Add next, prev and show commands

bin/inspector.ml

@@ -1,10 +1,40 @@
-let load_lines filename =
+module State = struct
-  In_channel.with_open_text filename In_channel.input_lines |> Array.of_list
+  type t = { lines : string array; cursor : int; size : int }
+
+  let create (fname : string) : t =
+    let lines =
+      In_channel.with_open_text fname In_channel.input_lines |> Array.of_list
+    in
+    { lines; cursor = 0; size = Array.length lines }
+
+  let show_line s : string = s.lines.(s.cursor)
+
+  let rec repl s =
+    print_string "inspector> ";
+    flush stdout;
+    try
+      match read_line () |> String.lowercase_ascii with
+      | "exit" | "quit" -> print_endline "bye"
+      | "next" ->
+          if s.cursor < s.size - 1 then repl { s with cursor = s.cursor + 1 }
+          else repl s
+      | "prev" ->
+          if s.cursor > 0 then repl { s with cursor = s.cursor - 1 } else repl s
+      | "show" ->
+          Printf.printf "[%d]: %s\n" s.cursor (show_line s);
+          repl s
+      | str ->
+          print_endline str;
+          repl s
+    with End_of_file -> print_endline "bye"
+end
 
 let () =
   if Array.length Sys.argv < 2 then (
     Printf.eprintf "Usage: %s <logfile>\n" (Filename.basename Sys.argv.(0));
     exit 1);
 
-  let contents = load_lines Sys.argv.(1) in
+  let s = State.create Sys.argv.(1) in
-  Printf.printf "Loaded %d lines\n" (Array.length contents)
+  Printf.printf "Loaded %d lines\n" s.size;
+
+  State.repl s