(* flan — milestone 2 driver. *)

let with_errors path f =
  try f () with
  | Flan.Loc.Error (loc, msg) ->
    Printf.eprintf "%s: %s\n" (Flan.Loc.to_string loc) msg;
    ignore path;
    exit 1

let summarise (d : Flan.Ast.decl) =
  let open Flan.Ast in
  match d.d with
  | Package n -> Printf.sprintf "package %s" n
  | Import (a, p) -> Printf.sprintf "import %s %S" a p
  | Defalias (n, _) -> Printf.sprintf "defalias %s" n
  | Defstruct (n, fs) -> Printf.sprintf "defstruct %s (%d fields)" n (List.length fs)
  | Defunion (n, vs) -> Printf.sprintf "defunion %s (%d cases)" n (List.length vs)
  | Defvar (n, _, _) -> Printf.sprintf "defvar %s" n
  | Defconst (n, _, _) -> Printf.sprintf "defconst %s" n
  | Declare (fn, csym) ->
    Printf.sprintf "declare %s (%d params) = %s" fn.name (List.length fn.params)
      csym
  | DeclareC (fn, csym) ->
    Printf.sprintf "declare-c %s (%d params) = %s" fn.name
      (List.length fn.params) csym
  | Defenum (n, ms) -> Printf.sprintf "defenum %s (%d members)" n (List.length ms)
  | Defn fn ->
    Printf.sprintf "defn %s (%d params, %s return, %d body forms)"
      fn.name (List.length fn.params)
      (match fn.ret with None -> "Unit" | Some _ -> "explicit")
      (List.length fn.fbody)

(* Every path past [parse] goes through [Load]: an import is resolved into the
   declarations it stands for, and the package's C shim and linker arguments
   come back with them. *)
let load path : Flan.Load.t =
  Flan.Load.program ~file:path (Flan.Parse.program (Flan.Reader.read_file path))

let checked path = Flan.Check.program (load path).decls

(* What the source called each parameter, per function. The typed IR refers to
   locals by slot index and records no names — [Check] has them in its scope
   list and drops them — so the debug info would otherwise print [p0] for
   every argument. Slots 0..n-1 are the parameters in order ([Tast.fn]), which
   is what makes this recoverable here, from declarations that are already in
   hand, rather than needing a change to the typed IR. It stops at the
   parameters: a let-bound local's name is genuinely not available without one.
   Only gathered for a debug build. *)
let param_names (l : Flan.Load.t) =
  List.filter_map
    (fun (d : Flan.Ast.decl) ->
       match d.Flan.Ast.d with
       | Flan.Ast.Defn fn ->
         Some (fn.Flan.Ast.name,
               List.map (fun (p : Flan.Ast.field) -> p.Flan.Ast.fname)
                 fn.Flan.Ast.params)
       | _ -> None)
    l.Flan.Load.decls

(* Bounds checks are on unless a build asks for them off — the release
   decision, not the optimisation level (NEXT.md, Bounds checks). *)
let no_checks_flag = "--no-bounds-checks"

(* A dev build is the one a REPL can attach to: every call goes through a cell
   so a redefinition can be installed, and the cells and globals are exported
   so a loaded module can reach them (NEXT.md, the dev loop). *)
let dev_flag = "--dev"

(* Source-level debugging: DWARF in the IR, -g on the C, and -O0 forced.
   Its own flag and not a mode of --dev, because the two answer different
   questions — --dev is "can I redefine this while it runs", --debug is "can I
   stop it and read it". See [Build.opts]. *)
let debug_flag = "--debug"

(* ASan and UBSan over the whole program, the runtime's C and the Flan alike.
   Its own flag for the same reason --debug is: it answers "is this program
   touching memory it does not own", which is neither of the other two
   questions. It does not imply -O0 — see [Build.opts], which also records
   what each of the two sanitizers actually reaches. *)
let sanitize_flag = "--sanitize"

let flags = [ no_checks_flag; dev_flag; debug_flag; sanitize_flag ]

