feat(medusa): Parsing CSV files (#1572)

* add: csv parser

* fix: tests

* fix: linting + comment

* add: missing dependency

* fix: generic transformers

* fix: address comments

* fix: make parser options generic

* add: support regex columns + fix missing columns bug

* improve test case

* add: support for reducer + tests

* fix: add comments to csv parser

packages/medusa/src/interfaces/abstract-parser.ts

@@ -0,0 +1,42 @@
+/**
+ * Generic parsing interface. All different parsing implementations (csv, json, etc.) should implement this interface
+ */
+export interface IParser<TResult, TParseOptions> {
+  /**
+   *
+   * @param readableStream readable stream to parse
+   * @param options options used for parsing by underlying parser implementation
+   */
+  parse(
+    readableStream: NodeJS.ReadableStream,
+    options?: TParseOptions
+  ): Promise<TResult[]>
+}
+
+/**
+ * Abstract class implementation of the IParser interface. All different parsing implementations should extend this class
+ */
+export abstract class AbstractParser<
+  TSchema,
+  TParserResult,
+  TParseOptions,
+  TOutputResult
+> implements IParser<TParserResult, TParseOptions>
+{
+  protected readonly $$schema: TSchema
+
+  protected constructor(schema: TSchema) {
+    this.$$schema = schema
+  }
+
+  public abstract parse(
+    readableStream: NodeJS.ReadableStream,
+    options?: TParseOptions
+  ): Promise<TParserResult[]>
+
+  /**
+   *
+   * @param data data to be built after parsing. Includes validation according to schema, transformation of values, etc.
+   */
+  public abstract buildData(data: TParserResult[]): Promise<TOutputResult[]>
+}