set expected json format

bin/view-json

@@ -50,6 +50,38 @@ $command = (new SingleCommandApplication())
             );
         } catch (FileHandlerException) {
             $io->error('invalid json file');
+            $io->writeln(
+                '
+                Expected Format
+  =======================================
+
+  [
+
+    {
+      "title": "The Catcher in the Rye",
+      "author": "J.D. Salinger",
+      "published_year": 1951
+    },
+    {
+      "title": "To Kill a Mockingbird",
+      "author": "Harper Lee",
+      "published_year": 1960
+    },
+    {
+      "title": "1984",
+      "author": "George Orwell",
+      "published_year": 1949
+    }
+
+  ]
+
+
+
+
+  =======================================
+
+         '
+            );
             return Command::FAILURE;
         }
 

src/JsonFileHandler.php

@@ -50,13 +50,14 @@ private function getRows(
             throw new FileHandlerException("{$filename} is not valid");
         }
 
-        $contents = json_decode($jsonContents, true);
-        if (!$contents || json_last_error() !== JSON_ERROR_NONE) {
+
+        if (!$contents = $this->isValidJson($jsonContents)) {
             throw new FileHandlerException(json_last_error_msg());
         }
 
+
         $count = 0;
-        $headers = array_keys(reset($contents));
+        $headers = array_keys($contents[0]);
         $indices = is_array($hideColumns) ? $this->setColumnsToHide($headers, $hideColumns) : [];
         foreach ($contents as $content) {
             if (!empty($indices)) {
@@ -71,4 +72,38 @@ private function getRows(
             }
         }
     }
+
+    /**
+     * @param string $jsonData
+     * @return array<int,array<string,string>>|false
+     */
+    private function isValidJson(string $jsonData): array|false
+    {
+        $data = json_decode($jsonData, true);
+
+        if (json_last_error() !== JSON_ERROR_NONE) {
+            return false;
+        }
+
+
+        if (!is_array($data)) {
+            return false;
+        }
+
+        if (!isset($data[0]) || !is_array($data[0])) {
+            return false;
+        }
+
+        $firstArrayKeys = array_keys($data[0]);
+
+        foreach ($data as $item) {
+            $currentArrayKeys = array_keys($item);
+
+            if ($firstArrayKeys !== $currentArrayKeys) {
+                return false;
+            }
+        }
+
+        return $data;
+    }
 }