use dune_site module to find inputs

this packages the inputs as part of the build and exposes the directory
to find them via a generated module. this way, inputs are a resource of
the library rather than an input.

this means that `dune exec aoc` and `dune utop` will always find the
file regardless of where they are invoked, which makes developing in
emacs simpler :)

aoc.opam

@@ -23,9 +23,11 @@ build: [
     name
     "-j"
     jobs
+    "--promote-install-files=false"
     "@install"
     "@runtest" {with-test}
     "@doc" {with-doc}
   ]
+  ["dune" "install" "-p" name "--create-install-files" name]
 ]
 dev-repo: "git+https://github.com/username/reponame.git"

dune-project

@@ -15,11 +15,14 @@
 
 (documentation https://url/to/documentation)
 
+(using dune_site 0.1)
+
 (package
  (name aoc)
  (synopsis "A short synopsis")
  (description "A longer description")
  (depends ocaml dune)
+ (sites (lib inputs))
  (tags
   (topics "to describe" your project)))
 

src/day1.ml

@@ -24,7 +24,7 @@ let part2 lines =
 ;;
 
 let print () =
-  let lines = Utils.lines_of_file "inputs/day1.tt" in
+  let lines = Utils.lines_of_input 1 in
   Printf.(
     printf "Day 1.1: %d\n" @@ part1 lines;
     printf "Day 1.2: %d\n" @@ part2 lines)

src/day2.ml

@@ -87,7 +87,7 @@ let part2 lines =
 ;;
 
 let print () =
-  let lines = Utils.lines_of_file "./inputs/day2.tt" in
+  let lines = Utils.lines_of_input 2 in
   Printf.(
     printf "Day 2.1: %d\n" @@ part1 lines;
     printf "Day 2.2: %d\n" @@ part2 lines)

src/dune

@@ -1,4 +1,12 @@
 (library
  (name aoc)
- (libraries stdio re)
+ (libraries stdio re dune-site)
  (preprocess (pps ppx_regexp)))
+
+(install
+ (section (site (aoc inputs)))
+ (files (glob_files ../inputs/*)))
+
+(generate_sites_module
+ (module inputs)
+ (sites aoc))

src/utils.ml

@@ -1,9 +1,9 @@
-let lines_of_file filename = Stdio.In_channel.(with_file filename ~f:input_lines)
-
-let rec print_int_list = function
-  | [] -> ()
-  | e :: l ->
-    print_int e;
-    print_string " ";
-    print_int_list l
+let lines_of_input day =
+  let base_path =
+    match Inputs.Sites.inputs with
+    | path :: _ -> path
+    | _ -> failwith "cant find sites path"
+  in
+  let path = Printf.sprintf "%s/day%d.tt" base_path day in
+  Stdio.In_channel.(with_file path ~f:input_lines)
 ;;