(* Goalfile Abstract Syntax Tree
 * Copyright (C) 2019 Richard W.M. Jones
 * Copyright (C) 2019 Red Hat Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *)

open Printf

open Utils

let rec to_constant env = function
  | Ast.EConstant (loc, c) -> c

  | EVar (loc, name) ->
     let expr = Ast.getvar env loc name in
     to_constant env expr

  | ESubsts (loc, str) ->
     CString (substitute env loc str)

  | EList (loc, _) ->
     failwithf "%a: list found where constant expression expected"
       Ast.string_loc loc

  | ECall (loc, name, args) ->
     let expr = Ast.getvar env loc name in
     (match expr with
      | EGoalDefn _ ->
         (* Goals don't return anything so they cannot be used in
          * constant expressions.  Use a function instead.
          *)
         failwithf "%a: cannot use goal call ‘%s’ in shell expansion"
           Ast.string_loc loc name

      | EFuncDefn (loc, func) ->
         to_constant env (call_function env loc name args func)

      | _ ->
         failwithf "%a: cannot use ‘%s’ in constant expression"
           Ast.string_loc loc name
     )

  | ETacticCtor (loc, name, _) ->
     failwithf "%a: cannot use tactic ‘%s’ in constant expression"
       Ast.string_loc loc name

  | EGoalDefn (loc, _) ->
     failwithf "%a: cannot use goal in constant expression"
       Ast.string_loc loc

  | EFuncDefn (loc, _) ->
     failwithf "%a: cannot use function in constant expression"
       Ast.string_loc loc

  | ETacticDefn (loc, _) ->
     failwithf "%a: cannot use tactic in constant expression"
       Ast.string_loc loc

and substitute env loc substs =
  let b = Buffer.create 13 in
  List.iter (
    function
    | Ast.SString s -> Buffer.add_string b s
    | SVar name ->
       let expr = Ast.getvar env loc name in
       match to_constant env expr with
       | Ast.CString s -> Buffer.add_string b s
  ) substs;
  Buffer.contents b

and to_shell_script env loc substs =
  let b = Buffer.create 13 in
  List.iter (
    function
    | Ast.SString s -> Buffer.add_string b s
    | SVar name ->
       let expr = Ast.getvar env loc name in
       let s = expr_to_shell_string env expr in
       Buffer.add_string b s
  ) substs;
  Buffer.contents b

and expr_to_shell_string env = function
  | Ast.EConstant (loc, CString s) -> Filename.quote s

  | EVar (loc, name) ->
     let expr = Ast.getvar env loc name in
     expr_to_shell_string env expr

  | ESubsts (loc, str) ->
     Filename.quote (substitute env loc str)

  | EList (loc, exprs) ->
     let strs = List.map (expr_to_shell_string env) exprs in
     (* These are shell quoted so we can just concat them with space. *)
     String.concat " " strs

  | ECall (loc, name, args) ->
     let expr = Ast.getvar env loc name in
     (match expr with
      | EGoalDefn _ ->
         (* Goals don't return anything so they cannot be used in
          * shell script expansions.  Use a function instead.
          *)
         failwithf "%a: cannot use goal call ‘%s’ in shell expansion"
           Ast.string_loc loc name

      | EFuncDefn (loc, func) ->
         expr_to_shell_string env (call_function env loc name args func)

      | _ ->
         failwithf "%a: cannot call ‘%s’ which is not a function"
           Ast.string_loc loc name
     )

  (* Tactics expand to the first parameter. *)
  | ETacticCtor (loc, _, []) -> Filename.quote ""
  | ETacticCtor (loc, _, (arg :: _)) -> expr_to_shell_string env arg

  | EGoalDefn (loc, _) ->
     failwithf "%a: cannot use goal in shell expansion"
       Ast.string_loc loc

  | EFuncDefn (loc, _) ->
     failwithf "%a: cannot use function in shell expansion"
       Ast.string_loc loc

  | ETacticDefn (loc, _) ->
     failwithf "%a: cannot use tactic in shell expansion"
       Ast.string_loc loc

