1 files changed, 81 insertions, 0 deletions
diff --git a/cli/js/web/fetch/multipart.ts b/cli/js/web/fetch/multipart.ts
index 792f9b5ee..654d4a0ea 100644
--- a/cli/js/web/fetch/multipart.ts
+++ b/cli/js/web/fetch/multipart.ts
@@ -1,5 +1,8 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
+import { Buffer } from "../../buffer.ts";
+import { bytesSymbol } from "../blob.ts";
+import { DomFileImpl } from "../dom_file.ts";
 import { DenoBlob } from "../blob.ts";
 import { TextEncoder, TextDecoder } from "../text_encoding.ts";
 import { getHeaderValueParams } from "../util.ts";
@@ -14,6 +17,84 @@ interface MultipartHeaders {
   disposition: Map<string, string>;
 }
 
+export class MultipartBuilder {
+  readonly boundary: string;
+  readonly formData: FormData;
+  readonly writer: Buffer;
+  constructor(formData: FormData, boundary?: string) {
+    this.boundary = boundary ?? this.#createBoundary();
+    this.formData = formData;
+    this.writer = new Buffer();
+  }
+
+  getContentType(): string {
+    return `multipart/form-data; boundary=${this.boundary}`;
+  }
+
+  getBody(): Uint8Array {
+    for (const [fieldName, fieldValue] of this.formData.entries()) {
+      if (fieldValue instanceof DomFileImpl) {
+        this.#writeFile(fieldName, fieldValue);
+      } else this.#writeField(fieldName, fieldValue as string);
+    }
+
+    this.writer.writeSync(encoder.encode(`\r\n--${this.boundary}--`));
+
+    return this.writer.bytes();
+  }
+
+  #createBoundary = (): string => {
+    return (
+      "----------" +
+      Array.from(Array(32))
+        .map(() => Math.random().toString(36)[2] || 0)
+        .join("")
+    );
+  };
+
+  #writeHeaders = (headers: string[][]): void => {
+    let buf = this.writer.empty() ? "" : "\r\n";
+
+    buf += `--${this.boundary}\r\n`;
+    for (const [key, value] of headers) {
+      buf += `${key}: ${value}\r\n`;
+    }
+    buf += `\r\n`;
+
+    this.writer.write(encoder.encode(buf));
+  };
+
+  #writeFileHeaders = (
+    field: string,
+    filename: string,
+    type?: string
+  ): void => {
+    const headers = [
+      [
+        "Content-Disposition",
+        `form-data; name="${field}"; filename="${filename}"`,
+      ],
+      ["Content-Type", type || "application/octet-stream"],
+    ];
+    return this.#writeHeaders(headers);
+  };
+
+  #writeFieldHeaders = (field: string): void => {
+    const headers = [["Content-Disposition", `form-data; name="${field}"`]];
+    return this.#writeHeaders(headers);
+  };
+
+  #writeField = (field: string, value: string): void => {
+    this.#writeFieldHeaders(field);
+    this.writer.writeSync(encoder.encode(value));
+  };
+
+  #writeFile = (field: string, value: DomFileImpl): void => {
+    this.#writeFileHeaders(field, value.name, value.type);
+    this.writer.writeSync(value[bytesSymbol]);
+  };
+}
+
 export class MultipartParser {
   readonly boundary: string;
   readonly boundaryChars: Uint8Array;