docs: add azure blob uploader example

uploader-examples/blob-uploader .ts

@@ -0,0 +1,73 @@
+import { Uploader } from 'ngx-uploadx';
+
+/**
+ *  Azure Blob Storage support
+ * @example
+ *   options: UploadxOptions = {
+ *     allowedTypes: 'image/*,video/*',
+ *     maxChunkSize: 512 * 1024 * 1024,
+ *     endpoint: `[signedURL]`,
+ *     uploaderClass: BlobUploader
+ *   };
+ */
+
+const BLOB_API_VERSION = '2022-11-02';
+
+export class BlobUploader extends Uploader {
+  blockList: string[] = [];
+  override async getFileUrl(): Promise<string> {
+    const oUrl = new URL(this.endpoint);
+    oUrl.pathname = [oUrl.pathname, this.file.name].join('/');
+    const url = oUrl.toString();
+    return url;
+  }
+
+  override async sendFileContent(): Promise<number | undefined> {
+    const { body, start, end } = this.getChunk();
+    const blockId = btoa(this.uploadId + String(start).padStart(15, '0'));
+    const url = this.url + `&comp=block&blockid=${encodeURIComponent(blockId)}`;
+    const headers = commonHeaders();
+    await this.request({ method: 'PUT', headers, url, body });
+    this.blockList.push(blockId);
+    if (end === this.size) {
+      await this.finish();
+    }
+    return this.responseStatus > 201 ? start : end;
+  }
+
+  async finish() {
+    const blocks = this.blockList.map(blockId => `<Latest>${blockId}</Latest>`).join('');
+    const body = `<?xml version="1.0" encoding="utf-8"?><BlockList>${blocks}</BlockList>`;
+    const url = `${this.url}&comp=blocklist`;
+    const headers = { ...commonHeaders(), 'Content-Type': 'text/xml; charset=UTF-8' };
+    await this.request({ method: 'PUT', headers, url, body });
+    return this.size;
+  }
+
+  override abort(): void {} // FIXME: Azurite does not support blob upload interrupts?!
+
+  override async getOffset(): Promise<number | undefined> {
+    const url = this.url + `&comp=blocklist&blocklisttype=all`;
+    const headers = commonHeaders();
+    try {
+      await this.request({ headers, url });
+      const parser = new DOMParser();
+      const xmlDoc = parser.parseFromString(this.response, 'text/xml');
+      const blocks = xmlDoc
+        .getElementsByTagName('UncommittedBlocks')[0]
+        .getElementsByTagName('Block');
+      const sizes = Array.from(blocks).map(
+        el => +(el.getElementsByTagName('Size')[0]?.textContent ?? '0')
+      );
+      return sizes.reduce((acc, v) => acc + v, 0);
+    } catch {}
+    return this.offset || 0;
+  }
+}
+
+function commonHeaders() {
+  return {
+    'x-ms-version': BLOB_API_VERSION,
+    'x-ms-date': new Date().toISOString()
+  };
+}