import { promises as fs } from 'node:fs';
import path from 'node:path';

import { PDFDocument } from 'pdf-lib';

import type { EoiContext } from '@/lib/services/eoi-context';

/**
 * Source PDF for the in-app EOI pathway. Must contain AcroForm fields whose
 * names match the Documenso template's `formValues` keys exactly:
 *
 *   Text:     Name, Email, Address, Yacht Name, Length, Width, Draft,
 *             Berth Number
 *   Checkbox: Lease_10, Purchase
 *
 * See assets/eoi-template/README.md for full details and the field mapping
 * doc at docs/eoi-documenso-field-mapping.md for the canonical list.
 */
const DEFAULT_EOI_TEMPLATE_PATH = path.join(process.cwd(), 'assets', 'eoi-template.pdf');

function eoiTemplatePath(): string {
  return process.env.EOI_TEMPLATE_PDF_PATH ?? DEFAULT_EOI_TEMPLATE_PATH;
}

export async function loadEoiTemplatePdf(): Promise<Uint8Array> {
  const filePath = eoiTemplatePath();
  try {
    return await fs.readFile(filePath);
  } catch (err) {
    throw new Error(
      `EOI source PDF not found at ${filePath}. Drop the same PDF used by the Documenso template (with AcroForm fields: Name, Email, Address, Yacht Name, Length, Width, Draft, Berth Number, Lease_10, Purchase) at this path, or override via EOI_TEMPLATE_PDF_PATH. Original error: ${(err as Error).message}`,
    );
  }
}

function formatAddress(address: EoiContext['client']['address']): string {
  if (!address) return '';
  return [address.street, address.city, address.country].filter(Boolean).join(', ');
}

function setText(form: ReturnType<PDFDocument['getForm']>, name: string, value: string): void {
  try {
    form.getTextField(name).setText(value);
  } catch {
    // Field absent or wrong type — skip silently so a slightly different PDF
    // template still produces output. Missing field issues surface in QA, not
    // at runtime as a 500.
  }
}

function setCheckbox(
  form: ReturnType<PDFDocument['getForm']>,
  name: string,
  checked: boolean,
): void {
  try {
    const cb = form.getCheckBox(name);
    if (checked) cb.check();
    else cb.uncheck();
  } catch {
    // See comment in setText.
  }
}

/**
 * Fills the AcroForm fields of the EOI source PDF with values drawn from
 * EoiContext. Field names mirror the Documenso template `formValues` keys so
 * a single source PDF can serve both pathways.
 *
 * The form is left interactive (not flattened) so a recipient can still tweak
 * fields if needed before signing.
 */
export async function fillEoiFormFields(
  pdfBytes: Uint8Array,
  context: EoiContext,
): Promise<Uint8Array> {
  const doc = await PDFDocument.load(pdfBytes);
  const form = doc.getForm();

  setText(form, 'Name', context.client.fullName);
  setText(form, 'Email', context.client.primaryEmail ?? '');
  setText(form, 'Address', formatAddress(context.client.address));
  // Yacht + berth (EOI Section 3) are optional — leave the AcroForm fields
  // blank when the interest hasn't been linked to either.
  setText(form, 'Yacht Name', context.yacht?.name ?? '');
  setText(form, 'Length', context.yacht?.lengthFt ?? '');
  setText(form, 'Width', context.yacht?.widthFt ?? '');
  setText(form, 'Draft', context.yacht?.draftFt ?? '');
  setText(form, 'Berth Number', context.berth?.mooringNumber ?? '');

  setCheckbox(form, 'Purchase', true);
  setCheckbox(form, 'Lease_10', false);

  return doc.save();
}

/**
 * Convenience: loads the source PDF from disk and returns the filled bytes.
 */
export async function generateEoiPdfFromTemplate(context: EoiContext): Promise<Uint8Array> {
  const bytes = await loadEoiTemplatePdf();
  return fillEoiFormFields(bytes, context);
}