// payment-modal.js — ES Module v2
// Supports: Multi-invoice, partial payments, unapplied (downpayments), editable amounts

let bankAccounts = [];
let paymentMethods = [];
let selectedInvoices = []; // { invoice, payAmount }
let dataLoaded = false;
let paymentMode = 'invoice'; // 'invoice' | 'unapplied'

// ============================================================
// Load QBO Data
// ============================================================

async function loadQboData() {
    if (dataLoaded) return;
    try {
        const [accRes, pmRes] = await Promise.all([
            fetch('/api/qbo/accounts'),
            fetch('/api/qbo/payment-methods')
        ]);
        if (accRes.ok) bankAccounts = await accRes.json();
        if (pmRes.ok) paymentMethods = await pmRes.json();
        dataLoaded = true;
    } catch (e) { console.error('Error loading QBO data:', e); }
}

// ============================================================
// Open / Close
// ============================================================

export async function openPaymentModal(invoiceIds = [], mode = 'invoice') {
    await loadQboData();
    paymentMode = mode;
    selectedInvoices = [];

    for (const id of invoiceIds) {
        try {
            const res = await fetch(`/api/invoices/${id}`);
            const data = await res.json();
            if (data.invoice) {
                selectedInvoices.push({
                    invoice: data.invoice,
                    payAmount: parseFloat(data.invoice.total)
                });
            }
        } catch (e) { console.error('Error loading invoice:', id, e); }
    }

    ensureModalElement();
    renderModalContent();
    document.getElementById('payment-modal').classList.add('active');
}

export function openDownpaymentModal() {
    openPaymentModal([], 'unapplied');
}

export function closePaymentModal() {
    const modal = document.getElementById('payment-modal');
    if (modal) modal.classList.remove('active');
    selectedInvoices = [];
}

// ============================================================
// Add / Remove Invoices
// ============================================================

async function addInvoiceById() {
    const input = document.getElementById('payment-add-invoice-id');
    const searchVal = input.value.trim();
    if (!searchVal) return;

    // Suche nach Invoice-Nummer oder ID
    try {
        const res = await fetch('/api/invoices');
        const allInvoices = await res.json();

        const match = allInvoices.find(inv =>
            String(inv.id) === searchVal ||
            String(inv.invoice_number) === searchVal
        );

        if (!match) {
            alert(`Keine Rechnung mit Nr/ID "${searchVal}" gefunden.`);
            return;
        }

        // Validierungen
        if (!match.qbo_id) {
            alert('Diese Rechnung ist noch nicht in QBO.');
            return;
        }
        if (match.paid_date) {
            alert('Diese Rechnung ist bereits bezahlt.');
            return;
        }
        if (selectedInvoices.find(si => si.invoice.id === match.id)) {
            alert('Diese Rechnung ist bereits in der Liste.');
            return;
        }
        if (selectedInvoices.length > 0 && match.customer_id !== selectedInvoices[0].invoice.customer_id) {
            alert('Alle Rechnungen müssen zum selben Kunden gehören.');
            return;
        }

        // Details laden
        const detailRes = await fetch(`/api/invoices/${match.id}`);
        const detailData = await detailRes.json();

        selectedInvoices.push({
            invoice: detailData.invoice,
            payAmount: parseFloat(detailData.invoice.total)
        });

        renderInvoiceList();
        updateTotal();
        input.value = '';
    } catch (e) {
        console.error('Error adding invoice:', e);
        alert('Fehler beim Suchen.');
    }
}

function removeInvoice(invoiceId) {
    selectedInvoices = selectedInvoices.filter(si => si.invoice.id !== invoiceId);
    renderInvoiceList();
    updateTotal();
}

function updatePayAmount(invoiceId, newAmount) {
    const si = selectedInvoices.find(s => s.invoice.id === invoiceId);
    if (si) {
        const val = parseFloat(newAmount) || 0;
        const max = parseFloat(si.invoice.total);
        si.payAmount = Math.min(val, max); // Nicht mehr als Total
    }
    updateTotal();
}

