import { ExcelRow } from '../types';

export interface MappingFieldPreview {
  sourceLabel: string;
  sourceIndex: number | null;
  targetField: string;
  value: any;
}

export interface BusinessCentralMappingPreview {
  articleNo: string;
  itemsPayload: Record<string, any>;
  itemUnitsOfMeasurePayload: Record<string, any>;
  itemsFields: MappingFieldPreview[];
  itemUnitsFields: MappingFieldPreview[];
}

function findHeaderIndex(headers: string[], patterns: string[]): number {
  const normalized = headers.map(h => String(h || '').toLowerCase());
  return normalized.findIndex(header =>
    patterns.every(pattern => header.includes(pattern.toLowerCase()))
  );
}

function formatDateForBc(value: any): string | null {
  if (value === null || value === undefined || value === '') return null;

  if (typeof value === 'number' && value >= 25569 && value <= 60000) {
    const excelEpoch = new Date(1899, 11, 30);
    const date = new Date(excelEpoch.getTime() + value * 86400000);
    return date.toISOString().split('T')[0];
  }

  const str = String(value).trim();
  if (!str) return null;
  if (/^\d{4}-\d{2}-\d{2}$/.test(str)) return str;

  const parsed = new Date(str);
  if (!Number.isNaN(parsed.getTime())) {
    return parsed.toISOString().split('T')[0];
  }

  return str;
}

function getValue(row: ExcelRow, index: number | null): any {
  if (index === null || index < 0) return null;
  const value = row[index];
  return value === undefined || value === '' ? null : value;
}

function toBcDecimal(value: any): number | null {
  if (value === null || value === undefined || value === '') return null;
  if (typeof value === 'number' && Number.isFinite(value)) return value;

  const normalized = String(value).trim().replace(/\s+/g, '').replace(',', '.');
  if (!normalized) return null;

  const parsed = Number(normalized);
  return Number.isFinite(parsed) ? parsed : null;
}

function makeFieldPreview(
  sourceLabel: string,
  sourceIndex: number | null,
  targetField: string,
  value: any
): MappingFieldPreview {
  return { sourceLabel, sourceIndex, targetField, value };
}

export function buildBusinessCentralMappingPreview(headers: string[], row: ExcelRow): BusinessCentralMappingPreview {
  const articleNoIdx = findHeaderIndex(headers, ['article', 'no']);
  const articleDetailsEnIdx = findHeaderIndex(headers, ['article', 'details', 'english']);
  const articleDetailsDeIdx = findHeaderIndex(headers, ['article', 'details', 'german']);
  const launchDateIdx = findHeaderIndex(headers, ['launch']);
  const readyToOrderDateIdx = findHeaderIndex(headers, ['ready']);
  const moqIdx = findHeaderIndex(headers, ['moq']);
  const shortDeIdx = findHeaderIndex(headers, ['short', 'description', 'german']);
  const shortEnIdx = findHeaderIndex(headers, ['short', 'description', 'english']);
  const cpnpIdx = findHeaderIndex(headers, ['cpnp']);

  const unitsOuterIdx = findHeaderIndex(headers, ['units', 'outer']);
  const innerWIdx = findHeaderIndex(headers, ['inner', 'w']);
  const innerLIdx = findHeaderIndex(headers, ['inner', 'l']);
  const innerHIdx = findHeaderIndex(headers, ['inner', 'h']);
  const outerWIdx = findHeaderIndex(headers, ['outer', 'w']);
  const outerLIdx = findHeaderIndex(headers, ['outer', 'l']);
  const outerHIdx = findHeaderIndex(headers, ['outer', 'h']);

  const articleNo = String(getValue(row, articleNoIdx) ?? '');

  const itemsPayload = {
    no: getValue(row, articleNoIdx),
    articleDetailsEnglish: getValue(row, articleDetailsEnIdx),
    articleDetailsGerman: getValue(row, articleDetailsDeIdx),
    launchDate: formatDateForBc(getValue(row, launchDateIdx)),
    readyToOrderDate: formatDateForBc(getValue(row, readyToOrderDateIdx)),
    minimumOrderQuantity: toBcDecimal(getValue(row, moqIdx)),
    shortDescriptionInGerman: getValue(row, shortDeIdx),
    shortDescriptionInEnglish: getValue(row, shortEnIdx),
    cpnpNo: getValue(row, cpnpIdx),
  };

  const itemUnitsOfMeasurePayload = {
    itemNo: getValue(row, articleNoIdx),
    qtyPerUnitOfMeasure6: toBcDecimal(getValue(row, unitsOuterIdx)),
    width4: toBcDecimal(getValue(row, innerWIdx)),
    length4: toBcDecimal(getValue(row, innerLIdx)),
    height4: toBcDecimal(getValue(row, innerHIdx)),
    width6: toBcDecimal(getValue(row, outerWIdx)),
    length6: toBcDecimal(getValue(row, outerLIdx)),
    height6: toBcDecimal(getValue(row, outerHIdx)),
  };

  return {
    articleNo,
    itemsPayload,
    itemUnitsOfMeasurePayload,
    itemsFields: [
      makeFieldPreview('Article No.', articleNoIdx, 'no', itemsPayload.no),
      makeFieldPreview('Article Details - English', articleDetailsEnIdx, 'articleDetailsEnglish', itemsPayload.articleDetailsEnglish),
      makeFieldPreview('Article Details - German', articleDetailsDeIdx, 'articleDetailsGerman', itemsPayload.articleDetailsGerman),
      makeFieldPreview('Launch Date', launchDateIdx, 'launchDate', itemsPayload.launchDate),
      makeFieldPreview('Ready to Order Date', readyToOrderDateIdx, 'readyToOrderDate', itemsPayload.readyToOrderDate),
      makeFieldPreview('MOQ', moqIdx, 'minimumOrderQuantity', itemsPayload.minimumOrderQuantity),
      makeFieldPreview('Short Description - German', shortDeIdx, 'shortDescriptionInGerman', itemsPayload.shortDescriptionInGerman),
      makeFieldPreview('Short Description - English', shortEnIdx, 'shortDescriptionInEnglish', itemsPayload.shortDescriptionInEnglish),
      makeFieldPreview('CPNP', cpnpIdx, 'cpnpNo', itemsPayload.cpnpNo),
    ],
    itemUnitsFields: [
      makeFieldPreview('Article No.', articleNoIdx, 'itemNo', itemUnitsOfMeasurePayload.itemNo),
      makeFieldPreview('Units Outer', unitsOuterIdx, 'qtyPerUnitOfMeasure6', itemUnitsOfMeasurePayload.qtyPerUnitOfMeasure6),
      makeFieldPreview('CDU/Inner W (cm)', innerWIdx, 'width4', itemUnitsOfMeasurePayload.width4),
      makeFieldPreview('CDU/Inner L (cm)', innerLIdx, 'length4', itemUnitsOfMeasurePayload.length4),
      makeFieldPreview('CDU/Inner H (cm)', innerHIdx, 'height4', itemUnitsOfMeasurePayload.height4),
      makeFieldPreview('Outer W (cm)', outerWIdx, 'width6', itemUnitsOfMeasurePayload.width6),
      makeFieldPreview('Outer L (cm)', outerLIdx, 'length6', itemUnitsOfMeasurePayload.length6),
      makeFieldPreview('Outer H (cm)', outerHIdx, 'height6', itemUnitsOfMeasurePayload.height6),
    ],
  };
}