refactor: simplify parser logic and duplicated code (#269)

Signed-off-by: Grant Timmerman <timmerman+devrel@google.com>

Author: grant

src/parsers.ts

@@ -0,0 +1,79 @@
+import CONSTANTS from "./constants";
+import { isString, isDefinedOrThrow, isStringOrObjectOrThrow, ValidationError } from "./event/validation";
+
+export abstract class Parser {
+  abstract parse(payload: Record<string, unknown> | string): unknown;
+}
+
+export class JSONParser implements Parser {
+  decorator?: Base64Parser;
+  constructor(decorator?: Base64Parser) {
+    this.decorator = decorator;
+  }
+
+  /**
+   * Parses the payload with an optional decorator
+   * @param {object|string} payload the JSON payload
+   * @return {object} the parsed JSON payload.
+   */
+  parse(payload: Record<string, unknown> | string): string {
+    if (this.decorator) {
+      payload = this.decorator.parse(payload);
+    }
+
+    isDefinedOrThrow(payload, new ValidationError("null or undefined payload"));
+    isStringOrObjectOrThrow(payload, new ValidationError("invalid payload type, allowed are: string or object"));
+    const parseJSON = (v: Record<string, unknown> | string): string => (isString(v) ? JSON.parse(v as string) : v);
+    return parseJSON(payload);
+  }
+}
+
+export class PassThroughParser extends Parser {
+  parse(payload: unknown): unknown {
+    return payload;
+  }
+}
+
+const jsonParser = new JSONParser();
+export const parserByContentType: { [key: string]: Parser } = {
+  [CONSTANTS.MIME_JSON]: jsonParser,
+  [CONSTANTS.MIME_CE_JSON]: jsonParser,
+  [CONSTANTS.DEFAULT_CONTENT_TYPE]: jsonParser,
+  [CONSTANTS.DEFAULT_CE_CONTENT_TYPE]: jsonParser,
+  [CONSTANTS.MIME_OCTET_STREAM]: new PassThroughParser(),
+};
+
+export class Base64Parser implements Parser {
+  decorator?: Parser;
+
+  constructor(decorator?: Parser) {
+    this.decorator = decorator;
+  }
+
+  parse(payload: Record<string, unknown> | string): string {
+    let payloadToParse = payload;
+    if (this.decorator) {
+      payloadToParse = this.decorator.parse(payload) as string;
+    }
+
+    return Buffer.from(payloadToParse as string, "base64").toString();
+  }
+}
+
+export interface MappedParser {
+  name: string;
+  parser: Parser;
+}
+
+export class DateParser extends Parser {
+  parse(payload: string): Date {
+    return new Date(Date.parse(payload));
+  }
+}
+
+export const parserByEncoding: { [key: string]: { [key: string]: Parser } } = {
+  base64: {
+    [CONSTANTS.MIME_CE_JSON]: new JSONParser(new Base64Parser()),
+    [CONSTANTS.MIME_OCTET_STREAM]: new PassThroughParser(),
+  },
+};

src/parsers/base64.ts

@@ -1,7 +1,7 @@
 import "mocha";
 import { expect } from "chai";
 
-import { JSONParser as Parser } from "../../src/parsers/";
+import { JSONParser as Parser } from "../../src/parsers";
 import { ValidationError } from "../../src/";
 
 describe("JSON Event Format Parser", () => {