// src/services/accounting-service.js
/**
 * Accounting Service
 * Read-only wrappers around QBO Accounts, TransactionList Register
 * and the P&L / Balance Sheet reports.
 *
 * Phase 1 — read-only. Keine lokale Cache-Tabelle, alles live aus QBO.
 */
const { getOAuthClient, getQboBaseUrl, makeQboApiCall } = require('../config/qbo');

// QBO minor version — fixiert für stabilen Field-Support
const QBO_MINOR_VERSION = '75';

function getClientInfo() {
    const oauthClient = getOAuthClient();
    const companyId = oauthClient.getToken().realmId;
    const baseUrl = getQboBaseUrl();
    return { oauthClient, companyId, baseUrl };
}

/**
 * Helper: extrahiert .json() aus QBO Response (kompatibel zu intuit-oauth)
 */
function getJson(response) {
    return response.getJson ? response.getJson() : response.json;
}

/**
 * Helper: hängt minorversion an URLs an, ohne bestehende Query-Strings zu zerschießen
 */
function withMinorVersion(url) {
    return url + (url.includes('?') ? '&' : '?') + 'minorversion=' + QBO_MINOR_VERSION;
}

/**
 * Wirft einen lesbaren Fehler bei QBO Faults
 */
function throwIfFault(data, context) {
    if (data && data.Fault && data.Fault.Error) {
        const msg = data.Fault.Error.map(e =>
            `${e.code}: ${e.Message}${e.Detail ? ' - ' + e.Detail : ''}`
        ).join('; ');
        const err = new Error(`QBO ${context} failed: ${msg}`);
        err.qboFault = data.Fault;
        throw err;
    }
}

// ────────────────────────────────────────────────────────────────────
// Accounts
// ────────────────────────────────────────────────────────────────────

/**
 * Lädt Accounts aus QBO. Optional gefiltert nach AccountType.
 *
 * @param {Object} opts
 * @param {string|null} opts.type   - z.B. 'Bank', 'Credit Card', 'Expense', 'Income'
 *                                    (akzeptiert auch 'CreditCard' für URL-Bequemlichkeit)
 * @param {boolean}     opts.activeOnly - default true
 */
async function listAccounts({ type = null, activeOnly = true } = {}) {
    const { companyId, baseUrl } = getClientInfo();

    let where = [];
    if (activeOnly) where.push("Active = true");
    if (type) {
        // Erlaube 'CreditCard' als URL-freundliche Variante
        const normalizedType = type === 'CreditCard' ? 'Credit Card' : type;
        // Apostrophe in QBO-Strings escaped man durch Verdoppelung
        const safe = normalizedType.replace(/'/g, "''");
        where.push(`AccountType = '${safe}'`);
    }

    const whereClause = where.length ? ' WHERE ' + where.join(' AND ') : '';
    const query = `SELECT * FROM Account${whereClause} ORDERBY Name ASC MAXRESULTS 1000`;

    const url = withMinorVersion(
        `${baseUrl}/v3/company/${companyId}/query?query=${encodeURIComponent(query)}`
    );

    const response = await makeQboApiCall({ url, method: 'GET' });
    const data = getJson(response);
    throwIfFault(data, 'Account query');

    const accounts = (data.QueryResponse && data.QueryResponse.Account) || [];

    // Schlanke, frontend-freundliche Form
    return accounts.map(a => ({
        id: a.Id,
        name: a.Name,
        fullyQualifiedName: a.FullyQualifiedName,
        accountType: a.AccountType,
        accountSubType: a.AccountSubType,
        classification: a.Classification, // Asset, Liability, Equity, Revenue, Expense
        currentBalance: a.CurrentBalance != null ? Number(a.CurrentBalance) : null,
        currency: a.CurrencyRef ? a.CurrencyRef.value : null,
        active: a.Active === true,
        syncToken: a.SyncToken
    }));
}

// ────────────────────────────────────────────────────────────────────
// Register (TransactionList Report)
// ────────────────────────────────────────────────────────────────────

/**
 * Liefert den Register eines Accounts (read-only).
 * Verwendet QBOs TransactionList Report — der ist für genau diesen Zweck gedacht
 * und liefert Date / TxnType / DocNum / Name / Account / Amount sauber zurück.
 *
 * @param {Object} opts
 * @param {string} opts.accountId  - QBO Account Id (Pflicht)
 * @param {string} opts.startDate  - YYYY-MM-DD
 * @param {string} opts.endDate    - YYYY-MM-DD
 */
async function getRegister({ accountId, startDate, endDate, includeSplits = true }) {
    if (!accountId) throw new Error('accountId is required');

    const { companyId, baseUrl } = getClientInfo();

    const params = new URLSearchParams();
    if (startDate) params.set('start_date', startDate);
    if (endDate)   params.set('end_date', endDate);
    params.set('source_account', String(accountId));
    params.set('minorversion', QBO_MINOR_VERSION);

    const url = `${baseUrl}/v3/company/${companyId}/reports/TransactionList?${params.toString()}`;

    const response = await makeQboApiCall({ url, method: 'GET' });
    const data = getJson(response);
    throwIfFault(data, 'TransactionList report');

    const result = normalizeTransactionListReport(data);

