Factor-out parsing the input file

solutions/01.zig

@@ -2,9 +2,44 @@ const std = @import("std");
 const print = std.debug.print;
 const util = @import("util.zig");
 
-pub fn main() !u32 {
-    var arr1: [1000]u32 = undefined;
-    var arr2: [1000]u32 = undefined;
+pub fn part_one() !u32 {
+    const arrays = try parseInputFileToArrays();
+    std.debug.print("{any}", .{arrays.first});
+    const arr1 = arrays.first;
+    const arr2 = arrays.second;
+
+    // Everything below this is the actual logic
+    const stdout = std.io.getStdOut().writer();
+    std.mem.sort(u32, arr1, {}, comptime std.sort.asc(u32));
+    std.mem.sort(u32, arr2, {}, comptime std.sort.asc(u32));
+
+    var sum: u32 = 0;
+    for (0..arr1.len) |index| {
+        const val1 = arr1[index];
+        const val2 = arr2[index];
+        if (val1 > val2) {
+            sum += (val1 -% val2);
+        } else {
+            sum += (val2 -% val1);
+        }
+    }
+    try stdout.print("{}", .{sum});
+    // Only used for testing - but later we'll have this return to an actual higher-level `main` function and have
+    // _that_ do printing.
+    return sum;
+}
+
+pub fn part_two() !u32 {
+    return 0;
+}
+
+fn parseInputFileToArrays() !struct { first: []u32, second: []u32 } {
+    // Wow this _sucks_. But there's no way (that I know of?) to find the number of lines in a file without parsing it,
+    // and we can't parse it without having created the array already, so... :shrug
+    const isTestCase = true;
+    const lengthOfArray: usize = if (isTestCase) 6 else 1000;
+    var arr1: [lengthOfArray]u32 = undefined;
+    var arr2: [lengthOfArray]u32 = undefined;
 
     // Reading the input...
     // Making use of example here: https://cookbook.ziglang.cc/01-01-read-file-line-by-line.html
@@ -12,7 +47,7 @@ pub fn main() !u32 {
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
 
-    const path = try util.getInputFile("01", true);
+    const path = try util.getInputFile("01", isTestCase);
     std.debug.print("Path is {s}\n", .{path});
     const file = try std.fs.cwd().openFile(path, .{});
     defer file.close();
@@ -47,26 +82,7 @@ pub fn main() !u32 {
         },
         else => return err, // Propagate error
     }
-
-    // Everything below this is the actual logic
-    const stdout = std.io.getStdOut().writer();
-    std.mem.sort(u32, &arr1, {}, comptime std.sort.asc(u32));
-    std.mem.sort(u32, &arr2, {}, comptime std.sort.asc(u32));
-
-    var sum: u32 = 0;
-    for (0..arr1.len) |index| {
-        const val1 = arr1[index];
-        const val2 = arr2[index];
-        if (val1 > val2) {
-            sum += (val1 -% val2);
-        } else {
-            sum += (val2 -% val1);
-        }
-    }
-    try stdout.print("{}", .{sum});
-    // Only used for testing - but later we'll have this return to an actual higher-level `main` function and have
-    // _that_ do printing.
-    return sum;
+    return .{ .first = &arr1, .second = &arr2 };
 }
 
 fn parseLineToNumbers(line: []u8) struct { first: u32, second: u32 } {
@@ -98,9 +114,10 @@ fn parseLineToNumbers(line: []u8) struct { first: u32, second: u32 } {
 
 const expect = std.testing.expect;
 
-test {
-    const filePath = try util.getInputFile("01", true);
-    const stdout = std.io.getStdOut().writer();
-    try stdout.print("{s}\n\n", .{filePath});
-    try expect(try main() == 11);
+test "part one" {
+    try expect(try part_one() == 11);
 }
+
+// test "part two" {
+//     try expect(try part_two() == 31);
+// }