/* 文件：xiaohongshu/paginator.ts — 小红书内容分页器：按切图比例自动分页，确保表格和图片不跨页。 */

import { NMPSettings } from '../settings';

/**
 * 分页结果
 */
export interface PageInfo {
    index: number;           // 页码（从 0 开始）
    content: string;         // 该页的 HTML 内容
    height: number;          // 该页内容的实际高度（用于调试）
}

/**
 * 解析横竖比例字符串为数值
 */
function parseAspectRatio(ratio: string): { width: number; height: number } {
    const parts = ratio.split(':').map(p => parseFloat(p.trim()));
    if (parts.length === 2 && parts[0] > 0 && parts[1] > 0) {
        return { width: parts[0], height: parts[1] };
    }
    return { width: 3, height: 4 };
}

/**
 * 计算目标页面高度
 */
function getTargetPageHeight(settings: NMPSettings): number {
    const ratio = parseAspectRatio(settings.sliceImageAspectRatio);
    return Math.round((settings.sliceImageWidth * ratio.height) / ratio.width);
}

/**
 * 判断元素是否为不可分割元素（表格、图片、代码块等）
 */
function isIndivisibleElement(element: Element): boolean {
    const tagName = element.tagName.toLowerCase();
    // 表格、图片、代码块、公式等不应跨页
    return ['table', 'img', 'pre', 'figure', 'svg'].includes(tagName) ||
           element.classList.contains('math-block') ||
           element.classList.contains('mermaid') ||
           element.classList.contains('excalidraw');
}

/**
 * 将 HTML 内容分页
 * @param articleElement 文章预览的 DOM 元素
 * @param settings 插件设置
 * @returns 分页结果数组
 */
export async function paginateArticle(
    articleElement: HTMLElement,
    settings: NMPSettings
): Promise<PageInfo[]> {
    const pageHeight = getTargetPageHeight(settings);
    const pageWidth = settings.sliceImageWidth;
    
    // 创建临时容器用于测量
    const measureContainer = document.createElement('div');
    measureContainer.style.cssText = `
        position: absolute;
        left: -9999px;
        top: 0;
        width: ${pageWidth}px;
        visibility: hidden;
    `;
    document.body.appendChild(measureContainer);

    const pages: PageInfo[] = [];
    let currentPageContent: Element[] = [];
    let currentPageHeight = 0;
    let pageIndex = 0;

    // 克隆文章内容以避免修改原始 DOM
    const clonedArticle = articleElement.cloneNode(true) as HTMLElement;
    const children = Array.from(clonedArticle.children);

    for (const child of children) {
        const childClone = child.cloneNode(true) as HTMLElement;
        measureContainer.innerHTML = '';
        measureContainer.appendChild(childClone);
        
        // 等待浏览器完成渲染
        await new Promise(resolve => setTimeout(resolve, 10));
        
        const childHeight = childClone.offsetHeight;
        const isIndivisible = isIndivisibleElement(child);

        // 判断是否需要换页
        if (currentPageHeight + childHeight > pageHeight && currentPageContent.length > 0) {
            // 如果是不可分割元素且加入后会超出，先保存当前页
            if (isIndivisible) {
                pages.push({
                    index: pageIndex++,
                    content: wrapPageContent(currentPageContent),
                    height: currentPageHeight
                });
                currentPageContent = [child];
                currentPageHeight = childHeight;
            } else {
                // 可分割元素（段落等），尝试加入当前页
                if (currentPageHeight + childHeight <= pageHeight * 1.1) {
                    // 允许 10% 的溢出容差
                    currentPageContent.push(child);
                    currentPageHeight += childHeight;
                } else {
                    // 超出太多，换页
                    pages.push({
                        index: pageIndex++,
                        content: wrapPageContent(currentPageContent),
                        height: currentPageHeight
                    });
                    currentPageContent = [child];
                    currentPageHeight = childHeight;
                }
            }
        } else {
            // 加入当前页
            currentPageContent.push(child);
            currentPageHeight += childHeight;
        }
    }

    // 保存最后一页
    if (currentPageContent.length > 0) {
        pages.push({
            index: pageIndex,
            content: wrapPageContent(currentPageContent),
            height: currentPageHeight
        });
    }

    // 清理临时容器
    document.body.removeChild(measureContainer);

    return pages;
}

/**
 * 包装页面内容为完整的 HTML
 */
function wrapPageContent(elements: Element[]): string {
    const wrapper = document.createElement('div');
    wrapper.className = 'xhs-page-content';
    elements.forEach(el => {
        wrapper.appendChild(el.cloneNode(true));
    });
    return wrapper.innerHTML;
}

/**
 * 渲染单个页面到容器
 */
export function renderPage(
    container: HTMLElement,
    pageContent: string,
    settings: NMPSettings
): void {
    const pageHeight = getTargetPageHeight(settings);
    const pageWidth = settings.sliceImageWidth;
    
    container.innerHTML = '';
    container.style.cssText = `
        width: ${pageWidth}px;
        min-height: ${pageHeight}px;
        max-height: ${pageHeight}px;
        overflow: hidden;
        box-sizing: border-box;
        padding: 40px;
        background: white;
    `;
    
    const contentDiv = document.createElement('div');
    contentDiv.className = 'xhs-page-content';
    contentDiv.innerHTML = pageContent;
    container.appendChild(contentDiv);
}