feat: bytey blog

Author: iBotPeaches

blog/2025/2025-01-21-introducing-bytey/index.mdx

@@ -0,0 +1,73 @@
+---
+slug: 2025/introducing-bytey
+title: Introducing Bytey - A Google Polyline Encoding library
+authors: [connort]
+tags: [php, google, polyline, encoding]
+---
+
+One day we saw an interesting crash that one of our applications was generating a URL so long that Google's static map generation refused to generate it. With a bit of research we discovered lodged in the official [documentation](https://developers.google.com/maps/documentation/maps-static/start#url-size-restriction) that there was a known limit.
+
+:::note
+
+_Maps Static API URLs are restricted to 16384 characters in size. In practice, you will probably not have need for URLs longer than this, unless you produce complicated maps with a high number of markers and paths._
+
+:::
+
+This led us to discovering that Google had the [Encoded Polyline Algorithm Format](https://developers.google.com/maps/documentation/utilities/polylinealgorithm) designed to help pack information in the URL into a dense binary format in plain ASCII text in order to reduce characters. This blog is our journey to writing a little package to accomplish this in PHP.
+
+{/* truncate */}
+
+We did start with a bit of research if any library existed for this, but nothing we found existed in a modern PHP format with a software license we could leverage. Thankfully this was a 10-step algorithm that we could implement in a fresh new library. The algorithm works roughly in this way:
+
+1. Starts with the signed coordinate pairs (`(38.5, -120.2)`)
+2. Converts the values into integers that were rounded. (`3850000`, `-12020000`)
+3. Converts the values into binary, supporting negatives by using two's complement.
+4. Left shifting the binary one bit to optionally invert if negative.
+5. Break the binary value into 5-bit chunks reversed.
+6. Optionally OR each value with `0x20` if another chunk applies.
+7. Convert each value to decimal and add `63` to each one.
+8. Convert the value to ASCII (`_p~iF~ps|U`)
+
+You can see how `38.5` became `_p~iF` and `-120.2` became `~ps|U`. The first coordinate doesn't have much of a cost savings, but as the coordinate pairs continue and each pair has the offset from the previous you can tell how the data savings begin to take place.
+
+We wrote a quick PHPUnit test to confirm our implementation of the algorithm, and it matched Google's documentation.
+
+```php
+#[DataProvider('googleDataProvider')]
+public function test_google_polyline_encode(array $coordinates, string $expected): void {
+  $this->assertEquals($expected, Bytey::googlePolylineEncode($coordinates));
+}
+
+public static function googleDataProvider(): array {
+  return [
+    'simple example' => [
+      'coordinates' => [
+        [-179.9832104],
+      ],
+      'expected' => '`~oia@',
+    ],
+    'rounding example' => [
+      'coordinates' => [
+        [48.000006, 2.000004],
+        [48.00001, 2.00000],
+      ],
+      'expected' => 'a_~cH_seK??',
+    ],
+    'google example' => [
+      'coordinates' => [
+        [38.5, -120.2],
+        [40.7, -120.95],
+        [43.252, -126.453],
+      ],
+      'expected' => '_p~iF~ps|U_ulLnnqC_mqNvxq`@',
+    ],
+  ];
+}
+```
+
+So we took our affected entity that was generating a 19.5k character URL and ran it through the algorithm. The new URL was 3.3k characters, which suggested an 83% reduction in character length. A few more real life tests, and we had a fix out the door and a new package built.
+
+Thus, [Bytey](https://github.com/sourcetoad/Bytey) was born.
+
+* [GitHub Repo](https://github.com/sourcetoad/Bytey)
+* [Google's Polyline Docs](https://developers.google.com/maps/documentation/utilities/polylinealgorithm)