feat: Add MessageMedia.fromUrl method (#769)

src/structures/MessageMedia.js

@@ -3,6 +3,8 @@
 const fs = require('fs');
 const path = require('path');
 const mime = require('mime');
+const fetch = require('node-fetch');
+const { URL } = require('url');
 
 /**
  * Media attached to a message
@@ -43,6 +45,56 @@ class MessageMedia {
 
         return new MessageMedia(mimetype, b64data, filename);
     }
+
+    /**
+     * Creates a MessageMedia instance from a URL
+     * @param {string} url
+     * @param {Object} [options]
+     * @param {number} [options.unsafeMime=false]
+     * @param {object} [options.client]
+     * @param {object} [options.reqOptions]
+     * @param {number} [options.reqOptions.size=0]
+     * @returns {Promise<MessageMedia>}
+     */
+    static async fromUrl(url, options = {}) {
+        let mimetype;
+
+        if (!options.unsafeMime) {
+            const pUrl = new URL(url);
+            mimetype = mime.getType(pUrl.pathname);
+
+            if (!mimetype)
+                throw new Error('Unable to determine MIME type');
+        }
+
+        async function fetchData (url, options) {
+            const reqOptions = Object.assign({ headers: { accept: 'image/* video/* text/* audio/*' } }, options);
+            const response = await fetch(url, reqOptions);
+            const mime = response.headers.get('Content-Type');
+            let data = '';
+
+            if (response.buffer) {
+                data = (await response.buffer()).toString('base64');
+            } else {
+                const bArray = new Uint8Array(await response.arrayBuffer());
+                bArray.forEach((b) => {
+                    data += String.fromCharCode(b);
+                });
+                data = btoa(data);
+            }
+            
+            return { data, mime };
+        }
+
+        const res = options.client
+            ? (await options.client.pupPage.evaluate(fetchData, url, options.reqOptions))
+            : (await fetchData(url, options.reqOptions));
+
+        if (!mimetype)
+            mimetype = res.mime;
+
+        return new MessageMedia(mimetype, res.data, null);
+    }
 }
 
 module.exports = MessageMedia;