/**
 * kb-controller.js — Knowledge Base Management Controller
 * =========================================================
 * Handles specialized navigation and multi-file upload for policy documents.
 * * Hardened for Enterprise MVC:
 * - Integrates globally with `apiFetch` for automatic CSRF & HTTP-Only cookies.
 * - Utilises `SecurityUtils` for XSS immunity on dynamic DOM generation.
 * - Enforces Vercel Serverless batch constraints (max 5 files).
 */

(function () {
    'use strict';

    // ── Elements & State ───────────────────────────────────────────────────
    const kbTabs = document.querySelectorAll('.nav-tab');
    const kbPanels = document.querySelectorAll('.content-panel');
    const kbDropzone = document.getElementById('kb-dropzone');
    const kbFileInput = document.getElementById('pdf-input');
    const kbChipsContainer = document.getElementById('kb-file-chips');
    const kbUploadBtn = document.getElementById('process-upload-btn');
    const kbLoader = document.getElementById('loader');
    const kbLoaderText = document.getElementById('loader-text');
    const kbEmptyState = document.getElementById('empty-state');
    const kbDocsGrid = document.getElementById('documents-grid');
    const kbDocCount = document.getElementById('doc-count');

    let queuedFiles = [];
    let pollingInterval = null;

    console.info('[KBController] Initializing Knowledge Base specialized controller...');

    // ── Tabs Logic ──────────────────────────────────────────────────────────
    function initTabs() {
        if (!kbTabs.length) return;
        
        kbTabs.forEach(tab => {
            tab.addEventListener('click', (e) => {
                const targetId = tab.getAttribute('aria-controls');
                const targetPanel = document.getElementById(targetId);

                if (!targetPanel) return;

                // Toggle Active States
                kbTabs.forEach(t => {
                    t.classList.remove('active');
                    t.setAttribute('aria-selected', 'false');
                });
                kbPanels.forEach(p => p.classList.remove('active'));

                tab.classList.add('active');
                tab.setAttribute('aria-selected', 'true');
                targetPanel.classList.add('active');

                // Trigger actions
                if (tab.dataset.tab === 'documents') {
                    loadDocuments();
                } else {
                    stopPolling();
                }
            });
        });
    }

    // ── File Selection & Chips ──────────────────────────────────────────────
    function initFileHandlers() {
        if (kbDropzone) {
            kbDropzone.addEventListener('dragover', e => {
                e.preventDefault();
                kbDropzone.classList.add('drag-over');
            });
            kbDropzone.addEventListener('dragleave', () => kbDropzone.classList.remove('drag-over'));
            kbDropzone.addEventListener('drop', e => {
                e.preventDefault();
                kbDropzone.classList.remove('drag-over');
                handleFileSelect(Array.from(e.dataTransfer.files));
            });

        }

        if (kbFileInput) {
            kbFileInput.addEventListener('change', e => {
                handleFileSelect(Array.from(e.target.files));
            });
        }

        if (kbUploadBtn) {
            kbUploadBtn.addEventListener('click', () => {
                if (queuedFiles.length > 0) {
                    uploadDocuments(queuedFiles);
                }
            });
        }
    }

    function handleFileSelect(files) {
        if (!files || files.length === 0) return;
        const allowedExtensions = ['.pdf', '.doc', '.docx', '.txt', '.csv'];

        // Vercel Timeout Guard Enforcement (Max 5 files per batch)
        if (queuedFiles.length + files.length > 5) {
            SecurityUtils.showToast('Maximum 5 files allowed per upload batch to prevent server timeouts.', 'warning');
            files = files.slice(0, Math.max(0, 5 - queuedFiles.length));
        }

        for (const file of files) {
            const ext = file.name.substring(file.name.lastIndexOf('.')).toLowerCase();
            if (!allowedExtensions.includes(ext)) {
                SecurityUtils.showToast(`Unsupported format: ${file.name}`, 'error');
                continue;
            }
            if (file.size > 50 * 1024 * 1024) {
                SecurityUtils.showToast(`File too large (Max 50MB): ${file.name}`, 'error');
                continue;
            }
            if (!queuedFiles.some(f => f.name === file.name && f.size === file.size)) {
                queuedFiles.push(file);
            }
        }
        renderFileChips();
        updateUploadButton();
    }

    function renderFileChips() {
        if (!kbChipsContainer) return;
        kbChipsContainer.textContent = '';
        
        if (queuedFiles.length === 0) {
            kbChipsContainer.style.display = 'none';
            return;
        }

