diff --git a/app/Parser.php b/app/Parser.php
index b74cf7b9f7..5447179ed8 100644
--- a/app/Parser.php
+++ b/app/Parser.php
@@ -2,12 +2,180 @@
 
 namespace App;
 
-use Exception;
+ini_set('memory_limit', '8192M');
 
 final class Parser
 {
+    private const READ_CHUNK = 163_840;
+    private const PATH_SCAN_SIZE = 2_097_152;
+    private const PREFIX_LEN = 25; // "https://stitcher.io/blog/"
+    private const WRITE_BUF  = 1_048_576;
+
     public function parse(string $inputPath, string $outputPath): void
     {
-        throw new Exception('TODO');
+        \gc_disable();
+
+        $fileSize = \filesize($inputPath);
+
+        $dateIds = [];
+        $dates = [];
+        $dateCount = 0;
+        for ($y = 21; $y <= 26; $y++) {
+            for ($m = 1; $m <= 12; $m++) {
+                $maxD = match ($m) {
+                    2 => $y === 24 ? 29 : 28,
+                    4, 6, 9, 11 => 30,
+                    default => 31,
+                };
+                $mStr = ($m < 10 ? '0' : '') . $m;
+                $ymStr = "{$y}-{$mStr}-";
+                for ($d = 1; $d <= $maxD; $d++) {
+                    $key = $ymStr . (($d < 10 ? '0' : '') . $d);
+                    $dateIds[$key] = $dateCount;
+                    $dates[$dateCount] = $key;
+                    $dateCount++;
+                }
+            }
+        }
+
+        $dateIdBytes = [];
+        foreach ($dateIds as $date => $id) {
+            $dateIdBytes[$date] = \chr($id & 0xFF) . \chr($id >> 8);
+        }
+
+        $handle = \fopen($inputPath, 'rb');
+        \stream_set_read_buffer($handle, 0);
+        $raw = \fread($handle, \min(self::PATH_SCAN_SIZE, $fileSize));
+        \fclose($handle);
+
+        $pathIds = [];
+        $paths = [];
+        $pathCount = 0;
+        $pos = 0;
+        $lastNl = \strrpos($raw, "\n") ?: 0;
+
+        while ($pos < $lastNl) {
+            $nlPos = \strpos($raw, "\n", $pos + 52);
+            if ($nlPos === false) break;
+
+            $slug = \substr($raw, $pos + self::PREFIX_LEN, $nlPos - $pos - 51);
+            if (!isset($pathIds[$slug])) {
+                $pathIds[$slug] = $pathCount;
+                $paths[$pathCount] = $slug;
+                $pathCount++;
+            }
+
+            $pos = $nlPos + 1;
+        }
+        unset($raw);
+
+        $buckets = \array_fill(0, $pathCount, '');
+
+        $handle = \fopen($inputPath, 'rb');
+        \stream_set_read_buffer($handle, 0);
+        $remaining = $fileSize;
+
+        while ($remaining > 0) {
+            $toRead = $remaining > self::READ_CHUNK ? self::READ_CHUNK : $remaining;
+            $chunk = \fread($handle, $toRead);
+            $chunkLen = \strlen($chunk);
+
+            if ($chunkLen === 0) break;
+            $remaining -= $chunkLen;
+
+            $lastNl = \strrpos($chunk, "\n");
+            if ($lastNl === false) break;
+
+            $tail = $chunkLen - $lastNl - 1;
+            if ($tail > 0) {
+                \fseek($handle, -$tail, SEEK_CUR);
+                $remaining += $tail;
+            }
+
+            $p = self::PREFIX_LEN;
+            $fence = $lastNl - 800;
+
+            while ($p < $fence) {
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+
+                $sep = \strpos($chunk, ',', $p);
+                $buckets[$pathIds[\substr($chunk, $p, $sep - $p)]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+            }
+
+            while ($p < $lastNl) {
+                $sep = \strpos($chunk, ',', $p);
+                if ($sep === false || $sep >= $lastNl) break;
+                $slug = \substr($chunk, $p, $sep - $p);
+                if (!isset($pathIds[$slug])) {
+                    $pathIds[$slug] = $pathCount;
+                    $paths[$pathCount] = $slug;
+                    $buckets[$pathCount] = '';
+                    $pathCount++;
+                }
+                $buckets[$pathIds[$slug]] .= $dateIdBytes[\substr($chunk, $sep + 3, 8)];
+                $p = $sep + 52;
+            }
+        }
+
+        \fclose($handle);
+
+        $this->jsonize($outputPath, $buckets, $paths, $dates, $dateCount);
+    }
+
+    private function jsonize(string $filename, array $buckets, array $paths, array $dates, int $dateCount): void {
+        $datePrefixes = \array_map(fn($d) => '        "20' . $d . '": ', $dates);
+        $escapedPaths = \array_map(fn($p) => "\"\\/blog\\/" . \str_replace('/', '\\/', $p) . '"', $paths);
+
+        $file = \fopen($filename, 'wb');
+        \stream_set_write_buffer($file, self::WRITE_BUF);
+        \fwrite($file, '{');
+
+        $isFirst = true;
+        foreach ($paths as $pid => $path) {
+            if ($buckets[$pid] === '') continue;
+
+            $hits = \array_count_values(\unpack('v*', $buckets[$pid]));
+            $dateEntries = [];
+            for ($d = 0; $d < $dateCount; $d++) {
+                if (isset($hits[$d]))
+                    $dateEntries[] = $datePrefixes[$d] . $hits[$d];
+            }
+            if (!$dateEntries) continue;
+
+            $buf = $isFirst ? "\n    " : ",\n    ";
+            $isFirst = false;
+            $buf .= $escapedPaths[$pid] . ": {\n" . \implode(",\n", $dateEntries) . "\n    }";
+            \fwrite($file, $buf);
+        }
+
+        \fwrite($file, "\n}");
+        \fclose($file);
     }
-}
\ No newline at end of file
+}