    // ── NEU: Split-Details nachladen ──
    if (includeSplits) {
        const splitRows = result.rows.filter(r =>
            r.splitAccount === '-Split-' && r.qboId
        );
        if (splitRows.length) {
            const splits = await fetchSplitDetails(splitRows);
            result.rows.forEach(r => {
                if (r.qboId && splits[r.qboId]) {
                    r.splits = splits[r.qboId];
                }
            });
        }
    }

    return result;
}

/**
 * Normalisiert die QBO TransactionList Report Antwort in eine flache Liste.
 * Wir mappen über ColTitle (immer vorhanden), nicht über ColType (manchmal leer).
 */
function normalizeTransactionListReport(report) {
    const columns = (report.Columns && report.Columns.Column) || [];

    // Map: ColTitle (lowercase) → Index
    const colIndex = {};
    columns.forEach((c, i) => {
        if (c.ColTitle) colIndex[c.ColTitle.toLowerCase()] = i;
        if (c.ColType)  colIndex[c.ColType.toLowerCase()]  = i;
    });

    const resolve = (...candidates) => {
        for (const k of candidates) {
            const idx = colIndex[k.toLowerCase()];
            if (idx != null) return idx;
        }
        return null;
    };

    const idxDate    = resolve('Date', 'tx_date');
    const idxType    = resolve('Transaction Type', 'Type', 'txn_type');
    const idxDocNum  = resolve('Num', 'No.', 'doc_num');
    const idxPayee   = resolve('Name', 'Payee', 'name');
    const idxAccount = resolve('Account', 'account_name');
    const idxMemo    = resolve('Memo/Description', 'Memo', 'memo');
    const idxSplit   = resolve('Split', 'split_acc');
    const idxAmount  = resolve('Amount', 'subt_nat_amount', 'subt_nat_home_amount');
    const idxCleared = resolve('Cleared', 'cleared_status', 'clr');

    const cellAt = (colData, idx) => {
        if (idx == null) return null;
        const c = colData[idx];
        return c || null;
    };

    const rows = [];

    function walk(rowGroup) {
        if (!rowGroup) return;
        const items = Array.isArray(rowGroup) ? rowGroup : (rowGroup.Row || []);
        for (const r of items) {
            if (r.type === 'Section' || r.Rows) {
                walk(r.Rows && r.Rows.Row);
                continue;
            }
            if (!r.ColData) continue;

            const dateCell  = cellAt(r.ColData, idxDate);
            const typeCell  = cellAt(r.ColData, idxType);
            const docCell   = cellAt(r.ColData, idxDocNum);
            const payeeCell = cellAt(r.ColData, idxPayee);
            const acctCell  = cellAt(r.ColData, idxAccount);
            const memoCell  = cellAt(r.ColData, idxMemo);
            const splitCell = cellAt(r.ColData, idxSplit);
            const amtCell   = cellAt(r.ColData, idxAmount);
            const clrCell   = cellAt(r.ColData, idxCleared);

            const qboId =
                (dateCell && dateCell.id) ||
                (docCell  && docCell.id)  ||
                (typeCell && typeCell.id) ||
                null;

            let clearedStatus = null;
            if (clrCell && clrCell.value) {
                const v = String(clrCell.value).trim().toUpperCase();
                if (v === 'R' || v === 'C') clearedStatus = v;
            }

            rows.push({
                date:    dateCell  ? dateCell.value  : null,
                type:    typeCell  ? typeCell.value  : null,
                docNum:  docCell   ? docCell.value   : null,
                payee:   payeeCell ? payeeCell.value : null,
                account: acctCell  ? acctCell.value  : null,
                memo:    memoCell  ? memoCell.value  : null,
                amount:  amtCell && amtCell.value !== '' && amtCell.value != null
                            ? Number(amtCell.value) : null,
                splitAccount: splitCell ? splitCell.value : null,
                clearedStatus,
                qboId
            });
        }
    }

    walk(report.Rows && report.Rows.Row);

    return {
        meta: {
            reportName:  report.Header && report.Header.ReportName,
            startPeriod: report.Header && report.Header.StartPeriod,
            endPeriod:   report.Header && report.Header.EndPeriod,
            currency:    report.Header && report.Header.Currency,
            time:        report.Header && report.Header.Time
        },
        columns: columns.map(c => ({ title: c.ColTitle, type: c.ColType || c.type })),
        rows
    };
}

