Refine setup

build.zig

@@ -1,35 +1,33 @@
 const std = @import("std");
 
+const nr_of_days = 12;
+
 pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    // TODO: This should be a non-exhaustive enum with one option: all
-    const day = b.option(u8, "day", "Build day") orelse 1;
+    const run_all = b.step("run", "Run all days");
 
-    // TODO: Depending on the day chosen, only that day should compile, or all days
-    const exe = addDay(b, target, optimize, day);
-    b.installArtifact(exe);
+    const day_option = b.option(usize, "day", "Build day");
 
-    // run step
-    const run_exe = b.addRunArtifact(exe);
-    const run_step = b.step("run", "Run the binary");
-    run_step.dependOn(&run_exe.step);
-}
-
-fn addDay(
-    b: *std.Build,
-    target: std.Build.ResolvedTarget,
-    optimize: std.builtin.OptimizeMode,
-    day: u8,
-) *std.Build.Step.Compile {
-    return b.addExecutable(.{
-        .name = "aoc2025",
-        .root_module = b.createModule(.{
-            .root_source_file = b.path(b.fmt("src/day_{d}.zig", .{day})),
-            .target = target,
-            .optimize = optimize,
-        }),
-    });
+    for (1..nr_of_days + 1) |day| {
+        const exe = b.addExecutable(.{
+            .name = b.fmt("run-day{d:0>2}", .{day}),
+            .root_module = b.createModule(.{
+                .root_source_file = b.path("src/main.zig"),
+                .target = target,
+                .optimize = optimize,
+            }),
+        });
+        exe.root_module.addAnonymousImport("day", .{
+            .root_source_file = b.path(b.fmt("src/days/day{d:0>2}.zig", .{day})),
+        });
+        b.installArtifact(exe);
+
+        if (day_option == null or day_option == day) {
+            const run_cmd = b.addRunArtifact(exe);
+            run_all.dependOn(&run_cmd.step);
+        }
+    }
 }