implementing focus module

app/client/web/src/MediaFiles.ts

@@ -1,12 +1,76 @@
 import { Media } from 'databag-client-sdk'
 
 export class MediaFiles implements Media {
-  public async read(source: any): Promise<{ size: number, getData: (position: number, length: number)=>Promise<string> }> {
-    return { size: 0, getData: async (position: number, length: number)=>('') };
+
+  private base64ToUint8Array(base64: string): Uint8Array {
+    var binaryString = atob(base64);
+    var bytes = new Uint8Array(binaryString.length);
+    for (var i = 0; i < binaryString.length; i++) {
+      bytes[i] = binaryString.charCodeAt(i);
+    }
+    return bytes;
   }
 
-  public async write(): Promise<{ setData: (data: string)=>Promise<void>, getPath: ()=>Promise<string> }> {
-    return { setData: async (data: string)=>{}, getPath: async ()=>('') };
+  private arrayBufferToBase64(buffer: ArrayBuffer): string {
+    let binary = '';
+    const bytes = new Uint8Array(buffer);
+    for (let i = 0; i < bytes.byteLength; i++) {
+      binary += String.fromCharCode(bytes[i]);
+    } 
+    return window.btoa(binary);
   }
-}
+
+  private loadFileData(file: any): Promise<ArrayBuffer> {
+    return new Promise(resolve => {
+      const reader = new FileReader()
+      reader.onloadend = (res) => { resolve(reader.result as ArrayBuffer) }
+      reader.readAsArrayBuffer(file)
+    })
+  };
+
+  public async read(source: any): Promise<{ size: number, getData: (position: number, length: number)=>Promise<string>, close: ()=>Promise<void> }> {
+    const data = await this.loadFileData(source);
+    const size = data.byteLength;
+
+    const getData = async (position: number, length: number) => {
+      if (position + length > data.byteLength) {
+        throw new Error('invalid read request');
+      }
+      const block = data.slice(position, position + length);
+      return this.arrayBufferToBase64(block);
+    }
+
+    const close = async () => {}
+
+    return { size, getData, close };
+  }
+
+  public async write(): Promise<{ setData: (data: string)=>Promise<void>, getUrl: ()=>Promise<string>, close: ()=>Promise<void> }> {
+    const blocks = [] as Uint8Array[];
+    let url = null as string | null;
+
+    const setData = async (data: string) => {
+      const block = this.base64ToUint8Array(data);
+      blocks.push(block);
+    }
+
+    const getUrl = async () => {
+      if (url) {
+        return url;
+      }
+      const blob = new Blob(blocks);
+      url = URL.createObjectURL(blob);
+      return url;
+    }
+
+    const close = async () => {
+      if (url) {
+        URL.revokeObjectURL(url);
+        url = null;
+      }
+    }
+    
+    return { setData, getUrl, close };
+  }
+}  
 

app/sdk/src/media.ts

@@ -0,0 +1,4 @@
+export interface Media {
+  read(source: any): Promise<{ size: number, getData: (position: number, length: number)=>Promise<string>, close: ()=>Promise<void> }>;
+  write(): Promise<{ setData: (data: string)=>Promise<void>, getUrl: ()=>Promise<string>, close: ()=>Promise<void> }>;
+}