/*
 * CSV and attachment export module (F2). Generates a CSV file from the current
 * report's answers and allows downloading individual attachments. XLSX and ZIP
 * export can be added by integrating SheetJS and JSZip libraries.
 */

import { state, getCurrentReport, getTemplateRecord } from './state.js';
import { dbGetAllByIndex } from './db.js';
import { STORE_ATTACHMENTS } from './constants.js';

/*
 * Exports the active report as a CSV file. Columns are derived from the template
 * definition so field labels appear as headers and field values as the row.
 */
export async function exportReportCSV() {
  const report = getCurrentReport();

  if (!report) {
    throw new Error('No report to export');
  }

  const template = getTemplateRecord(report.templateCode, report.templateVersion);

  if (!template) {
    throw new Error('Template definition needed for export');
  }

  const headers = [];
  const values = [];

  /* Meta columns. */
  headers.push('Report Number', 'Template', 'Version', 'Status', 'Created', 'Updated');
  values.push(
    report.reportNumber,
    report.templateCode,
    String(report.templateVersion),
    report.status,
    report.createdAt,
    report.updatedAt
  );

  /* Dynamic field columns derived from the template definition. */
  for (const section of template.definition.sections || []) {
    for (const field of section.fields || []) {
      if (field.type === 'attachment') {
        continue;
      }

      headers.push(field.label);
      const raw = report.answers[field.id];
      values.push(raw === undefined || raw === null ? '' : String(raw));
    }
  }

  const csvContent = [
    headers.map(csvEscape).join(','),
    values.map(csvEscape).join(',')
  ].join('\r\n');

  downloadBlob(
    new Blob([csvContent], { type: 'text/csv;charset=utf-8' }),
    `${report.reportNumber || 'report'}.csv`
  );
}

/*
 * Exports all attachments for the active report as individual file downloads.
 * A future iteration could bundle these into a ZIP archive using JSZip.
 */
export async function exportReportAttachments() {
  const report = getCurrentReport();

  if (!report) {
    throw new Error('No report to export');
  }

  const attachments = await dbGetAllByIndex(STORE_ATTACHMENTS, 'byReportId', report.id);

  for (const attachment of attachments) {
    downloadBlob(attachment.blob, attachment.generatedFilename);
  }
}

/* ── Helpers ────────────────────────────────────────────────────────────── */

function csvEscape(value) {
  const str = String(value).replace(/"/g, '""');
  return /[",\r\n]/.test(str) ? `"${str}"` : str;
}

function downloadBlob(blob, filename) {
  const url = URL.createObjectURL(blob);
  const anchor = document.createElement('a');
  anchor.href = url;
  anchor.download = filename;
  document.body.appendChild(anchor);
  anchor.click();
  anchor.remove();
  URL.revokeObjectURL(url);
}