/**
 * productList.js
 * 상품 그리드/테이블 렌더링, 지연 로딩 및 페이지네이션 제어
 */

import { state, saveSelection } from './state.js';
import { ITEMS_PER_PAGE, STATUS_META, STATUS_COLOR, PRODUCT_CONDITIONS } from './config.js';
import { updateSummary } from './main.js';

// ==========================================================================
// 1. 터치 및 호버 인터랙션 (Interaction)
// ==========================================================================

window.isDragging = false;
let touchStartX = 0;
let touchStartY = 0;
const isTouchDevice = 'ontouchstart' in window || navigator.maxTouchPoints > 0;

/** 터치 시작: 드래그 여부 판단 초기화 */
window.handleTouchStart = function (e) {
    window.isDragging = false;
    touchStartX = e.touches[0].clientX;
    touchStartY = e.touches[0].clientY;
};

/** 터치 이동: 일정 거리 이상 움직이면 클릭이 아닌 드래그로 간주 */
window.handleTouchMove = function (e) {
    const touchX = e.touches[0].clientX;
    const touchY = e.touches[0].clientY;
    if (Math.abs(touchX - touchStartX) > 10 || Math.abs(touchY - touchStartY) > 10) {
        window.isDragging = true;
    }
};

window.handleTouchEnd = function (e) {};

/** 썸네일 호버: 마우스 위치에 따른 이미지 교체 및 인디케이터 업데이트 */
window.handleThumbnailHover = function (e, id) {
    if (isTouchDevice) return;
    const product = state.visibleProducts.find((p) => p.id === id);
    if (!product || !product.images || product.images.length <= 1) return;

    const rect = e.currentTarget.getBoundingClientRect();
    const x = e.clientX - rect.left;
    const sectionWidth = rect.width / product.images.length;
    const index = Math.floor(x / sectionWidth);

    const thumb = document.getElementById(`thumb-${id}`);
    const indicators = document.querySelector(`#indicator-${id}`)?.children;

    if (thumb && product.images[index]) {
        thumb.style.backgroundImage = `url("${product.images[index]}")`;
    }
    if (indicators) {
        Array.from(indicators).forEach((dot, i) => {
            dot.classList.toggle('bg-white', i === index);
            dot.classList.toggle('scale-125', i === index);
            dot.classList.toggle('bg-white/40', i !== index);
        });
    }
};

/** 호버 해제: 첫 번째 이미지로 복구 */
window.handleThumbnailLeave = function (id) {
    if (isTouchDevice) return;
    const product = state.visibleProducts.find((p) => p.id === id);
    const thumb = document.getElementById(`thumb-${id}`);
    const indicators = document.querySelector(`#indicator-${id}`)?.children;

    if (thumb && product) thumb.style.backgroundImage = `url("${product.images[0]}")`;
    if (indicators) {
        Array.from(indicators).forEach((dot, i) => {
            dot.classList.toggle('bg-white', i === 0);
            dot.classList.toggle('scale-125', i === 0);
            dot.classList.toggle('bg-white/40', i !== 0);
        });
    }
};

/** 개별 체크박스 토글 */
window.toggleSelectItem = function (id) {
    if (state.selectedIds.has(id)) state.selectedIds.delete(id);
    else state.selectedIds.add(id);
    
    saveSelection();
    renderProducts(state.currentPage);
    updateSummary();
};

// ==========================================================================
// 2. 메인 렌더링 컨트롤러 (Main Rendering)
// ==========================================================================

/**
 * 상태에 따른 상품 목록 렌더링 실행
 * @param {number} page - 현재 페이지 번호
 */
export function renderProducts(page = 1) {
    const grid = document.getElementById('product-grid');
    const tableWrapper = document.getElementById('product-table-wrapper');
    const paginationContainer = document.getElementById('pagination');

    if (!grid || !tableWrapper) return;

