Add failure analyzer for incorrect pcap file

src/main/java/ru/serega6531/packmate/exception/analyzer/PcapFileNotFoundFailureAnalyzer.java

@@ -0,0 +1,44 @@
+package ru.serega6531.packmate.exception.analyzer;
+
+import org.springframework.boot.diagnostics.AbstractFailureAnalyzer;
+import org.springframework.boot.diagnostics.FailureAnalysis;
+import ru.serega6531.packmate.exception.PcapFileNotFoundException;
+
+import java.io.File;
+import java.util.Arrays;
+import java.util.List;
+
+public class PcapFileNotFoundFailureAnalyzer extends AbstractFailureAnalyzer<PcapFileNotFoundException> {
+    @Override
+    protected FailureAnalysis analyze(Throwable rootFailure, PcapFileNotFoundException cause) {
+        String description = "The file " + cause.getFile().getAbsolutePath() + " was not found";
+        String existingFilesMessage;
+
+
+        File[] existingFiles = cause.getDirectory().listFiles();
+
+        if (existingFiles == null) {
+            return new FailureAnalysis(
+                    description,
+                    "Make sure you've put the pcap file to the ./pcaps directory, not the root directory. " +
+                            "The directory currently does not exist",
+                    cause
+            );
+        }
+
+
+        if (existingFiles.length == 0) {
+            existingFilesMessage = "The pcaps directory is currently empty";
+        } else {
+            List<String> existingFilesNames = Arrays.stream(existingFiles).map(File::getName).toList();
+            existingFilesMessage = "The files present in " + cause.getDirectory().getAbsolutePath() + " are: " + existingFilesNames;
+        }
+
+        return new FailureAnalysis(
+                description,
+                "Please verify the file name. Make sure you've put the pcap file to the ./pcaps directory, not the root directory.\n" +
+                        existingFilesMessage,
+                cause
+        );
+    }
+}