// ============================================================
// DOM
// ============================================================

function ensureModalElement() {
    let modal = document.getElementById('payment-modal');
    if (!modal) {
        modal = document.createElement('div');
        modal.id = 'payment-modal';
        modal.className = 'modal fixed inset-0 bg-black bg-opacity-50 z-50 justify-center items-start pt-10 overflow-y-auto';
        document.body.appendChild(modal);
    }
}

function renderModalContent() {
    const modal = document.getElementById('payment-modal');
    if (!modal) return;

    const accountOptions = bankAccounts.map(acc =>
        `<option value="${acc.id}">${acc.name}</option>`
    ).join('');

    const filteredMethods = paymentMethods.filter(pm =>
        pm.name.toLowerCase().includes('check') || pm.name.toLowerCase().includes('ach')
    );
    const methodsToShow = filteredMethods.length > 0 ? filteredMethods : paymentMethods;
    const methodOptions = methodsToShow.map(pm =>
        `<option value="${pm.id}">${pm.name}</option>`
    ).join('');

    const today = new Date().toISOString().split('T')[0];
    const isUnapplied = paymentMode === 'unapplied';
    const title = isUnapplied ? '💰 Record Downpayment' : '💰 Record Payment';

    modal.innerHTML = `
        <div class="bg-white rounded-lg shadow-2xl w-full max-w-2xl mx-auto p-8">
            <div class="flex justify-between items-center mb-4">
                <h2 class="text-2xl font-bold text-gray-800">${title}</h2>
                <button onclick="window.paymentModal.close()" class="text-gray-400 hover:text-gray-600">
                    <svg class="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12" />
                    </svg>
                </button>
            </div>

            <!-- Mode Tabs -->
            <div class="flex gap-2 mb-4">
                <button onclick="window.paymentModal.switchMode('invoice')"
                    class="px-4 py-2 rounded-md text-sm font-medium ${!isUnapplied ? 'bg-blue-600 text-white' : 'bg-gray-100 text-gray-600 hover:bg-gray-200'}">
                    Against Invoice(s)
                </button>
                <button onclick="window.paymentModal.switchMode('unapplied')"
                    class="px-4 py-2 rounded-md text-sm font-medium ${isUnapplied ? 'bg-blue-600 text-white' : 'bg-gray-100 text-gray-600 hover:bg-gray-200'}">
                    Downpayment (Unapplied)
                </button>
            </div>

            ${isUnapplied ? renderUnappliedSection() : renderInvoiceSection()}

            <!-- Payment Details -->
            <div class="grid grid-cols-2 gap-4 mb-6">
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Payment Date</label>
                    <input type="date" id="payment-date" value="${today}"
                           class="w-full px-3 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500">
                </div>
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Reference # (Check / ACH)</label>
                    <input type="text" id="payment-reference" placeholder="Check # or ACH ref"
                           class="w-full px-3 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500">
                </div>
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Payment Method</label>
                    <select id="payment-method"
                            class="w-full px-3 py-2 border border-gray-300 rounded-md bg-white focus:ring-blue-500 focus:border-blue-500">
                        ${methodOptions}
                    </select>
                </div>
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Deposit To</label>
                    <select id="payment-deposit-to"
                            class="w-full px-3 py-2 border border-gray-300 rounded-md bg-white focus:ring-blue-500 focus:border-blue-500">
                        ${accountOptions}
                    </select>
                </div>
            </div>

            <!-- Total -->
            <div class="bg-gray-50 p-4 rounded-lg mb-6">
                <div class="flex justify-between items-center">
                    <span class="text-lg font-bold text-gray-700">Total Payment:</span>
                    <span id="payment-total" class="text-2xl font-bold text-blue-600">$0.00</span>
                </div>
            </div>

            <!-- Actions -->
            <div class="flex justify-end space-x-3">
                <button onclick="window.paymentModal.close()"
                        class="px-6 py-2 bg-gray-200 text-gray-700 rounded-md hover:bg-gray-300">Cancel</button>
                <button onclick="window.paymentModal.submit()" id="payment-submit-btn"
                        class="px-6 py-2 bg-green-600 text-white rounded-md hover:bg-green-700 font-semibold">
                    💰 Record Payment in QBO
                </button>
            </div>
        </div>`;

