/**
 * AAMOS Bank CSV Parsers
 * Stöder: Swedbank, SEB, Handelsbanken, Nordea, auto-detect
 */

/**
 * Normalisera svenska siffror: "1 500,00" → 1500.00
 */
function parseSwedishNumber(str) {
  if (str == null || str === '') return null;
  // Ta bort mellanslagsseparatorer, ersätt komma med punkt
  const cleaned = String(str).trim().replace(/\s/g, '').replace(',', '.');
  const val = parseFloat(cleaned);
  return isNaN(val) ? null : val;
}

/**
 * Splitta en CSV-rad med hänsyn till citattecken
 */
function splitRow(line, delimiter) {
  const result = [];
  let current = '';
  let inQuotes = false;
  for (let i = 0; i < line.length; i++) {
    const ch = line[i];
    if (ch === '"') {
      inQuotes = !inQuotes;
    } else if (!inQuotes && ch === delimiter) {
      result.push(current.trim().replace(/^"|"$/g, ''));
      current = '';
    } else {
      current += ch;
    }
  }
  result.push(current.trim().replace(/^"|"$/g, ''));
  return result;
}

/**
 * Hitta rader (skippa tomma rader)
 */
function getLines(csv) {
  return csv.split('\n').map(l => l.replace(/\r$/, '')).filter(l => l.trim() !== '');
}

// ── Swedbank ──────────────────────────────────────────────────────────────────
// Format: Datum;Transaktion;Kategori;Belopp;Saldo
export function parseSwedbank(csv) {
  const lines = getLines(csv);
  const headerLine = lines[0];
  const headers = splitRow(headerLine, ';').map(h => h.trim());

  const iDatum       = headers.findIndex(h => /^datum$/i.test(h));
  const iTransaktion = headers.findIndex(h => /^transaktion$/i.test(h));
  const iBelopp      = headers.findIndex(h => /^belopp$/i.test(h));
  const iSaldo       = headers.findIndex(h => /^saldo$/i.test(h));

  if (iDatum === -1 || iBelopp === -1) {
    throw new Error('Swedbank: saknar kolumnerna Datum och/eller Belopp');
  }

  const rows = [];
  for (let i = 1; i < lines.length; i++) {
    const cols = splitRow(lines[i], ';');
    const amount = parseSwedishNumber(cols[iBelopp]);
    if (amount == null) continue;
    rows.push({
      date:        (cols[iDatum] || '').trim(),
      description: (cols[iTransaktion] || '').trim(),
      amount,
      balance:     iSaldo >= 0 ? parseSwedishNumber(cols[iSaldo]) : null,
      raw:         lines[i],
    });
  }
  return rows;
}

// ── SEB ───────────────────────────────────────────────────────────────────────
// Format: Bokföringsdatum,Valutadatum,Namn/Beskrivning,Belopp,Saldo
export function parseSEB(csv) {
  const lines = getLines(csv);
  const headerLine = lines[0];
  const headers = splitRow(headerLine, ',').map(h => h.trim());

  const iBokDatum = headers.findIndex(h => /bokf[öo]ringsdatum/i.test(h));
  const iNamn     = headers.findIndex(h => /namn|beskrivning/i.test(h));
  const iBelopp   = headers.findIndex(h => /^belopp$/i.test(h));
  const iSaldo    = headers.findIndex(h => /^saldo$/i.test(h));

  if (iBokDatum === -1 || iBelopp === -1) {
    throw new Error('SEB: saknar kolumnerna Bokföringsdatum och/eller Belopp');
  }

  const rows = [];
  for (let i = 1; i < lines.length; i++) {
    const cols = splitRow(lines[i], ',');
    const amount = parseSwedishNumber(cols[iBelopp]);
    if (amount == null) continue;
    rows.push({
      date:        (cols[iBokDatum] || '').trim(),
      description: (iNamn >= 0 ? cols[iNamn] : '').trim(),
      amount,
      balance:     iSaldo >= 0 ? parseSwedishNumber(cols[iSaldo]) : null,
      raw:         lines[i],
    });
  }
  return rows;
}

// ── Handelsbanken ─────────────────────────────────────────────────────────────
// Format: Datum\tText\tBelopp\tSaldo (tab-separerat)
export function parseHandelsbanken(csv) {
  const lines = getLines(csv);
  const headerLine = lines[0];
  const headers = splitRow(headerLine, '\t').map(h => h.trim());

  const iDatum  = headers.findIndex(h => /^datum$/i.test(h));
  const iText   = headers.findIndex(h => /^text$/i.test(h));
  const iBelopp = headers.findIndex(h => /^belopp$/i.test(h));
  const iSaldo  = headers.findIndex(h => /^saldo$/i.test(h));

  if (iDatum === -1 || iBelopp === -1) {
    throw new Error('Handelsbanken: saknar kolumnerna Datum och/eller Belopp');
  }

  const rows = [];
  for (let i = 1; i < lines.length; i++) {
    const cols = splitRow(lines[i], '\t');
    const amount = parseSwedishNumber(cols[iBelopp]);
    if (amount == null) continue;
    rows.push({
      date:        (cols[iDatum] || '').trim(),
      description: (iText >= 0 ? cols[iText] : '').trim(),
      amount,
      balance:     iSaldo >= 0 ? parseSwedishNumber(cols[iSaldo]) : null,
      raw:         lines[i],
    });
  }
  return rows;
}