and run_code ?(quiet = false) env loc code =
  let code = to_shell_script env loc code in
  let code =
    "source " ^ Filename.quote Cmdline.prelude_sh_file ^ "\n" ^
    "set -e\n" ^
    (if not quiet then "set -x\n" else "") ^
    "\n" ^
    code in

  let chan = Unix.open_process_in code in
  let b = Buffer.create 1024 in
  (try
     while true do
       Buffer.add_string b (input_line chan);
       Buffer.add_char b '\n'
     done
   with End_of_file -> ());
  let st = Unix.close_process_in chan in
  let i =
    match st with
    | Unix.WEXITED i -> i
    | Unix.WSIGNALED i ->
       failwithf "%a: killed by signal %d" Ast.string_loc loc i
    | Unix.WSTOPPED i ->
       failwithf "%a: stopped by signal %d" Ast.string_loc loc i in
  i, Buffer.contents b

and evaluate_goal_arg env = function
  | Ast.EVar (loc, name) ->
     let expr = Ast.getvar env loc name in
     evaluate_goal_arg env expr

  | ESubsts (loc, str) ->
     let str = substitute env loc str in
     Ast.EConstant (loc, Ast.CString str)

  | EList (loc, exprs) ->
     Ast.EList (loc, List.map (evaluate_goal_arg env) exprs)

  | ETacticCtor (loc, name, exprs) ->
     Ast.ETacticCtor (loc, name, List.map (evaluate_goal_arg env) exprs)

  | ECall (loc, name, args) ->
     let expr = Ast.getvar env loc name in
     (match expr with
      | EGoalDefn _ ->
         (* Goals don't return anything so they cannot be used in
          * goal args.  Use a function instead.
          *)
         failwithf "%a: cannot use goal call ‘%s’ in goal argument"
           Ast.string_loc loc name

      | EFuncDefn (loc, func) ->
         call_function env loc name args func

      | _ ->
         failwithf "%a: cannot call ‘%s’ which is not a function"
           Ast.string_loc loc name
     )

  | EConstant _
  | EGoalDefn _
  | EFuncDefn _
  | ETacticDefn _ as e -> e

(* Functions are only called from goal args or when substituting
 * into a shell script or constant expression (this may change if we
 * implement ‘:=’ assignment for variables).  This evaluates a
 * function by running the associated shell script and parsing
 * the output as an expression, string or list of strings.
 *)
and call_function env loc name args (params, returning, code) =
  (* This is used to print the function in debug and error messages only. *)
  let debug_func =
    sprintf "%s (%s) returning %s" name
      (String.concat ", " (List.map (Ast.string_expr ()) args))
      (match returning with RetExpr -> "expression"
                          | RetString -> "string"
                          | RetStrings -> "strings") in
  Cmdline.debug "%a: running function %s" Ast.string_loc loc debug_func;

  (* Evaluate function args.  Must be done before updating the environment. *)
  let args = List.map (evaluate_goal_arg env) args in

  (* Create a new environment which maps the parameter names to
   * the args.
   *)
  let env =
    let params =
      try List.combine params args
      with Invalid_argument _ ->
        failwithf "%a: calling function %s with wrong number of arguments, expecting %d args but got %d args"
          Ast.string_loc loc debug_func
          (List.length params) (List.length args) in
    List.fold_left (fun env (k, v) -> Ast.Env.add k v env) env params in

  let r, b = run_code env loc code in
  if r <> 0 then (
    eprintf "*** function ‘%s’ failed with exit code %d\n" name r;
    exit 1
  );

  match returning with
  | RetExpr -> Parse.parse_expr (sprintf "function:%s" name) b
  | RetString -> Ast.EConstant (loc, Ast.CString b)
  | RetStrings ->
     (* run_code always adds \n after the final line, so when we
      * read it back we will get a final empty string which we
      * have to drop.  XXX Probably better to preserve the lines
      * read from the external command.
      *)
     let strs = nsplit "\n" b in
     let strs = List.rev strs in
     let strs = match strs with "" :: xs -> xs | xs -> xs in
     let strs = List.rev strs in
     let strs = List.map (fun s -> Ast.EConstant (loc, Ast.CString s)) strs in
     EList (loc, strs)