window.addEventListener('DOMContentLoaded', () => {
    const CLP = new Intl.NumberFormat('es-CL', { style: 'currency', currency: 'CLP', maximumFractionDigits: 0 });

    // --- Selección de Elementos del DOM ---
    const invoiceInput = document.getElementById('invoice-input');
    const budgetInput = document.getElementById('budget-input');
    const dropzone = document.getElementById('dropzone');
    const budgetDropzone = document.getElementById('budget-dropzone');
    const tbody = document.getElementById('tbody');
    const totalSpan = document.getElementById('total');
    const errorEl = document.getElementById('error');
    const budgetErrorEl = document.getElementById('budget-error');
    const processBtn = document.getElementById('process-btn');
    const resetBtn = document.getElementById('reset-btn');
    const recordsTbody = document.getElementById('records-tbody');
    
    const summaryBudgetEl = document.getElementById('summary-budget');
    const summarySpentEl = document.getElementById('summary-spent');
    const summaryVariationEl = document.getElementById('summary-variation');
    const budgetProgressBar = document.getElementById('budget-progress-bar');
    // Este es el elemento que causaba el problema, ahora debería existir en tu HTML
    const summaryBudgetFilenameEl = document.getElementById('summary-budget-filename');


    // --- Almacenamiento de Datos en Memoria ---
    const docs = [];
    const records = [];
    let budgetFile = null;

    // --- Funciones de Simulación y Ayuda ---
    const formatDate = isoString => new Date(isoString).toLocaleDateString('es-CL');
    const randomAmount = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
    const randomFolio = () => 'F' + Math.floor(100000 + Math.random() * 900000);

    const parseCSVForAmount = content => {
        const lines = content.split('\n');
        for (const line of lines) {
            const matches = line.match(/(\d{1,3}(?:\.\d{3})*|\d+)/g);
            if (matches && matches.length > 0) {
                const amount = parseInt(matches[0].replace(/\./g, ''));
                if (!isNaN(amount) && amount > 1000) return amount;
            }
        }
        return null;
    };

    // --- Funciones para Actualizar la Interfaz (Render) ---
    const renderDocs = () => {
        totalSpan.textContent = `${docs.length} en total`;
        tbody.innerHTML = '';
        if (docs.length === 0) {
            tbody.innerHTML = `<tr><td colspan="5" class="empty">Aún no hay documentos.</td></tr>`;
        } else {
            docs.forEach((doc, index) => {
                const tr = document.createElement('tr');
                let documentCell = doc.name;
                if (doc.file && doc.file.type.startsWith('image/')) {
                    const imageURL = URL.createObjectURL(doc.file);
                    documentCell = `<img src="${imageURL}" alt="${doc.name}" class="thumbnail" />`;
                }
                tr.innerHTML = `
                    <td>${index + 1}</td>
                    <td>${doc.folio}</td>
                    <td>${documentCell}</td>
                    <td>${formatDate(doc.loadedAt)}</td>
                    <td>${CLP.format(doc.amount)}</td>`;
                tbody.appendChild(tr);
            });
        }
    };

    const updateSummary = () => {
        const totalDocsAmount = docs.reduce((sum, doc) => sum + (doc.amount || 0), 0);
        const budgetAmount = budgetFile ? budgetFile.amount : 0;
        const variation = budgetAmount - totalDocsAmount;

        summaryBudgetEl.textContent = CLP.format(budgetAmount);
        summarySpentEl.textContent = CLP.format(totalDocsAmount);
        summaryVariationEl.textContent = CLP.format(variation);
        summaryVariationEl.style.color = variation < 0 ? 'var(--red)' : 'var(--green)';

        // Esta sección ahora funcionará porque el elemento existe
        if (budgetFile && summaryBudgetFilenameEl) {
            summaryBudgetFilenameEl.textContent = budgetFile.name;
        } else if (summaryBudgetFilenameEl) {
            summaryBudgetFilenameEl.textContent = '';
        }

        if (budgetAmount > 0) {
            const usagePercent = Math.max(0, (totalDocsAmount / budgetAmount) * 100);
            budgetProgressBar.style.width = `${Math.min(usagePercent, 100)}%`;
            if (usagePercent > 100) {
                budgetProgressBar.style.backgroundColor = 'var(--red)';
            } else if (usagePercent > 80) {
                budgetProgressBar.style.backgroundColor = 'var(--yellow)';
            } else {
                budgetProgressBar.style.backgroundColor = 'var(--green)';
            }
        } else {
            budgetProgressBar.style.width = '0%';
        }
    };
    