(* [--target=wasm32-wasi] and [--target=web], the two cross targets. Unlike
   the flags above, a target
   carries a value, so it is matched by prefix and stripped from the residual
   arguments by the same test — otherwise [-o out --target=X] falls into the
   usage error. *)
let target_prefix = "--target="

let is_flag a =
  List.mem a flags || String.starts_with ~prefix:target_prefix a

let target_of args =
  List.find_map
    (fun a ->
       if String.starts_with ~prefix:target_prefix a then
         Some (String.sub a (String.length target_prefix)
                 (String.length a - String.length target_prefix))
       else None)
    args

let () =
  match Array.to_list Sys.argv with
  | _ :: "read" :: files when files <> [] ->
    List.iter
      (fun path ->
         with_errors path (fun () ->
           Flan.Reader.read_file path
           |> List.iter (fun f -> print_endline (Flan.Form.to_string f))))
      files
  | _ :: "parse" :: files when files <> [] ->
    List.iter
      (fun path ->
         with_errors path (fun () ->
           Flan.Reader.read_file path
           |> Flan.Parse.program
           |> List.iter (fun d -> print_endline (summarise d))))
      files
  | _ :: "check" :: files when files <> [] ->
    List.iter
      (fun path ->
         with_errors path (fun () ->
           let p = checked path in
           List.iter
             (fun (g : Flan.Tast.global) ->
                Printf.printf "%s %s %s\n"
                  (if g.gconst then "defconst" else "defvar")
                  g.gname (Flan.Types.to_string g.gty))
             p.globals;
           List.iter
             (fun (f : Flan.Tast.fn) ->
                Printf.printf "defn %s : (Fn [%s] %s)  %d slots\n" f.name
                  (String.concat " "
                     (List.map Flan.Types.to_string f.params))
                  (Flan.Types.to_string f.ret) (Array.length f.slots))
             p.fns))
      files
  (* The generated C, for looking at. A wrong FFI binding is wrong in the
     wrapper, and the wrapper is not on disk anywhere — [Build] hands the text
     straight to clang — so without this the only way to read one is to catch
     it in the object cache. *)
  | _ :: "shim" :: files when files <> [] ->
    List.iter
      (fun path ->
         with_errors path (fun () ->
           match (checked path).Flan.Tast.cshim with
           | [] -> Printf.printf "%s: no declare-c, so no generated C\n" path
           | parts -> List.iter (fun (_, src) -> print_string src) parts))
      files
  (* The IR is target-independent — [Emit] writes no triple and no datalayout,
     which is what lets one .ll serve both targets — so there is nothing for a
     target to change here. Refused rather than accepted and ignored: silently
     swallowing a flag is the shape the house rule exists to prevent. *)
  | _ :: "emit" :: args when target_of args <> None ->
    prerr_endline
      "flan emit: --target is refused — the emitted IR carries no triple and \
       no datalayout, and the target is chosen at build.";
    exit 2
  | _ :: "emit" :: args when List.exists (fun a -> not (is_flag a)) args ->
    let checks = not (List.mem no_checks_flag args) in
    let dev = List.mem dev_flag args in
    let debug = List.mem debug_flag args in
    (* --sanitize changes the IR — every [define] names the attribute group
       ASan's pass selects on — so [emit] has to honour it or what this prints
       is not what a sanitized build compiles. *)
    let sanitize = List.mem sanitize_flag args in
    let files = List.filter (fun a -> not (is_flag a)) args in
    List.iter
      (fun path ->
         with_errors path (fun () ->
           let l = load path in
           let pnames = if debug then param_names l else [] in
           Flan.Check.program l.decls
           |> Flan.Emit.program ~checks ~dev ~debug ~pnames ~sanitize
           |> print_string))
      files
  | _ :: "build" :: path :: rest ->
    let checks = not (List.mem no_checks_flag rest) in
    let dev = List.mem dev_flag rest in
    let debug = List.mem debug_flag rest in
    let sanitize = List.mem sanitize_flag rest in
    let target = target_of rest in
    let out =
      match List.filter (fun a -> not (is_flag a)) rest with
      | [ "-o"; o ] -> o
      | [] ->
        let base = Filename.remove_extension (Filename.basename path) in
        (* A wasm module is not an executable and must not be named like one:
           the extension is what tells a runtime, and a reader, what it is. *)
        (* A web build is three files — the page, its JS and the module — and
           the page is the one named here: emcc derives the other two from it,
           and it is the one a browser opens. *)
        (match target with
         | Some t when Flan.Build.is_web t -> base ^ ".html"
         | Some t when String.starts_with ~prefix:"wasm32" t -> base ^ ".wasm"
         | _ -> base)
      | _ ->
        prerr_endline
          "usage: flan build <file.flan> [-o out] [--no-bounds-checks] \
           [--dev] [--debug] [--sanitize] [--target=wasm32-wasi|web]";
        exit 2
    in
    with_errors path (fun () ->
      let l = load path in
      let p = Flan.Check.program l.decls in
      (* The link follows the program, not the import list: a package nothing
         reachable calls into contributes no C and no linker argument, and its
         functions are not emitted either. That is what lets one file import
         raylib and still be buildable for wasm32. *)
      let p, csrcs, lflags = Flan.Reach.link ~dev l p in
      ignore (Flan.Build.executable
                ~opts:{ Flan.Build.default with checks; dev; debug; sanitize;
                                                target }
                ~csrcs ~lflags ~pnames:(if debug then param_names l else [])
                p ~out))
  (* The daemon an editor talks to: one session, the program it belongs to
     running beside it, and a socket. Unlike [flan reload] the session persists,
     so a defvar added by one evaluation is part of what the next one is checked
     against — and it owns the build, which is what makes its layout rules
     describe the process that is actually running. *)
  | _ :: "dev" :: path :: rest ->
    (* --debug builds the host *and* every module this daemon sends with DWARF,
       which is one flag because it is one decision: a line breakpoint in a
       .flan buffer needs a line table on the host to fire at all, and one in
       each redefinition module to still be firing after C-c C-c. It implies
       -O0 on both, so it is asked for rather than assumed. *)
    let debug = List.mem debug_flag rest in
    let rest = List.filter (fun a -> not (is_flag a)) rest in
    let sock =
      match rest with
      | [ "-s"; s ] -> s
      | [] -> Filename.concat (Filename.dirname path) ".flan-dev.sock"
      | _ ->
        prerr_endline "usage: flan dev <program.flan> [-s socket] [--debug]";
        exit 2
    in
    with_errors path (fun () -> Flan.Dev.start ~debug ~file:path ~sock ())

