added wrapper

README.md

@@ -4,7 +4,7 @@ this flake builds a package containing a program for each problem in this years
 
 ## adding a problem
 
-create a folder in `code/src` for the problem, then add an entry with the following format into `code/aoc2021.cabal`:
+create a folder in `code/src` for the problem, then add an entry with the following format into `code/aoc2021-programs.cabal`:
 
 ```
 executable aoc2021-XX
@@ -25,3 +25,11 @@ nix build git+https://git.p7.co.nz/thornAvery/aoc2021
 ```
 
 or you can add the overlay defined in the flake
+
+## running
+
+this flake defines a wrapper script that automates passing input to the problems.
+
+in order to use it, the problem folder must include `XX-input.txt`, where `XX` is the suffix defined in the cabal file.
+
+the default package provides a wrapper `aoc2021`, which when invoked with `aoc2021 XX` will cat the contents of `XX-input.txt` to the program `aoc2021-XX` (as defined in the cabal file).

code/aoc2021-programs.cabal

@@ -1,12 +1,12 @@
 cabal-version: 1.12
 
-name:       aoc2021
+name:       aoc2021-programs
 version:    0.0.0.1
 license:    MIT
 build-type: Simple
 
-synopsis: aoc2021 problem 01
-description: aoc2021 problem 01
+synopsis: aoc2021 problems
+description: aoc2021 problems
 
 author: Thorn Avery
 maintainer: ta@p7.co.nz

code/src/01/01-input.txt

@@ -0,0 +1,4 @@
+hello this is a test!
+this is a second line!
+newline!
+eof!

code/src/01/01.md

@@ -0,0 +1,3 @@
+# Problem 01
+
+

flake.nix

@@ -14,8 +14,9 @@
       };
       in rec {
         defaultPackage = packages.aoc2021;
-        packages = inputs.flake-utils.lib.flattenTree
-          ((import ./nix/utils.nix) { inherit pkgs; inherit inputs; });
+        packages = (inputs.flake-utils.lib.flattenTree
+          ((import ./nix/utils.nix) { inherit pkgs; inherit inputs; }))
+          // { aoc2021 = pkgs.aoc2021; };
         hydraJobs = builtins.listToAttrs
         (map (s: { name = s; value = {
             ${system} = packages.${s};

nix/overlay.nix

@@ -1,4 +1,5 @@
 inputs: final: prev: {
+  aoc2021 = final.callPackage (import ./wrapper) { pkgs = final; };
   haskellPackages = prev.haskellPackages.override {
     overrides = haskellSelf: haskellSuper:
       ((import ./utils.nix) { inherit inputs; pkgs = prev; })

nix/wrapper/default.nix

@@ -0,0 +1,14 @@
+{ pkgs, ... }: pkgs.stdenv.mkDerivation {
+  name = "aoc2021";
+  buildInputs = [ pkgs.haskellPackages.aoc2021-programs ];
+  src = ../../.;
+  installPhase = ''
+    mkdir -p $out/{bin,files}
+    cat > $out/bin/aoc2021 << EOF
+    #!/bin/bash
+    cat $out/files/\''${1}-input.txt | ${pkgs.haskellPackages.aoc2021-programs}/bin/aoc2021-\''${1}
+    EOF
+    chmod +x $out/bin/aoc2021
+    find code/ -type f | grep -i input.txt$ | xargs -i cp {} $out/files
+  '';
+}