3 files changed, 67 insertions, 2 deletions
diff --git a/2025/ocaml/lib/application/day_1.ml b/2025/ocaml/lib/application/day_1.ml
index 7ddac8b..bc0d5cc 100644
--- a/2025/ocaml/lib/application/day_1.ml
+++ b/2025/ocaml/lib/application/day_1.ml
@@ -1 +1,49 @@
-let run () = failwith "day 1 not implemented"
+open Domain.Day_1
+
+let rec input_to_lines input =
+  let lines =
+    String.split_on_char '\n' input |> List.filter (fun l -> l <> "")
+  in
+  pp_lines lines ; lines
+
+and pp_lines = function
+  | [] ->
+      ()
+  | h :: t ->
+      Logs.debug (fun m -> m "Line=%s" h) ;
+      pp_lines t
+
+let parse_line line =
+  Scanf.sscanf line "%c%d" (fun d n ->
+      match d with
+      | 'L' ->
+          Dial.Left n
+      | 'R' ->
+          Dial.Right n
+      | _ ->
+          failwith "invalid direction" )
+
+let lines_to_turns =
+  List.map (fun (l : string) ->
+      Logs.debug (fun m -> m "parsing %s into turn" l) ;
+      let turn = parse_line l in
+      Logs.debug (fun m -> m "%s" (Dial.pp_direction turn)) ;
+      turn )
+
+let rec turn_aux count current = function
+  | [] ->
+      count
+  | h :: t ->
+      let current' = Dial.turn current h in
+      Logs.debug (fun m -> m "dial at %d" (Dial.to_int current')) ;
+      if Dial.to_int current' = 0 then turn_aux (count + 1) current' t
+      else turn_aux count current' t
+
+let turn current = turn_aux 0 current
+
+let solve input () =
+  let lines = input_to_lines input in
+  let turns = lines_to_turns lines in
+  let start = Dial.start in
+  let answer = turn start turns in
+  answer
diff --git a/2025/ocaml/lib/application/day_1.mli b/2025/ocaml/lib/application/day_1.mli
new file mode 100644
index 0000000..73631f1
--- /dev/null
+++ b/2025/ocaml/lib/application/day_1.mli
@@ -0,0 +1,4 @@
+val solve : string -> unit -> int
+(** [solve input ()] is the solution for the first day of advent of code 2025 for [input].
+    The solution for an empty input is [Domain.Day_1.Dial.(to_int start)].
+    Requires: [input] to be a multiline string using `\n` as it's line separator. *)
diff --git a/2025/ocaml/lib/presentation/cli.ml b/2025/ocaml/lib/presentation/cli.ml
index 08b1552..6344d07 100644
--- a/2025/ocaml/lib/presentation/cli.ml
+++ b/2025/ocaml/lib/presentation/cli.ml
@@ -1,6 +1,19 @@
+let day_1_example = {|L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82|}
+
 let run_day = function
   | 1 ->
-      Application.Day_1.run ()
+      let answer = Application.Day_1.solve day_1_example () in
+      Logs.app (fun m -> m "%d" answer) ;
+      0
   | _ ->
       failwith "day not implemented"