feat: implement getFileById method

src/models/ApiResponse.ts

@@ -1,8 +1,10 @@
+import { type AxiosResponse } from 'axios';
 import { FieldType } from '../enums/FieldType';
 import { App } from './App';
 import { CollectionResponse } from './CollectionResponse';
 import { CreatedWithIdResponse } from './CreatedWithIdResponse';
 import { Field } from './Field';
+import { File } from './File';
 import { FileInfo } from './FileInfo';
 import { FormulaField } from './FormulaField';
 import { GetPagedAppsResponse } from './GetPagedAppsResponse';
@@ -221,6 +223,41 @@ export class ApiResponse<T> {
     );
   }
 
+  public asFileType(response: AxiosResponse): ApiResponse<File> {
+    const apiResponse = this as ApiResponse<any>;
+
+    let fileName = response.headers['content-disposition']
+      .split(';')[1]
+      .split('=')[1];
+
+    fileName = fileName.substring(1, fileName.length - 1);
+
+    const contentType =
+      response.headers['content-type'] ??
+      response.headers['Content-Type'] ??
+      null;
+
+    let contentLength =
+      response.headers['content-length'] ??
+      response.headers['Content-Length'] ??
+      0;
+
+    contentLength = parseInt(contentLength);
+
+    const file = new File(
+      apiResponse.data,
+      fileName,
+      contentType,
+      contentLength
+    );
+
+    return new ApiResponse<File>(
+      apiResponse.statusCode,
+      apiResponse.message,
+      file
+    );
+  }
+
   /**
    * @method asFileCollectionType - Converts the field item to the appropriate field object based upon the field item's type.
    * @param fieldItem - The field item to convert.

src/models/File.ts

@@ -0,0 +1,46 @@
+import { type Readable } from 'stream';
+
+/**
+ * @class File - Represents a file retrieved from Onspring.
+ */
+export class File {
+  /**
+   * @property {Readable} stream - The stream of the file.
+   */
+  public stream: Readable;
+
+  /**
+   * @property {string} fileName - The name of the file.
+   */
+  public fileName: string;
+
+  /**
+   * @property {string} contentType - The content type of the file.
+   */
+  public contentType: string;
+
+  /**
+   * @property {number} contentLength - The content length of the file.
+   */
+  public contentLength: number;
+
+  /**
+   * @constructor - Creates a new instance of File.
+   * @param {Readable} stream - The stream of the file.
+   * @param {string} fileName - The name of the file.
+   * @param {string} contentType - The content type of the file.
+   * @param {number} contentLength - The content length of the file.
+   * @returns {File} - A new instance of File.
+   */
+  constructor(
+    stream: Readable,
+    fileName: string,
+    contentType: string,
+    contentLength: number
+  ) {
+    this.stream = stream;
+    this.fileName = fileName;
+    this.contentType = contentType;
+    this.contentLength = contentLength;
+  }
+}

src/models/OnspringClient.ts

@@ -1,10 +1,10 @@
 import axios from 'axios';
-import { type AxiosInstance, type AxiosRequestConfig } from 'axios';
+import { PagingRequest } from './PagingRequest';
 import { ArgumentValidator } from './ArgumentValidator';
 import { EndpointFactory } from './EndpointFactory';
 import { ApiResponseFactory } from './ApiResponseFactory';
+import { type AxiosInstance, type AxiosRequestConfig } from 'axios';
 import { type ApiResponse } from './ApiResponse';
-import { PagingRequest } from './PagingRequest';
 import { type GetPagedAppsResponse } from './GetPagedAppsResponse';
 import { type App } from './App';
 import { type CollectionResponse } from './CollectionResponse';
@@ -13,6 +13,7 @@ import { type GetPagedFieldsResponse } from './GetPagedFieldsResponse';
 import { type SaveFileRequest } from './SaveFileRequest';
 import { type CreatedWithIdResponse } from './CreatedWithIdResponse';
 import { type FileInfo } from './FileInfo';
+import { type File } from './File';
 
 /**
  * @class OnspringClient - A client that can communicate with the Onspring API.
@@ -200,6 +201,37 @@ export class OnspringClient {
     return apiResponse.asFileInfoType();
   }
 
+  /**
+   * @method getFileById - Gets a file by its id.
+   * @param {number} recordId - The id of the record that the file is attached to.
+   * @param {number} fieldId - The id of the field that the file is attached to.
+   * @param {number} fileId - The id of the file to get.
+   * @returns {Promise<ApiResponse<File>>} - A promise that resolves to an ApiResponse of type File.
+   */
+  public async getFileById(
+    recordId: number,
+    fieldId: number,
+    fileId: number
+  ): Promise<ApiResponse<File>> {
+    const endpoint = EndpointFactory.getFileByIdEndpoint(
+      recordId,
+      fieldId,
+      fileId
+    );
+
+    const response = await this._client.get(endpoint, {
+      responseType: 'stream',
+    });
+
+    const apiResponse = ApiResponseFactory.getApiResponse<any>(response);
+
+    if (apiResponse.isSuccessful === false) {
+      return apiResponse;
+    }
+
+    return apiResponse.asFileType(response);
+  }
+
   /**
    * @method saveFile - Saves a file to a record in Onspring.
    * @param {SaveFileRequest} request - The request that will be used to save the file.