From db6bfd99a0165e0e1aedefb26e5b570d9aebaa27 Mon Sep 17 00:00:00 2001
From: Dave Supplee <dwsupplee@gmail.com>
Date: Thu, 2 Mar 2017 20:23:01 -0500
Subject: [PATCH] ensure timestamps retain microsecond precision

---
 src/BigQuery/ValueMapper.php            | 49 +++++++++++++++++++++++--
 tests/unit/BigQuery/ValueMapperTest.php | 17 ++++++++-
 2 files changed, 61 insertions(+), 5 deletions(-)

diff --git a/src/BigQuery/ValueMapper.php b/src/BigQuery/ValueMapper.php
index 2d6bfe0b481..9121dcc2b58 100644
--- a/src/BigQuery/ValueMapper.php
+++ b/src/BigQuery/ValueMapper.php
@@ -106,10 +106,7 @@ public function fromBigQuery(array $value, array $schema)
             case self::TYPE_TIME:
                 return new Time(new \DateTime($value));
             case self::TYPE_TIMESTAMP:
-                $timestamp = new \DateTime();
-                $timestamp->setTimestamp((float) $value);
-
-                return new Timestamp($timestamp);
+                return $this->timestampFromBigQuery($value);
             case self::TYPE_RECORD:
                 return $this->recordFromBigQuery($value, $schema['fields']);
             default:
@@ -325,4 +322,48 @@ private function assocArrayToParameter(array $struct)
             ['structValues' => $values]
         ];
     }
+
+    /**
+     * Converts a timestamp in string format received from BigQuery to a
+     * {@see Google\Cloud\BigQuery\Timestamp}.
+     *
+     * @param string $value The timestamp.
+     * @return Timestamp
+     */
+    private function timestampFromBigQuery($value)
+    {
+        // If the string contains 'E' convert from exponential notation to
+        // decimal notation. This doesn't cast to a float because precision can
+        // be lost.
+        if (strpos($value, 'E')) {
+            list($value, $exponent) = explode('E', $value);
+            list($firstDigit, $remainingDigits) = explode('.', $value);
+
+            if (strlen($remainingDigits) > $exponent) {
+                $value = $firstDigit . substr_replace($remainingDigits, '.', $exponent, 0);
+            } else {
+                $value = $firstDigit . str_pad($remainingDigits, $exponent, '0') . '.0';
+            }
+        }
+
+        list($unixTimestamp, $microSeconds) = explode('.', $value);
+        $dateTime = new \DateTime("@$unixTimestamp");
+
+        // If the timestamp is before the epoch, make sure we account for that
+        // before concatenating the microseconds.
+        if ($microSeconds > 0 && $unixTimestamp[0] === '-') {
+            $microSeconds = 1000000 - (int) str_pad($microSeconds, 6, '0');
+            $dateTime->modify('-1 second');
+        }
+
+        return new Timestamp(
+            new \DateTime(
+                sprintf(
+                    '%s.%s+00:00',
+                    $dateTime->format('Y-m-d H:i:s'),
+                    $microSeconds
+                )
+            )
+        );
+    }
 }
diff --git a/tests/unit/BigQuery/ValueMapperTest.php b/tests/unit/BigQuery/ValueMapperTest.php
index 58a57ccc255..157ba271958 100644
--- a/tests/unit/BigQuery/ValueMapperTest.php
+++ b/tests/unit/BigQuery/ValueMapperTest.php
@@ -134,10 +134,25 @@ public function bigQueryValueProvider()
                 new Time(new \DateTime('12:15:15'))
             ],
             [
-                ['v' => '1438712914'],
+                ['v' => '1.438712914E9'],
                 ['type' => 'TIMESTAMP'],
                 new Timestamp(new \DateTime('2015-08-04 18:28:34Z'))
             ],
+            [
+                ['v' => '2678400.0'],
+                ['type' => 'TIMESTAMP'],
+                new Timestamp(new \DateTime('1970-02-01'))
+            ],
+            [
+                ['v' => '-3.1561919984985E8'],
+                ['type' => 'TIMESTAMP'],
+                new Timestamp(new \DateTime('1960-01-01 00:00:00.150150Z'))
+            ],
+            [
+                ['v' => '9.4668480015015E8'],
+                ['type' => 'TIMESTAMP'],
+                new Timestamp(new \DateTime('2000-01-01 00:00:00.150150Z'))
+            ],
             [
                 [
                     'v' => [