// ────────────────────────────────────────────────────────────────────
// Reports — Profit & Loss, Balance Sheet
// ────────────────────────────────────────────────────────────────────

function buildReportUrl(reportName, params) {
    const { companyId, baseUrl } = getClientInfo();
    const usp = new URLSearchParams();
    Object.entries(params).forEach(([k, v]) => {
        if (v != null && v !== '') usp.set(k, v);
    });
    usp.set('minorversion', QBO_MINOR_VERSION);
    return `${baseUrl}/v3/company/${companyId}/reports/${reportName}?${usp.toString()}`;
}

/**
 * Profit & Loss Report
 * @param {Object} opts
 * @param {string} opts.startDate         - YYYY-MM-DD
 * @param {string} opts.endDate           - YYYY-MM-DD
 * @param {string} opts.accountingMethod  - 'Accrual' | 'Cash' (default 'Accrual')
 */
async function getProfitAndLoss({ startDate, endDate, accountingMethod = 'Accrual' } = {}) {
    const url = buildReportUrl('ProfitAndLoss', {
        start_date: startDate,
        end_date: endDate,
        accounting_method: accountingMethod
    });
    const response = await makeQboApiCall({ url, method: 'GET' });
    const data = getJson(response);
    throwIfFault(data, 'ProfitAndLoss report');
    return data;
}

/**
 * Balance Sheet Report
 * @param {Object} opts
 * @param {string} opts.asOfDate          - YYYY-MM-DD (mapped to end_date)
 * @param {string} opts.accountingMethod  - 'Accrual' | 'Cash' (default 'Accrual')
 */
async function getBalanceSheet({ asOfDate, accountingMethod = 'Accrual' } = {}) {
    const url = buildReportUrl('BalanceSheet', {
        end_date: asOfDate,
        accounting_method: accountingMethod
    });
    const response = await makeQboApiCall({ url, method: 'GET' });
    const data = getJson(response);
    throwIfFault(data, 'BalanceSheet report');
    return data;
}
/**
 * Lädt für eine Liste von Split-Transaktionen die Einzel-Lines aus QBO.
 * Wir laden nur das, was als Split markiert ist und einen qboId hat.
 *
 * Returns: Map<qboId, Array<{account, amount, description}>>
 */
async function fetchSplitDetails(splitRows) {
    if (!splitRows || splitRows.length === 0) return {};

    const { companyId, baseUrl } = getClientInfo();

    // Group by Type, weil QBO unterschiedliche Endpoints für Purchase/Deposit/JournalEntry hat
    const result = {};

    for (const row of splitRows) {
        if (!row.qboId) continue;

        // Type → QBO endpoint name
        const endpoint = mapTypeToEndpoint(row.type);
        if (!endpoint) continue;

        try {
            const url = withMinorVersion(
                `${baseUrl}/v3/company/${companyId}/${endpoint}/${row.qboId}`
            );
            const response = await makeQboApiCall({ url, method: 'GET' });
            const data = getJson(response);

            // Response shape: { Purchase: {...} } or { Deposit: {...} } etc.
            const txn = data[capitalize(endpoint)] || data[endpoint];
            if (!txn || !txn.Line) continue;

            const lines = txn.Line
                .filter(l => l.DetailType !== 'SubTotalLineDetail')
                .map(l => {
                    const detail = l.AccountBasedExpenseLineDetail
                                || l.DepositLineDetail
                                || l.JournalEntryLineDetail
                                || {};
                    const acctRef = detail.AccountRef || {};
                    return {
                        account: acctRef.name || null,
                        amount: l.Amount != null ? Number(l.Amount) : null,
                        description: l.Description || null
                    };
                })
                .filter(l => l.account || l.amount != null);

            if (lines.length) result[row.qboId] = lines;
        } catch (err) {
            // Einzelne Fehler nicht den ganzen Register killen lassen
            console.warn(`Split detail fetch failed for ${row.type} ${row.qboId}:`, err.message);
        }
    }

    return result;
}

function mapTypeToEndpoint(type) {
    if (!type) return null;
    const t = type.toLowerCase();
    if (t.includes('expense') || t.includes('check'))      return 'purchase';
    if (t.includes('deposit'))                              return 'deposit';
    if (t.includes('journal'))                              return 'journalentry';
    if (t.includes('bill payment'))                         return 'billpayment';
    if (t.includes('bill'))                                 return 'bill';
    if (t.includes('credit card'))                          return 'purchase';
    if (t.includes('paycheck') || t.includes('payroll'))    return null; // QBO blockt Paycheck-API
    if (t.includes('tax payment'))                          return null; // dito
    return null;
}

function capitalize(s) {
    return s.charAt(0).toUpperCase() + s.slice(1);
}
module.exports = {
    listAccounts,
    getRegister,
    getProfitAndLoss,
    getBalanceSheet,
    fetchSplitDetails,
    // exposed for testing/debugging
    normalizeTransactionListReport
};