import * as XLSX from 'xlsx';

export function getBcConfig(env = process.env) {
  const legacyWriteMethod = String(env.BC_WRITE_METHOD || 'PATCH').toUpperCase();
  const legacyWriteUrlTemplate = env.BC_WRITE_URL_TEMPLATE || `{{itemsUrl}}('{{itemNo}}')`;
  const legacyWriteBodyTemplate = env.BC_WRITE_BODY_TEMPLATE || JSON.stringify({ cpnpNo: '{{cpnpNo}}' });

  return {
    tenantId: env.BC_TENANT_ID || 'fab724f7-6b6d-4e3b-86e3-8c1e05e36b2a',
    clientId: env.BC_CLIENT_ID || '6f832138-cb48-43e7-8601-efca120b45dc',
    clientSecret: env.BC_CLIENT_SECRET,
    companyId: env.BC_COMPANY_ID || '2acec35c-7d06-ed11-82f8-0022485ceea3',
    writeMethod: legacyWriteMethod,
    writeUrlTemplate: legacyWriteUrlTemplate,
    writeBodyTemplate: legacyWriteBodyTemplate,
    itemsWriteMethod: String(env.BC_ITEMS_WRITE_METHOD || legacyWriteMethod).toUpperCase(),
    itemsWriteUrlTemplate: env.BC_ITEMS_WRITE_URL_TEMPLATE || legacyWriteUrlTemplate,
    itemsWriteBodyTemplate: env.BC_ITEMS_WRITE_BODY_TEMPLATE || null,
    itemUnitsWriteMethod: env.BC_UOM_WRITE_METHOD ? String(env.BC_UOM_WRITE_METHOD).toUpperCase() : 'PATCH',
    itemUnitsWriteUrlTemplate: env.BC_UOM_WRITE_URL_TEMPLATE || `{{itemUnitsOfMeasureUrl}}('{{itemNo}}')`,
    itemUnitsWriteBodyTemplate: env.BC_UOM_WRITE_BODY_TEMPLATE || null,
  };
}

export function getTokenUrl(config) {
  return `https://login.microsoftonline.com/${config.tenantId}/oauth2/v2.0/token`;
}

export function getItemsUrl(config) {
  return `https://api.businesscentral.dynamics.com/v2.0/${config.tenantId}/production/api/craze/integrations/v1.0/companies(${config.companyId})/items`;
}

let tokenCache = { token: null, expiresAt: 0 };

export async function getBCToken(config) {
  const now = Date.now();
  if (tokenCache.token && now < tokenCache.expiresAt) {
    return tokenCache.token;
  }

  if (!config.clientSecret) {
    throw new Error('BC_CLIENT_SECRET env var not set');
  }

  const body = new URLSearchParams({
    grant_type: 'client_credentials',
    client_id: config.clientId,
    client_secret: config.clientSecret,
    scope: 'https://api.businesscentral.dynamics.com/.default',
  });

  const res = await fetch(getTokenUrl(config), {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body,
  });

  const data = await res.json();
  if (!data.access_token) {
    throw new Error('BC token error: ' + JSON.stringify(data));
  }

  tokenCache = { token: data.access_token, expiresAt: now + 55 * 60 * 1000 };
  return data.access_token;
}

export async function fetchAllItems(config, token) {
  const items = [];
  let url = `${getItemsUrl(config)}?$top=1000`;

  while (url) {
    const res = await fetch(url, {
      headers: { Authorization: `Bearer ${token}`, Accept: 'application/json' },
    });

    if (!res.ok) {
      const txt = await res.text();
      throw new Error(`BC GET items failed (${res.status}): ${txt}`);
    }

    const json = await res.json();
    if (Array.isArray(json.value)) {
      items.push(...json.value);
    }

    url = json['@odata.nextLink'] || null;
  }

  return items;
}

export async function findItem(config, token, articleNo) {
  const filter = encodeURIComponent(`no eq '${articleNo}'`);
  const url = `${getItemsUrl(config)}?$filter=${filter}&$select=systemId,no,cpnpNo`;
  const res = await fetch(url, {
    headers: { Authorization: `Bearer ${token}`, Accept: 'application/json' },
  });
  if (!res.ok) {
    const txt = await res.text();
    throw new Error(`BC GET items failed (${res.status}): ${txt}`);
  }
  const json = await res.json();
  const items = json.value || [];
  console.log('[bc-proxy] GET items result:', JSON.stringify(items));
  if (items.length === 0) throw new Error(`Item not found in BC: ${articleNo}`);
  return items[0];
}

export async function patchItemCpnpNo(config, token, item, cpnpNo) {
  const etag = item['@odata.etag'] || '*';
  const itemsUrl = getItemsUrl(config);
  const url = config.writeUrlTemplate
    .replaceAll('{{itemsUrl}}', itemsUrl)
    .replaceAll('{{tenantId}}', config.tenantId)
    .replaceAll('{{companyId}}', config.companyId)
    .replaceAll('{{itemNo}}', encodeURIComponent(String(item.no)))
    .replaceAll('{{systemId}}', encodeURIComponent(String(item.systemId || '')))
    .replaceAll('{{cpnpNo}}', String(cpnpNo));
  const bodyText = config.writeBodyTemplate
    .replaceAll('{{itemsUrl}}', itemsUrl)
    .replaceAll('{{tenantId}}', config.tenantId)
    .replaceAll('{{companyId}}', config.companyId)
    .replaceAll('{{itemNo}}', String(item.no))
    .replaceAll('{{systemId}}', String(item.systemId || ''))
    .replaceAll('{{cpnpNo}}', String(cpnpNo));
  console.log('[bc-proxy] WRITE url:', url);
  const headers = {
    Authorization: `Bearer ${token}`,
    'Content-Type': 'application/json',
  };
  if ((config.writeMethod || 'PATCH') === 'PATCH') {
    headers['If-Match'] = etag;
  }
  const res = await fetch(url, {
    method: config.writeMethod || 'PATCH',
    headers,
    body: bodyText,
  });
  if (!res.ok) {
    const txt = await res.text();
    throw new Error(`BC write failed (${res.status}): ${txt}`);
  }
  return true;
}

export function normalizeValue(value) {
  if (value === null || value === undefined) return '';
  if (value instanceof Date) return value.toISOString();
  if (typeof value === 'object') return JSON.stringify(value);
  return value;
}

export function buildWorkbook(items) {
  const headers = [];
  const seen = new Set();

  items.forEach(item => {
    Object.keys(item || {}).forEach(key => {
      if (key.startsWith('@odata.')) return;
      if (seen.has(key)) return;
      seen.add(key);
      headers.push(key);
    });
  });

  const rows = items.map(item => {
    const row = {};
    headers.forEach(key => {
      row[key] = normalizeValue(item?.[key]);
    });
    return row;
  });

  const ws = XLSX.utils.json_to_sheet(rows, { header: headers });
  ws['!autofilter'] = {
    ref: XLSX.utils.encode_range({
      s: { c: 0, r: 0 },
      e: { c: Math.max(headers.length - 1, 0), r: Math.max(rows.length, 0) },
    }),
  };

  const wb = XLSX.utils.book_new();
  XLSX.utils.book_append_sheet(wb, ws, 'Items');
  return wb;
}