/**
 * Canvas 平台适配器
 * 封装微信小程序 Canvas API，为未来 Web 平台迁移做准备
 */

export interface CanvasInitResult {
    canvas: WechatMiniprogram.Canvas;
    ctx: CanvasRenderingContext2D;
    width: number;
    height: number;
}

/**
 * 初始化 Canvas 节点
 * @param selector Canvas 选择器 (如 '#canvasContent')
 * @param wrapperSelector 容器选择器 (如 '#canvasWrapper')
 * @param aspectRatio 宽高比 (width / height)
 */
export function initCanvas(
    selector: string,
    wrapperSelector: string,
    aspectRatio: number,
): Promise<CanvasInitResult> {
    return new Promise((resolve, reject) => {
        const query = wx.createSelectorQuery();
        query
            .select(wrapperSelector)
            .boundingClientRect((rect) => {
                if (!rect) {
                    reject(new Error('Canvas wrapper not found'));
                    return;
                }

                const boxWidth = rect.width;
                const boxHeight = boxWidth / aspectRatio;

                wx.createSelectorQuery()
                    .select(selector)
                    .fields({ node: true, size: true })
                    .exec((res) => {
                        if (!res[0]) {
                            reject(new Error('Canvas node not found'));
                            return;
                        }

                        const canvas = res[0].node;
                        const ctx = canvas.getContext('2d');
                        const dpr = wx.getSystemInfoSync().pixelRatio;

                        canvas.width = boxWidth * dpr;
                        canvas.height = boxHeight * dpr;
                        ctx.scale(dpr, dpr);

                        resolve({ canvas, ctx, width: boxWidth, height: boxHeight });
                    });
            })
            .exec();
    });
}

/**
 * Canvas 导出为临时文件路径
 */
export function canvasToTempFilePath(
    canvas: WechatMiniprogram.Canvas,
    options?: { quality?: number; fileType?: 'png' | 'jpg' },
): Promise<string> {
    return new Promise((resolve, reject) => {
        wx.canvasToTempFilePath({
            canvas,
            fileType: options?.fileType || 'png',
            quality: options?.quality || 1,
            success: (res) => resolve(res.tempFilePath),
            fail: reject,
        });
    });
}

/**
 * 加载图片到 Canvas
 */
export function loadImage(
    canvas: WechatMiniprogram.Canvas,
    src: string,
): Promise<WechatMiniprogram.Image> {
    return new Promise((resolve, reject) => {
        const img = canvas.createImage();
        img.onload = () => resolve(img);
        img.onerror = reject;
        img.src = src;
    });
}