    // [1] 결과 없음 처리
    if (state.visibleProducts.length === 0) {
        renderEmpty(grid, tableWrapper, paginationContainer);
        return;
    }

    // [2] 페이지 데이터 슬라이싱
    const startIndex = (page - 1) * ITEMS_PER_PAGE;
    const pagedProducts = state.visibleProducts.slice(startIndex, startIndex + ITEMS_PER_PAGE);

    // [3] 뷰 모드에 따른 렌더링
    if (state.viewMode === 'grid') {
        renderGridView(grid, tableWrapper, pagedProducts);
    } else {
        renderTableView(grid, tableWrapper, pagedProducts);
    }

    updateSelectAllCheckbox(page);
    renderPagination();
}

/** 검색 결과가 없을 때의 UI */
function renderEmpty(grid, tableWrapper, paginationContainer) {
    grid.classList.remove('grid');
    grid.classList.add('hidden');
    tableWrapper.classList.add('hidden');
    
    const emptyMsg = `
        <div class="col-span-full flex flex-col items-center justify-center py-20 w-full text-center">
            <svg class="w-20 h-20 text-slate-300 dark:text-slate-700 mb-6" viewBox="0 -960 960 960" fill="currentColor">
                <path d="M138.5-138.5Q80-197 80-280t58.5-141.5Q197-480 280-480t141.5 58.5Q480-363 480-280t-58.5 141.5Q363-80 280-80t-141.5-58.5ZM824-120 568-376q-12-13-25.5-26.5T516-428q38-24 61-64t23-88q0-75-52.5-127.5T420-760q-75 0-127.5 52.5T240-580q0 6 .5 11.5T242-557q-18 2-39.5 8T164-535q-2-11-3-22t-1-23q0-109 75.5-184.5T420-840q109 0 184.5 75.5T680-580q0 43-13.5 81.5T629-428l251 252-56 56Zm-615-61 71-71 70 71 29-28-71-71 71-71-28-28-71 71-71-71-28 28 71 71-71 71 28 28Z"/>
            </svg>
            <h3 class="text-xl font-bold text-slate-900 dark:text-white mb-2">검색 결과가 없습니다</h3>
            <p class="text-slate-500 dark:text-slate-400 text-sm">입력하신 검색어나 선택한 필터를 확인해 주세요.</p>
        </div>`;
    
    grid.innerHTML = emptyMsg;
    grid.classList.remove('hidden');
    if (paginationContainer) paginationContainer.innerHTML = '';
}

// ==========================================================================
// 3. 그리드 & 테이블 뷰 상세 (View Details)
// ==========================================================================

/** 그리드 뷰 렌더링 */
function renderGridView(grid, tableWrapper, products) {
    grid.classList.replace('hidden', 'grid');
    tableWrapper.classList.add('hidden');
    
    const summaryBar = document.getElementById('selection-summary');
    if (summaryBar) summaryBar.classList.add('hidden');

    grid.innerHTML = products.map(product => createProductCardHTML(product)).join('');
    setupLazyLoading();
}

/** 그리드 개별 카드 HTML */
function createProductCardHTML(product) {
    const isSold = STATUS_META[product.status]?.soldOut === true;
    const isNonSale = product.status === '미판매';
    const conditionConfig = PRODUCT_CONDITIONS[product.specs?.condition];
    const conditionDisplay = conditionConfig ? conditionConfig.label : product.specs?.condition || '';

    return `
        <div class="product-card group flex flex-col gap-4 cursor-pointer"
             data-id="${product.id}"
             onclick="if(!window.isDragging) window.openModal('${product.id}')"
             ontouchstart="window.handleTouchStart(event)"
             ontouchmove="window.handleTouchMove(event)"
             ontouchend="window.handleTouchEnd(event)"
             onmousemove="window.handleThumbnailHover(event, '${product.id}')" 
             onmouseleave="window.handleThumbnailLeave('${product.id}')">
            
