import { isImageData } from "./isImageData"

/**
 * 把 ImageData 编码成二进制数据（Blob）
 *  ImageData 是包含图片像素数据数组和宽高信息的对象
 * @param data ImageData 或 HTMLImageElement
 * @param type 图片格式如 image/gif, image/png, image/jpeg, image/webp
 * @param quality 质量参数 0~1（toDataURL 为 jpeg, webp 用的的质量参数）
 * @return {Promise<Blob>}
 */
export async function imageEncode(
    data: ImageData | HTMLImageElement | ImageBitmap,
    type = "image/png",
    quality?: number
): Promise<Blob> {
    let canvas!: HTMLCanvasElement
    let ctx!: CanvasRenderingContext2D

    if (!canvas) {
        canvas = document.createElement("canvas")
        ctx = <any>canvas.getContext("2d")
        if (!ctx) throw new Error("Could not create canvas context")
    }

    canvas.width = data.width
    canvas.height = data.height
    ctx.clearRect(0, 0, canvas.width, canvas.height)


    if (isImageData(data)) {
        ctx.putImageData(<ImageData>data, 0, 0)
    } else {
        ctx.drawImage(<HTMLImageElement | ImageBitmap>data, 0, 0)
    }

    let blob: Blob | null

    if ("toBlob" in canvas) {
        blob = await new Promise<Blob | null>((re) => canvas.toBlob(re, type, quality))
    } else {
        // Windows Edge
        const dataUrl = (canvas as HTMLCanvasElement).toDataURL(type, quality)
        const result = /data:([^;]+);base64,(.*)$/.exec(dataUrl)

        if (!result) throw Error("Data URL reading failed")

        const outputType = result[1]
        const binaryStr = atob(result[2])
        const data = new Uint8Array(binaryStr.length)

        for (let i = 0; i < data.length; i += 1) {
            data[i] = binaryStr.charCodeAt(i)
        }

        blob = new Blob([data], { type: outputType })
    }

    // canvas.remove()
    if (!blob) throw Error("Encoding failed")
    return blob
}