"use client";

import { useEffect, useMemo, useState } from "react";
import { useRouter } from "next/navigation";
import { fmtGBP, fmtDate } from "../lib/pb";

type Invoice = {
  id: string;
  invoice_no: string;
  invoice_date: string;
  buyer_name_variant: string;
  customer_order_no: string;
  invoice_total: number;
};

const STORAGE_KEY = "jei:selected-invoices";

function todayYYYYMMDD(): string {
  const d = new Date();
  const y = d.getFullYear();
  const m = String(d.getMonth() + 1).padStart(2, "0");
  const day = String(d.getDate()).padStart(2, "0");
  return `${y}${m}${day}`;
}

function nextBatchRefSuggestion(): string {
  // We don't fetch today's count server-side; this is a client suggestion only.
  // Server validates uniqueness on submit.
  return `BATCH-${todayYYYYMMDD()}-001`;
}

export default function UnpaidClient({ initialRecords }: { initialRecords: Invoice[] }) {
  const router = useRouter();
  const records = initialRecords;
  const [selected, setSelected] = useState<Set<string>>(new Set());
  const [hydrated, setHydrated] = useState(false);
  const [modalOpen, setModalOpen] = useState(false);
  const [batchRef, setBatchRef] = useState(nextBatchRefSuggestion());
  const [paymentDate, setPaymentDate] = useState(() => new Date().toISOString().slice(0, 10));
  const [popFile, setPopFile] = useState<File | null>(null);
  const [zarPaid, setZarPaid] = useState<string>(""); // optional ZAR amount actually paid; "" means omitted
  const [submitting, setSubmitting] = useState(false);
  const [error, setError] = useState<string | null>(null);

  // Hydrate selection from localStorage
  useEffect(() => {
    try {
      const raw = localStorage.getItem(STORAGE_KEY);
      if (raw) {
        const arr = JSON.parse(raw);
        if (Array.isArray(arr)) {
          // Only keep IDs that are still in the unpaid list
          const validIds = new Set(records.map((r) => r.id));
          setSelected(new Set(arr.filter((id: any) => validIds.has(id))));
        }
      }
    } catch (_) {
      // ignore parse errors
    }
    setHydrated(true);
  }, [records]);

  // Persist on change
  useEffect(() => {
    if (!hydrated) return;
    try {
      localStorage.setItem(STORAGE_KEY, JSON.stringify(Array.from(selected)));
    } catch (_) {
      // localStorage may be unavailable (e.g. private mode)
    }
  }, [selected, hydrated]);

  const selectedRecords = useMemo(
    () => records.filter((r) => selected.has(r.id)),
    [records, selected],
  );
  const total = useMemo(
    () => selectedRecords.reduce((s, r) => s + (r.invoice_total || 0), 0),
    [selectedRecords],
  );

  function toggleAll(checked: boolean) {
    if (checked) setSelected(new Set(records.map((r) => r.id)));
    else setSelected(new Set());
  }

  function toggleOne(id: string, checked: boolean) {
    setSelected((prev) => {
      const next = new Set(prev);
      if (checked) next.add(id);
      else next.delete(id);
      return next;
    });
  }

  const allChecked = records.length > 0 && selected.size === records.length;

  async function submitPayment(e: React.FormEvent) {
    e.preventDefault();
    setError(null);
    if (!popFile) {
      setError("POP file is required");
      return;
    }
    setSubmitting(true);
    try {
      const fd = new FormData();
      fd.set("batch_ref", batchRef);
      fd.set("payment_date", paymentDate);
      fd.set("pop_file", popFile);
      fd.set("invoice_ids", JSON.stringify(Array.from(selected)));
      // Optional ZAR paid: only set when the user typed something, so the API
      // treats missing as "no ZAR amount recorded" rather than as 0.
      if (zarPaid.trim() !== "") {
        fd.set("zar_paid", zarPaid.trim());
      }
      const resp = await fetch("/api/payments/create", { method: "POST", body: fd });
      const json = await resp.json().catch(() => ({}));
      if (!resp.ok) {
        setError(json?.error || `HTTP ${resp.status}`);
        return;
      }
      // Success: clear selection, close modal, refresh
      setSelected(new Set());
      setModalOpen(false);
      router.refresh();
    } catch (e: any) {
      setError(String(e?.message || e));
    } finally {
      setSubmitting(false);
    }
  }

