open Printf

module Platform = Util.Platform

(* configuration flags ------------------------------------------------------ *)
let interpret_ll = ref false   (* run the ll interpreter? *)
let print_ll_flag = ref false       (* print the generated ll code? *)
let print_x86_flag = ref false      (* print the generated x86 code? *)
let clang = ref false          (* use the clang backend? *)
let assemble = ref true        (* assemble the .s to .o files? *)
let link = ref true            (* combine multiple .o files executable? *)
let execute_x86 = ref false    (* run the resulting x86 program? *)
let executable_filename = ref "a.out"


(* files processed during this run of the compiler *)
let files : string list ref = ref []

let link_files = ref []
let add_link_file path =
  link_files := path :: (!link_files)


(* terminal output ---------------------------------------------------------- *)

let print_banner s =
  let rec dashes n = if n = 0 then "" else "-"^(dashes (n-1)) in
  printf "%s %s\n%!" (dashes (79 - (String.length s))) s

let print_ll file ll_ast =
    print_banner (file ^ ".ll");
    print_endline (Llutil.string_of_prog ll_ast)

let print_x86 file asm_str =
    print_banner file;
    print_endline asm_str

(* file i/o ----------------------------------------------------------------- *)

let read_file (file:string) : string =
  let lines = ref [] in
  let channel = open_in file in
  try while true; do
      lines := input_line channel :: !lines
  done; ""
  with End_of_file ->
    close_in channel;
    String.concat "\n" (List.rev !lines)

let write_file (file:string) (out:string) =
  let channel = open_out file in
  fprintf channel "%s" out;
  close_out channel


(* running the generated code ----------------------------------------------- *)

let interpret program args : string =
  let result = Llinterp.interp_prog program args in
  Llinterp.string_of_sval result

let string_of_file (f:in_channel) : string =
  let rec _string_of_file (stream:string list) (f:in_channel) : string list=
    try
      let s = input_line f in
      _string_of_file (s::stream) f
    with
      | End_of_file -> stream
  in
    String.concat "\n" (List.rev (_string_of_file [] f))

let run_executable timeout arg pr =
  let cmd = sprintf "%s%s %s" Platform.dot_path pr arg in
  Platform.timeout_sh timeout cmd (fun _ i -> i)

let run_executable_to_tmpfile timeout arg pr tmp =
  let cmd = sprintf "%s%s %d > %s 2>&1" Platform.dot_path pr arg tmp in
  Platform.timeout_sh timeout cmd Platform.ignore_error


let run_program (args:string) (executable:string) (tmp_out:string) : string =
  let _ =
    let cmd =
      sprintf "%s%s %s > %s 2>&1" Platform.dot_path executable args tmp_out
    in
    Platform.sh cmd Platform.ignore_error
  in
  let fi = open_in tmp_out in
  let result = string_of_file fi in
  let _ = close_in fi in
    result


(* compiler pipeline -------------------------------------------------------- *)

(* These functions implement the compiler pipeline for a single ll file:
     - parse the file
     - compile to a .s file using either clang or backend.ml
     - assemble the .s to a .o file using clang
*)
let parse_ll_file filename =
  let program = read_file filename |>
                Lexing.from_string |>
                Llparser.prog Lllexer.token
  in
  program


let process_ll_ast path file ll_ast =
  let _ = if !print_ll_flag then print_ll file ll_ast in

  (* Optionally interpret it using the cs131 reference interperter. *)
  let _ = if !interpret_ll then
      let result = interpret ll_ast [] in
      Printf.printf "Interpreter Result: %s\n" result
  in

  (* generated file names *)
  let dot_s_file = Platform.gen_name !Platform.output_path file ".s" in
  let dot_o_file = Platform.gen_name !Platform.output_path file ".o" in

  let _ =
    if !clang then begin
      Platform.verb "* compiling with clang";
      Platform.clang_compile path dot_s_file;
      if !print_x86_flag then begin
        print_banner dot_s_file;
        Platform.sh (Printf.sprintf "cat %s" dot_s_file) Platform.raise_error
      end
    end else begin
      Platform.verb "* compiling with cs131 backend";
      let asm_ast = Backend.compile_prog ll_ast in
      let asm_str = X86.string_of_prog asm_ast in
      let _ = if !print_x86_flag then print_x86 dot_s_file asm_str in
      let _ = write_file dot_s_file asm_str in
      ()
    end
  in
  let _ = if !assemble then Platform.assemble dot_s_file dot_o_file in
  let _ = add_link_file dot_o_file in
  ()

let process_ll_file path file =
  let _ = Platform.verb @@ Printf.sprintf "* processing file: %s\n" path in
  let ll_ast = parse_ll_file path in
  process_ll_ast path file ll_ast

(* process files based on extension ----------------------------------------- *)

let process_file path =
  let basename, ext = Platform.path_to_basename_ext path in
  begin match ext with
    | "ll" -> process_ll_file path basename
    | "o" -> add_link_file path
    | "c" -> add_link_file path
    | _ -> failwith @@ Printf.sprintf "found unsupported file type: %s" path
  end

(* process each file separately and then link all of them together *)
let process_files files =
  if (List.length files) > 0 then begin

    List.iter process_file files;

    ( if !assemble && !link then
        Platform.link (List.rev !link_files) !executable_filename );

    ( if !assemble && !link && !execute_x86 then
        let ret = run_executable 10 "" !executable_filename in
        print_banner @@ Printf.sprintf "Executing: %s" !executable_filename;
        Printf.printf "* %s returned %d\n" !executable_filename ret )
  end