1 files changed, 29 insertions, 0 deletions
diff --git a/2021/build.rs b/2021/build.rs
new file mode 100644
index 0000000..adbcf87
--- /dev/null
+++ b/2021/build.rs
@@ -0,0 +1,29 @@
+use std::env;
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    println!("cargo:rerun-if-env-changed=AOCDAY");
+    println!("cargo:rerun-if-env-changed=AOCPART");
+
+    if let Ok(version) = env::var("AOCDAY") {
+        let version = version.parse::<u32>()?;
+        match version {
+            1..=2 => println!("cargo:rustc-cfg=day{:02}", version),
+            _ => panic!("Not a valid day")
+        };
+    } else {
+        panic!("No date specified");
+    }
+
+    if let Ok(version) = env::var("AOCPART") {
+        let version = version.parse::<u32>()?;
+        match version {
+            1..=2 => println!("cargo:rustc-cfg=part{}", version),
+            _ => panic!("Not a valid part")
+        };
+    } else {
+        panic!("No part specified");
+    }
+
+    Ok(())
+}