document.addEventListener('DOMContentLoaded', function() {
    const collectionsList = document.getElementById('collections-list');
    const modal = document.getElementById('collection-modal');
    const deleteModal = document.getElementById('delete-collection-modal');
    const form = document.getElementById('collection-form');
    const typeSelect = document.getElementById('collection-type');
    const querySection = document.getElementById('query-builder-section');
    const queryInput = document.getElementById('collection-query');
    const previewBtn = document.getElementById('preview-query-btn');
    const queryStatus = document.getElementById('query-status');
    const previewResults = document.getElementById('query-preview-results');
    let deleteTargetId = null;

    typeSelect.addEventListener('change', function() {
        querySection.style.display = this.value === 'dynamic' ? '' : 'none';
        if (this.value !== 'dynamic') {
            queryInput.value = '';
            previewResults.style.display = 'none';
            queryStatus.textContent = '';
        }
    });

    async function loadCollections() {
        try {
            const collections = await LinkSync.getCollections();
            renderCollections(Array.isArray(collections) ? collections : []);
        } catch (err) {
            collectionsList.innerHTML = `<div class="empty-state"><p>Failed to load collections: ${err.message}</p></div>`;
        }
    }

    function renderCollections(collections) {
        if (!collections || collections.length === 0) {
            collectionsList.innerHTML = '<div class="empty-state"><p>No collections found.</p><button class="btn btn-primary" id="empty-add-col-btn">+ Create your first collection</button></div>';
            document.getElementById('empty-add-col-btn').addEventListener('click', openCollectionModal);
            return;
        }

        collectionsList.innerHTML = collections.map(col => `
            <div class="collection-card">
                <h3>${escapeHtml(col.name)}</h3>
                <p>${escapeHtml(col.description || 'No description')}</p>
                <div class="meta">
                    <span class="badge badge-${col.query_type}">${col.query_type}</span>
                    <span class="badge ${col.is_public ? 'badge-public' : 'badge-private'}">${col.is_public ? 'Public' : 'Private'}</span>
                </div>
                ${col.query_type === 'dynamic' && col.query_expression ? `<div class="query-hint"><small>${escapeHtml(col.query_expression.expression || '')}</small></div>` : ''}
                <div class="actions">
                    <button class="btn btn-sm btn-outline" data-action="edit" data-id="${col.id}">Edit</button>
                    <button class="btn btn-sm btn-danger" data-action="delete" data-id="${col.id}">Delete</button>
                </div>
            </div>
        `).join('');

        collectionsList.querySelectorAll('[data-action="edit"]').forEach(btn => {
            btn.addEventListener('click', () => editCollection(btn.dataset.id));
        });
        collectionsList.querySelectorAll('[data-action="delete"]').forEach(btn => {
            btn.addEventListener('click', () => confirmDeleteCollection(btn.dataset.id));
        });
    }

    function openCollectionModal(col = null) {
        document.getElementById('collection-modal-title').textContent = col ? 'Edit Collection' : 'Create Collection';
        document.getElementById('collection-id').value = (col && col.id) ? col.id : '';
        document.getElementById('collection-name').value = col ? col.name : '';
        document.getElementById('collection-description').value = col ? (col.description || '') : '';
        document.getElementById('collection-type').value = col ? col.query_type : 'static';
        document.getElementById('collection-public').checked = col ? col.is_public : false;

        if (col && col.query_type === 'dynamic' && col.query_expression) {
            queryInput.value = col.query_expression.expression || '';
            querySection.style.display = '';
        } else {
            queryInput.value = '';
            querySection.style.display = 'none';
        }
        previewResults.style.display = 'none';
        queryStatus.textContent = '';

        modal.style.display = 'flex';
    }

    async function editCollection(id) {
        try {
            const collections = await LinkSync.getCollections();
            const col = (Array.isArray(collections) ? collections : []).find(c => c.id === id);
            if (col) openCollectionModal(col);
        } catch (err) {
            alert('Failed to load collection details');
        }
    }

