From e31878ceb12c3cb6deba8cbfbff9cd3f2de4de17 Mon Sep 17 00:00:00 2001
From: Adrien Crivelli <adrien.crivelli@gmail.com>
Date: Mon, 5 Feb 2018 21:33:23 +0900
Subject: [PATCH] Check for MIME type to know if CSV reader can read a file

CSV reader used to accept any file without any kind of check. That made
users incorrectly believe that things were ok, even though there is no
way for CSV reader to read anything else that plain text files.

Fixes #167
---
 CHANGELOG.md                                 |  1 +
 src/PhpSpreadsheet/Reader/Csv.php            | 19 +++++++++-----
 tests/PhpSpreadsheetTests/Reader/CsvTest.php | 26 ++++++++++++++++++++
 tests/data/Reader/CSV/empty.csv              |  0
 4 files changed, 40 insertions(+), 6 deletions(-)
 create mode 100644 tests/data/Reader/CSV/empty.csv

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6dc867a2..47734383 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Avoid potentially unsupported PSR-16 cache keys - [#354](https://github.com/PHPOffice/PhpSpreadsheet/issues/354) 
+- Check for MIME type to know if CSV reader can read a file - [#167](https://github.com/PHPOffice/PhpSpreadsheet/issues/167) 
 
 ## [1.1.0] - 2018-01-28
 
diff --git a/src/PhpSpreadsheet/Reader/Csv.php b/src/PhpSpreadsheet/Reader/Csv.php
index c31a37f5..76bac01a 100644
--- a/src/PhpSpreadsheet/Reader/Csv.php
+++ b/src/PhpSpreadsheet/Reader/Csv.php
@@ -195,11 +195,11 @@ class Csv extends BaseReader
             }
 
             $meanSquareDeviations[$delimiter] = array_reduce(
-                $series,
-                function ($sum, $value) use ($median) {
-                    return $sum + pow($value - $median, 2);
-                }
-            ) / count($series);
+                    $series,
+                    function ($sum, $value) use ($median) {
+                        return $sum + pow($value - $median, 2);
+                    }
+                ) / count($series);
         }
 
         // ... and pick the delimiter with the smallest mean square deviation (in case of ties, the order in potentialDelimiters is respected)
@@ -476,6 +476,13 @@ class Csv extends BaseReader
 
         fclose($this->fileHandle);
 
-        return true;
+        $type = mime_content_type($pFilename);
+        $supportedTypes = [
+            'text/csv',
+            'text/plain',
+            'inode/x-empty',
+        ];
+
+        return in_array($type, $supportedTypes, true);
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Reader/CsvTest.php b/tests/PhpSpreadsheetTests/Reader/CsvTest.php
index 003478fa..85f60721 100644
--- a/tests/PhpSpreadsheetTests/Reader/CsvTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/CsvTest.php
@@ -63,4 +63,30 @@ class CsvTest extends TestCase
             ],
         ];
     }
+
+    /**
+     * @dataProvider providerCanLoad
+     *
+     * @param bool $expected
+     * @param string $filename
+     */
+    public function testCanLoad($expected, $filename)
+    {
+        $reader = new Csv();
+        self::assertSame($expected, $reader->canRead($filename));
+    }
+
+    public function providerCanLoad()
+    {
+        return [
+            [false, 'data/Reader/Ods/data.ods'],
+            [false, 'data/Reader/Xml/WithoutStyle.xml'],
+            [true, 'data/Reader/CSV/enclosure.csv'],
+            [true, 'data/Reader/CSV/semicolon_separated.csv'],
+            [true, 'data/Reader/HTML/csv_with_angle_bracket.csv'],
+            [true, 'data/Reader/CSV/empty.csv'],
+            [true, '../samples/Reader/sampleData/example1.csv'],
+            [true, '../samples/Reader/sampleData/example2.csv'],
+        ];
+    }
 }
diff --git a/tests/data/Reader/CSV/empty.csv b/tests/data/Reader/CSV/empty.csv
new file mode 100644
index 00000000..e69de29b