import { NextRequest, NextResponse } from "next/server";
import { prisma } from "@/lib/db";
import { Prisma } from "@prisma/client";
import * as XLSX from "xlsx";

export async function GET(req: NextRequest) {
  try {
    const { searchParams } = new URL(req.url);
    const search = searchParams.get("search") || "";
    const statuses = searchParams.getAll("status");
    const sourceTabs = searchParams.getAll("sourceTab");
    const priorities = searchParams.getAll("priority");
    const hasEmail = searchParams.get("hasEmail");
    const emailOnly = searchParams.get("emailOnly") === "true";
    const format = searchParams.get("format") || "csv"; // "csv" | "xlsx"

    const where: Prisma.LeadWhereInput = {};
    if (search) {
      where.OR = [
        { domain: { contains: search } },
        { companyName: { contains: search } },
        { contactName: { contains: search } },
        { email: { contains: search } },
      ];
    }
    if (statuses.length > 0) where.status = { in: statuses };
    if (sourceTabs.length > 0) where.sourceTab = { in: sourceTabs };
    if (priorities.length > 0) where.priority = { in: priorities };
    if (hasEmail === "yes" || emailOnly) where.email = { not: null };
    else if (hasEmail === "no") where.email = null;

    const leads = await prisma.lead.findMany({
      where,
      orderBy: { capturedAt: "desc" },
      take: 10000,
    });

    const rows = leads.map(l => ({
      "Status": l.status,
      "Priorität": l.priority,
      "Unternehmen": l.companyName || "",
      "Domain": l.domain || "",
      "Kontaktname": l.contactName || "",
      "Jobtitel": l.contactTitle || "",
      "E-Mail": l.email || "",
      "E-Mail Konfidenz": l.emailConfidence != null ? Math.round(l.emailConfidence * 100) + "%" : "",
      "LinkedIn": l.linkedinUrl || "",
      "Telefon": l.phone || "",
      "Quelle": l.sourceTab,
      "Suchbegriff": l.sourceTerm || "",
      "Tags": l.tags ? JSON.parse(l.tags).join(", ") : "",
      "Land": l.country || "",
      "Mitarbeiter": l.headcount || "",
      "Branche": l.industry || "",
      "Notizen": l.notes || "",
      "Erfasst am": new Date(l.capturedAt).toLocaleString("de-DE"),
      "Kontaktiert am": l.contactedAt ? new Date(l.contactedAt).toLocaleString("de-DE") : "",
      "SERP Rang": l.serpRank?.toString() || "",
      "SERP URL": l.serpUrl || "",
      "SERP Titel": l.serpTitle || "",
      "SERP Snippet": l.serpSnippet || "",
      "Lead ID": l.id,
    }));

    const filename = `leadflow-vault-${new Date().toISOString().split("T")[0]}`;

    if (format === "xlsx") {
      const ws = XLSX.utils.json_to_sheet(rows);

      // Column widths
      ws["!cols"] = [
        { wch: 14 }, { wch: 10 }, { wch: 28 }, { wch: 28 }, { wch: 22 },
        { wch: 22 }, { wch: 32 }, { wch: 14 }, { wch: 30 }, { wch: 16 },
        { wch: 12 }, { wch: 24 }, { wch: 20 }, { wch: 8 }, { wch: 10 },
        { wch: 16 }, { wch: 30 }, { wch: 18 }, { wch: 18 }, { wch: 8 },
        { wch: 40 }, { wch: 30 }, { wch: 40 }, { wch: 28 },
      ];

      const wb = XLSX.utils.book_new();
      XLSX.utils.book_append_sheet(wb, ws, "LeadVault");

      const arr = XLSX.write(wb, { type: "array", bookType: "xlsx" }) as number[];
      const buf = new Uint8Array(arr).buffer;

      return new NextResponse(buf, {
        headers: {
          "Content-Type": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
          "Content-Disposition": `attachment; filename="${filename}.xlsx"`,
        },
      });
    }

    // CSV — UTF-8 BOM so Excel opens it correctly + \r\n line endings
    const headers = Object.keys(rows[0] ?? {
      "Status": "", "Priorität": "", "Unternehmen": "", "Domain": "", "Kontaktname": "",
      "Jobtitel": "", "E-Mail": "", "E-Mail Konfidenz": "", "LinkedIn": "", "Telefon": "",
      "Quelle": "", "Suchbegriff": "", "Tags": "", "Land": "", "Mitarbeiter": "",
      "Branche": "", "Notizen": "", "Erfasst am": "", "Kontaktiert am": "",
      "SERP Rang": "", "SERP URL": "", "SERP Titel": "", "SERP Snippet": "", "Lead ID": "",
    });

    const escape = (v: string) =>
      v.includes(",") || v.includes('"') || v.includes("\n") || v.includes("\r")
        ? `"${v.replace(/"/g, '""')}"`
        : v;

    const csv =
      "\uFEFF" + // UTF-8 BOM — tells Excel to use UTF-8
      [
        headers.map(escape).join(","),
        ...rows.map(r => headers.map(h => escape(String(r[h as keyof typeof r] ?? ""))).join(",")),
      ].join("\r\n"); // Windows line endings for Excel

    return new NextResponse(csv, {
      headers: {
        "Content-Type": "text/csv; charset=utf-8",
        "Content-Disposition": `attachment; filename="${filename}.csv"`,
      },
    });
  } catch (err) {
    console.error("GET /api/leads/export error:", err);
    return NextResponse.json({ error: "Export failed" }, { status: 500 });
  }
}