Add help

lib/repl.ml

@@ -1,15 +1,43 @@
+type command = { description : string; run : State.t -> State.t }
+
+module Cmd = Map.Make (String)
+
+let commands =
+  [
+    ( "next",
+      { description = "Move cursor to the next log line"; run = State.next } );
+    ( "prev",
+      { description = "Move cursor to the previous line"; run = State.prev } );
+    ( "show",
+      {
+        description = "Display the current log line";
+        run =
+          (fun s ->
+            Printf.printf "[%d]: %s\n" (State.cursor s) (State.show_line s);
+            s);
+      } );
+  ]
+  |> List.to_seq |> Cmd.of_seq
+
+let help () =
+  Printf.printf "Available commands:\n";
+  Cmd.iter
+    (fun cmd args -> Printf.printf "  %-11s %s\n" cmd args.description)
+    commands;
+  print_endline "  exit, quit  Exit the inspector"
+
 let rec loop state =
   print_string "inspector> ";
   flush stdout;
   try
-    match read_line () |> String.lowercase_ascii with
+    let cmd = read_line () |> String.lowercase_ascii in
+    match cmd with
+    | "" -> loop state
     | "exit" | "quit" -> print_endline "bye"
-    | "next" -> loop (State.next state)
-    | "prev" -> loop (State.prev state)
-    | "show" ->
-        Printf.printf "[%d]: %s\n" (State.cursor state) (State.show_line state);
-        loop state
-    | str ->
-        print_endline str;
-        loop state
+    | _ -> (
+        match Cmd.find_opt cmd commands with
+        | Some c -> loop (c.run state)
+        | None ->
+            Printf.printf "Unknown command: %s\n" cmd;
+            loop state)
   with End_of_file -> print_endline "bye"