repl session commands: load, reset, quit; emacs load-file binding

1 files changed, 64 insertions, 16 deletions

diff --git a/bin/main.ml b/bin/main.ml
index eb212d2..26375da 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -44,30 +44,78 @@ let run_file path =
   | Ok statements -> (
       match run_statements statements with Ok () -> () | Error () -> exit 1)
 
+let declarations statements =
+  List.filter
+    (function Sol.Ast.Directive ("Query", _) -> false | _ -> true)
+    statements
+
+(* Feeding statements into the session: declarations accumulate,
+   queries answer immediately, and a failure changes nothing, so the
+   session only ever holds an admitted program. *)
+let feed history statements =
+  match run_statements (history @ statements) with
+  | Ok () -> history @ declarations statements
+  | Error () -> history
+
+let strip_quotes s =
+  let n = String.length s in
+  if n >= 2 && s.[0] = '"' && s.[n - 1] = '"' then String.sub s 1 (n - 2)
+  else s
+
+let load_file history argument =
+  let path = strip_quotes argument in
+  match In_channel.with_open_text path In_channel.input_all with
+  | exception Sys_error message ->
+      prerr_endline message;
+      history
+  | contents -> (
+      match Sol.Front.parse_string contents with
+      | Error message ->
+          prerr_endline (path ^ ": " ^ message);
+          history
+      | Ok statements ->
+          let next = feed history statements in
+          if next != history then
+            Printf.printf "loaded %s: %d declarations, %d queries run.\n" path
+              (List.length (declarations statements))
+              (List.length statements - List.length (declarations statements));
+          next)
+
 let repl () =
-  print_endline "Sol. Statements accumulate; Query expression: ... runs.";
+  print_endline
+    "Sol. Statements accumulate; Query expression: ... runs; :help for commands.";
   let rec loop history =
     print_string "sol> ";
     flush stdout;
     match In_channel.input_line stdin with
     | None -> ()
-    | Some line when String.trim line = "" -> loop history
     | Some line -> (
-        match Sol.Front.parse_string line with
-        | Error message ->
-            prerr_endline message;
+        let line = String.trim line in
+        match String.index_opt line ' ' with
+        | _ when line = "" -> loop history
+        | _ when line = ":quit" -> ()
+        | _ when line = ":reset" ->
+            print_endline "session cleared.";
+            loop []
+        | _ when line = ":help" ->
+            print_endline
+              ":load FILE   bring a program into the session (atomic: a rejected file changes nothing)\n\
+               :reset       clear the session\n\
+               :quit        leave";
+            loop history
+        | Some i when String.sub line 0 i = ":load" ->
+            loop
+              (load_file history
+                 (String.trim (String.sub line i (String.length line - i))))
+        | _ when String.length line > 0 && line.[0] = ':' ->
+            prerr_endline "unknown command; :help lists them.";
             loop history
-        | Ok statements -> (
-            let declarations =
-              List.filter
-                (function
-                  | Sol.Ast.Directive ("Query", _) -> false
-                  | _ -> true)
-                statements
-            in
-            match run_statements (history @ statements) with
-            | Ok () -> loop (history @ declarations)
-            | Error () -> loop history))
+        | _ -> (
+            match Sol.Front.parse_string line with
+            | Error message ->
+                prerr_endline message;
+                loop history
+            | Ok statements -> loop (feed history statements)))
   in
   loop []