        kbChipsContainer.style.display = 'flex';
        queuedFiles.forEach((file, index) => {
            const chip = document.createElement('div');
            chip.className = 'file-chip';
            
            const icon = document.createElement('span');
            icon.className = 'material-symbols-rounded';
            const ext = file.name.substring(file.name.lastIndexOf('.')).toLowerCase();
            icon.textContent = (ext === '.pdf') ? 'picture_as_pdf' : (ext === '.csv') ? 'table_chart' : 'description';
            
            const name = document.createElement('span');
            name.className = 'chip-name';
            name.textContent = file.name; 
            
            const removeBtn = document.createElement('button');
            removeBtn.className = 'chip-remove';
            removeBtn.type = 'button';
            removeBtn.innerHTML = '<span class="material-symbols-rounded" style="font-size:1.1rem">close</span>';
            removeBtn.title = 'Remove file';
            
            removeBtn.addEventListener('click', (e) => {
                e.stopPropagation();
                queuedFiles.splice(index, 1);
                renderFileChips();
                updateUploadButton();
            });

            chip.appendChild(icon);
            chip.appendChild(name);
            chip.appendChild(removeBtn);
            kbChipsContainer.appendChild(chip);
        });
    }

    function updateUploadButton() {
        if (kbUploadBtn) {
            kbUploadBtn.disabled = (queuedFiles.length === 0);
        }
    }

    // ── API Operations ──────────────────────────────────────────────────────
    async function uploadDocuments(files) {
        if (!files.length) return;

        const formData = new FormData();
        files.forEach(file => formData.append('file', file));

        if (kbLoader) {
            kbLoader.hidden = false;
            if (kbLoaderText) kbLoaderText.textContent = `Uploading & Indexing ${files.length} document(s)...`;
        }
        
        SecurityUtils.setButtonLoading(kbUploadBtn, true);

        try {
            // Use global apiFetch for automatic CSRF injection and HTTP-Only cookie forwarding
            const data = await apiFetch('/kb/upload', {
                method: 'POST',
                body: formData
            });

            if (data.success) {
                SecurityUtils.showToast(`Successfully queued ${data.results.length} document(s) for indexing`, 'success');
                queuedFiles = [];
                renderFileChips();
                updateUploadButton();
                
                // Automatically Switch to Manage tab to view indexing progress
                const docTab = document.querySelector('[data-tab="documents"]');
                if (docTab) docTab.click();
            }
        } catch (err) {
            ErrorHandler.showError(err);
        } finally {
            if (kbLoader) kbLoader.hidden = true;
            if (kbFileInput) kbFileInput.value = '';
            SecurityUtils.setButtonLoading(kbUploadBtn, false);
        }
    }

    async function loadDocuments(quiet = false) {
        if (!quiet && kbLoader) {
            kbLoader.hidden = false;
            if (kbLoaderText) kbLoaderText.textContent = 'Loading policy library...';
        }

        try {
            const data = await apiFetch('/kb/documents');

            if (data.success) {
                renderDocuments(data.documents);
                // Cache documents locally for offline viewing
                try {
                    localStorage.setItem('qualora_kb_docs_v1', JSON.stringify(data.documents));
                } catch (e) { /* ignore storage errors */ }
                // Check if any docs are actively indexing to start/stop polling
                const isIndexing = data.documents.some(d => ['indexing', 'pending'].includes(d.status));
                if (isIndexing) startPolling();
                else stopPolling();
            }
        } catch (err) {
            console.error('[KB] loadDocuments failed:', err);
            // Fallback to cached documents in localStorage
            try {
                const cached = localStorage.getItem('qualora_kb_docs_v1');
                if (cached) {
                    const docs = JSON.parse(cached);
                    renderDocuments(docs);
                    if (window.SecurityUtils && !quiet) window.SecurityUtils.showToast('Using cached KB documents (offline)', 'info');
                    // If any doc shows indexing, start polling to try refreshing status
                    const isIndexing = docs.some(d => ['indexing', 'pending'].includes(d.status));
                    if (isIndexing) startPolling();
                    else stopPolling();
                    return;
                }
            } catch (cacheErr) {
                console.error('[KB] cached docs parse failed:', cacheErr);
            }
            if (!quiet) ErrorHandler.showError(err);
        } finally {
            if (!quiet && kbLoader) kbLoader.hidden = true;
        }
    }

