open StdLabels

module Ast = struct
  type 'a variable = { pos : 'a; name : string; index : 'a expression option }
  [@@deriving eq, show]

  and 'a expression =
    | Integer of 'a * string
    | Literal of 'a * string
    | Ident of 'a variable
    | BinaryOp of 'a * T.boperator * 'a expression * 'a expression
    | Op of 'a * T.uoperator * 'a expression
    | Function of 'a * T.function_ * 'a expression list
  [@@deriving eq, show]

  and 'a condition = 'a * 'a expression * 'a statement list

  and 'a statement =
    | If of {
        loc : 'a;
        then_ : 'a condition;
        elifs : 'a condition list;
        else_ : 'a statement list;
      }
    | Act of { loc : 'a; label : 'a expression; statements : 'a statement list }
    | Declaration of ('a * 'a variable * T.assignation_operator * 'a expression)
    | Expression of 'a expression
    | Comment of 'a
    | Call of 'a * T.keywords * 'a expression list
    | Location of 'a * string
  [@@deriving eq, show]
end

(** Default implementation for the expression *)
module Expression : S.Expression with type t' = S.pos Ast.expression = struct
  type t = S.pos Ast.expression
  type t' = t

  let v : t * Report.t list -> t' * Report.t list = fun (t, r) -> (t, r)

  let integer : S.pos -> string -> t S.repr =
   fun pos i r -> (Ast.Integer (pos, i), r)

  let literal : S.pos -> string -> t S.repr =
   fun pos l r -> (Ast.Literal (pos, l), r)

  let function_ : S.pos -> T.function_ -> t S.repr list -> t S.repr =
   fun pos name args r ->
    let args = List.map ~f:(fun f -> fst (f r)) args in
    (Ast.Function (pos, name, args), r)

  let uoperator : S.pos -> T.uoperator -> t S.repr -> t S.repr =
   fun pos op expression r ->
    let expression = fst (expression r) in
    (Ast.Op (pos, op, expression), r)

  let boperator : S.pos -> T.boperator -> t S.repr -> t S.repr -> t S.repr =
   fun pos op op1 op2 r ->
    let op1 = fst (op1 r) and op2 = fst (op2 r) in
    (Ast.BinaryOp (pos, op, op1, op2), r)

  let ident : (S.pos, t S.repr) S.variable -> t S.repr =
   fun { pos; name; index } r ->
    let index = Option.map (fun i -> fst (i r)) index in
    (Ast.Ident { pos; name; index }, r)
end

module Instruction :
  S.Instruction
    with type expression = Expression.t' S.repr
     and type t' = S.pos Ast.statement = struct
  type t = S.pos Ast.statement
  type t' = t

  let v = Fun.id

  type expression = Expression.t' S.repr

  let call : S.pos -> T.keywords -> expression list -> t S.repr =
   fun pos name args report ->
    let args = List.map ~f:(fun f -> fst (f [])) args in
    (Ast.Call (pos, name, args), report)

  let location : S.pos -> string -> t S.repr =
   fun loc label report -> (Ast.Location (loc, label), report)

  let comment : S.pos -> t S.repr = fun pos report -> (Ast.Comment pos, report)

  let expression : expression -> t S.repr =
   fun expr report -> (Ast.Expression (fst (expr [])), report)

  type clause = S.pos * expression * t S.repr list

  let if_ :
      S.pos -> clause -> elifs:clause list -> else_:t S.repr list -> t S.repr =
   fun pos predicate ~elifs ~else_ report ->
    let clause (pos, expr, repr) =
      let repr = List.map ~f:(fun instr -> fst @@ instr []) repr in
      (pos, fst @@ expr [], repr)
    in
    let elifs = List.map ~f:clause elifs
    and else_ = List.map ~f:(fun instr -> fst @@ instr []) else_ in

    (Ast.If { loc = pos; then_ = clause predicate; elifs; else_ }, report)

  let act : S.pos -> label:expression -> t S.repr list -> t S.repr =
   fun pos ~label statements report ->
    let label = fst (label [])
    and statements = List.map ~f:(fun instr -> fst @@ instr []) statements in
    (Ast.Act { loc = pos; label; statements }, report)

  let assign :
      S.pos ->
      (S.pos, expression) S.variable ->
      T.assignation_operator ->
      expression ->
      t S.repr =
   fun pos_loc { pos; name; index } op expr report ->
    (*let index = Option.map (fun i -> fst @@ Expression.observe (i [])) index*)
    let index = Option.map (fun f -> fst @@ f []) index in
    let expr = fst (expr []) in
    (Ast.Declaration (pos_loc, { pos; name; index }, op, expr), report)
end

module Location = struct
  type instruction = S.pos Ast.statement S.repr
  type repr = S.pos * S.pos Ast.statement list

  let location : S.pos -> instruction list -> repr =
   fun pos block ->
    let block = List.map block ~f:(fun b -> fst @@ b []) in
    (pos, block)
end