Copilot chat: Document import supports pdf (#700)

Currently the document import feature only supports .txt files. We would
like to support PDF files as well.

### Description
1. Add PdfPig 0.1.8 to the project as the lib to read PDFs.
2. Update READMEs.

samples/apps/copilot-chat-app/README.md

@@ -83,6 +83,7 @@ First, let’s set up and verify the back-end API server is running.
       ```bash
       REACT_APP_BACKEND_URI=https://localhost:40443/
       REACT_APP_AAD_CLIENT_ID=00000000-0000-0000-0000-000000000000
+      REACT_APP_AAD_AUTHORITY=https://login.microsoftonline.com/common
       ```
    
    1. To build and run the front-end application

samples/apps/copilot-chat-app/importdocument/README.md

@@ -42,4 +42,12 @@ Importing documents enables Copilot Chat to have up-to-date knowledge of specifi
    > Currently only supports txt files. A sample file is provided under ./sample-docs.
 
    Importing may take some time to generate embeddings for each piece/chunk of a document.
-5. Chat with the bot. Example: ![](../images/Document-Memory-Sample.png)
+5. Chat with the bot.
+
+   Examples:
+
+   With [ms10k.txt](./sample-docs/ms10k.txt):
+   ![](../images/Document-Memory-Sample-1.png)
+
+   With [Microsoft Responsible AI Standard v2 General Requirements.pdf](./sample-docs/Microsoft-Responsible-AI-Standard-v2-General-Requirements.pdf):
+   ![](../images/Document-Memory-Sample-2.png)

samples/apps/copilot-chat-app/webapi/Controllers/DocumentImportController.cs

@@ -8,6 +8,8 @@
 using SemanticKernel.Service.Config;
 using SemanticKernel.Service.Model;
 using SemanticKernel.Service.Skills;
+using UglyToad.PdfPig;
+using UglyToad.PdfPig.DocumentLayoutAnalysis.TextExtractor;
 
 namespace SemanticKernel.Service.Controllers;
 
@@ -25,7 +27,12 @@ private enum SupportedFileType
         /// <summary>
         /// .txt
         /// </summary>
-        Txt
+        Txt,
+
+        /// <summary>
+        /// .pdf
+        /// </summary>
+        Pdf,
     };
 
     private readonly IServiceProvider _serviceProvider;
@@ -87,6 +94,9 @@ public async Task<IActionResult> ImportDocumentAsync(
                 case SupportedFileType.Txt:
                     fileContent = await this.ReadTxtFileAsync(formFile);
                     break;
+                case SupportedFileType.Pdf:
+                    fileContent = this.ReadPdfFile(formFile);
+                    break;
                 default:
                     return this.BadRequest($"Unsupported file type: {fileType}");
             }
@@ -113,6 +123,7 @@ private SupportedFileType GetFileType(string fileName)
         return extension switch
         {
             ".txt" => SupportedFileType.Txt,
+            ".pdf" => SupportedFileType.Pdf,
             _ => throw new ArgumentOutOfRangeException($"Unsupported file type: {extension}"),
         };
     }
@@ -128,6 +139,27 @@ private async Task<string> ReadTxtFileAsync(IFormFile file)
         return await streamReader.ReadToEndAsync();
     }
 
+    /// <summary>
+    /// Read the content of a PDF file, ignoring images.
+    /// </summary>
+    /// <param name="file">An IFormFile object.</param>
+    /// <returns>A string of the content of the file.</returns>
+    private string ReadPdfFile(IFormFile file)
+    {
+        var fileContent = string.Empty;
+
+        using var pdfDocument = PdfDocument.Open(file.OpenReadStream());
+        foreach (var page in pdfDocument.GetPages())
+        {
+            var text = ContentOrderTextExtractor.GetText(page);
+            fileContent += text;
+        }
+
+        Console.WriteLine(fileContent);
+
+        return fileContent;
+    }
+
     /// <summary>
     /// Parse the content of the document to memory.
     /// </summary>

samples/apps/copilot-chat-app/webapi/CopilotChatApi.csproj

@@ -38,6 +38,7 @@
     <PackageReference Include="Microsoft.CognitiveServices.Speech" Version="1.27.0" />
     <PackageReference Include="Microsoft.Extensions.Options.DataAnnotations" Version="7.0.0" />
     <PackageReference Include="Microsoft.Identity.Web" Version="2.9.0" />
+    <PackageReference Include="PdfPig" Version="0.1.8-alpha-20230423-3898f" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.5.0" />
   </ItemGroup>
 

samples/apps/copilot-chat-app/webapp/src/components/chat/ChatInput.tsx

@@ -182,7 +182,7 @@ export const ChatInput: React.FC<ChatInputProps> = (props) => {
                         type="file"
                         ref={documentFileRef}
                         style={{ display: 'none' }}
-                        accept='.txt'
+                        accept='.txt,.pdf'
                         multiple={false}
                         onChange={() => importDocument()}
                     />