could not generate the PO PDF." };
  }

  const company = po.company?.name ?? "Pelagia Marine Services Pvt. Ltd.";
  const vendorName = po.vendor?.contacts?.[0]?.name || po.vendor?.name || "Sir/Madam";
  const sender = session.user.name ?? "";

  const subject = `Purchase Order ${po.poNumber}`;
  const body = [
    `Dear ${vendorName},`,
    "",
    `Please find our Purchase Order ${po.poNumber} at the link below:`,
    link,
    "",
    "(The link is valid for 7 days.)",
    "",
    "Regards,",
    sender,
    company,
  ].join("\n");

  const mailto = `mailto:${encodeURIComponent(to)}?subject=${encodeURIComponent(subject)}&body=${encodeURIComponent(body)}`;
  return { ok: true, mailto, to };
}