    function confirmDeleteCollection(id) {
        deleteTargetId = id;
        deleteModal.style.display = 'flex';
    }

    function closeModal() {
        modal.style.display = 'none';
        form.reset();
        querySection.style.display = 'none';
        previewResults.style.display = 'none';
        queryStatus.textContent = '';
    }

    function closeDeleteModal() {
        deleteModal.style.display = 'none';
        deleteTargetId = null;
    }

    document.getElementById('new-collection-btn').addEventListener('click', () => openCollectionModal());
    document.getElementById('collection-modal-close').addEventListener('click', closeModal);
    document.getElementById('collection-cancel-btn').addEventListener('click', closeModal);
    document.getElementById('delete-collection-cancel-btn').addEventListener('click', closeDeleteModal);

    modal.querySelector('.modal-overlay').addEventListener('click', closeModal);
    deleteModal.querySelector('.modal-overlay').addEventListener('click', closeDeleteModal);

    previewBtn.addEventListener('click', async function() {
        const expression = queryInput.value.trim();
        if (!expression) {
            queryStatus.textContent = 'Enter a query expression';
            queryStatus.style.color = 'var(--warning)';
            return;
        }
        queryStatus.textContent = 'Loading...';
        queryStatus.style.color = 'var(--text-muted)';
        try {
            const results = await LinkSync.previewQuery(expression);
            const count = Array.isArray(results) ? results.length : 0;
            queryStatus.textContent = `${count} result${count !== 1 ? 's' : ''}`;
            queryStatus.style.color = 'var(--success)';
            if (count > 0) {
                previewResults.innerHTML = `<div class="query-preview-count">${count} matching links:</div>` +
                    results.slice(0, 10).map(link => `
                        <div class="query-preview-item">
                            <a href="${escapeHtml(link.url)}" target="_blank">${escapeHtml(link.title)}</a>
                        </div>
                    `).join('') +
                    (count > 10 ? `<div class="query-preview-count">...and ${count - 10} more</div>` : '');
                previewResults.style.display = '';
            } else {
                previewResults.innerHTML = '<div class="empty-state"><p>No matching links</p></div>';
                previewResults.style.display = '';
            }
        } catch (err) {
            queryStatus.textContent = err.message;
            queryStatus.style.color = 'var(--error)';
            previewResults.style.display = 'none';
        }
    });

    form.addEventListener('submit', async function(e) {
        e.preventDefault();
        const saveBtn = document.getElementById('collection-save-btn');
        saveBtn.disabled = true;
        saveBtn.textContent = 'Saving...';

        const id = document.getElementById('collection-id').value;
        const isEdit = id && id !== '' && id !== 'undefined';
        const queryType = document.getElementById('collection-type').value;
        const data = {
            name: document.getElementById('collection-name').value,
            description: document.getElementById('collection-description').value || null,
            query_type: queryType,
            is_public: document.getElementById('collection-public').checked,
        };

        if (queryType === 'dynamic') {
            const expression = queryInput.value.trim();
            if (expression) {
                data.query_expression = { expression };
            }
        }

        try {
            if (isEdit) {
                await LinkSync.updateCollection(id, data);
            } else {
                await LinkSync.createCollection(data);
            }
            closeModal();
            loadCollections();
        } catch (err) {
            alert('Failed to save collection: ' + err.message);
        } finally {
            saveBtn.disabled = false;
            saveBtn.textContent = 'Save';
        }
    });

    document.getElementById('confirm-delete-collection-btn').addEventListener('click', async function() {
        if (!deleteTargetId) return;
        try {
            await LinkSync.deleteCollection(deleteTargetId);
            closeDeleteModal();
            loadCollections();
        } catch (err) {
            alert('Failed to delete collection: ' + err.message);
        }
    });

    const urlParams = new URLSearchParams(window.location.search);
    if (urlParams.get('action') === 'new') {
        openCollectionModal();
    }

    loadCollections();

    function escapeHtml(str) {
        if (!str) return '';
        const div = document.createElement('div');
        div.textContent = str;
        return div.innerHTML;
    }
});