refactor(matrix): convert matrix into domain module

2 files changed, 152 insertions, 104 deletions

diff --git a/2025/ocaml/lib/application/d04p01.ml b/2025/ocaml/lib/application/d04p01.ml
index 2cc5f5d..4bf38ad 100644
--- a/2025/ocaml/lib/application/d04p01.ml
+++ b/2025/ocaml/lib/application/d04p01.ml
@@ -1,106 +1,4 @@
-(** [input_to_matrix input] is a 2D Array where each line of the [input] is
-    a row and each character in that line is a column.
-    Requires: all lines in input are of equal length. *)
-let input_to_matrix input =
-  let lines =
-    input |> String.split_on_char '\n'
-    |> List.filter_map (fun line ->
-        let trimmed = String.trim line in
-        if trimmed <> "" then Some trimmed else None )
-  in
-  let row_count = List.length lines in
-  let column_count =
-    match List.nth_opt lines 1 with
-    | None ->
-        failwith "first line should not be empty"
-    | Some line ->
-        String.length line
-  in
-  let matrix = Array.make_matrix column_count row_count "" in
-  List.iteri
-    (fun y line ->
-      String.iteri (fun x char -> matrix.(x).(y) <- Char.escaped char) line )
-    lines ;
-  matrix
-
-(** [pp_matrix matrix] is the [input] that was used to create the [matrix]
-    via [input_to_matrix input]. *)
-let pp_matrix matrix =
-  let row_count = Array.length matrix in
-  let column_count = Array.length matrix.(0) in
-  let matrix' = Array.make_matrix row_count column_count "" in
-  Array.iteri
-    (fun x row -> Array.iteri (fun y c -> matrix'.(y).(x) <- c) row)
-    matrix ;
-  matrix'
-  |> Array.map @@ Array.fold_left (fun acc c -> acc ^ c) ""
-  |> Array.fold_left
-       (fun acc line -> if acc = "" then line else acc ^ "\n" ^ line)
-       ""
-
 let solve input () =
-  let matrix = input |> input_to_matrix in
-  Logs.debug (fun m -> m "\n%s" @@ pp_matrix matrix) ;
+  let matrix = Domain.Matrix.M.of_string input in
+  Logs.debug (fun m -> m "\n%s" @@ Domain.Matrix.M.pp (fun s -> s) matrix) ;
   0
-
-let%expect_test "matrix created from input is pretty-printed as the same matrix"
-    =
-  let example =
-    {|..@@.@@@@.
-@@@.@.@.@@
-@@@@@.@.@@
-@.@@@@..@.
-@@.@@@@.@@
-.@@@@@@@.@
-.@.@.@.@@@
-@.@@@.@@@@
-.@@@@@@@@.
-@.@.@@@.@.|}
-  in
-  print_string @@ pp_matrix @@ input_to_matrix example ;
-  [%expect
-    {|..@@.@@@@.
-@@@.@.@.@@
-@@@@@.@.@@
-@.@@@@..@.
-@@.@@@@.@@
-.@@@@@@@.@
-.@.@.@.@@@
-@.@@@.@@@@
-.@@@@@@@@.
-@.@.@@@.@.|}]
-
-let%expect_test "direct access of the matrix is in form matrix.(x).(y)" =
-  let example =
-    {|..@@.@@@@.
-@@@.@.@.@@
-@@@@@.@.@@
-@.@@@@..@.
-@@.@@@@.@@
-.@@@@@@@.@
-.@.@.@.@@@
-@.@@@.@@@@
-.@@@@@@@@.
-@.@.@@@.@.|}
-  in
-  let matrix = input_to_matrix example in
-  print_string matrix.(0).(0) ;
-  [%expect "."] ;
-  print_string matrix.(1).(0) ;
-  [%expect "."] ;
-  print_string matrix.(2).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(3).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(4).(0) ;
-  [%expect "."] ;
-  print_string matrix.(5).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(6).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(7).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(8).(0) ;
-  [%expect "@"] ;
-  print_string matrix.(9).(0) ;
-  [%expect "."]
diff --git a/2025/ocaml/lib/domain/matrix.ml b/2025/ocaml/lib/domain/matrix.ml
new file mode 100644
index 0000000..bb703fc
--- /dev/null
+++ b/2025/ocaml/lib/domain/matrix.ml
@@ -0,0 +1,150 @@
+module M : sig
+  type 'a t = 'a array array
+
+  val empty : int -> int -> 'a -> 'a t
+  (** [empty rows columns initial] is an empty 2D array of size [rows] * [columns]
+      where each element in the array is initialized to [initial]. *)
+
+  val of_list : 'a list list -> 'a t
+  (** *)
+
+  val of_string : string -> string t
+  (** [of_string str] is a 2D array where every character is an element. *)
+
+  val get : 'a t -> int -> int -> 'a
+  (** [get matrix x y] is an alias for [matrix.(y).(x)] *)
+
+  val pp : ('a -> string) -> 'a t -> string
+  (** [pp matrix string_of_elt] is the string representation of the [matrix]
+      where [string_of_elt] is called on each element. *)
+end = struct
+  type 'a t = 'a array array
+
+  let empty cols rows initial = Array.make_matrix cols rows initial
+
+  let of_list lst = Array.of_list @@ List.map Array.of_list lst
+
+  let of_string str =
+    let lines =
+      str |> String.split_on_char '\n'
+      |> List.filter_map (fun line ->
+          let trimmed = String.trim line in
+          if trimmed <> "" then Some trimmed else None )
+    in
+    let char_lst =
+      List.map
+        (fun s -> s |> String.to_seq |> List.of_seq |> List.map Char.escaped)
+        lines
+    in
+    of_list char_lst
+
+  let get matrix x y = matrix.(y).(x)
+
+  let pp string_of_elt matrix =
+    Array.fold_left
+      (fun col_acc arr ->
+        let row =
+          Array.fold_left
+            (fun row_acc elt -> row_acc ^ string_of_elt elt)
+            "" arr
+        in
+        if col_acc = "" then row else col_acc ^ "\n" ^ row )
+      "" matrix
+end
+
+let%expect_test "matrix created from input is pretty-printed as the same matrix"
+    =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  print_string @@ M.pp (fun s -> s) @@ M.of_string example ;
+  [%expect
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}]
+
+let%expect_test "direct access of the matrix is in form matrix.(y).(x)" =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  let matrix = M.of_string example in
+  print_string matrix.(0).(0) ;
+  [%expect "."] ;
+  print_string matrix.(0).(1) ;
+  [%expect "."] ;
+  print_string matrix.(0).(2) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(3) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(4) ;
+  [%expect "."] ;
+  print_string matrix.(0).(5) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(6) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(7) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(8) ;
+  [%expect "@"] ;
+  print_string matrix.(0).(9) ;
+  [%expect "."]
+
+let%expect_test "[M.get matrix x y] is an alias for [matrix.(y).(x)]" =
+  let example =
+    {|..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.|}
+  in
+  let matrix = M.of_string example in
+  print_string @@ M.get matrix 0 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 1 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 2 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 3 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 4 0 ;
+  [%expect "."] ;
+  print_string @@ M.get matrix 5 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 6 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 7 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 8 0 ;
+  [%expect "@"] ;
+  print_string @@ M.get matrix 9 0 ;
+  [%expect "."]