// ── Nordea ────────────────────────────────────────────────────────────────────
// Format: Bokföringsdag;Belopp;Avsändare;Mottagare;Namn;Rubrik;Saldo
export function parseNordea(csv) {
  const lines = getLines(csv);
  const headerLine = lines[0];
  const headers = splitRow(headerLine, ';').map(h => h.trim());

  const iBokDag  = headers.findIndex(h => /bokf[öo]ringsdag/i.test(h));
  const iBelopp  = headers.findIndex(h => /^belopp$/i.test(h));
  const iNamn    = headers.findIndex(h => /^namn$/i.test(h));
  const iRubrik  = headers.findIndex(h => /^rubrik$/i.test(h));
  const iSaldo   = headers.findIndex(h => /^saldo$/i.test(h));

  if (iBokDag === -1 || iBelopp === -1) {
    throw new Error('Nordea: saknar kolumnerna Bokföringsdag och/eller Belopp');
  }

  const rows = [];
  for (let i = 1; i < lines.length; i++) {
    const cols = splitRow(lines[i], ';');
    const amount = parseSwedishNumber(cols[iBelopp]);
    if (amount == null) continue;
    // Beskrivning: kombinera Namn + Rubrik
    const namePart   = (iNamn   >= 0 ? cols[iNamn]   : '').trim();
    const rubrikPart = (iRubrik >= 0 ? cols[iRubrik] : '').trim();
    const description = [namePart, rubrikPart].filter(Boolean).join(' — ');
    rows.push({
      date:        (cols[iBokDag] || '').trim(),
      description,
      amount,
      balance:     iSaldo >= 0 ? parseSwedishNumber(cols[iSaldo]) : null,
      raw:         lines[i],
    });
  }
  return rows;
}

// ── Auto-detect ───────────────────────────────────────────────────────────────
export function detectBank(csv) {
  const firstLine = getLines(csv)[0] || '';
  const lower = firstLine.toLowerCase();

  // Handelsbanken: tab-separerad med Datum, Text
  if (firstLine.includes('\t')) return 'handelsbanken';

  // Nordea: semikolon, innehåller "bokföringsdag"
  if (lower.includes('bokf') && lower.includes('ringsdag') && firstLine.includes(';')) return 'nordea';

  // SEB: komma-separerad, innehåller "bokföringsdatum" eller "valutadatum"
  if ((lower.includes('bokf') && lower.includes('ringsdatum') || lower.includes('valutadatum')) && firstLine.includes(',')) return 'seb';

  // Swedbank: semikolon, innehåller "transaktion"
  if (lower.includes('transaktion') && firstLine.includes(';')) return 'swedbank';

  // Fallback: prova utifrån separator
  if (firstLine.includes(';')) {
    if (lower.includes('belopp') && lower.includes('saldo')) return 'nordea'; // educated guess
    return 'swedbank';
  }
  if (firstLine.includes(',')) return 'seb';
  return null;
}

// ── Unified parse ─────────────────────────────────────────────────────────────
export function parseCSV(bank, csv) {
  const resolvedBank = bank === 'auto' ? detectBank(csv) : bank;
  if (!resolvedBank) throw new Error('Kunde inte auto-detektera bankformat');

  switch (resolvedBank.toLowerCase()) {
    case 'swedbank':       return { bank: 'swedbank',       rows: parseSwedbank(csv) };
    case 'seb':            return { bank: 'seb',            rows: parseSEB(csv) };
    case 'handelsbanken':  return { bank: 'handelsbanken',  rows: parseHandelsbanken(csv) };
    case 'nordea':         return { bank: 'nordea',         rows: parseNordea(csv) };
    default:
      throw new Error(`Okänt bankformat: ${resolvedBank}`);
  }
}

export const SUPPORTED_FORMATS = {
  swedbank: {
    delimiter: ';',
    columns: ['Datum', 'Transaktion', 'Kategori', 'Belopp', 'Saldo'],
    date_format: 'YYYY-MM-DD',
    number_format: 'swedish (komma decimal, mellanslagstusentalsseparator)',
  },
  seb: {
    delimiter: ',',
    columns: ['Bokföringsdatum', 'Valutadatum', 'Namn/Beskrivning', 'Belopp', 'Saldo'],
    date_format: 'YYYY-MM-DD',
    number_format: 'decimal punkt',
  },
  handelsbanken: {
    delimiter: 'tab',
    columns: ['Datum', 'Text', 'Belopp', 'Saldo'],
    date_format: 'YYYY-MM-DD',
    number_format: 'swedish (komma decimal, mellanslagstusentalsseparator)',
  },
  nordea: {
    delimiter: ';',
    columns: ['Bokföringsdag', 'Belopp', 'Avsändare', 'Mottagare', 'Namn', 'Rubrik', 'Saldo'],
    date_format: 'YYYY-MM-DD',
    number_format: 'decimal punkt',
  },
};