    const renderRecords = () => {
        recordsTbody.innerHTML = '';
        if (records.length === 0) {
            recordsTbody.innerHTML = `<tr><td class="empty" colspan="5">No hay registros todavía.</td></tr>`;
        } else {
            records.forEach((record, index) => {
                const tr = document.createElement('tr');
                const variationColor = record.diff < 0 ? 'var(--red)' : 'var(--green)';
                const sign = record.diff >= 0 ? '+' : '';
                tr.innerHTML = `
                    <td>${record.docsCount}</td>
                    <td>${CLP.format(record.docsSum)}</td>
                    <td>${CLP.format(record.budget)}</td>
                    <td style="color: ${variationColor}; font-weight: bold;">${sign}${CLP.format(record.diff)}</td>
                    <td><button class="delete-btn" data-index="${index}">Eliminar</button></td>`;
                recordsTbody.appendChild(tr);
            });
        }
    };

    const addInvoiceFiles = files => {
        errorEl.textContent = '';
        Array.from(files).forEach(file => {
            docs.unshift({
                name: file.name,
                loadedAt: new Date().toISOString(),
                file: file,
                amount: randomAmount(10000, 250000),
                folio: randomFolio()
            });
        });
        renderDocs();
        updateSummary();
    };

    const setBudgetFile = file => {
        if (!file || !file.name.toLowerCase().endsWith('.csv')) {
            budgetErrorEl.textContent = 'Solo se permite un archivo CSV.'; return;
        }
        budgetErrorEl.textContent = '';
        const reader = new FileReader();
        reader.onload = e => {
            const content = e.target.result;
            let amount = parseCSVForAmount(content) || randomAmount(200000, 2000000);
            budgetFile = { name: file.name, loadedAt: new Date().toISOString(), amount: amount, file: file };
            updateSummary();
        };
        reader.readAsText(file);
    };

    // --- Asignación de Eventos ---
    invoiceInput.addEventListener('change', () => { addInvoiceFiles(invoiceInput.files); invoiceInput.value = ''; });
    budgetInput.addEventListener('change', () => { if (budgetInput.files.length > 0) { setBudgetFile(budgetInput.files[0]); budgetInput.value = ''; } });
    ['dragenter', 'dragover'].forEach(e => dropzone.addEventListener(e, evt => { evt.preventDefault(); evt.stopPropagation(); dropzone.classList.add('drag'); }));
    ['dragleave', 'drop'].forEach(e => dropzone.addEventListener(e, evt => {
        evt.preventDefault(); evt.stopPropagation(); dropzone.classList.remove('drag');
        if (e === 'drop') addInvoiceFiles(evt.dataTransfer.files);
    }));
    ['dragenter', 'dragover'].forEach(e => budgetDropzone.addEventListener(e, evt => { evt.preventDefault(); evt.stopPropagation(); budgetDropzone.classList.add('drag'); }));
    ['dragleave', 'drop'].forEach(e => budgetDropzone.addEventListener(e, evt => {
        evt.preventDefault(); evt.stopPropagation(); budgetDropzone.classList.remove('drag');
        if (e === 'drop' && evt.dataTransfer.files.length > 0) setBudgetFile(evt.dataTransfer.files[0]);
    }));
    processBtn.addEventListener('click', async () => {
        if (!budgetFile || docs.length === 0) { alert('Carga un presupuesto y al menos un documento.'); return; }
        const totalDocs = docs.reduce((sum, d) => sum + d.amount, 0);
        records.push({ docsCount: docs.length, docsSum: totalDocs, budget: budgetFile.amount, diff: budgetFile.amount - totalDocs });
        renderRecords();
    });

    resetBtn.addEventListener('click', () => {
        if (confirm('¿Estás seguro? Se borrarán todos los datos de la simulación.')) {
            docs.length = 0;
            records.length = 0;
            budgetFile = null;
            errorEl.textContent = '';
            budgetErrorEl.textContent = '';
            renderDocs();
            updateSummary();
            renderRecords();
        }
    });

    recordsTbody.addEventListener('click', e => {
        if (e.target.classList.contains('delete-btn')) {
            const index = parseInt(e.target.dataset.index, 10);
            if (!isNaN(index)) { records.splice(index, 1); renderRecords(); }
        }
    });

    // --- Estado Inicial ---
    updateSummary();
    renderDocs();
    renderRecords();
});