Azure Storage

const express = require("express");
const { BlobServiceClient, StorageSharedKeyCredential }
   = require("@azure/storage-blob");                        #1
 
const PORT = process.env.PORT;
const STORAGE_ACCOUNT_NAME = 
   process.env.STORAGE_ACCOUNT_NAME;                        #2
const STORAGE_ACCESS_KEY = 
   process.env.STORAGE_ACCESS_KEY;                          #3
 
function createBlobService() {                                #4
  const sharedKeyCredential = new StorageSharedKeyCredential(
    STORAGE_ACCOUNT_NAME, STORAGE_ACCESS_KEY
  );
  const blobService = new BlobServiceClient(
    `https://${STORAGE_ACCOUNT_NAME}.blob.core.windows.net`,
    sharedKeyCredential
  );
  return blobService;
}
 
const app = express();
 
app.get("/video", async (req, res) => {                      #5
 
  const videoPath = req.query.path;                          #6
  
  const containerName = "videos";                            #7
  const blobService = createBlobService();                   #8
  const containerClient = 
     blobService.getContainerClient(containerName);        #9
  const blobClient = 
     containerClient.getBlobClient(videoPath);             #10
 
  const properties = 
     await blobClient.getProperties();                     #11
 
  res.writeHead(200, {                                       #12
    "Content-Length": properties.contentLength,
    "Content-Type": "video/mp4",
  });
 
  const response = await blobClient.download();              #13
  response.readableStreamBody.pipe(res);                     #14
});
 
app.listen(PORT);
#1 Loads the Azure Storage SDK so our code can interact with the Azure Storage API
#2 Gets the name of the storage account from an environment variable
#3 Gets the name of the access key from an environment variable
#4 Helper function that connects to the Azure Storage API
#5 HTTP GET route for retrieving a video from Azure Storage. Note that the route handler uses the async keyword so that we can use JavaScript’s async/await syntax within. This is why we installed Express v5 beta in chapter 2.
#6 Specifies the path to the video in storage as an HTTP query parameter
#7 Hardcoded container name. Later, we can vary this for some purpose (e.g., by user ID so we can keep videos for each user separately).
#8 Connects to the Azure Storage API
#9 Connects the client for the Azure Storage container
#10 Connects the client for the “blob” (aka the file) that we’d like to retrieve
#11 Retrieves the video’s properties from Azure Storage
#12 Writes content length and MIME type to the HTTP response headers
#13 Starts the download of the specified file
#14 Pipes the video stream from Azure Storage to the HTTP response