            <div class="relative w-full aspect-card bg-slate-200 dark:bg-slate-800 rounded-xl overflow-hidden shadow-sm">
                <div id="thumb-${product.id}"
                     class="w-full h-full bg-center bg-no-repeat bg-cover absolute inset-0 transition-all duration-500 ${isSold ? 'grayscale opacity-60' : 'group-hover:scale-105'}"
                     style="background-image: none; will-change: background-image, transform;">
                </div>

                <div class="absolute top-3 left-3 z-10">
                    <span class="px-2 py-1 text-[10px] uppercase tracking-wider font-bold rounded ${STATUS_COLOR[product.status]} backdrop-blur-md border">${product.status}</span>
                </div>

                ${!isSold && product.images?.length > 1 ? `
                    <div id="indicator-${product.id}" class="absolute bottom-3 left-1/2 -translate-x-1/2 hidden md:flex gap-1.5 opacity-0 group-hover:opacity-100 transition-all duration-300 pointer-events-none z-10">
                        ${product.images.map((_, i) => `<div class="w-1.5 h-1.5 rounded-full transition-all duration-300 shadow-sm ${i === 0 ? 'bg-white scale-125' : 'bg-white/40'}"></div>`).join('')}
                    </div>` : ''}
            </div>

            <div class="flex flex-col gap-1.5">
                <div class="flex flex-col justify-between items-start sm:items-baseline gap-1">
                    <h3 class="text-slate-900 dark:text-white text-base font-semibold leading-tight break-keep ${isSold ? 'line-through text-slate-400' : ''}">${product.title}</h3>
                    <p class="text-base font-bold whitespace-nowrap ${isNonSale ? 'text-slate-400 font-medium text-xs uppercase' : 'text-slate-900 dark:text-white'}">
                        ${isNonSale ? 'Not for Sale' : `${product.currency || '₩'}${product.price.toLocaleString()}`}
                    </p>
                </div>
                <div class="flex flex-col">
                    ${conditionDisplay ? `<span class="text-[11px] font-medium text-slate-400 mb-0.5">${conditionDisplay}</span>` : ''}
                    <p class="text-slate-500 dark:text-slate-400 text-sm font-normal line-clamp-1 italic">${product.description}</p>
                </div>
            </div>
        </div>`;
}

/** 테이블 뷰 렌더링 */
function renderTableView(grid, tableWrapper, products) {
    grid.classList.add('hidden');
    tableWrapper.classList.remove('hidden');
    
    const tableBody = document.getElementById('product-table-body');
    tableBody.innerHTML = products.map(product => createTableRowHTML(product)).join('');
    updateSummary();
}

/** 테이블 개별 행 HTML */
function createTableRowHTML(product) {
    const meta = STATUS_META[product.status];
    const isSold = meta?.soldOut === true;
    const isSelectable = meta?.selectable !== false;
    const conditionConfig = PRODUCT_CONDITIONS[product.specs.condition];
    const conditionDisplay = conditionConfig ? conditionConfig.label : '상세 설명 참고 ℹ️';
    const conditionClass = conditionConfig ? conditionConfig.color : 'text-slate-500';

    return `
        <tr class="hover:bg-slate-50 dark:hover:bg-slate-800/50 transition-colors ${isSold ? 'opacity-50 grayscale cursor-not-allowed' : 'cursor-pointer'}" 
            onclick="if(event.target.type !== 'checkbox') { ${isSold ? "alert('판매 완료된 상품입니다.');" : `window.openModal('${product.id}')`} }">
            <td class="py-4 px-4 text-center" onclick="event.stopPropagation()">
                <input type="checkbox" class="product-check rounded border-slate-300 w-4 h-4 ${isSelectable ? 'cursor-pointer text-primary' : 'opacity-20 cursor-not-allowed'}"
                    ${state.selectedIds.has(product.id) ? 'checked' : ''} ${isSelectable ? '' : 'disabled'}
                    onchange="window.toggleSelectItem('${product.id}')">
            </td>
            <td class="py-4 px-4 font-semibold ${isSold ? 'line-through text-slate-400' : 'text-slate-900 dark:text-white'}">${product.title}</td>
            <td class="py-4 px-4 text-xs break-keep ${conditionClass}">${conditionDisplay}</td>
            <td class="py-4 px-4 text-right font-bold text-slate-900 dark:text-white">₩${product.price.toLocaleString()}</td>
            <td class="hidden lg:table-cell py-4 px-4 text-center">
                <span class="px-2 py-0.5 rounded text-[10px] font-bold border ${STATUS_COLOR[product.status]}">${product.status}</span>
            </td>
        </tr>`;
}

