export type ResultType = 'dataUrl' | 'text' | 'file';

export function toArray<T>(item: T | T[]): T[] {

if (Array.isArray(item)) {

return item;

}

return [item];

}

export function readFile(file: File, resultType: ResultType) {

return new Promise(resolve => {

if (resultType === 'file') {

resolve();

return;

}

const reader = new FileReader();

reader.onload = event => {

resolve((event.target as FileReader).result);

};

if (resultType === 'dataUrl') {

reader.readAsDataURL(file);

} else if (resultType === 'text') {

reader.readAsText(file);

}

});

}

export function isOversize(files: File | File[], maxSize: number): boolean {

return toArray(files).some(file => file.size > maxSize);

}

export type FileListItem = {

url?: string;

file?: File;

content?: string; // dataUrl

isImage?: boolean;

};

const IMAGE_REGEXP = /\.(jpeg|jpg|gif|png|svg|webp|jfif|bmp|dpg)/i;

export function isImageUrl(url: string): boolean {

return IMAGE_REGEXP.test(url);

}

export function isImageFile(item: FileListItem): boolean {

// some special urls cannot be recognized

// user can add `isImage` flag to mark it as an image url

if (item.isImage) {

return true;

}

if (item.file && item.file.type) {

return item.file.type.indexOf('image') === 0;

}

if (item.url) {

return isImageUrl(item.url);

}

if (item.content) {

return item.content.indexOf('data:image') === 0;

}

return false;

}