diff --git a/app/Parser.php b/app/Parser.php
index b74cf7b9f7..93cc4a27c6 100644
--- a/app/Parser.php
+++ b/app/Parser.php
@@ -2,12 +2,400 @@
 
 namespace App;
 
-use Exception;
-
-final class Parser
-{
-    public function parse(string $inputPath, string $outputPath): void
-    {
-        throw new Exception('TODO');
-    }
-}
\ No newline at end of file
+use App\Commands\Visit;
+
+final class Parser {
+	private const int URI_PREFIX_LEN = 25;	// "https://stitcher.io/blog/"
+	private const int READ_CHUNK_SIZE = 1_048_576;
+	private const int NEXT_PATH_OFFSET = 52;
+
+	private static string $input_path = '';
+	private static string $output_path = '';
+
+	private static ?array $date_list = null;
+	private static ?array $date_id_map = null;
+	private static ?array $date_prefixes = null;
+	private static int $date_count = 0;
+
+	private static ?array $path_base_map = null;
+	private static ?array $path_id_map = null;
+	private static ?array $path_prefixes = null;
+	private static int $path_count = 0;
+
+	public function parse(string $input_path, string $output_path): void {
+		gc_disable();
+
+		Parser::buildDateList();
+		Parser::buildPathMap();
+
+		Parser::$input_path = $input_path;
+		Parser::$output_path = $output_path;
+
+		$counts = array_fill(0, Parser::$path_count * Parser::$date_count, 0);
+
+		// count visits and collect paths in first-appearance order from the csv
+		$encountered_paths = Parser::countVisits($counts);
+
+		Parser::writePrettyJson($counts, $encountered_paths);
+	}
+
+	// build a list of all the dates we'll be counting - in our case the start of 2021 to the end of 2026
+	private static function buildDateList(): void {
+		if (!empty(Parser::$date_list) && !empty(Parser::$date_id_map)) {
+			return;
+		}
+
+		Parser::$date_list = [];
+		Parser::$date_id_map = [];
+		Parser::$date_prefixes = [];
+
+		for ($year = 2021; $year <= 2026; ++$year) {
+			for ($month = 1; $month <= 12; ++$month) {
+				$max_day = match ($month) {
+					2 => Parser::isLeapYear($year) ? 29 : 28,
+					4, 6, 9, 11 => 30,
+					default => 31,
+				};
+
+				for ($day = 1; $day <= $max_day; ++$day) {
+					$date =
+						$year . '-' .
+						($month < 10 ? '0' : '') . $month . '-' .
+						($day < 10 ? '0' : '') . $day;
+
+					Parser::$date_list[Parser::$date_count] = $date;
+					Parser::$date_id_map[$date] = Parser::$date_count;
+					Parser::$date_prefixes[Parser::$date_count] = "        \"" . $date . '": ';
+					++Parser::$date_count;
+				}
+			}
+		}
+	}
+
+	private static function buildPathMap()
+	{
+		if (!empty(Parser::$path_base_map) && !empty(Parser::$path_id_map)) {
+			return;
+		}
+
+		Parser::$path_base_map = [];
+		Parser::$path_id_map = [];
+		Parser::$path_prefixes = [];
+
+		foreach (Visit::all() as $visit) {
+			$path = substr($visit->uri, self::URI_PREFIX_LEN);
+			Parser::$path_base_map[$path] = Parser::$path_count * Parser::$date_count;
+			Parser::$path_id_map[$path] = Parser::$path_count;
+			Parser::$path_prefixes[Parser::$path_count] = "    \"\/blog\/" . str_replace('/', '\/', $path) . "\": {\n";
+			Parser::$path_count++;
+		}
+	}
+
+	private static function isLeapYear(int $year): bool {
+		return ($year % 4 === 0 && $year % 100 !== 0) || ($year % 400 === 0);
+	}
+
+	// count the visits to each blogpost and record the order in which paths first appeared in the csv
+	private static function countVisits(array &$counts): array {
+		$input = fopen(Parser::$input_path, 'r');
+
+		stream_set_read_buffer($input, 0);
+
+		$tail = '';
+		$seen_paths = [];
+		$encountered_paths = [];
+		$path_cache = [];
+
+		// optimization - read 1mb of data every time
+		while (!feof($input)) {
+			$buffer = fread($input, Parser::READ_CHUNK_SIZE);
+
+			if ($buffer === '') {
+				break;
+			}
+
+			if ($tail !== '') {
+				$buffer = $tail . $buffer;
+			}
+
+			$last_newline = strrpos($buffer, "\n");
+			if ($last_newline === false) {
+				$tail = $buffer;
+				continue;
+			}
+
+			$chunk_len = $last_newline;
+			$p = self::URI_PREFIX_LEN;
+			$fence = $chunk_len - 1024;
+
+			while ($p < $fence) {
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+				$p = $sep + self::NEXT_PATH_OFFSET;
+			}
+
+			// safe chunk for the fallback's end
+			while ($p < $chunk_len) {
+				$sep = strpos($buffer, ',', $p);
+				if ($sep === false || $sep >= $chunk_len) {
+					break;
+				}
+
+				$path = substr($buffer, $p, $sep - $p);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($buffer, $sep + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+
+				$p = $sep + self::NEXT_PATH_OFFSET;
+			}
+
+			$tail = substr($buffer, $last_newline + 1);
+		}
+
+		if ($tail !== '') {
+			$comma = strpos($tail, ',');
+			if ($comma !== false && $comma > self::URI_PREFIX_LEN) {
+				$path = substr($tail, self::URI_PREFIX_LEN, $comma - self::URI_PREFIX_LEN);
+				$path_base = $path_cache[$path] ??= (Parser::$path_base_map[$path] ?? null);
+
+				if ($path_base !== null) {
+					if (!isset($seen_paths[$path])) {
+						$seen_paths[$path] = true;
+						$encountered_paths[] = $path;
+					}
+
+					$date = substr($tail, $comma + 1, 10);
+					$date_id = Parser::$date_id_map[$date] ?? null;
+					if ($date_id !== null) {
+						++$counts[$path_base + $date_id];
+					}
+				}
+			}
+		}
+
+		fclose($input);
+
+		return $encountered_paths;
+	}
+
+	private static function writePrettyJson(array $counts, array $encountered_paths): void {
+		$output = fopen(Parser::$output_path, 'w');
+
+		fwrite($output, "{\n");
+
+		$separator = '';
+
+		foreach ($encountered_paths as $path) {
+			$path_id = Parser::$path_id_map[$path];
+			$base = $path_id * Parser::$date_count;
+
+			$first_date_id = -1;
+			for ($date_id = 0; $date_id < Parser::$date_count; ++$date_id) {
+				if ($counts[$base + $date_id] !== 0) {
+					$first_date_id = $date_id;
+					break;
+				}
+			}
+
+			if ($first_date_id === -1) {
+				continue;
+			}
+
+			$buffer = $separator;
+			$buffer .= Parser::$path_prefixes[$path_id];
+			$buffer .= Parser::$date_prefixes[$first_date_id] . $counts[$base + $first_date_id];
+
+			for ($date_id = $first_date_id + 1; $date_id < Parser::$date_count; ++$date_id) {
+				$count = $counts[$base + $date_id];
+				if ($count === 0) {
+					continue;
+				}
+
+				$buffer .= ",\n";
+				$buffer .= Parser::$date_prefixes[$date_id] . $count;
+			}
+
+			$buffer .= "\n    }";
+
+			fwrite($output, $buffer);
+			$separator = ",\n";
+		}
+
+		fwrite($output, "\n}");
+		fclose($output);
+	}
+}