// ==========================================================================
// 4. 유틸리티 및 페이지네이션 (Utils)
// ==========================================================================

/** 전체 선택 체크박스 상태 동기화 */
function updateSelectAllCheckbox(page) {
    const selectAllCheck = document.getElementById('select-all-current');
    if (!selectAllCheck) return;

    const startIndex = (page - 1) * ITEMS_PER_PAGE;
    const currentSelectableItems = state.visibleProducts
        .slice(startIndex, startIndex + ITEMS_PER_PAGE)
        .filter((p) => STATUS_META[p.status]?.selectable !== false);

    selectAllCheck.checked = currentSelectableItems.length > 0 && 
                             currentSelectableItems.every((p) => state.selectedIds.has(p.id));
}

/** Intersection Observer를 이용한 썸네일 지연 로딩 */
function setupLazyLoading() {
    const observer = new IntersectionObserver((entries) => {
        entries.forEach((entry) => {
            if (entry.isIntersecting) {
                const card = entry.target;
                const productId = card.getAttribute('data-id');
                const product = state.visibleProducts.find((p) => p.id === productId);
                const thumb = document.getElementById(`thumb-${productId}`);

                if (product && thumb) {
                    thumb.style.backgroundImage = `url("${product.images[0]}")`;
                    // 마우스 호버를 대비해 나머지 이미지 미리 로드
                    if (!STATUS_META[product.status]?.soldOut && product.images.length > 1) {
                        product.images.slice(1).forEach(url => { const img = new Image(); img.src = url; });
                    }
                }
                observer.unobserve(card);
            }
        });
    }, { threshold: 0.1 });

    document.querySelectorAll('.product-card').forEach((card) => observer.observe(card));
}

/** 페이지네이션 버튼 렌더링 */
export function renderPagination() {
    const container = document.getElementById('pagination');
    if (!container) return;

    const totalPages = Math.ceil(state.visibleProducts.length / ITEMS_PER_PAGE);
    const { currentPage } = state;

    let html = `<button onclick="changePage(${currentPage - 1})" class="size-10 flex items-center justify-center ${currentPage === 1 ? 'invisible' : ''}">
                    <svg viewBox="0 0 24 24" fill="none" stroke="#64748B" stroke-width="3" stroke-linecap="round" stroke-linejoin="round" class="w-5 h-5"><path d="M15 18l-6-6 6-6" /></svg>
                </button>`;

    for (let i = 1; i <= totalPages; i++) {
        html += `<button onclick="changePage(${i})" class="size-10 font-bold rounded-lg ${i === currentPage ? 'bg-primary text-white' : 'text-slate-500'}">${i}</button>`;
    }

    html += `<button onclick="changePage(${currentPage + 1})" class="size-10 flex items-center justify-center ${currentPage === totalPages ? 'invisible' : ''}">
                <svg viewBox="0 0 24 24" fill="none" stroke="#64748B" stroke-width="3" stroke-linecap="round" stroke-linejoin="round" class="w-5 h-5"><path d="M9 18l6-6-6-6" /></svg>
            </button>`;

    container.innerHTML = html;
}

/** 페이지 변경 처리 */
export function changePage(page) {
    state.currentPage = page;
    renderProducts(page);
    window.scrollTo({ top: 0, behavior: 'smooth' });
}