/**
 * Collabora 页数信息获取模块
 *
 * @encoding UTF-8
 */

/**
 * 页数信息接口
 */
export interface PageInfo {
    totalPages: number;
    currentPage: number;
    timestamp: number;
}

/**
 * Collabora PostMessage 数据类型
 */
interface CollaboraMessageData {
    MessageId?: string;
    msgId?: string;
    // bundle.js _postMessage 发送的格式
    Values?: {
        Command?: string;
        Status?: string;
        totalPages?: number;
        currentPage?: number;
        timestamp?: number;
        pages?: number;
        [key: string]: unknown;
    };
    // 原始插件返回的格式
    args?: {
        Command?: string;
        Status?: string;
        totalPages?: number;
        currentPage?: number;
        timestamp?: number;
        [key: string]: unknown;
    };
    [key: string]: unknown;
}



/**
 * 解析 PostMessage 数据
 */
function parseMessageData(data: unknown): CollaboraMessageData {
    if (typeof data === 'string') {
        return JSON.parse(data) as CollaboraMessageData;
    }
    return data as CollaboraMessageData;
}


/**
 * 通过 PostMessage 请求页数信息
 *
 * 使用自定义 custompostMessage 插件获取文档页数。
 * 注意: Collabora 的页码是从 0 开始的。
 *
 * @param iframeWindow - iframe 的 contentWindow
 * @returns Promise，解析为页数信息
 *
 * @example
 * ```typescript
 * const info = await requestPageInfo(iframeWindow);
 * console.log(`文档共 ${info.totalPages} 页，当前在第 ${info.currentPage + 1} 页`);
 * ```
 */
export async function requestPageInfo(iframeWindow: Window): Promise<PageInfo> {
    return new Promise((resolve, reject) => {
        const timeout = setTimeout(() => {
            cleanup();
            reject(new Error('请求页数信息超时'));
        }, 5000);

        const handleMessage = (event: MessageEvent) => {
            try {
                if (event.source !== iframeWindow) {
                    return;
                }

                const data = parseMessageData(event.data);

                // bundle.js 的 _postMessage 会将消息转换为:
                // { MessageId: 'custompostMessage_Resp', Values: { Command: 'GET_PAGE_INFO', ... } }
                // 所以我们需要监听 MessageId 而不是 msgId
                if (
                    data.MessageId === 'custompostMessage_Resp' &&
                    data.Values?.Command === 'GET_PAGE_INFO' &&
                    data.Values?.Status === 'success'
                ) {
                    clearTimeout(timeout);
                    cleanup();

                    const info: PageInfo = {
                        totalPages: data.Values.totalPages || 0,
                        currentPage: data.Values.currentPage || 0,
                        timestamp: data.Values.timestamp || Date.now(),
                    };

                    resolve(info);
                }
            } catch (error) {
                clearTimeout(timeout);
                cleanup();
                reject(error);
            }
        };

        const cleanup = () => {
            window.removeEventListener('message', handleMessage);
        };

        window.addEventListener('message', handleMessage);

        // 发送请求消息
        const message = {
            MessageId: 'custompostMessage',
            Values: {
                Command: 'GET_PAGE_INFO',
                Args: {},
            },
        };

        iframeWindow.postMessage(JSON.stringify(message), '*');
    });
}