    if (!isUnapplied) {
        renderInvoiceList();
    }
    updateTotal();
}

function renderInvoiceSection() {
    return `
        <div class="mb-6">
            <label class="block text-sm font-medium text-gray-700 mb-2">Invoices</label>
            <div id="payment-invoice-list" class="border border-gray-200 rounded-lg max-h-60 overflow-y-auto"></div>
            <div class="mt-2 flex items-center gap-2">
                <input type="text" id="payment-add-invoice-id" placeholder="Invoice # oder ID..."
                       class="flex-1 px-3 py-1.5 border border-gray-300 rounded-md text-sm"
                       onkeydown="if(event.key==='Enter'){event.preventDefault();window.paymentModal.addById();}">
                <button onclick="window.paymentModal.addById()"
                        class="px-3 py-1.5 bg-blue-600 text-white rounded-md text-sm hover:bg-blue-700">+ Add</button>
            </div>
        </div>`;
}

function renderUnappliedSection() {
    return `
        <div class="mb-6">
            <div class="bg-yellow-50 border border-yellow-200 rounded-lg p-4 mb-4">
                <p class="text-sm text-yellow-800">
                    <strong>Downpayment / Vorabzahlung:</strong> Das Geld wird als Kundenguthaben in QBO verbucht
                    und kann später einer Rechnung zugeordnet werden.
                </p>
            </div>
            <div class="grid grid-cols-2 gap-4">
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Customer</label>
                    <select id="payment-customer" class="w-full px-3 py-2 border border-gray-300 rounded-md bg-white text-sm">
                        <option value="">-- Kunde wählen --</option>
                        ${(window.customers || []).filter(c => c.qbo_id).map(c =>
                            `<option value="${c.id}" data-qbo-id="${c.qbo_id}">${c.name}</option>`
                        ).join('')}
                    </select>
                </div>
                <div>
                    <label class="block text-sm font-medium text-gray-700 mb-1">Amount</label>
                    <input type="number" id="payment-unapplied-amount" step="0.01" min="0" placeholder="0.00"
                           class="w-full px-3 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500"
                           oninput="window.paymentModal.updateTotal()">
                </div>
            </div>
        </div>`;
}

function renderInvoiceList() {
    const container = document.getElementById('payment-invoice-list');
    if (!container) return;

    if (selectedInvoices.length === 0) {
        container.innerHTML = `<div class="p-4 text-center text-gray-400 text-sm">Keine Rechnungen — bitte unten hinzufügen</div>`;
        return;
    }

    container.innerHTML = selectedInvoices.map(si => {
        const inv = si.invoice;
        const total = parseFloat(inv.total);
        const isPartial = si.payAmount < total;

        return `
        <div class="flex items-center justify-between px-4 py-3 border-b border-gray-100 last:border-0 hover:bg-gray-50">
            <div class="flex-1">
                <span class="font-medium text-gray-900">#${inv.invoice_number || 'Draft'}</span>
                <span class="text-gray-500 text-sm ml-2">${inv.customer_name || ''}</span>
                <span class="text-gray-400 text-xs ml-2">(Total: $${total.toFixed(2)})</span>
                ${isPartial ? '<span class="text-xs text-yellow-600 ml-2 font-semibold">Partial</span>' : ''}
            </div>
            <div class="flex items-center gap-2">
                <span class="text-gray-500 text-sm">$</span>
                <input type="number" step="0.01" min="0.01" max="${total}"
                       value="${si.payAmount.toFixed(2)}"
                       onchange="window.paymentModal.updateAmount(${inv.id}, this.value)"
                       class="w-28 px-2 py-1 border border-gray-300 rounded text-sm text-right font-semibold
                              ${isPartial ? 'bg-yellow-50 border-yellow-300' : ''}">
                <button onclick="window.paymentModal.removeInvoice(${inv.id})"
                        class="text-red-400 hover:text-red-600 text-sm ml-1">✕</button>
            </div>
        </div>`;
    }).join('');
}

function updateTotal() {
    const totalEl = document.getElementById('payment-total');
    if (!totalEl) return;

    let total = 0;
    if (paymentMode === 'unapplied') {
        const amountInput = document.getElementById('payment-unapplied-amount');
        total = parseFloat(amountInput?.value) || 0;
    } else {
        total = selectedInvoices.reduce((sum, si) => sum + si.payAmount, 0);
    }