  return (
    <>
      <div className="bg-white rounded-lg shadow overflow-hidden">
        <table className="w-full text-sm">
          <thead className="bg-slate-100 text-left">
            <tr>
              <th className="px-3 py-2 w-10">
                <input
                  type="checkbox"
                  aria-label="Select all"
                  checked={allChecked}
                  onChange={(e) => toggleAll(e.target.checked)}
                />
              </th>
              <th className="px-3 py-2">Date</th>
              <th className="px-3 py-2">Invoice No</th>
              <th className="px-3 py-2">Buyer</th>
              <th className="px-3 py-2">PO</th>
              <th className="px-3 py-2 text-right">Total (£)</th>
            </tr>
          </thead>
          <tbody>
            {records.length === 0 && (
              <tr>
                <td colSpan={6} className="px-3 py-8 text-center text-slate-500">
                  No unpaid invoices. All caught up 🎉
                </td>
              </tr>
            )}
            {records.map((r) => (
              <tr key={r.id} className="border-t hover:bg-blue-50">
                <td className="px-3 py-2">
                  <input
                    type="checkbox"
                    aria-label={`Select invoice ${r.invoice_no}`}
                    checked={selected.has(r.id)}
                    onChange={(e) => toggleOne(r.id, e.target.checked)}
                  />
                </td>
                <td className="px-3 py-2">{fmtDate(r.invoice_date)}</td>
                <td className="px-3 py-2 font-medium">{r.invoice_no}</td>
                <td className="px-3 py-2">{r.buyer_name_variant}</td>
                <td className="px-3 py-2 text-slate-600">{r.customer_order_no || "—"}</td>
                <td className="px-3 py-2 text-right tabular-nums">{fmtGBP(r.invoice_total)}</td>
              </tr>
            ))}
          </tbody>
        </table>
      </div>

      {selected.size > 0 && (
        <div className="sticky bottom-0 bg-white border-t shadow-lg p-4 flex items-center justify-between">
          <div className="text-sm">
            <span className="font-semibold">{selected.size}</span> selected ·{" "}
            <span className="font-semibold tabular-nums">{fmtGBP(total)}</span>
          </div>
          <button
            className="bg-brand text-white rounded px-4 py-2 hover:bg-brand-dark disabled:opacity-50"
            disabled={selected.size === 0}
            onClick={() => {
              setBatchRef(nextBatchRefSuggestion());
              setModalOpen(true);
            }}
          >
            Create Payment
          </button>
        </div>
      )}
      {selected.size === 0 && records.length > 0 && (
        <div className="text-sm text-slate-500 text-center py-4">
          Tick invoices above to create a payment batch.
        </div>
      )}

      {modalOpen && (
        <div className="fixed inset-0 bg-black/50 flex items-center justify-center z-50 p-4">
          <div className="bg-white rounded-lg shadow-xl max-w-md w-full p-6 space-y-4">
            <h2 className="text-lg font-semibold">Create Payment Batch</h2>

            <div className="text-sm bg-slate-50 rounded p-3">
              Bundling <strong>{selectedRecords.length}</strong> invoices for{" "}
              <strong className="tabular-nums">{fmtGBP(total)}</strong>.
            </div>

            <form onSubmit={submitPayment} className="space-y-3">
              <div>
                <label className="text-xs text-slate-500">Batch reference</label>
                <input
                  type="text"
                  value={batchRef}
                  onChange={(e) => setBatchRef(e.target.value)}
                  pattern="[A-Za-z0-9 _\-\/.,:()&#'+]{1,100}"
                  required
                  className="w-full border rounded px-3 py-2 font-mono"
                />
              </div>
              <div>
                <label className="text-xs text-slate-500">Payment date</label>
                <input
                  type="date"
                  value={paymentDate}
                  onChange={(e) => setPaymentDate(e.target.value)}
                  required
                  className="w-full border rounded px-3 py-2"
                />
              </div>
              <div>
                <label className="text-xs text-slate-500">POP file (PDF, JPG, PNG — max 8 MB)</label>
                <input
                  type="file"
                  accept=".pdf,.jpg,.jpeg,.png,application/pdf,image/jpeg,image/png"
                  required
                  onChange={(e) => setPopFile(e.target.files?.[0] || null)}
                  className="w-full border rounded px-3 py-2"
                />
              </div>
              <div>
                <label className="text-xs text-slate-500">ZAR Paid <span className="text-slate-400">(optional)</span></label>
                <input
                  type="number"
                  step="0.01"
                  min="0"
                  inputMode="decimal"
                  value={zarPaid}
                  onChange={(e) => setZarPaid(e.target.value)}
                  placeholder="e.g. 12500.00"
                  className="w-full border rounded px-3 py-2 tabular-nums"
                />
              </div>

              {error && (
                <div className="bg-red-50 border border-red-200 text-red-800 rounded p-3 text-sm">
                  {error}
                </div>
              )}

              <div className="flex gap-2 justify-end">
                <button
                  type="button"
                  className="px-4 py-2 rounded border hover:bg-slate-50"
                  onClick={() => {
                    setModalOpen(false);
                    setError(null);
                  }}
                  disabled={submitting}
                >
                  Cancel
                </button>
                <button
                  type="submit"
                  className="bg-brand text-white rounded px-4 py-2 hover:bg-brand-dark disabled:opacity-50"
                  disabled={submitting}
                >
                  {submitting ? "Saving…" : "Confirm & Save"}
                </button>
              </div>
            </form>
          </div>
        </div>
      )}
    </>
  );
}