    // ── UI Renderers ────────────────────────────────────────────────────────
    
    function renderDocuments(documents) {
        if (!kbDocsGrid || !kbEmptyState) return;

        if (!documents || documents.length === 0) {
            kbEmptyState.hidden = false;
            kbDocsGrid.hidden = true;
            if (kbDocCount) kbDocCount.textContent = '0 documents';
            return;
        }

        kbEmptyState.hidden = true;
        kbDocsGrid.hidden = false;
        if (kbDocCount) kbDocCount.textContent = `${documents.length} document${documents.length !== 1 ? 's' : ''}`;

        // Clear existing content and use fragment for performance
        kbDocsGrid.textContent = '';
        const fragment = document.createDocumentFragment();
        
        documents.forEach(doc => {
            fragment.appendChild(createDocCard(doc));
        });
        
        kbDocsGrid.appendChild(fragment);
    }

    function createDocCard(doc) {
        const card = document.createElement('div');
        const safeStatus = SecurityUtils.escapeHTML(doc.status);
        card.className = `doc-card ${safeStatus}`;
        
        const ext = doc.filename.substring(doc.filename.lastIndexOf('.')).toLowerCase();
        const iconName = (ext === '.pdf') ? 'picture_as_pdf' : (ext === '.csv') ? 'table_chart' : 'description';

        // XSS Safeguard: Encode values before HTML injection
        const safeName = SecurityUtils.escapeHTML(doc.filename);
        const safeDate = doc.created_at ? SecurityUtils.escapeHTML(new Date(doc.created_at).toLocaleDateString()) : 'Unknown';
        const chunkCount = SecurityUtils.escapeHTML(doc.chunk_count || 0);
        const displayStatus = safeStatus.charAt(0).toUpperCase() + safeStatus.slice(1);
        const atlasIndexed = Boolean(doc.vector_indexed);
        const chromaIndexed = Boolean(doc.chroma_indexed);
        const atlasStatusText = atlasIndexed ? '✅ Indexed' : '⏳ Pending';
        const chromaStatusText = chromaIndexed ? '✅ Indexed' : '⏳ Pending';

        card.innerHTML = `
            <div class="doc-card-header">
                <span class="material-symbols-rounded doc-icon">${iconName}</span>
                <div class="doc-info">
                    <h4 class="doc-name">${safeName}</h4>
                    <div class="doc-meta">
                        <span>${safeDate}</span>
                    </div>
                </div>
            </div>
            <div class="doc-status-details">
                <p><strong>Status:</strong> ${displayStatus}</p>
                <p><strong>Total Vector Chunks:</strong> ${chunkCount}</p>
                <p><strong>Atlas DB (Primary):</strong> ${atlasStatusText}</p>
                <p><strong>ChromaDB (Local):</strong> ${chromaStatusText}</p>
            </div>
            <div class="doc-actions">
                <button class="doc-action-btn view-btn" data-id="${doc._id}">view</button>
                <button class="doc-action-btn delete-btn" data-id="${doc._id}" title="Delete">
                    <span class="material-symbols-rounded" style="font-size:1.1rem">delete</span>
                </button>
            </div>
        `;

        card.querySelector('.view-btn').addEventListener('click', () => viewDocumentFile(doc._id));
        card.querySelector('.delete-btn').addEventListener('click', () => deleteDocument(doc._id));

        return card;
    }

    // ── Action Handlers ─────────────────────────────────────────────────────
    
    async function deleteDocument(docId) {
        const confirmed = await SecurityUtils.showConfirmDialog(
            'Delete Document', 
            'Permanently delete this policy document? All vector index chunks will be removed.', 
            'Delete', 
            'Cancel'
        );
        
        if (!confirmed) return;
        
        try {
            await apiFetch(`/kb/${docId}`, { method: 'DELETE' });
            SecurityUtils.showToast('Document deleted successfully', 'success');
            loadDocuments();
        } catch (err) {
            ErrorHandler.showError(err);
        }
    }

    function viewDocumentFile(docId) {
        window.open(`/api/kb/${encodeURIComponent(docId)}/file`, '_blank', 'noopener,noreferrer');
    }

    // ── Polling ─────────────────────────────────────────────────────────────
    
    function startPolling() {
        if (pollingInterval) return;
        // 5s polling interval keeps backend CPU strain minimal
        pollingInterval = setInterval(() => loadDocuments(true), 5000);
    }

    function stopPolling() {
        if (pollingInterval) {
            clearInterval(pollingInterval);
            pollingInterval = null;
        }
    }

    // ── Initialization ──────────────────────────────────────────────────────────
    initTabs();
    initFileHandlers();
    loadDocuments();

})();