    totalEl.textContent = `$${total.toFixed(2)}`;
}

// ============================================================
// Submit
// ============================================================

async function submitPayment() {
    const paymentDate = document.getElementById('payment-date').value;
    const reference = document.getElementById('payment-reference').value;
    const methodSelect = document.getElementById('payment-method');
    const depositSelect = document.getElementById('payment-deposit-to');
    const methodId = methodSelect.value;
    const methodName = methodSelect.options[methodSelect.selectedIndex]?.text || '';
    const depositToId = depositSelect.value;
    const depositToName = depositSelect.options[depositSelect.selectedIndex]?.text || '';

    if (!paymentDate || !methodId || !depositToId) {
        alert('Bitte alle Felder ausfüllen.');
        return;
    }

    let body;

    if (paymentMode === 'unapplied') {
        // --- Downpayment ---
        const custSelect = document.getElementById('payment-customer');
        const customerId = custSelect?.value;
        const customerQboId = custSelect?.selectedOptions[0]?.getAttribute('data-qbo-id');
        const amount = parseFloat(document.getElementById('payment-unapplied-amount')?.value) || 0;

        if (!customerId || !customerQboId) { alert('Bitte Kunde wählen.'); return; }
        if (amount <= 0) { alert('Bitte Betrag eingeben.'); return; }

        body = {
            mode: 'unapplied',
            customer_id: parseInt(customerId),
            customer_qbo_id: customerQboId,
            total_amount: amount,
            payment_date: paymentDate,
            reference_number: reference,
            payment_method_id: methodId,
            payment_method_name: methodName,
            deposit_to_account_id: depositToId,
            deposit_to_account_name: depositToName
        };

        if (!confirm(`Downpayment $${amount.toFixed(2)} an QBO senden?`)) return;

    } else {
        // --- Normal / Partial / Multi ---
        if (selectedInvoices.length === 0) { alert('Bitte Rechnungen hinzufügen.'); return; }

        const total = selectedInvoices.reduce((s, si) => s + si.payAmount, 0);
        const nums = selectedInvoices.map(si => `#${si.invoice.invoice_number || si.invoice.id}`).join(', ');
        const hasPartial = selectedInvoices.some(si => si.payAmount < parseFloat(si.invoice.total));

        let msg = `Payment $${total.toFixed(2)} für ${nums} an QBO senden?`;
        if (hasPartial) msg += '\n⚠️ Enthält Teilzahlung(en).';
        if (!confirm(msg)) return;

        body = {
            mode: 'invoice',
            invoice_payments: selectedInvoices.map(si => ({
                invoice_id: si.invoice.id,
                amount: si.payAmount
            })),
            payment_date: paymentDate,
            reference_number: reference,
            payment_method_id: methodId,
            payment_method_name: methodName,
            deposit_to_account_id: depositToId,
            deposit_to_account_name: depositToName
        };
    }

    const submitBtn = document.getElementById('payment-submit-btn');
    submitBtn.innerHTML = '⏳ Wird gesendet...';
    submitBtn.disabled = true;
    if (typeof showSpinner === 'function') showSpinner('Erstelle Payment in QBO...');

    try {
        const response = await fetch('/api/qbo/record-payment', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(body)
        });
        const result = await response.json();

        if (response.ok) {
            alert(`✅ ${result.message}`);
            closePaymentModal();
            if (window.invoiceView) window.invoiceView.loadInvoices();
        } else {
            alert(`❌ Fehler: ${result.error}`);
        }
    } catch (error) {
        console.error('Payment error:', error);
        alert('Netzwerkfehler.');
    } finally {
        submitBtn.innerHTML = '💰 Record Payment in QBO';
        submitBtn.disabled = false;
        if (typeof hideSpinner === 'function') hideSpinner();
    }
}

function switchMode(mode) {
    paymentMode = mode;
    renderModalContent();
}

// ============================================================
// Expose
// ============================================================

window.paymentModal = {
    open: openPaymentModal,
    openDownpayment: openDownpaymentModal,
    close: closePaymentModal,
    submit: submitPayment,
    addById: addInvoiceById,
    removeInvoice: removeInvoice,
    updateAmount: updatePayAmount,
    updateTotal: updateTotal,
    switchMode: switchMode
};