  (* One redefinition, built the way an editor will ask for it: a session over
     the program the process was built from, and a file of the forms that
     changed. The session works out which names are new and whether the change
     is one a running process can be told at all — neither of which a command
     given only a list of function names could. *)
  | _ :: "reload" :: prog :: forms :: rest ->
    let debug = List.mem debug_flag rest in
    let rest = List.filter (fun a -> not (is_flag a)) rest in
    let out =
      match rest with
      | [ "-o"; o ] -> o
      | [] -> Filename.remove_extension (Filename.basename forms) ^ ".so"
      | _ ->
        prerr_endline
          "usage: flan reload <program.flan> <forms.flan> [-o out.so] [--debug]";
        exit 2
    in
    with_errors forms (fun () ->
      let t, _ = Flan.Session.create ~debug ~file:prog () in
      let src = In_channel.with_open_bin forms In_channel.input_all in
      let c = Flan.Session.eval ~origin:forms t src in
      let opts = { Flan.Build.default with dev = true; debug } in
      let timing = Flan.Build.shared ~opts ~ir:c.Flan.Session.ir ~out () in
      Printf.eprintf "%s  %s  llc %.1fms  ld %.1fms\n" out
        (String.concat " " c.Flan.Session.fns) timing.Flan.Build.llc_ms
        timing.Flan.Build.link_ms)
  (* [run] builds and execs. A .wasm is not executable, and picking a runtime
     for it is a decision this command has no business making, so a cross
     target is refused here by name rather than half-supported. *)
  | _ :: "run" :: _ :: args when target_of args <> None ->
    prerr_endline
      "flan run: --target is refused — a cross-built module is not something \
       this host can exec. Use flan build --target=... and a wasm runtime.";
    exit 2
  | _ :: "run" :: path :: args ->
    with_errors path (fun () ->
      let exe =
        Filename.concat (Filename.get_temp_dir_name ())
          (Printf.sprintf "flan-run-%d" (Unix.getpid ()))
      in
      let l = load path in
      let p = Flan.Check.program l.decls in
      let p, csrcs, lflags = Flan.Reach.link l p in
      ignore (Flan.Build.executable ~csrcs ~lflags p ~out:exe);
      let code =
        Sys.command (String.concat " " (List.map Filename.quote (exe :: args)))
      in
      (try Sys.remove exe with Sys_error _ -> ());
      exit code)
  | _ ->
    prerr_endline
      "usage: flan (read|parse|check|emit|shim) <file.flan>...\n\
      \       flan build <file.flan> [-o out] [--no-bounds-checks] [--dev] \
       [--debug] [--sanitize] [--target=wasm32-wasi|web]\n\
      \       flan run <file.flan> [args...]\n\
      \       flan reload <program.flan> <forms.flan> [-o out.so]\n\
      \       flan dev <program.flan> [-s socket]";
    exit 2